U.S. patent application number 10/674324 was filed with the patent office on 2004-09-02 for nerve stimulation and conduction block therapy.
This patent application is currently assigned to Beta Medical, Inc.. Invention is credited to Conrad, Timothy R., Knudson, Mark B., Tweden, Katherine S., Wilson, Richard R..
Application Number | 20040172085 10/674324 |
Document ID | / |
Family ID | 32907599 |
Filed Date | 2004-09-02 |
United States Patent
Application |
20040172085 |
Kind Code |
A1 |
Knudson, Mark B. ; et
al. |
September 2, 2004 |
Nerve stimulation and conduction block therapy
Abstract
A treatment apparatus and method have a stimulation electrode
adapted for placement on a nerve of a patient at a stimulation site
and a stimulation signal generator for generating a stimulation
signal at the stimulation electrode and selected to electrically
stimulate a nerve to induce bi-directional propagation of nervous
impulses in a stimulated nerve. The apparatus includes a blocking
member for placement on the nerve at a blocking site and creating
localized conditions at the blocking site that at least partially
diminish transmission of nerve impulses past the blocking site.
Inventors: |
Knudson, Mark B.;
(Shoreview, MN) ; Wilson, Richard R.; (Arden
Hills, MN) ; Tweden, Katherine S.; (Mahtomedi,
MN) ; Conrad, Timothy R.; (Eden Prairie, MN) |
Correspondence
Address: |
Merchant & Gould P.C.
P.O. Box 2903
Minneapolis
MN
55402-0903
US
|
Assignee: |
Beta Medical, Inc.
|
Family ID: |
32907599 |
Appl. No.: |
10/674324 |
Filed: |
September 29, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10674324 |
Sep 29, 2003 |
|
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|
10358093 |
Feb 3, 2003 |
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Current U.S.
Class: |
607/40 |
Current CPC
Class: |
A61N 1/05 20130101; A61N
1/321 20130101; A61N 1/3606 20130101; A61N 1/36071 20130101; A61N
1/36007 20130101; A61N 1/36053 20130101; A61N 1/0551 20130101 |
Class at
Publication: |
607/040 |
International
Class: |
A61N 001/18 |
Claims
We claim:
1. An apparatus for treating at least one of a plurality of
disorders of a patient attributable at least in part to neural
activity, said apparatus comprising: a stimulation electrode
adapted for placement on a nerve of a patient at a stimulation
site; a stimulation signal generator for generating a stimulation
signal at said stimulation electrode and selected to electrically
stimulate a nerve to induce bi-directional propagation of nervous
impulses in a stimulated nerve; a blocking member for placement on
said nerve at a blocking site and creating localized conditions at
said blocking site that at least partially diminish transmission of
nerve impulses past said blocking site.
2. An apparatus according to claim 1 wherein said blocking member
includes a drug-delivery member for delivery of a pharmacologic
lock at said blocking site.
3. An apparatus according to claim 1 wherein said blocking member
is an electrically controlled blocking member.
4. An apparatus according to claim 3 wherein said blocking member
is cryogenic.
5. An apparatus according to claim 3 wherein said blocking member
creates and electrical signal at said blocking site with an
electrical frequency selected to at least partially diminish said
transmission.
6. An apparatus according to claim 1 comprising a controller for
selectively controlling parameters of said blocking and said
stimulation.
7. An apparatus according to claim 6 wherein said controller is
implantable within said patient's body.
8. An apparatus according to claim 6 wherein said controller is
inductively coupled to said stimulation electrode and said blocking
member to electrically controlling said electrode and member remote
from an interior of said patient's body.
9. An apparatus according to claim 1 wherein said blocking member
is one of at least two blocking members for disposition on said
nerve on opposite sides of said stimulation electrode.
10. An apparatus according to claim 1 wherein said nerve is a vagus
nerve.
11. An apparatus according to claim 6 including a sensor to sense a
physiologic parameter of an organ and said controller connected to
said sensor to regulate said blocking in response to said sensed
parameter.
12. A method for treating at least one of a plurality of disorders
of a patient, said method comprising: electrically stimulating a
vagus nerve of said patient at a stimulation site with a
stimulation signal selected to have a therapeutic effect on a
target organ; applying an electrical blocking signal to said vagus
nerve at a blocking site on a side of said stimulation site
opposite said target organ; said blocking signal selected to at
least partially block nerve impulses to a second organ on a side of
said blocking site opposite said stimulation site.
13. A method according to claim 12 wherein said blocking signal is
variable by a controller to regulate transmission nerve impulses
past said blocking site.
14. A method according to claim 13 comprising sensing a physiologic
parameter of said second organ and regulating said blocking signal
in response to said sensed parameter.
15. A method according to claim 14 wherein said target organ is a
gastro-intestinal organ and said second organ is a heart.
16. A method according to claim 15 wherein said disorder is any one
of a plurality of gastrointestinal diseases.
17. A method according to claim 14 wherein said target organ is a
brain and said second organ is a heart.
18. A method according to claim 17 wherein said disorder is any one
of a plurality of diseases associated with the central nervous
system.
19. A method according to claim 18 wherein said disease is selected
from a group including dementia, schizophrenia, depression,
borderline personality disorder, epilepsy and Parkinson's disease.
Description
I. CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application is a continuation-in-part
application of U.S. patent application Ser. No. 10/358,093 filed
Feb. 3, 2003 and entitled "Method and Apparatus for Treatment of
Gastroesophageal Disease (GERD)". The present application discloses
and claims subject matter disclosed in the following commonly
assigned and copending U.S. patent applications filed on the same
date as the present application and in the name of the same
inventors: U.S. patent application Ser. No. not yet assigned,
entitled "Enteric Rhythm Management", having Attorney Docket No.
14283.1USI2 and U.S. patent application Ser. No. not yet assigned,
entitled "Nerve Conduction Block Treatment", having Attorney Docket
No. 14283.1USI1.
II. BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention pertains to treatments of disorders
associated, at least in part, with neural activity. These may
include, without limitation, gastrointestinal, pancreo-biliary,
cardio-respiratory and central nervous system disorders (including
neurological and psychiatric, psychological and panic disorders).
More particularly, this invention pertains to treatment of such
disorders through management of neural impulse stimulation and
blocking.
[0004] 2. Description of the Prior Art
[0005] A. Functional Gastrointestinal Disorders (FGIDs)
[0006] Functional Gastrointestinal Disorders (FGIDs) are a
diagnostic grouping having diagnostic criteria based on
symptomatology, because the pathophysiology of these diseases is
multifactorial with some pathophysiologic mechanisms in common.
FGIDs are thought to be due to altered autonomic nervous system
balance and to be pathophysiological combinations of: (1) abnormal
GI motility; (2) visceral hypersensitivity; and, (3) brain-gut
interactions. Tougas, "The Autonomic Nervous System in Functional
Bowel Disorders", Gut, Vol. 47 (Suppl IV), pp. iv78-iv80 (2000) and
Drossman, "Rome II: A Multinational Consensus Document on
Gastrointestinal Disorders--The Functional Gastrointestinal
Disorders and the Rome II Process", Gut, Vol. 45 (Suppl II):II1-II5
(1999). The FGIDs of interest to the present invention are
functional dyspepsia (dysmotility-like) and irritable bowel
syndrome (IBS).
[0007] 1. Functional Dyspepsia (Dysmotility-Like)
[0008] Functional dyspepsia (dysmotility-like), is diagnosed when a
patient's symptoms, in the absence of other organic disease likely
to explain the symptoms, include persistent or recurrent pain or
discomfort centered in the upper abdomen that may be accompanied by
upper abdominal fullness, early satiety, bloating or nausea. Talley
et al., "Rome II: A Multinational Consensus Document on
Gastrointestinal Disorders--Functional Gastroduodenal Disorders"
Gut, Vol. 45 (Suppl II), pp. I37-II42 (1999).
[0009] A spectrum of dysmotilities has been documented in patients
with functional dyspepsia. These include delayed gastric emptying
of solids and liquids, reduced vagal tone, gastric dysrhythmias and
impaired gastric accommodation. Furthermore, some studies have
found good correlation between symptoms and indices of dysmotility,
while others have not. Stanghellini V, et al., "Delayed Gastric
Emptying of Solids in Patients with Functional Dyspepsia",
Gastroenterol, (1996) 110:1036-1042. Undeland K A, et al., "Wide
Gastric Antrum and Low Vagal Tone in Patients with Diabetes
Mellitus Type 1 Compared to Patients with Functional Dyspepsia and
Healthy Individuals", Dig Dis Sci, (1996) 41:9-16. Tack J, et al.,
"Role of Impaired Gastric Accommodation to a Meal in Functional
Dyspepsia", Gastroenterol, (1998) 115:1346-1352. Wilmer A, et al.,
"Ambulatory Gastrojejunal Manometry in Severe Motility-like
Dyspepsia: Lack of Correlation between Dysmotility, Symptoms and
Gastric Emptying", Gut, (1998) 42:235-242. Tack J, et al., "Symptom
Pattern and Gastric Emptying Rate Assessed by the Octanoic Acid
Breath Test in Functional Dyspepsia" [abstract]. Gastroenterol,
(1998) 114:A301. Cuomo R, et al., "Functional Dyspepsia Symptoms,
Gastric Emptying and Satiety Provocation Test: Analysis of
Relationships", Scand J Gastroenterol, (2001) 36:1030-1036.
Sarnelli G, et al., "Symptoms Associated with Impaired Gastric
Emptying of Solids and Liquids in Functional Dyspepsia", Am J
Gastroenterol, (2003) 98:783-788.
[0010] 2. Irritable Bowel Syndrome (IBS)
[0011] The second FGID of interest, IBS, is diagnosed when a
patient's symptoms include persistent abdominal pain or discomfort,
in the absence of other explanatory organic disease, along with at
least two of the following: relief of pain with defecation, onset
of symptoms associated with a change in frequency of stools and/or
onset of symptoms associated with a change in appearance/form of
stools. Thompson W G, et al., "Rome II: A Multinational Consensus
Document on Gastrointestinal Disorders--Functional Bowel Disorders
and Functional Abdominal Pain", Gut, (1999) ; 45(Suppl
II):II43-II47.
[0012] In addition to colonic dysmotility, a number of other GI
motility abnormalities have been identified, including delayed
gastric emptying, gastroparesis, and small intestine motility
abnormalities. Vassallo M J, et al., "Colonic Tone and Motility in
Patients with Irritable Bowel Syndrome", Mayo Clin Proc, (1992);
67:725-731. Van Wijk H J, et al., "Gastric Emptying and Dyspeptic
Symptoms in the Irritable Bowel Syndrome", Scand J Gastroenterol,
(1992); 27:99-102. Evans P R, et al., "Gastroparesis and Small
Bowel Dysmotility in Irritable Bowel Syndrome", Dig Dis Sci
(1997);42:2087-2093. Cann P A, et al. "Irritable Bowel Syndrome:
Relationship of Disorders in the Transit of a Single Solid Meal to
Symptoms Patterns", Gut, (1983); 24:405-411. Kellow J E, et al.,
"Dysmotility of the Small Intestine in Irritable Bowel Syndrome",
Gut, (1988); 29:1236-1243. Evans P R, et al., "Jejunal Sensorimotor
Dysfunction in Irritable Bowel Syndrome: Clinical and Psychosocial
Features", Gastroenterol, (1996); 110:393-404. Schmidt T, et al.,
"Ambulatory 24-Hour Jejunal Motility in Diarrhea-Predominant
Irritable Bowel Syndrome", J Gastroenterol, (1996); 31:581-589.
Simren M, et al., "Abnormal Propagation Pattern of Duodenal
Pressure Waves in the Irritable Bowel Syndrome (IBS)", Dig Dis Sci,
(2000); 45:2151-2161.
[0013] A related finding is that patients with
constipation-predominant IBS have evidence of decreased vagal tone,
while diarrhea-predominant IBS is associated with evidence of
increased sympathetic activity. Aggarwal A, et al., "Predominant
Symptoms in Irritable Bowel Syndrome Correlate with Specific
Autonomic Nervous system Abnormalities", Gastroenterol, (1994);
106:945-950.
[0014] There is no cure for IBS. Treatments include supportive
palliative care (antidiarrheals, dietary modification and
counseling).
[0015] A recently approved drug to treat selected patients with
FGIDs is tegaserod maleate sold under the tradename "Zelnorm.RTM."
by Novartis Pharmaceuticals Corp., East Hanover, N.J., USA. The
product literature on Zelnorm recognizes the enteric nervous system
is a key element in treating IBS. The literature suggests
Zelnorm.RTM. acts to enhance basal motor activity and to normalize
impaired motility. Novartis product description, Zelnorm.RTM., July
2002 (T2002-19). Zelnorm's approved use is limited to females with
constipation-related IBS. It is for short-term use only.
[0016] B. Gastroparesis
[0017] The third disease indication discussed here, gastroparesis
(or delayed gastric emptying) is associated with upper GI symptoms
such as nausea, vomiting fullness, bloating and early satiety.
Gastroparesis can be caused by many underlying conditions. The most
important, because of chronicity and prevalence, are diabetes,
idiopathic and post-surgical. Hornbuckle K, et al. "The Diagnosis
and Work-Up of the Patient with Gastroparesis", J Clin
Gastroenterol, (2000); 30:117-124. GI dysmotility in the form of
delayed gastric emptying is, by definition, present in these
patients.
[0018] In patients with Type 1 diabetes mellitus and delayed
gastric emptying, there appears to be a relationship between
delayed gastric emptying and low vagal tone. Merio R, et al., "Slow
Gastric Emptying in Type 1 Diabetes: Relation to Autonomic and
Peripheral Neuropathy, Blood Glucose, and Glycemic Control",
Diabetes Care, (1997); 20:419-423. A related finding is that
patients with Type 1 diabetes have low vagal tone in association
with increased gastric antral size, possibly contributing to the
dysmotility-associated symptoms seen in these patients. Undeland K
A, et al., "Wide Gastric Antrum and Low Vagal Tone in Patients with
Diabetes Mellitus Type 1 Compared to Patients with Functional
Dyspepsia and Healthy Individuals", Dig Dis Sci, (1996);
41:9-16.
[0019] The current treatments for gastroparesis are far from
satisfactory. They include supportive care, such as dietary
modification, prokinetic drugs, and; when required, interventions
such as intravenous fluids and placement of a nasogastric tube may
be needed.
[0020] C. Gastroesophageal Reflux Disease (GERD)
[0021] The fourth indication, GERD, can be associated with a wide
spectrum of symptoms, including dyspepsia, reflux of gastric
contents into the mouth, dysphagia, persistent cough, refractory
hyperreactive airway disease and even chronic serous otitis media.
Sontag S J, et al., "Asthmatics with Gastroesophageal Reflux: Long
Term Results of a Randomized Trial of Medical and Surgical
Antireflux Therapies", Am J Gastroenterol, (2003); 98:987-999.
Poelmans J, et al., "Prospective Study on the Incidence of Chronic
Ear Complaints Related to Gastroesophageal Reflux and on the
Outcome of Antireflux Therapy", Ann Otol Rhinol Laryngol, (2002);
111:933-938.
[0022] GERD is considered to be a chronic condition for which
long-term medical therapy and/or surgical therapy is often deemed
necessary, in significant part because esophageal adenocarcinoma is
sometimes a consequence of GERD. DeVault K R, et al., "Updated
Guidelines for the Diagnosis and Treatment of Gastroesophageal
Reflux Disease", Am J Gastroenterol, (1999); 94:1434-1442.
Lagergren J, et al., "Symptomatic Gastroesophageal Reflux as a Risk
Factor for Esophageal Adenocarcinoma", New Engl J Med, (1999);
340:825-831.
[0023] The underlying pathophysiological mechanisms in GERD are
considered to be transient lower esophageal relaxations (TLESRs) in
the presence of either an inadequate pressure gradient between the
stomach and the esophagus across the lower esophageal sphincter
and/or low amplitude esophageal activity at times when gastric
contents do reflux into the esophagus. In addition, gastric
distention is thought to be associated with an increase in TLESRs.
Mittal R K, et al., "Mechanism of Disease: The Esophagogastric
Junction", New Engl J Med, (1997); 336:924-932. Scheffer R C, et
al., "Elicitation of Transient Lower Oesophageal Sphincter
Relaxations in Response to Gastric Distension", Neurogastroenterol
Motil, (2002); 14:647-655.
[0024] GERD is generally considered to be the result of a motility
disorder which permits the abnormal and prolonged exposure of the
esophageal lumen to acidic gastric contents. Hunt, "The
Relationship Between The Control Of pH And Healing And Symptom
Relief In Gastro-Oesophageal Reflux Disease", Ailment Pharmacol
Ther., 9 (Suppl. 1) pp. 3-7 (1995). Many factors are believed to
contribute to the onset of GERD. These include transient lower
esophageal sphincter relaxations (as previously described),
decreased LES resting tone, delayed stomach emptying and an
ineffective esophageal clearance.
[0025] Certain drugs have had some effectiveness at controlling
GERD but fail to treat underlying causes of the disease. Examples
of such drugs are H.sub.2-receptor antagonists (which control
gastric acid secretion in the basal state) and proton pump
inhibitors (which control meal-stimulated acid secretion). Hunt,
id. Both classes of drugs can raise intragastric pH to or about 4
for varying durations. Hunt, supra.
[0026] Surgery treatments are also employed for the treatment of
GERD and include techniques for bulking the lower esophageal
sphincter such as fundoplication and techniques described in U.S.
Pat. No. 6,098,629 Johnson et al, Aug. 8, 2000. Other surgical
techniques include placement of pacemakers for stimulating muscle
contractions in the esophageal sphincter, the stomach muscles or in
the pyloric valve. U.S. Pat. No. 6,104,955 to Bourgeois, U.S. Pat.
No. 5,861,014 to Familoni.
[0027] A summary of GERD treatments can be found in DeVault, et
al., "Updated Guidelines for the Diagnosis and Treatment of
Gastroesophageal Reflux Disease", Amer. J. of Gastroenterology,
Vol. 94, No. 6, pp. 1434-1442 (1999).
[0028] Notwithstanding multiple attempts at various types of
treatment, GERD continues to be a serious disease proving to be
difficult to treat by any of the foregoing prior art techniques. In
view of the foregoing and notwithstanding various efforts
exemplified in the prior art, there remains a need for an effective
treatment for GERD. It is an object of the present invention to
provide a novel treatment and novel apparatus for the treatment of
GERD.
[0029] D. Electrical Stimulation to Treat GI Disorders
[0030] Treatment of gastrointestinal diseases through nerve
stimulation nave been suggested. For example, U.S. Pat. No.
6,238,423 to Bardy dated May 29, 2001 describes a constipation
treatment involving electrical stimulation of the muscles or
related nerves of the gut. U.S. Pat. No. 6,571,127 to Ben-Haim et
al. dated May 27, 2003 describes increasing motility by applying an
electrical field to the GI tract. U.S. Pat. No. 5,540,730 to Terry,
Jr. et al., dated Jul. 30, 1996 describes a motility treatment
involving vagal stimulation to alter GI contractions in response to
a sense condition indicative of need for treatment. The '730 patent
also uses a definition of dysmotility more restrictive than in the
present application. In the '730 patent, dysmotility is described
as hyper- or hypo-contractility. In the present application,
dysmotility is a broader concept to refer to all abnormalities of
gastric emptying or bowel transfer regardless of cause. U.S. Pat.
No. 6,610,713 to Tracey dated Aug. 26, 2003 describes inhibiting
release of a proinflammatory cytokine by treating a cell with a
cholinergic agonist by stimulating efferent vagus nerve activity to
inhibit the inflammatory cytokine cascade.
[0031] A substantial body of literature is developed on nerve
stimulation. For example, in Dapoigny et al., "Vagal influence on
colonic motor activity in conscious nonhuman primates", Am. J.
Physiol., 262: G231-G236 (1992), vagal influence on colonic motor
activity was investigated in conscious monkeys. To block antidromic
interference, the vagus was blocked via vagal cooling and a vagal
stimulation electrode was implanted distal to the vagal block. It
was noted that vagal efferent stimulation increased contractile
frequency and that the vagus has either a direct or indirect
influence on fasting and fed colonic motor activity throughout the
colon, and that a non-adrenergic, noncholinergic inhibitory pathway
is under vagal control.
[0032] Colonic and gastric stimulation are also described in a
number of articles associated with M. P. Mintchev. These include:
Mintchev, et al., "Electrogastrographic impact of multi-site
functional gastric electrical stimulation", J. of Medical Eng.
& Tech., Vol. 23, No. 1 pp. 5-9 (1999); Rashev, et al.,
"Three-dimensional static parametric modeling of phasic colonic
contractions for the purpose of microprocessor-controlled
functional stimulation", J. of Medical Eng. & Tech., Vol. 25,
No. 3 pp. 85-96 (2001); Lin et al., "Hardware--software co-design
of portable functional gastrointestinal stimulator system", J. of
Medical Eng. & Tech., Vol. 27, No. 4 pp. 164-177 (2003); Amaris
et al., "Microprocessor controlled movement of solid colonic
content using sequential neural electrical stimulation", Gut, 50:
pp 475-479 (2002) and Rashev et al., "Microprocessor-Controlled
Colonic Peristalsis", Digestive Diseases and Sciences, Vol. 47, No.
5, pp. 1034-1048 (2002).
[0033] The foregoing references describe nerve stimulation to
stimulate muscular contraction in the GI tract. As will be more
fully discussed, the present invention utilizes vagal stimulation
to improve vagal tone (similar in concept to improving cardiac
electrical tone through cardiac pacing) and/or to treat GI
disorders by altering the nature of duodenum contents by
stimulation pancreatic and biliary output. The invention is also
applicable to treating other diseases such as neuropsychiatric
disorders.
[0034] Vagal tone has been shown to be associated with dyspepsia.
Hjelland, et al., "Vagal tone and meal-induced abdominal symptoms
in healthy subjects", Digestion, 65: 172-176 (2002). Also, Hausken,
et al., "Low Vagal Tone and Antral Dysmotility in Patients with
Functional Dyspepsia", Psychosomatic Medicine, 55: 12-22 (1993).
Also, decreased vagal tone has been associated with irritable bowel
syndrome. Heitkemper, et al., "Evidence for Automatic Nervous
System Imbalance in Women with Irritable Bowel Syndrome", Digestive
Diseases and Sciences, Vol. 43, No. 9, pp. 2093-2098 (1998).
[0035] Also, as will be discussed, the present invention includes,
in several embodiments, a blocking of a nerve (such as the vagal
nerve) to avoid antidromic influences during stimulation. Cryogenic
nerve blocking of the vagus is described in Dapoigny et al., "Vagal
influence on colonic motor activity in conscious nonhuman
primates", Am. J. Physiol., 262: G231-G236 (1992). Electrically
induced nerve blocking is described in Van Den Honert, et al.,
"Generation of Unidirectionally Propagated Action Potentials in a
Peripheral Nerve by Brief Stimuli", Science, Vol. 206, pp.
1311-1312. An electrical nerve block is described in Solomonow, et
al., "Control of Muscle Contractile Force through Indirect
High-Frequency Stimulation", Am. J. of Physical Medicine, Vol. 62,
No. 2, pp. 71-82 (1983) and Petrofsky, et al., "Impact of
Recruitment Order on Electrode Design for Neural Prosthetics of
Skeletal Muscle", Am. J. of Physical Medicine, Vol. 60, No. 5, pp.
243-253 (1981). A neural prosthesis with an electrical nerve block
is also described in U.S. Patent Application Publication No. U.S.
2002/0055779 A1 to Andrews published May 9, 2002. A cryogenic vagal
block and resulting effect on gastric emptying are described in
Paterson C A, et al., "Determinants of Occurrence and Volume of
Transpyloric Flow During Gastric Emptying of Liquids in Dogs:
Importance of Vagal Input", Dig Dis Sci, (2000); 45:1509-1516.
III. SUMMARY OF THE INVENTION
[0036] According to a preferred embodiment of the present
invention, a method and apparatus are disclosed for treating at
least one of a plurality of gastrointestinal disorders of a patient
characterized at least in part by an altered autonomic balance or
altered motility. The method includes electrically stimulating an
enteric nervous system of the patient to enhance a functional tone
of the enteric nervous system.
[0037] Enteric rhythm management (ERM) treats GI diseases in which
dysmotility is thought to play a major role. This therapy is based
on the physiological actions of pancreatic exocrine secretion and
bile on the composition (osmolality and pH) and the digestion
(enzymatic activity and, in the case of fats, emulsification) of
intraduodenal chyme, thereby presenting a novel approach to
regulating the motility of the GI tract and, in particular, gastric
emptying and the digestion and propulsion of chyme through the
duodenum and into the jejunum and ileum.
[0038] ERM as a therapy for GI diseases involving dysmotility is
based on the following: (1) pacing the delivery of pancreatic
exocrine secretion and bile can be used to either up- or
down-regulate at least two aspects of GI motility--gastric emptying
and small bowel transit--by modulating the osmolality, the pH and
the digestion, including emulsification as needed, of
intra-duodenal chyme; (2) pacing the efferent activity of the
intra-abdominal vagus nerve as needed while blocking afferent
activity of that same nerve as needed can be used to treat GI
dysmotility in patients with either increased or decreased vagal
tone as a component of their disease; and, (3) treating GI
dysmotility disorders can and often does require flexibility in
adjusting treatment algorithms based on symptomatic response
because of inter-patient differences with a diagnostic group and
because of intra-patient variability over time.
[0039] The goals of enteric rhythm management in gastroparesis are:
1) to regulate the composition and digestion of duodenal chyme and,
by so doing, to facilitate gastric emptying through the modulatory
effect of duodenal chemo- and mechanoreceptors on the pylorus and
2) to up-regulate or down-regulate vagal tone to optimize
gastricintestinal motility and symptom relief.
[0040] In patient with GERD, ERM utilizing a physiologic enteric
pacing device will, as described earlier, allow pacing of the
delivery of pancreatic exocrine secretion and bile, thereby
initiating pyloric relaxation, gastric emptying and consequent
reduction in gastric distention, leading to a decrease in the
underlying mechanism of GERD, that is, TLESRs.
[0041] Kellow J E, et al., "Rome II: A Multinational Consensus
Document on Gastrointestinal Disorders--Principles of Applied
Neurogastroenterology: Physiology/Motility-Sensation", Gut, (1999);
45(Suppl II):II17-II24. Paterson C A, et al., "Determinants of
Occurrence and Volume of Transpyloric Flow During Gastric Emptying
of Liquids in Dogs: Importance of Vagal Input", Dig Dis Sci,
(2000); 45:1509-1516. Tougas G, "The Autonomic Nervous System in
Functional Bowel Disorders", Gut, (2000); 47(Suppl IV):iv78-iv80.
Guyton A C, et al., "Propulsion and Mixing of Food in the
Alimentary Tract", Textbook of Medical Physiology, 10.sup.th ed.
Philadelphia: W. B. Saunders and Company, 200:728-737. Guyton A C,
et al., "Secretory Functions of the Alimentary Tract", Textbook of
Medical Physiology, 10.sup.th ed. Philadelphia: W. B. Saunders and
Company, 200:738-753. Schwartz M P, et al., "Human Duodenal Motor
Activity in Response to Acid and Different Nutrients", Dig Dis Sci,
(2001); 46:1472-1481. Schwartz M P, et al., "Chemospecific
Alterations in Duodenal Perception and Motor Response in Functional
Dyspepsia", Am J Gastroenterol, (2001); 96:2596-2602.
[0042] ERM involves pacing and thereby regulating the timing and
the volume of pancreatic exocrine secretion and bile delivered to
the intraluminal contents of the duodenum. In one embodiment, this
is accomplished with a small, laparoscopically implantable and
programmable medical device called a physiologic enteric pacing
device. Three leads are positioned intra-abdominally and then
connected to a subcutaneous, programmable pulse generator. A pacing
lead may be placed on the anterior vagal trunk and another pacing
lead may be placed on the posterior vagal trunk. One or more
intra-abdominal electrode, i.e. blocking electrodes, may be placed
on the vagus nerve proximal to the pacing leads.
[0043] An additional embodiment of the present invention pertains
to treating at least one of a plurality of gastrointestinal
disorders of a patient by electrically stimulating a vagus nerve of
the patient at a stimulation site proximal to at least one site of
vagal innervation of a gastrointestinal organ. The electrical
stimulation includes applying a stimulation signal at the
stimulation site. A proximal electrical blocking signal is applied
to the vagus nerve at a proximal blocking site proximal to the
stimulation site. The proximal blocking signal is selected to at
least partially block nerve impulses proximal to the proximal
blocking site.
[0044] The invention further includes a treatment apparatus having
a stimulation electrode adapted for placement on a nerve of a
patient at a stimulation site and a stimulation signal generator
for generating a stimulation signal at the stimulation electrode
and selected to electrically stimulate a nerve to induce
bi-directional propagation of nervous impulses in a stimulated
nerve. The apparatus includes a blocking member for placement on
the nerve at a blocking site and creating localized conditions at
the blocking site that at least partially diminish transmission of
nerve impulses past the blocking site.
[0045] A still further embodiment of the present invention includes
a method for treating at least one of a plurality of disorders of a
patient where the disorders are associated with a gastrointestinal
tract of a patient where the disorders are characterized at least
in part by hyper-tonal vagal activity innervating at least one of a
plurality of alimentary tract organs of the patient at an
innervation site. The method includes applying a neural conduction
block to a vagus nerve of the patient at a blocking site proximal
to the innervation site. The neural conduction block is selected to
at least partially block nerve impulses on the vagus nerve distal
to the blocking site.
[0046] A yet further embodiment pertains to a treatment apparatus
having an electrically controllable neural conduction electrode
adapted to be placed on a vagus nerve of a patient at a blocking
site proximal to an innervation site. A blocking signal generator
generates a blocking signal selected to at least partially block
nerve impulses on the vagus nerve distal to the blocking site.
[0047] A still additional embodiment of the present invention
includes a method for treating at least one of a plurality of
disorders of a patient by electrically stimulating a vagus nerve at
a stimulation site with a stimulation signal selected to nave a
therapeutic effect on a target organ. An electrical blocking signal
is applied to the vagus nerve at a blocking site on a side of said
stimulation site opposite the target organ. The blocking signal is
selected to at least partially block nerve impulses to a second
organ on a side of said blocking site opposite the stimulation
site. In specific examples, the target organ may be
gastrointestinal or central nervous with the other organ being
cardio-respiratory.
IV. BRIEF DESCRIPTION OF THE DRAWINGS
[0048] FIG. 1 is a schematic representation of a gastric-emptying
feedback loop with a patient-controlled stimulator for stimulating
an organ of the loop;
[0049] FIG. 2 is a view similar to FIG. 1 with an automatic
controller replacing the patient-controller of FIG. 1 and with
feedback circuits to the automatic controller schematically
represented;
[0050] FIG. 3 is a schematic illustration of an alimentary tract
(GI tract plus non-GI organs such as the pancreas and liver) and
its relation to vagal and enteric innervation;
[0051] FIG. 4 is the view of FIG. 3 showing the application of a
pacing electrode according to an embodiment of the present
invention;
[0052] FIG. 5 is a schematic representation of pacing system;
[0053] FIG. 6 is the view of FIG. 4 showing the application of a
nerve conduction block electrode proximal to the pacing
electrode;
[0054] FIG. 7 is the view of FIG. 6 showing the application of a
nerve conduction block electrode distal to the pacing electrode;
and
[0055] FIG. 8 is the view of FIG. 3 showing the application of a
nerve conduction block electrode according to an embodiment of the
present invention.
V. DESCRIPTION OF THE PREFERRED EMBODIMENT
[0056] With reference now to the various drawing figures in which
identical elements are numbered identically throughout, a
description of the preferred embodiment of the present invention
will now be described.
[0057] A. Invention of Parent Application
[0058] FIGS. 1 and 2 and the description which follow are from the
aforementioned U.S. patent application Ser. No. 10/358,093 filed
Feb. 3, 2003 filed Feb. 3, 2003 and entitled "Method and Apparatus
for Treatment of Gastroesophageal Disease (GERD)".
[0059] With initial reference to FIG. 1, a gastric emptying
feedback loop is shown schematically for ease of illustration. The
feedback loop illustrates a patient's stomach S which is provided
with food from the esophagus E. A lower esophageal sphincter LES is
shown positioned between the esophagus E and the stomach S. The
lower esophageal sphincter normally provides control of reflux of
stomach contents into the esophagus E.
[0060] On a proximal or lower end of the stomach S the stomach
discharges into the superior duodenum D which is an upper portion
of the intestines. The superior duodenum D and the stomach S are
separated by a pyloric valve PV which opens to permit gastric
emptying from the stomach into the duodenum D.
[0061] Also schematically illustrated in FIG. 1 are nerve paths N
providing signal flow paths from both the superior duodenum D and
the stomach S to the brain B. An efferent Vagal nerve VN connects
the brain B to the pancreas P of the patient. A conduit (pancreatic
duct PD) extends from the pancreas P and discharges into the
superior duodenum D.
[0062] The presence of food contents within the duodenum D (such
contents being referred to as "chyme") may prevent passage of
gastric content of the stomach S past the pyloric valve PV into the
duodenum D. As long as such gastric contents cannot be passed into
the duodenum D, such contents can be forced retrograde past the
lower esophageal sphincter LES and into the esophagus E creating
the symptoms and discomfort of GERD. The contents discharging from
the stomach S into the duodenum D are acidic (and high osmolality)
and reside in the duodenum D until pH is elevated (close to a
neutral pH of 6-7) and osmolality is normalized.
[0063] The elevation of pH and reduction of osmolality of chyme in
the duodenum D results from exocrine secretion being administered
from the pancreas P and from bile from the liver into the duodenum
D. This raises the pH and lowers the osmolality of the duodenum D
content permitting discharge from the duodenum D and thereby
permitting gastric emptying across the pyloric valve PV.
[0064] According to the present invention gastroesophageal reflux
disease (GERD) results from a derangement of the feedback loops
involved in upper GI digestion and motility control. This problem
encompasses receptors and reflexes that regulate the propulsive
contractions of the stomach, upper duodenum and biliary tree and
the secretions of the exocrine pancreas. The interaction of these
receptors and reflexes control gastric emptying (by coordinating
gastric propulsive contractions and sphincter [primarily pyloric]
tone) and regulate the pH and osmolality of the chyme in the
duodenum. This chemo-regulation is mediated through control of bile
delivery and stimulation of secretion by the exocrine pancreas of
fluid delivered to the superior duodenum. Chey et al., "Neural
Hormonal Regulation of Exocrine Pancreatic Secretion",
Pancreatology, pp. 320-335 (2001).
[0065] Normally, ingestate delivered to the stomach is mixed by low
intensity gastric mixing contractions with the enzymatic, ionic,
including hydrogen ion (H.sup.+), and water secretions of the
glands of the stomach. When the material is adequately reduced in
size and is a smooth consistency, the fluid, now called chyme, is
delivered to the ampulla of the small intestine by the much
stronger propulsive, or emptying, contractions of the stomach
coupled with transitory relaxation of the pyloric sphincter. This
material is at a very low pH (about 2) and high osmolality, which
activates receptors, including those for H.sup.+ and osmotic
pressure, which are abundant in the wall of the ampulla. This
receptor activation initiates the series of reflexes that cause
pancreatic exocrine secretion to be delivered into the superior
duodenum and ampulla. This fluid contains digestive enzymes, water
and buffering compounds to raise the pH, and reduce the osmolality,
of the chyme.
[0066] Once a neutral pH and physiological osmolality are achieved,
then propulsive contractions in the superior duodenum move the
chyme out of the superior portion into the length of the duodenum;
At which point the stretch and baro-receptors in the ampulla allow
the pyloric sphincter to relax and another bolus of gastric
contents is delivered into the ampulla by the peristaltic gastric
emptying contractions. This material, at a very low pH (less than
2), activates hydrogen ion (H.sup.+) on receptors of the ampulla
(upper most portion of the duodenum) causing the pancreatic fluids
to be delivered to the material in the ampulla restarting the cycle
as described above. Chapter 3, "The Stomach", Gastrointestinal
System, 2.sup.nd Ed., M. S. Long editor, Mosby Publisher, London
(2002).
[0067] If the control system is down regulated by, for example, by
increased pH of gastric contents entering the ampulla, feedback may
thereby be reduced from the H.sup.+ receptors in the duodenum that
stimulate pancreatic exocrine secretion and bile delivery to the
duodenum, then movement of chyme from the superior duodenum is
delayed, causing delay of gastric emptying. Mabayo, et al.,
"Inhibition of Food Passage by Osmeprazole in the Chicken",
European J. of Pharmacology, pp. 161-165 (1995).
[0068] In GERD, this reflex is inhibited in such a way that the
stomach empties more slowly so that the gastric emptying
contractions force gastric contents to flow retrograde into the
esophagus. This is a result of the situation in which the gastric
emptying contractions are vigorous but must operate against a
contracted pyloric sphincter. These vigorous peristaltic
contractions eventually begin to force gastric contents to flow
retrograde into the esophagus because of the inherent imbalance
between a very strong pyloric sphincter and a much weaker
gastroesophageal sphincter. The delay in gastric emptying is
directly related to a slow down in the transport of chyme out of
the ampulla and superior duodenum. The drugs used to treat this
disease raise pH further dampening the hydrogen-receptor-pancreatic
secretion loop, further delaying gastric emptying. Benini, "Gastric
Emptying and Dyspeptic Symptoms in Patients with Gastroesophageal
Reflux", Amer. J. of Gastroenterology, pp. 1351-1354 (1996).
[0069] The present invention is directed towards reestablishing the
link between gastric emptying and pancreatic secretion delivery,
thereby addressing the main pathology of this disease by shortening
chyme residence time in the superior duodenum so that intestinal
contents move into the distal digestive tract in a more normal
manner. According to a first embodiment, this is done by
stimulating the H+ ion receptors or by stimulation of the pancreas
directly or via its para-sympathetic innervation (pre-ganglionic
Vagal nerves). Stimulation of pancreatic exocrine secretion has
been shown by direct stimulation of the thoracic vagus nerves in
dogs. Kaminski et al., "The Effect of Electrical Vagal Stimulation
on Canine Pancreatic Exocrine Function", Surgery, pp. 545-552
(1975). This results in a more rapid (normal) neutralization of
chyme in the ampulla, allowing it move down the duodenum more
quickly so that gastric emptying is returned to a more normal
pace.
[0070] Acidity (pH) can be assessed by measuring bicarbonate. It
will be understood that references to -H includes such indirect
measurements. Also, effects of the therapy described herein can be
assessed and/or controlled by measuring an indication of pancreatic
exocrine secretion or bile (e.g., HCO.sub.3.sup.-).
[0071] An alternative embodiment uses gastrocopic delivery of a
paralyzing agent (e.g. botulism toxin) to the pyloric valve along
with use of H2 antagonists or PPI's to manage the acidity of the
chyme reaching the duodenum.
[0072] As an additional alternative to pancreatic stimulation, the
gall bladder can be stimulated to encourage bile movement into the
duodenum. Shown schematically in the figures, the gall bladder GB
resides below the liver L. The gall bladder is connected to the
small intestine (specifically the duodenum D) via a bile duct BD.
The bile duct BD can discharge directly into the duodenum D or via
the pancreatic duct PD as shown. The bile can normalize the chyme
to accelerate duodenal emptying. Bile consists of bile acids
(detergents that emulsify lipids), cholesterol, phospholipids,
electrolytes such as (Na.sup.+, K.sup.+, Ca.sup.+2, Cl.sup.-,
HCO.sub.3.sup.-) and H.sub.2O. Chapter 4, "The Liver and Biliary
Tract", Gastrointestinal System, 2.sup.nd Ed., M. S. Long editor,
Mosby Publisher, London (2002). The gall bladder GB or bile duct
can be stimulated indirectly via stimulation of the vagal nerve VN
or directly stimulated by an electrode 11 (shown in phantom
lines).
[0073] As illustrated in the figures, an electrical stimulator 10,
20 which may be implanted is provided which alternatively may be
directly connected to the Vagal nerve VN or the pancreas P to
stimulate the pancreas directly or indirectly to excrete exocrine
into the duodenum D (or more distally into the small
intestine--e.g., into the jejunum) and increase the pH of chyme in
the duodenum D as described. Alternatively, the same can be done to
promote bile release. The frequency may be varied to maximize the
response and selectively stimulate exocrine instead of endocrine
secretions. Rosch et al., "Frequency-Dependent Secretion of
Pancreatic Amylase, Lipase, Trypsin, and Chymotrypsin During Vagal
Stimulation in Rats", Pancreas, pp. 499-506 (1990). See, also,
Berthoud et al., "Characteristics of Gastric and Pancreatic
Reponses to Vagal Stimulation with Varied Frequencies: Evidence for
Different Fiber Calibers?", J. Auto. Nervous Sys., pp. 77-84 (1987)
(showed frequency-response relationship with insulin, i.e.,
significantly less insulin was released at lower frequencies--2 Hz
v. 8 Hz--also, frequency-response curves evidenced distinctly
different profiles for gastric, pancreatic and cardiovascular
responses.) Slight insulin release can maximize pancreatic exocrine
secretion. Chey et al., "Neural Hormonal Regulation of Exocrine
Pancreatic Secretion", Pancreatology, pp. 320-335 (2001).
[0074] With a patient control stimulation as shown in FIG. 1, the
patient may activate the stimulator 10 by remote transmitter to
stimulate an electrical charge either after eating (e.g., about 60
to 90 minutes after eating) or on onset of GERD symptoms. It will
be appreciated that there are a wide variety of nerve stimulators
and organ stimulators available for implantation and are
commercially available and which include connectors for connecting
directly to nerves.
[0075] FIG. 2 illustrates an additional embodiment where the
patient activated loop is replaced with an automatic loop having a
programmable stimulator 20 which receives as an input signals from
sensors in the duodenum to measure pH, osmolality or strain (e.g.,
from baro-sensors) on the duodenum indicating filling or may
measure acidity in the esophagus or strain on the lower esophageal
sphincter LES or stomach S all of which may be provided to the
implantable controller 20 which can be provided with desirable
software to process the incoming signals and generate a stimulating
signal to either the vagal nerve, the pancreas P or the duodenum D
(or jejunum) directly in response to such received signals. It will
be appreciated that stimulators and controllers are well within the
skill of the art. U.S. Pat. No. 5,540,730 teaches a neurostimulator
to stimulate a vagus nerve to treat a motility disorder. U.S. Pat.
No. 5,292,344 teaches gastrointestinal sensors, including pH
sensors.
[0076] B. Application of Parent Application to Treatments Other
than GERD
[0077] In addition to treatment of GERD, the foregoing invention is
applicable to treatment of a plurality of GI diseases associated
with delayed gastric emptying or altered autonomic activity. These
include functional gastrointestinal disorders and gastroparesis.
Furthermore, applicants have determined that duodenal content
impacts a plurality of motility disorders throughout the bowels and
can diseases associated with dysmotility (e.g., irritable bowel
syndrome). Accordingly it is an object of the present invention to
use the teachings of the aforementioned parent application to treat
GI disorders associated with delayed gastric emptying and abnormal
intestinal transport.
[0078] C. Additional Disclosure of the Present Application
[0079] 1. Enteric Innervation
[0080] FIG. 3 is a schematic illustration of an alimentary tract
(GI tract plus non-GI organs such as the pancreas and ball bladder,
collectively labeled PG) and its relation to vagal and enteric
innervation. The lower esophageal sphincter (LES) acts as a gate to
pass food into the stomach S and, assuming adequate function of all
components, prevent reflux. The pylorus PV controls passage of
chyme from the stomach S into the intestines I (collectively shown
in the figures and including the large intestine or colon and the
small intestine including the duodenum, jejunum and ileum).
[0081] The biochemistry of the contents of the intestines I is
influenced by the pancreas P and gall bladder PG which discharge
into the duodenum. This discharge is illustrated by dotted arrow
A.
[0082] The vagus nerve VN transmits signals to the stomach S,
pylorus PV, pancreas and gall bladder PG directly. Originating in
the brain, there is a common vagus nerve VN in the region of the
diaphragm (not shown). In the region of the diaphragm, the vagus VN
separates into anterior and posterior components with both acting
to innervate the GI tract. In FIGS. 3, 5-8, the anterior and
posterior vagus nerves are not shown separately. Instead, the vagus
nerve VN is shown schematically to include both anterior and
posterior nerves.
[0083] The vagus nerve VN contains both afferent and efferent
components sending signals away from and to, respectively, its
innervated organs.
[0084] In addition to influence from the vagus nerve VN, the GI and
alimentary tracts are greatly influenced by the enteric nervous
system ENS. The enteric nervous system ENS is an interconnected
network of nerves, receptors and actuators throughout the GI tract.
There are many millions of nerve endings of the enteric nervous
system ENS in the tissues of the GI organs. For ease of
illustration, the enteric nervous system ENS is illustrated as a
line enveloping the organs innervated by the enteric nervous system
ENS
[0085] The vagus nerve VN innervates, at least in part, the enteric
nervous system ENS (schematically illustrated by vagal trunk VN3
which represents many vagus-ENS innervation throughout the cut).
Also, receptors in the intestines I connect to the enteric nervous
system ENS. Arrow B in the figures illustrates the influence of
duodenal contents on the enteric nervous system ENS as a feedback
to the secretion function of the pancreas, liver and gall bladder.
Specifically, receptors in the intestine I respond the biochemistry
of the intestine contents (which are chemically modulated by the
pancreao-biliary output of Arrow A). This biochemistry includes pH
and osmolality.
[0086] In the figures, vagal trunks VN1, VN2, VN4 and VN6
illustrate schematically the direct vagal innervation of the GI
organs of the LES, stomach S, pylorus PV and intestines I. Trunk
VN3 illustrates direct communication between the vagus VN and the
ENS. Trunk VN5 illustrates direct vagal innervation of the pancreas
and gall bladder. Enteric nerves ENS1-ENS4 represent the multitude
of enteric nerves in the stomach S, pylorus PV, pancreas and gall
bladder PG and intestines I.
[0087] While communicating with the vagus nerve VN, the enteric
nervous system ENS can act independently of the vagus and the
central nervous system. For example, in patients with a severed
vagus nerve (vagotomy--an historical procedure for treating
ulcers), the enteric nervous system can operate the gut. Most
enteric nerve cells are not directly innervated by the vagus.
Gershon, "The Second Brain", Harper Collins Publishers, Inc, New
York, N.Y. p. 19 (1998)
[0088] In FIG. 3, the vagus VN and its trunks (illustrated as
VN1-VN6) and the enteric nervous system ENS are shown in phantom
lines to illustrate reduced vagal and enteric nerve tone (i.e.,
sub-optimal nerve transmission levels). Reduced vagal and enteric
tone contribute directly to the ineffectiveness of the GI organs as
well as indirectly (through reduced pancreatic/biliary output). The
reduced pancreatic/biliary output is illustrated by the dotted
presentation of arrow A. As previously discussed, the vagus can be
stimulated to stimulate pancreatic or biliary output. Therefore,
the reduced output of arrow A results in a reduced feedback
illustrated by the dotted presentation of arrow B.
[0089] 2. Enteric Rhythm Management (ERM)
[0090] The benefits of the present invention are illustrated in
FIG. 4 where a stimulating or pacing electrode PE is applied to the
vagus VN. While only one electrode is shown in FIG. 4, separate
electrodes could be applied to both the anterior and posterior
vagus nerves (or to the common vagus or vagal branches). In a
preferred embodiment, the electrode PE is placed a few centimeters
below the diaphragm and proximal to stomach and pancreo/biliary
innervation. While this placement is presently preferred for ease
of surgical access, other placement locations may be used.
[0091] By pacing the vagus through the pacing electrode, vagal tone
is optimized by either up- or down-regulation. With reference to
the para-sympathetic and enteric nervous systems, "tone" refers to
basal activity of a nerve or nervous system facilitating
appropriate physiologic response to a patient's internal
environment. For example, low vagal tone implies a reduction in
vagus nerve activity resulting in decreased response of the
alimentary tract to ingested food. As used in the present
application, "pacing" is not limited to mean timed events
coordinated with specifically timed physiologic events. Instead,
pacing means any electrical stimulation of a nerve trunk to induce
bi-directional propagation of nervous impulses in the stimulated
nerve.
[0092] The operating effectiveness of the vagus is enhanced so that
local physiological signals generated in the enteric nervous system
(or sent to the brain from the organs) are more appropriately
responded to within the alimentary tract. Due to its innervation of
the enteric nervous system, pacing of the vagus enhances the
functional tone of the enteric nervous system. By enhancing the
functional tone it will be noted that the stimulation pacing is
elevating the degree of functionality of the vagus and enteric
nerves. In this context, "pacing" is not meant to mean timed pulsed
coordinated with muscular contractions or synchronized with other
invents. Pacing means elevating the activity level of the
nerves.
[0093] Tonal enhancement of the vagus and enteric nerves is
illustrated by the solid lines for the nerves VN, ENS in FIG. 4.
Vagal trunk VN5 is in solid line to illustrate enhanced tone of the
many vagal nerve components communicating with the enteric nervous
system ENS. Direct vagal innervation of the LES, stomach S, pylorus
PV and intestines I remains shown as low tone indicated by phantom
lines VN1, VN2, VN4, VN6. The tonal pacing described herein is not
intended to trigger or drive the muscular contractility of these
organs. The stimulation is not intended to be timed to trigger
contractility and is not provided with an energy level sufficient
to drive peristaltic contractions. Instead, these functions remain
controlled by the central and enteric nerves systems. The enhanced
nerve tone provided by the present invention permits these
functions to occur.
[0094] Pacing to enhance vagal tone is not initiated in response to
any senses event (or in anticipation of an immediate need to GI
activity). Instead, the pacing can be done intermittently over the
day to provide an enhanced level of operating functionality to the
vagus. By way of non-limiting example, the stimulation pacing can
be done during awake hours. For example, every ten minutes, pacing
signals can be sent to the pacing electrodes. The pacing signals
have a duration of 30 seconds with a current of 4 mA, a frequency
of 12 Hz and an impulse duration of 2 msec. These parameters are
representative only. A wide range of signal parameters may be used
to stimulate the vagus nerve. Examples of these are recited in the
afore-referenced literature
[0095] As will be further discussed, the present invention permits
ERM to be uniquely designed and modified by an attending physician
to meet the specific needs of individual patients. For example,
pacing can be limited to discrete intervals in the morning,
afternoon and evening with the patient free to coordinate meals
around these events.
[0096] In addition to enhancing vagal and enteric tone directly,
the pacing also enhances the pancreatic and biliary output for the
reasons discussed above. Namely, while ERM does not drive muscular
events over nerve trunks VN1, VN2, VN4, VN6, the enhanced tone
stimulates pancreo-biliary output over trunk VN5 (illustrated by
the solid line of VN5 in FIG. 4). This enhanced output is
illustrated as solid arrow A' in FIG. 4. As a consequence there is
a greater feedback to the intestinal receptors as illustrated by
solid arrow B' in FIG. 4. This enhanced biochemistry feedback
further enhances the tone of the enteric nervous system ENS.
[0097] 3. Implantable Pacing Circuit
[0098] A representative pacing circuit 100 is schematically shown
in FIG. 5. Similar to cardiac pacing devices, an implantable
controller 102 contains an induction coil 104 for inductive
electrical coupling to a coil 106 of an external controller 108.
The implantable controller 102 includes anterior and posterior
pulse generators 110, 112 electrically connected through conductors
114, 116 to anterior and posterior pacing electrodes 118, 120 for
attachment to anterior and posterior trunks, respectively, of the
vagus nerve VN. The implantable controller 102 also includes a
battery 122 and a CPU 124 which includes program storage and
memory. The timing and parameters of the pulse at the electrodes
118, 120 can be adjusted by inductively coupling the external
controller 108 to the implantable controller 102 and inputting
pacing parameters (e.g., pulse width, frequency and amplitude).
[0099] While a fully implantable controller 102 is desirable, it is
not necessary. For example, the electrodes 118, 120 can be
implanted connected to a receiving antenna placed near the body
surface. The control circuits (i.e., the elements 124, 110, 112 and
108) can be housed in an external pack worn by the patient with a
transmitting antenna held in place on the skin over the area of the
implanted receiving antenna. Such a design is forward-compatible in
that the implanted electrodes can be later substituted with the
implantable controller 102 at a later surgery if desired.
[0100] Although not shown in FIG. 5, the controller 102 can also
include circuits generating nerve conduction block signals (as will
be described) which connect to electrodes which may be positioned
on a nerve proximally, distally (or both) of the electrodes 118,
120.
[0101] 4. Nerve Conduction Block
[0102] FIG. 6 shows an alternative embodiment using a nerve
conduction blocking electrode PBE proximal to the pacing electrode
for providing a conduction block. A nerve block is, functionally
speaking, a reversible vagotomy. Namely, application of the block
at least partially prevents nerve transmission across the site of
the block. Removal of the block restores normal nerve activity at
the site. A block is any localized imposition of conditions that at
least partially diminish transmission of impulses.
[0103] The vagal block may be desirable in some patients since
unblocked pacing may result in afferent vagal and antidromic
efferent signals having undesired effect on organs innervated by
the vagus proximal to the GI tract (e.g., undesirable cardiac
response). Further, the afferent signals of the pacing electrode PE
can result in a central nervous system response that tends to
offset the benefits of the pacing electrode on the ENS and
pancreo/biliary function. thereby reducing the GI and enteric
rhythm management effectiveness of vagal pacing.
[0104] The block may be intermittent and applied only when the
vagus is paced by the pacing electrode PE. The preferred nerve
conduction block is an electronic block created by a signal at the
vagus by an electrode PBE controlled by the implantable controller
(such as controller 102 or an external controller). The nerve
conduction block can be any reversible block. For example,
cryogenics (either chemically or electronically induced) or drug
blocks can be used. An electronic cryogenic block may be a Peltier
solid-state device which cools in response to a current and may be
electrically controlled to regulate cooling. Drug blocks may
include a pump-controlled subcutaneous drug delivery.
[0105] With such an electrode conduction block, the block
parameters (signal type and timing) can be altered by a controller
and can be coordinated with the pacing signals to block only during
pacing. A representative blocking signal is a 500 Hz signal with
other parameters (e.g., timing and current) matched to be the same
as the pacing signal). While an alternating current blocking signal
is described, a direct current (e.g., -70 mV DC) could be used. The
foregoing specific examples of blocking signals are representative
only. Other examples and ranges of blocking signals are described
in the afore-mentioned literature (all incorporated herein by
reference). As will be more fully described, the present invention
gives a physician great latitude in selected pacing and blocking
parameters for individual patients.
[0106] Similar to FIG. 4, the vagus VN and enteric nervous system
ENS in FIG. 6 distal to the block PBE are shown in solid lines to
illustrate enhanced tone (except for the direct innervation VN1,
VN2, VN4, VN6 to the GI tract organs). Similarly, arrows A', B' are
shown in solid lines to illustrate the enhanced pancreo-biliary
output and resultant enhanced feedback stimulation to the enteric
nervous system ENS. The proximal vagus nerve segment VNP proximal
to the block PBE is shown in phantom lines to illustrate it is not
stimulated by the pacing electrode PE while the blocking electrode
PBE is activated.
[0107] 5. Proximal and Distal Blocking
[0108] FIG. 7 illustrates the addition over FIG. 6 of a nerve
conductive DBE distal to the pacing electrode PE. The proximal
block PBE prevents adverse events resulting from afferent signals
and heightens the GI effectiveness by blocking antidromic
interference as discussed with reference to FIG. 6.
[0109] In FIG. 7, the distal block DBE is provided in the event
there is a desire to isolate the pacing effect of electrode PE. For
example, a physician may which to enhance the vagus and enteric
activity in the region proximal to the duodenum but may wish to
avoid stimulating pancreo-biliary output. For example, a patient
may have a GI problem without apparent colon dysfunction (e.g.,
gastroparesis functional dyspepsia without bowel symptoms). Placing
the distal block DBE on a branch of the vagus between the pacing
electrode PE and the pancreas and gall bladder PG prevents
increased pancreo-biliary output and resultant feedback
(illustrated by dotted arrows A and B in FIG. 7 and dotted distal
vagal nerve segment VND and vagal trunk VN5).
[0110] 6. Blocking As An Independent Therapy
[0111] FIG. 8 illustrates an alternative embodiment of the
invention.
[0112] In certain patients, the vagus nerve may be hyperactive
contributing to diarrhea-dominant IBS. Use of a blocking electrode
alone in the vagus permits down-regulating the vagus nerve VN, the
enteric nervous system ENS and pancreo-biliary output. The block
down-regulates efferent signal transmission. In FIG. 8, the
hyperactive vagus is illustrated by the solid line of the proximal
vagus nerve segment VNP. The remainder of the vagus and enteric
nervous system are shown in reduced thickness to illustrate
down-regulation of tone. The pancreo-biliary output (and resulting
feedback) is also reduced. In FIG. 8, the blocking electrode BE is
shown high on the vagus relative to the GI tract innervation (e.g.,
just below the diaphragm), the sole blocking electrode could be
placed lower (e.g., just proximal to pancreo/biliary innervation
VN5).
[0113] 7. Application to Obesity
[0114] The foregoing discussion has been described in a preferred
embodiment of treating FGIDs, gastroparesis and GERD. Obesity is
also treatable with the present invention.
[0115] Recent literature describes potential obesity treatments
relative to gut hormone fragment peptide YY.sub.3-36. See, e.g.,
Batterham, et al., "Inhibition of Food Intake in Obese Subjects by
Peptide YY3-36", New England J. Med., pp. 941-948 (Sep. 4, 2003)
and Korner et al., "To Eat or Not to Eat--How the Gut Talks to the
Brain", New England J. Med., pp. 926-928 (Sep. 4, 2003). The
peptide YY.sub.3-36 (PPY) has the effect of inhibiting gut motility
through the phenomena of the ileal brake. Vagal afferents create a
sensation of satiety.
[0116] The present invention can electrically simulate the effects
of PPY by using the vagal block to down-regulate afferent vagal
activity to create a desired sensation of satiety. Since the
down-regulation does not require continuous blocking signals, the
beneficial efferent signals are permitted.
[0117] 8. Application to Other Therapies
[0118] There are numerous suggestions for vagal pacing or
stimulation to treat a wide variety of diseases. For example, U.S.
Pat. No. 5,188,104 dated Feb. 23, 1993 describes vagal stimulation
to treat eating disorders. U.S. Pat. No. 5,231,988 dated Aug. 3,
1993 describes vagal stimulation to treat endocrine disorders. U.S.
Pat. No. 5,215,086 dated Jun. 1, 1993 describes vagal stimulation
to treat migraines. U.S. Pat. No. 5,269,303 dated Dec. 14, 1993
describes vagal stimulation to treat dementia. U.S. Pat. No.
5,330,515 dated Jul. 19, 1994 describes vagal stimulation to treat
pain. U.S. Pat. No. 5,299,569 dated Apr. 5, 1994 describes vagal
stimulation to treat neuropsychiatric disorders. U.S. Pat. No.
5,335,657 dated Aug. 9, 1994 describes vagal stimulation to treat
sleep disorders. U.S. Pat. No. 5,707,400 dated Jan. 13, 1998
describes vagal stimulation to treat refractory hypertension. U.S.
Pat. No. 6,473,644 dated Oct. 29, 2002 describes vagal stimulation
to treat heart failure. U.S. Pat. No. 5,571,150 dated Nov. 5, 1996
describes vagal stimulation to treat patients in comas. As
previously described, U.S. Pat. No. 5,540,730 dated Jul. 30, 1996
describes vagal stimulation to treat motility disorders and U.S.
Pat. No. 6,610,713 dated Aug. 26, 2003 describes vagal stimulation
to inhibit inflammatory cytokine production. All of the foregoing
U.S. patents listed in this paragraph are incorporated herein by
reference.
[0119] All of the foregoing suffer from undesired effects of vagal
pacing on cardiovascular, gastrointestinal or other organs. Nerve
conduction blocking permits longer pulse durations which would
otherwise have adverse effects on other organs such as those of the
cardiovascular or gastrointestinal systems. In accordance with the
present invention, all of the foregoing disclosures can be modified
by applying a blocking electrode and blocking signal as disclosed
herein to prevent adverse side effects. By way of specific example,
pacing a vagus nerve in the thoracic cavity or neck combined with a
blocking electrode on the vagus nerve distal to the pacing
electrode can be used to treat neuropsychiatric disorders (such as
depression and schizophrenia) and Parkinson's and epilepsy and
dementia. In such treatments, the blocking electrode is placed
distal to the stimulating electrode 25 shown in FIGS. 4 and 2,
respectively, of each of U.S. Pat. Nos. 5,269,303 and 5,299,569.
The present invention thereby enables the teachings of the
afore-referenced patents listed in foregoing two paragraphs.
[0120] As described, the parameters of the stimulating and blocking
electrodes can be inputted via a controller and, thereby, modified
by a physician. Also, FIG. 2 illustrates a feedback for controlling
a stimulating electrode. Feedbacks for stimulating electrodes are
also described in the patents incorporated by reference. The
blocking electrode can also be controlled by an implanted
controller and feedback system. For example, physiologic parameters
(e.g., heart rate, blood pressure, etc.) can be monitored. The
blocking signal can be regulated by the controller to maintain
measured parameters in a desired range. For example, blocking can
be increased to maintain heart rate within a desired rate range
during stimulation pacing.
[0121] 9. Opportunity for Physician to Alter Treatment for Specific
Patient
[0122] Gastrointestinal disorders are complex. For many, the
precise mechanism is of the disorder is unknown. Diagnosis and
treatment are often iterative processes. The present invention is
particularly desirable for treating such disorders.
[0123] Use of proximal and distal blocking electrodes in
combination with one or more pacing electrode permits a physician
to alter an operating permutation of the electrodes. This permits
regional and local up- or down-regulation of the nervous system and
organs. Further, pacing parameters (duty cycle, current, frequency,
pulse length) can all be adjusted. Therefore, the treating
physician has numerous options to alter a treatment to meet the
needs of a specific patient.
[0124] In addition, a physician can combine the present invention
with other therapies (such as drug therapies like prokinetic
agents).
[0125] With the foregoing detailed description of the present
invention, it has been shown how the objects of the invention have
been attained in a preferred manner. Modifications and equivalents
of disclosed concepts such as those which might readily occur to
one skilled in the art, are intended to be included in the scope of
the claims which are appended hereto.
* * * * *