Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
2001-04-19
2003-08-26
Schaetzle, Kennedy (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
Reexamination Certificate
active
06611715
ABSTRACT:
FIELD OF INVENTION
This invention relates generally to medical device used for adjunct (add-on) treatment for obesity, more specifically a medical device used for adjunct (add-on) therapy for obesity and compulsive eating disorders with electrical stimulation neuromodulation using an implanted lead-receiver and an external stimulator.
BACKGROUND
Obesity results from excessive accumulation of fat in the body. It is caused by ingestion of greater amounts of food than can be used by the body for energy. The excess food, whether fats, carbohydrates, or proteins, is then stored almost entirely as fat in the adipose tissue, to be used later for energy. There can be various causes of obesity including, psychogenic, neurogenic, genetic, and other metabolic related factors. Treatment of obesity depends on decreasing energy input below energy expenditure. Treatment has included among other things various drugs, starvation and even stapling or surgical resection of a portion of the stomach.
The 10
th
cranial nerve or the vagus nerve plays a role in mediating afferent information from the stomach to the satiety center in the brain. The vagus nerve arises directly from the brain, but unlike the other cranial nerves extends well beyond the head. At its farthest extension it reaches the lower parts of the intestines. This is shown schematically in
FIG. 1A
, and in more detail in FIG.
1
B.
Observations on the profound effect of electrical stimulation of the vagus nerve on central nervous system (CNS) activity extends back to the 1930's. In 1988 it was reported in the
American Journal of Physiology
, that the afferent vagal fibers from the stomach wall increased their firing rate when the stomach was filled. Accordingly, extra-physiologic electrical stimulation of the vagus nerve, from just above the stomach level, should produce appetite supression by causing the patient to experience satiety.
The present invention is primarily directed to apparatus and method for electrical stimulation neuromodulation of the vagus nerve, to treat compulsive overeating and obesity with an implanted lead-receiver and an external stimulator with predetermined programs. Upon experiencing the compulsive craving, the obese patient can voluntarily activate the stimulus generator by activating a predetermined program.
The vagus nerve
54
provides an easily accessible, peripheral route to modulate central nervous system (CNS) function. In the human body there are two vagus nerves (VN), the right VN and the left VN. Each vagus nerve is encased in the carotid sheath along with the carotid artery and jugular vein. The innervation of the right and left vagus nerves is different. The innervation of the right vagus nerve is such that stimulating it results in profound bradycardia (slowing of the heart rate). The left vagus nerve has some innervation to the heart, but mostly innervates the visceral organs such as the gastrointestinal tract. It is known that stimulation of the left vagus nerve does not cause any significant deleterious side effects.
Neuromodulation
One of the fundamental features of the nervous system is its ability to generate and conduct electrical impulses. These can take the form of action potentials, which is defined as a single electrical impulse passing down an axon, and is shown schematically in FIG.
2
. The top portion of the figure (A) shows conduction over mylinated axon (fiber) and the bottom portion (B) shows conduction over nonmylinated axon (fiber). These electrical signals will travel along the nerve fibers.
The nerve impulse (or action potential) is an “all or nothing” phenomenon. That is to say, once the threshold stimulus intensity is reached an action potential
7
will be generated. This is shown schematically in FIG.
3
. The bottom portion of the figure shows a train of action potentials.
Most nerves in the human body are composed of thousands of fibers of different sizes. This is shown schematically in FIG.
4
. The different sizes of nerve fibers, which carry signals to and from the brain, are designated by groups A, B, and C. The vagus nerve, for example, may have approximately 100,000 fibers of the three different types, each carrying signals. Each axon or fiber of that nerve conducts only in one direction, in normal circumstances.
In a cross section of peripheral nerve it is seen that the diameter of individual fibers vary substantially. The largest nerve fibers are approximately 20 &mgr;m in diameter and are heavily myelinated (i.e., have a myelin sheath, constituting a substance largely composed of fat), whereas the smallest nerve fibers are less than 1 &mgr;m in diameter and are unmyelinated. As shown in
FIG. 5
, when the distal part of a nerve is electrically stimulated, a compound action potential is recorded by an electrode located more proximally. A compound action potential contains several peaks or waves of activity that represent the summated response of multiple fibers having similar conduction velocities. The waves in a compound action potential represent different types of nerve fibers that are classified into corresponding functional categories as shown in the table below,
Conduction
Fiber
Fiber
Velocity
Diameter
Type
(m/sec)
(&mgr;m)
Myelination
A Fibers
Alpha
70-120
12-20
Yes
Beta
40-70
5-12
Yes
Gamma
10-50
3-6
Yes
Delta
6-30
2-5
Yes
B Fibers
5-15
<3
Yes
C Fibers
0.5-2.0
0.4-1.2
No
The diameters of group A and group B fibers include the thickness of the myelin sheaths. Group A is further subdivided into alpha, beta, gamma, and delta fibers in decreasing order of size. There is some overlapping of the diameters of the A, B, and C groups because physiological properties, especially in the form of the action potential, are taken into consideration when defining the groups. The smallest fibers (group C) are unmyelinated and have the slowest conduction rate, whereas the myelinated fibers of group B and group A exhibit rates of conduction that progressively increase with diameter.
Compared to unmyelinated fibers, myelinated fibers are typically larger, conduct faster, have very low stimulation thresholds, and exhibit a particular strength-duration curve or respond to a specific pulse width versus amplitude for stimulation. The A and B fibers can be stimulated with relatively narrow pulse widths, from 50 to 200 microseconds (&mgr;s), for example. The A fiber conducts slightly faster than the B fiber and has a slightly lower threshold. The C fibers are very small, conduct electrical signals very slowly, and have high stimulation thresholds typically requiring a wider pulse width (300-1,000 &mgr;s) and a higher amplitude for activation. Because of their very slow conduction, C fibers would not be highly responsive to rapid stimulation. Selective stimulation of only A and B fibers is readily accomplished. The requirement of a larger and wider pulse to stimulate the C fibers, however, makes selective stimulation of only C fibers, to the exclusion of the A and B fibers, virtually unachievable inasmuch as the large signal will tend to activate the A and B fibers to some extent as well.
The vagus nerve is composed of somatic and visceral afferents and efferents. Usually, nerve stimulation activates signals in both directions (bi-directionally). It is possible however, through the use of special electrodes and waveforms, to selectively stimulate a nerve in one direction only (unidirectionally). The vast majority of vagus nerve fibers are C fibers, and a majority are visceral afferents having cell bodies lying in masses or ganglia in the skull. The central projections terminate largely in the nucleus of the solitary tract, which sends fibers to various regions of the brain (e.g., the thalamus, hypothalamus and amygdala).
Vagus nerve stimulation is a means of directly affecting central function. As shown in
FIG. 6
, cranial nerves have both afferent pathway
19
(inward conducting nerve fibers which convey impulses toward the brain) and efferent pathway
21
(outward conducting nerve fibers which convey impulses to an effector). The vagus ne
Droesch Kristen
Schaetzle Kennedy
LandOfFree
Apparatus and method for neuromodulation therapy for obesity... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus and method for neuromodulation therapy for obesity..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus and method for neuromodulation therapy for obesity... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3106869