US 20110015548 A1
Method and apparatus for treating obesity by use of transesophageal delivery of energy to interrupt the function of vagal nerves.
1. A method for reducing obesity comprising the steps of:
introducing an energy delivery device into the esophagus and positioning said source below the diaphragm,
energizing said delivery device, and delivering energy to the site of at least one vagal nerve branch on the outer wall of the esophagus.
2. The method of
3. The method of
4. The method of claim wherein the energy is high intensity focused ultrasound.
5. The method of
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9. The method of
10. Apparatus for interrupting function of vagal nerves comprising:
an energy delivery device,
a carrier for said energy delivery device, said carrier being adapted to locate said source of energy in the esophagus, and
an actuator for energizing said energy delivery device such that energy is delivered to a vagal nerve branch.
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Obesity has become an ever-increasing health problem. While such voluntary weight reduction programs as dieting and exercise have been helpful for some, many obese persons have required surgery to address their obesity problem. Two such surgical procedures are vertical banded gastroplasty (VBG) and the Roux-en-Y gastric bypass procedure. Both such procedures are now well known, but they are invasive in nature and involve reducing the size of the stomach. While these procedures have demonstrated a reasonable level of efficacy, there has remained a need for an obesity treatment that would not involve the patient trauma of invasive surgery and would yet be effective.
The present invention is, in general, directed to the treatment of obesity by creating an interruption of the vagal nerve, preferably in the region of the esophagus, by minimally or noninvasive means. While the present invention is not to be tied to any particular theory of operation, it appears that a hunger signal is expressed by ghrelin, a peptide primarily produced in the stomach, and transmitted to the brain through the vagal nerve. The literature e.g., “The Role of the Gastric Afferent Vagal Nerve in Ghrelin-Induced Feeding and Growth Hormone Secretion in Rats,” Gastroenterology 2002:123:1120-1128 (October 2002) by Yukari Date et al. and “Gastroplasty for Obesity: Long-term Weight Loss Improved by Vagotomy,” World Journal of Surgery, Vol. 17, No. 1, January/February 1993, by Kral et al., supports this theory. The Date et al. article concluded that blockade of the gastric vagal afferent abolished ghrelin-induced feeding in rats and the Kral et al. article concluded that vagotomy combined with gastroplasty was more effective in controlling weight loss than gastroplasty alone. These articles are incorporated by reference herein.
More specifically, a preferred embodiment of the present invention is directed to interrupting the function of the gastric vagal nerve in the region of the esophagus by using an ablating or other nerve dysfunction causing device installed in the esophagus which delivers ablating energy to one or more vagal nerve branches in a transesophageal manner. The anatomy of the vagal nerve complex varies somewhat from person to person, but, common to all is a structure comprising multiple vagal nerve branches located on the outer wall of the esophagus which run generally longitudinally along the esophagus wall. The present invention contemplates interrupting the function of one or more vagal nerve branches in a transesophageal manner by using various types of energy including radio frequency (RF) energy, high intensity ultrasound, high intensity focused ultrasound, and other types of energy as described in more detail below.
Typically, there are two main branches, or trunks, of the vagal nerve which are located approximately 180° from each other on the outer wall of the esophagus. Depending on patient needs, it may be sufficient to interrupt only a portion of the fibers in the nerve. In this regard, it is to be noted that, in general, myelinated vagal nerve fibers, i.e., fibers that have an outer coating, are efferent. In contrast, afferent vagal nerves are unmyelinated and have no outer covering. For some patients, it may be sufficient to interrupt the function of only the afferent vagal fibers.
The ultimate objective is, of course, substantial weight loss by the patient as a result of a substantial decrease in the ghrelin hunger signal transmitted through the vagal nerve branches. Thus, the success of the procedure described herein will, to some extent, be patient-dependent and, in some patients, it may be necessary to interrupt both the afferent and efferent vagal branches.
In practicing the present invention, the energy source may be installed in the esophagus through the throat, but nasogastric access through the nose and extracorporeal application are also contemplated. The energy may be delivered to the vagal nerve through the esophagus wall, e.g., when ultrasound is used, or by causing an energy delivery device, e.g., an electrode to be passed through the wall of the esophagus.
Still other energy sources can be used to interrupt the function of the vagal nerves including thermal, microwave, laser and cryogenic energy. Alternatively, the vagal nerve function can be interrupted by transesophageal delivery of a neurotoxin such as capsaicin, atropine, or botulinum toxin. Still further, mechanical means can be used to crush the vagal nerve, e.g., with a clip or pincer, or the vagal nerve can be cut transesophageally with an appropriate cutting instrument. In a preferred embodiment of the present invention, the vagal nerve will be interrupted in the vicinity of the zig-zag line, also known as the Z-line, which is generally located in the lower esophagus between the cardiac notch of the stomach and the diaphragm.
Before turning to the manner in which the present invention functions, it is believed that it will be useful to briefly review the anatomy of the stomach and the esophagus. The esophagus is a muscular tube that carries food from the throat to the stomach and which passes through the diaphragm. The top end of the esophagus is the narrowest part of the entire digestive system and is encircled by a sphincter (circular muscle) that is normally closed but can open to allow the passage of food. There is a similar sphincter at the point where the esophagus enters the stomach. The walls of the esophagus consist of strong muscle fibers arranged in bundles, some circular and others longitudinal. The inner lining of the esophagus consists of smooth squamous epithelium (flattened cells).
As shown in
In the present invention, the needle probes can irradiate around the complete circumference of the device as shown in
If the patient's anatomy makes it desirable, an ablation device 5 can be provided with an energy delivery component 15 which is adjustable such that energy can be delivered perpendicularly to the probe or at an angle to the probe.
When a needle probe is used to deliver energy according to the present invention, the device can be provided with temperature sensors such as thermocouples which are disposed in the distal region of the needle probes. The needle probes can be formed of a variety of materials including nickel-titanium alloy. The needle probes can assume a linear or curved shape when deployed. The device may also be provided with means for cooling the treatment site with a suitable fluid such as water, air, or other liquid or gas, to control the temperature at the treatment site. Thus, the temperature sensor can either cause a cooling medium to be provided or shut off the delivery of energy through one or more needle probes.
In a preferred embodiment of the present invention, high intensity focused ultrasound (HIFU) is used to ablate the vagal nerve branches. The HIFU energy can be transmitted transesophageally to ablate the vagal nerves on the outer wall of the esophagus.
Although the esophagus is generally illustrated anatomically as a generally cylindrical tube, in its relaxed condition it assumes a more elliptical configuration which can be characterized as floppy. In other words, somewhat like a sock before it is put upon a foot, it does not assume a generally circular configuration unless it contains food, but otherwise has a configuration in which the opposing walls of the esophagus are closer together than they would be when in a circular configuration as shown in
Ultrasound heating technology, including high-intensity ultrasound and HIFU are well understood. For example, Chapter 12, entitled “Ultrasound heating technology,” of “Thermo-radiotherapy and Thermo-chemotherapy,” vol. 1, edited by Seegenschmiedt, Fessenden and Vernon, contains a thorough explanation of the use of ultrasound in thermal therapy. This chapter is incorporated by reference herein.
The present invention is not to be considered to be limited to the embodiments described above, but is of the full scope of the appended claims.