Epirepsiu Jl(Supp1. 2):S38-S39, 1990 Raven &ss, Ltd., New Yo& 8 1990 International Lurgue Against Epilepsy
Surgical Technique for Implantation of the Neurocybernetic Prosthesis Steven A. Reid Department of Neurological Surgery, University of Florida College of Medicine, and Neurosurgery Section, Department of Veterans Affairs Medical Center, Gainesville, Florida
Summary: The surgical technique for the implantation of the neurocybernetic prosthesis is described in detail. This procedure is straightforward and is easily carried out
by surgeons familiar with carotid surgery. Key Words: Epilepsy-Seizures-Vagugus nerve-Electrical stimulation-Minor surgery.
The neurocybernetic prosthesis (Cyberonics, Inc., Webster, TX) is an implantable device designed to stimulate electrically the vagus nerve. Experimental studies have shown that vagus nerve stimulation causes desynchronization of the electroencephalogram and can inhibit or abort certain epileptic seizures. The surgical implantation of this device is described here. It is strongly recommended that the procedure be carried out with the patient under general anesthesia until the surgeon is comfortable with the approach. Thereafter, local anesthesia may be used, if so desired. The anesthetized patient is placed in a supine position with the head turned slightly to the right. The skin of the left anterolateral neck and chest is prepared and draped in the usual sterile manner for surgery. Left-sided implantations are recommended because stimulation of the right vagus nerve can elicit profound bradycardia. A linear skin incision is made with a No. 15 blade to the level of the platysma parallel to the anterior border of the sternocleidomastoid muscle. This incision is similar to the usual carotid endarterectomy incision and extends approximately from the angle of the jaw to the lower anterior neck. The platysma is penetrated with Metzenbaum scissors and is divided. The anterior border of the sternocleidomastoid is identified
and the carotid artery is palpated in the carotid sheath through the loose tissue medial to this muscle. The carotid sheath is then exposed by blunt dissection with toothed forceps and Metzenbaum scissors. At this point, the surgeon may turn attention to the infraclavicular area. A 10-cm horizontal linear incision is made approximately 8 cm inferior to the middle portion of the clavicle. A subcutaneous pocket that will later contain the generator package is made by bluntly elevating the subcutaneous fat from the pectoralis fascia using Metzenbaum or curved Mayo scissors. We have found the disposable Codman shuntpassing tool to be very helpful for passing the electrode leads from the infraclavicular incision to the cervical incision. This instrument is directed in a subcutaneous plane from the subcutaneous pocket to the inferior aspect of the cervical incision, taking great care to insure that it passes superficial to the clavicle and does not penetrate the carotid sheath. The plastic clip is cut from the end of the shunt passer and the spiral electrodes are wrapped around the end of the plastic rod, which protrudes from the center of the shunt passer. The end of the plastic rod is then crushed with a needle holder to create a flange distal to the spiral electrodes. The spiral electrodes are then gently pulled into the aluminum tubing of the shunt passer. It is necessary to pull the leads a short distance into the shunt passer only until both spiral electrodes are completely inside. At this point, the surgeon can grasp the proximal
Address correspondence and reprint requests to Dr.S. A. Reid at Department of Neurological Surgery, University of Florida College of Medicine, Gainesville, FL,32608, U.S.A.
S38
NEUROC YBERNETIC PROSTHESIS
end of the shunt-passer tubing in the cervical incision and pull the entire assembly through. This method minimizes damage to the delicate spiral electrodes. The electrodes are then removed from the shunt-passer tubing and placed out of the surgeon’s way on the patient’s chest under a lap pad dampened with Bacitracin solution. Self-retaining retractors are next positioned to allow visualization of the carotid sheath. This structure is opened over a length of approximately 7 cm, exposing the common carotid artery and the internal jugular vein. The vagus nerve can usually be quickly located in the loose tissue posterior to and between the carotid artery and the internaljugular vein. This is most easily found by performing blunt dissection in this tissue in a direction parallel to the nerve. When the nerve is located, soft rubber vessel loops are passed around it to allow for gentle traction and elevation. At least 3 cm of the nerve must be exposed and freed from surrounding tissues. The spiral electrodes are then wrapped around the nerve using smooth forceps. The shortest lead (the one with the striped wire) is placed first. This lead will be the most distal on the vagus nerve. In applying each electrode to the nerve the central turn of the spiral must be positioned first, and then the upper and lower turns are each wrapped around the nerve in turn. Some surgeons may be more comfortable doing this portion of the procedure with magnified vision. After the lower electrode is in
s39
place, the second electrode is wrapped around the nerve in a similar manner. The spiral anchoring tether is then applied to the nerve inferior to the electrodes in a similar manner. The Silastic ties on the tether are used to anchor the lead wires. At this point, the leads should be tested to insure impedance between 400 and 3,000 a. The leads are then connected to the generator pack, as described in the physician’s manual for the device. A large Sshaped turn or loop is made with the leads in the neck to provide strain relief and slack. A suture sleeve can then be placed over the lead and sutured to the fascia. Another approach to anchoring the leads is to use two or three Silastic slings tightly wrapped around the leads and sutured to the fascia. Do not attach the lead to muscle, as this may result in excessive lead movement. Wherever possible, the leads should run parallel to the nerve, carotid sheath, and sternomastoid muscle. The generator is placed in the subcutaneous pocket and the wounds are closed in layers. We prefer subcuticular skin closure with 4-0 Dexon for a cosmetically pleasing scar. We have found the procedure as described above to be technically straightforward. It can be easily performed in about 1 h in most cases. It is recommended that this procedure be carried out by neurological surgeons familiar with the surgical approach for carotid endarterectomy.
Epilepsia. Vol. 31. Suppl. 2. 1990
Surgical Technique for Implantation of the Neurocybernetic Prosthesis Steven A. Reid Department of Neurological Surgery, University of Florida College of Medicine, and Neurosurgery Section, Department of Veterans Affairs Medical Center, Gainesville, Florida
Summary: The surgical technique for the implantation of the neurocybernetic prosthesis is described in detail. This procedure is straightforward and is easily carried out
by surgeons familiar with carotid surgery. Key Words: Epilepsy-Seizures-Vagugus nerve-Electrical stimulation-Minor surgery.
The neurocybernetic prosthesis (Cyberonics, Inc., Webster, TX) is an implantable device designed to stimulate electrically the vagus nerve. Experimental studies have shown that vagus nerve stimulation causes desynchronization of the electroencephalogram and can inhibit or abort certain epileptic seizures. The surgical implantation of this device is described here. It is strongly recommended that the procedure be carried out with the patient under general anesthesia until the surgeon is comfortable with the approach. Thereafter, local anesthesia may be used, if so desired. The anesthetized patient is placed in a supine position with the head turned slightly to the right. The skin of the left anterolateral neck and chest is prepared and draped in the usual sterile manner for surgery. Left-sided implantations are recommended because stimulation of the right vagus nerve can elicit profound bradycardia. A linear skin incision is made with a No. 15 blade to the level of the platysma parallel to the anterior border of the sternocleidomastoid muscle. This incision is similar to the usual carotid endarterectomy incision and extends approximately from the angle of the jaw to the lower anterior neck. The platysma is penetrated with Metzenbaum scissors and is divided. The anterior border of the sternocleidomastoid is identified
and the carotid artery is palpated in the carotid sheath through the loose tissue medial to this muscle. The carotid sheath is then exposed by blunt dissection with toothed forceps and Metzenbaum scissors. At this point, the surgeon may turn attention to the infraclavicular area. A 10-cm horizontal linear incision is made approximately 8 cm inferior to the middle portion of the clavicle. A subcutaneous pocket that will later contain the generator package is made by bluntly elevating the subcutaneous fat from the pectoralis fascia using Metzenbaum or curved Mayo scissors. We have found the disposable Codman shuntpassing tool to be very helpful for passing the electrode leads from the infraclavicular incision to the cervical incision. This instrument is directed in a subcutaneous plane from the subcutaneous pocket to the inferior aspect of the cervical incision, taking great care to insure that it passes superficial to the clavicle and does not penetrate the carotid sheath. The plastic clip is cut from the end of the shunt passer and the spiral electrodes are wrapped around the end of the plastic rod, which protrudes from the center of the shunt passer. The end of the plastic rod is then crushed with a needle holder to create a flange distal to the spiral electrodes. The spiral electrodes are then gently pulled into the aluminum tubing of the shunt passer. It is necessary to pull the leads a short distance into the shunt passer only until both spiral electrodes are completely inside. At this point, the surgeon can grasp the proximal
Address correspondence and reprint requests to Dr.S. A. Reid at Department of Neurological Surgery, University of Florida College of Medicine, Gainesville, FL,32608, U.S.A.
S38
NEUROC YBERNETIC PROSTHESIS
end of the shunt-passer tubing in the cervical incision and pull the entire assembly through. This method minimizes damage to the delicate spiral electrodes. The electrodes are then removed from the shunt-passer tubing and placed out of the surgeon’s way on the patient’s chest under a lap pad dampened with Bacitracin solution. Self-retaining retractors are next positioned to allow visualization of the carotid sheath. This structure is opened over a length of approximately 7 cm, exposing the common carotid artery and the internal jugular vein. The vagus nerve can usually be quickly located in the loose tissue posterior to and between the carotid artery and the internaljugular vein. This is most easily found by performing blunt dissection in this tissue in a direction parallel to the nerve. When the nerve is located, soft rubber vessel loops are passed around it to allow for gentle traction and elevation. At least 3 cm of the nerve must be exposed and freed from surrounding tissues. The spiral electrodes are then wrapped around the nerve using smooth forceps. The shortest lead (the one with the striped wire) is placed first. This lead will be the most distal on the vagus nerve. In applying each electrode to the nerve the central turn of the spiral must be positioned first, and then the upper and lower turns are each wrapped around the nerve in turn. Some surgeons may be more comfortable doing this portion of the procedure with magnified vision. After the lower electrode is in
s39
place, the second electrode is wrapped around the nerve in a similar manner. The spiral anchoring tether is then applied to the nerve inferior to the electrodes in a similar manner. The Silastic ties on the tether are used to anchor the lead wires. At this point, the leads should be tested to insure impedance between 400 and 3,000 a. The leads are then connected to the generator pack, as described in the physician’s manual for the device. A large Sshaped turn or loop is made with the leads in the neck to provide strain relief and slack. A suture sleeve can then be placed over the lead and sutured to the fascia. Another approach to anchoring the leads is to use two or three Silastic slings tightly wrapped around the leads and sutured to the fascia. Do not attach the lead to muscle, as this may result in excessive lead movement. Wherever possible, the leads should run parallel to the nerve, carotid sheath, and sternomastoid muscle. The generator is placed in the subcutaneous pocket and the wounds are closed in layers. We prefer subcuticular skin closure with 4-0 Dexon for a cosmetically pleasing scar. We have found the procedure as described above to be technically straightforward. It can be easily performed in about 1 h in most cases. It is recommended that this procedure be carried out by neurological surgeons familiar with the surgical approach for carotid endarterectomy.
Epilepsia. Vol. 31. Suppl. 2. 1990
