The overall goal of this surgical intervention is to treat patients with chronic therapy-resistant and neuropathic trigeminal pain using minimally invasive subcutaneous nerve field stimulation as a method of neuromodulation. This method can help treat patients with therapy-resistant chronic trigeminal pain such as trigeminal neuralgia or post-therapeutic trigeminal neuropathy who have failed conservative and standard surgical treatment. The main advantage of this technique is that it is minimally invasive, does not destroy any nerve tissue, and its success can be tested in a period of trial stimulation before undergoing permanent implantation.
We offer this treatment as an alternative to destructive techniques such as Radiofrequency Thermocoagulation or Gamma Knife Radiosurgery. After a patient has carried out a 12-day stimulation trial, according to the text protocol, turn the anesthetized patient's head to the side contralateral to the pain. Then, place a pillow under the ipsilateral shoulder to expose the clavicle.
Shave the area around the ear on the painful side of the face. Then remove any loose hair. If necessary, tape away the surrounding hair to prevent it from moving into the surgical field.
Next, thoroughly disinfect the surgical field from the facial area around the ear and down to the clavicle area. From the X-rays of the out-patient appointment, use a sterile surgical pen to mark the desired position of the permanent electrodes in the marks of the previous skin punctures for guidance. For the first trigeminal branch, choose a position on the lateral side of the forehead at which to puncture the skin, roughly 10 centimeters lateral and one centimeter above the medial border of the eyebrow.
For the second trigeminal branch, choose a position that is located roughly one centimeter anterior to the tragus. Do not perform a skin puncture two centimeters or more anterior to the tragus to spare facial nerve fibers from injury. For the third trigeminal branch, choose a position that is located roughly one centimeter anterior and four centimeters below the tragus.
Correct planning of electrode insertion is crucial to the success of this technique as the parasthesia provoked by the stimulation should cover the entire painful area. Use a 14-gauge Tuohy needle to perform a skin puncture at a previously marked position. As the subcutaneous tissue of the facial area is thinner than on other body parts, make sure to stay half a centimeter below the skin surface to prevent skin perforation or direct muscle stimulation.
Make a one centimeter-long vertical incision in the supra-auricular area. And form a small subcutaneous pocket. Take the stylets from the Tuohy cannulas and subcutaneously tunnel them from the site of the skin puncture to the supra-auricular incision.
Insert another Tuohy cannula to subcutaneously tunnel from the supra-auricular incision to the site of the skin puncture. And then insert the electrodes into the Tuohy cannula with the contacts located in the painful area. Remove the Tuohy cannulas and the electrode stylets.
And insert the distal end of the electrode into the cannula. Remove the Tuohy cannula while using forceps to keep the electrode in place. Then use a 3-0 non-absorbable silk suture to fix the electrode to the muscle fascia to prevent electrode dislocation.
Next, perform a six centimeter long infraclavicular incision and manually form a subcutaneous pocket to house the IPG. Use bipolar electrical forceps to coagulate any bleeding vessels. Insert a tunneling spear into the infraclavicular incision and subcutaneously tunnel behind the ear towards the supra-auricular incision.
Make a small retroauricular incision for the spear to exit the skin. Then, tunnel with a second spear from the supra-auricular to the retroauricular incision. Remove the spear stylets.
And insert the electrodes until the electrodes are buried in the subcutaneous tissue without any loops or kinks. After tunneling the electrodes to the retroauricular incision, tunnel them from here to the infraclavicular incision. Then remove the spear by pulling it out of the infraclavicular incision while using forceps to keep the electrodes in place.
Connect the electrodes to the IPG. And use torque screws to secure them. Use a non-absorbable 3-0 silk suture to suture the IPG to the pectoralis muscle fascia to prevent IPG dislocation.
Perform skin closure with absorbable 3-0 subcutaneous sutures and non-absorbable 3-0 cutaneous sutures in the facial area. And absorbable 3-0 intracutaneous sutures at the site of the IPG. Then disinfect all wounds.
Clean the surgical field with saline. And apply sterile draping. Carry out post-operative care according to the text protocol.
In one case series, 10 patients who suffered from pain from the conditions listed in this table underwent test stimulation for subcutaneous trigeminal nerve field stimulation, or sTNFS, and received permanent implantation of electrodes and an IPG. Following an 11-month follow-up, eight of the 10 patients responded to the therapy with pain reduced from 9.3 to 0.75 on the Visual Analog Scale. In another recently published series, eight patients were tested with sTNFS.
After a mean follow-up of 15.2 months, six of the eight patients proceeded to permanent implantation. And according the VAS, pain was reduced from 8.5 to 1.4 points. The series is also the first to describe a 73%reduction in the mean number of painful daily attacks.
The chart shown here was all patients with permanent implantations treated with sTNFS. A mean reduction of 6.8 VAS points and the mean reduction of 12.2 in the number of daily attacks was achieved. Trial electrode placement takes roughly 15 minutes.
The surgery for permanent implantation can be performed within one hour and patients can be discharged on the next day. Subcutaneous trigeminal nerve field stimulation can provide a sustained therapeutic effect on both pain intensity and frequency of painful attacks. The amount of pain medication and its side effects can then be reduced.
After watching this video, you should have a good understanding of how to perform trial electrode placement and permanent implantation surgery for subcutaneous trigeminal nerve field stimulation.
