How effective is it?
Studies have shown that more than 90 percent of procedures will eliminate the pain of trigeminal neuralgia in properly selected candidates. The median duration of pain relief is about two years, and everyone is different; this means your pain could stay away for a few months, or up to eight years following a balloon compression rhizotomy. For many patients, the pain is eliminated immediately following the procedure; for others, the effects take a few days.
What are the side effects of balloon compression?
By injuring the trigeminal nerve, an element of numbness is introduced. 92% of patients say that this numbness is mild. Numbness is not an absence of sensation. It is another form of sensation called dysesthesia. If severe enough it can be interpreted as burning, scalding, searing, tingling, itching, stinging, cool, cold, even freezing. Such sensations result from significant nerve injury, which must be avoided. Fortunately, these are rare occurrences.
One other side effect is temporary weakness of the chewing muscles on the same side as the surgery. The trigeminal nerve has a branch that has motor function to these muscles. This can lead to temporary aching pain in the jaw joint. Such a pain is treatable with Tylenol and this weakness resolves over the course of several weeks.
What is the experience like?
The procedure takes one hour to complete. The patient is sedated during the procedure and is able to return home within a few hours with a band aid covering the needle entry site.
How long does pain relief last?
Pain can recur when the nerve insulation heals. Such recurrence is expected, because the planned injury is a mild one. Recurrence rate is 30% to 50% within three to five years. When pain recurs, compression can be repeated.
Percutaneous stereotactic radiofrequency rhizotomy (PSR) produces a controlled injury to the trigeminal nerve and is therefore able to trade numbness for relief of TN pain. It does so by temperature-monitored heating of the trigeminal nerve fibers. The extent of numbness can vary, but in general, the amount of numbness is proportional to the duration of relief. Too much numbness can also be a problem because it can cause uncomfortable sensations.
PSR can limit numbness to a specific part of the face, especially if the pain originates in the lower face, jaw, or tongue. It is probably the only procedure that can reliably limit numbness to that part of the face. This is helpful because the more widespread the numbness, the harder it can be to tolerate. Numbness of the upper face that includes the surface of the eye creates the risk of eye irritation or even corneal scarring with loss of vision. Absolute control of the lesion is not possible, however, and sometimes one gets more numbness than planned despite the surgeon’s best efforts.
PSR can cause numbness in all three trigeminal divisions if necessary, but once the ophthalmic division is to be included, balloon compression offers at least some protection of the corneal reflex. For some reason, corneal reflex nerve fibers seem to be less vulnerable to the pressure of the balloon than to the heat of the radiofrequency electrode.
- Patients are briefly anesthetized with an intravenous medication. An entry point for the needle electrode is selected in the cheek an inch to the side of the corner of the mouth.
- Trajectory guidance points can be marked on the face to help the surgeon set the proper angle of approach with the needle. The needle is passed to the floor of the skull to an opening where one of the three divisions of the trigeminal nerve enters the skull. The needle is then positioned in a dip in the skull base called Meckel’s cave. This is where the tip will lie among the nerve fibers of the trigeminal root and Gasserian ganglion (A ganglion is a swelling in the nerve that serves as a relay center for sensation on the face to the brain.).
- The sharp inner needle used for insertion is then exchanged for a radiofrequency electrode. Patients are woken up to the point of “sleepy but effective communication.” Current is passed through the electrode to cause small shocks in the face, hopefully without triggering a TN attack. This allows the surgeon to maneuver the electrode to the correct location where stimulation is felt in the trigeminal division where the patient normally gets TN pains.
- Once properly localized, the patient is again lightly anesthetized and the electrode’s radiofrequency current is turned up to the point that it causes the nerve fibers to heat up. At 50° centigrade, nerve conduction temporarily stops. At 60°, the proteins in the nerve fibers start to coagulate, and part of the nerve is injured. Between lesions, the patient is woken so that the location and degree of numbness can be tested until it is exactly what the surgeon wants for that specific patient.
Most patients are willing to exchange their TN pain for their mild new numbness. Over time, there is some diminishment of the numbness and some accommodation to it. Like putting on a new pair of shoes, the new sensation is stronger at first, but the brain starts to see it as the “new norm” over time. Recurrence of pain in spite of continued numbness is well known and one of the mysteries of the disease. It is presumed that this represents some intensification or progression of the disease, which must be within the nerve.
PSR can be repeated for recurrence, but each repeat procedure carries the need for more numbness and therefore the increased risk of troublesome numbness. PSR is one of the oldest and yet still one of the best procedures to relieve TN pain. It is an outpatient procedure with an acceptably low risk profile and can be an exceptionally good option for patients with medical reasons to avoid open surgery.
Glycerol injection is also an outpatient or overnight procedure. It is performed with intravenous sedation. A thin needle is introduced through a puncture in the cheek, next to the mouth and guided through a natural opening in the base of the skull. Just inside this opening is the trigeminal ganglion where all three nerves come together. A small amount of a substance called glycerol is injected into the nerve after your doctor identifies the fibers of the nerve using a special x-ray test. The glycerol bathes the ganglion. The glycerol inactivates the short-circuit of the pain fibers in the nerve.