Treatment Options for Trigeminal Neuralgia

image showing two tablets of Tegretol (carbamazepine)

Medical Treatment

Treatment of TN is primarily medical (pharmacological) and a large majority of TN patients gets relevant relief from the painful bursts using drug therapy. The most efficient drugs are carbamazepine and oxcarbazepine. These drugs stabilize the excitability of the nerve cell membrane by blocking voltage-sensitive sodium channels. If the bursts promptly disappear following even a relatively low dose of one of these drugs the diagnosis of TN is confirmed. Unfortunately, both carbamazepine and oxcarbazepine may give rise to severe side effects. Other, less efficient, drugs must then be tried. These include anti-epileptics, antidepressants and pain-killers.

Symbolic picture of a surgeon holding a scalpel

Surgical Treatment

Since any surgical procedure carries some risk, no patient with TN who responds well to medication should be operated. Surgery becomes an option when doses cannot be increased because of side effects. In principle, surgery falls into three categories: (i) open neurosurgery, (ii) percutaneous procedures and (iii) stereotactic radiosurgery.

Microvascular Decompression

Open neurosurgery, referred to as microvascular decompression or MVD, is based on the assumption that the pain symptoms are caused by a blood vessel compressing the trigeminal nerve root. The procedure implies that a skin incision is made behind the ear, a hole is drilled in the skull bone and the brain coverings are opened. Using either a microscope or an endoscope the neurosurgeon enters the cranial cavity, exposes the trigeminal nerve and inserts a buffering patch, usually made of teflon or muscle, between the nerve and the blood vessel. The success rate of this operation is very high provided that there is a significant neuro-vascular conflict. When such conflict is lacking some neurosurgeons proceed with a so-called internal neurolysis, also called neuro-combing, procedure. The results and complications of this latter procedure are significantly worse.

Complication Profile for MVD

Hearing loss on the side of the operation is not uncommon. Most cases are temporary or partial.
Facial numbness is common but usually temporary.
Cerebrospinal fluid (CSF) leaks can occur because the surgery requires opening of the dural membrane. This is rare but in some cases requires a reoperation or a lumbal drainage. CSF can leak from the incision or, rarely, through the nose or ear.
Bleeding, infarction, edema or infection within the cranial cavity are very rare but serious complications.
MVD is not always a permanent cure, the recurrence rate is about 4% per year.

X-ray image showing a needle inserted into Meckels cave and the inflated pear-shaped balloon

Balloon Compression, Radiofrequency and Glycerol Blockade

These percutaneous procedures imply that the trigeminal ganglion is reached with a cannula using x-ray guidance. The trigeminal ganglion is situated in a little pocket on the skull base named Meckel's cave and can be reached through a hole in the skull base, the foramen ovale. In balloon compression (BC) a microballoon is inserted into Meckel's cave. The balloon is inflated for 1-2 minutes exerting a gentle compression on the ganglion. On the X-ray screen the balloon acquires a characteristical pear-shape (see figure). In radiofrequency (RF) lesioning an electrode is used to slightly heat the ganglion for a short time and in glycerol blockade (GB) the fluid space surrounding the ganglion is injected with glycerol causing a mild chemical irritation of the ganglion.

Complication Profile for Percutaneous Procedures

BC, RF and GB are all minimally invasive procedures and thus very safe. The complication profile is similar. The GB is generally considered the safest but also the least efficient. RF lesioning may give rise to corneal sensitivity loss not seen in BC or GB. Due to its simplicity and excellent long term efficiency the BC is becoming more and more popular.

Facial numbness is frequent and considered inherent to the procedure. The numbness usually improves in the months following surgery but some numbness may stay permanently.
Temporary or, rarely, permanent weakening of the jaw muscles used for chewing.
Painful numbness (anesthesia dolorosa) or abnormal sensations on the face is very rare (<1%), but may occur. Anestesia dolorosa is the most feared complication.
Herpes lesions are a common temporary reaction.
Transient bradycardia or cardiac arrest during the inflation of the balloon is common but is never seen to be harmful.
The procedures has a somewhat higher recurrence rate than MVD. The recurrence rate for balloon compression is about 4,5% per year.

Image showing a patient in the gamma knife

Stereotactic Radiosurgery

Here, a lesion in the most proximal part of the trigeminal nerve is produced using focused radiation. Since the procedure is non-invasive it carries minimal risks. On the other hand the recurrence rate is considerably higher than for MVD or percutaneous procedures. Another disadvantage is that the effect on the pain is not seen until several weeks after the procedure. The most significant complication is facial numbness occurring in approximately 5-10% of patients.

Botox Treatment

Botulinum toxin type A is used as an off-label adjunct since it appears to provide clinically meaningful pain relief and functional improvement for some patients with TN. It has a favorable safety profile and probably does no harm but is not FDA-approved.