Trigeminal Neuralgia

Trigeminal neuralgia is a facial pain syndrome consisting of brief duration electric shock like pains affecting (usually) one side of the face). It typically responds to anti-epileptic medications such as carbamazapine (Tegretol).

Many other causes for facial pain exist, and the diagnosis of trigeminal neuralgia rests upon a “clinical” diagnosis by an expert- there is no scan or blood test that can make the diagnosis.

Dr Jonker has a special interest in surgery for trigeminal neuralgia and regularly performs treatment for this condition including microvascular decompression, percutaneous rhizotomy and stereotactic radiosurgery (see below for more detail on these techniques).

After your procedure is performed a plan will be made for gradually reducing your medication. Most patients stop all medication around 1 month after surgery.

Treatment consists of an initial assessment, to determine whether surgery is appropriate and which technique might be suitable. Additional scans may need to be obtained at this point. Sometimes adjustments to medication are initially more appropriate than surgery. The most common procedure recommended is microvascular decompression (MVD).

Trigeminal Nerve

The brain has 12 “cranial nerves” which arise directly from the brain rather than the spinal cord. The fifth nerve is called the trigeminal nerve and is mainly concerned with sensation (feeling) on the face. Note that facial movement is controlled by a different nerve (the facial nerve). There are three main divisions (hence trigeminal) and these join together within the skull before moving back as a main trigeminal nerve into the brainstem.

Causes

Most trigeminal neuralgia is caused by a small blood vessel (usually an artery but sometimes a vein) compressing the trigeminal nerve at the area where it is entering the brainstem. This interferes with the myelin insulation of the nerve fibres and allows the production of abnormal electrical activity within these pain fibres.

Less commonly the insulation is damaged by multiple sclerosis, a stroke, a tumour or other causes.

Imaging

High quality MRI at 3 Tesla field strength is used to look for arterial or venous compression of the trigeminal nerve. This test can be very important at predicting which patients will respond to surgery, and also whether other unexpected causes such as multiple sclerosis are present. The quality of this MRI needs to be very high, and it may need to be repeated if you have already had an MRI done but it is not of sufficient quality.

Treatment

Initial treatment is usually with the anticonvulsant medications. It is unusual for genuine trigeminal neuralgia to fail to respond to these medications, however sometimes the response is incomplete or quite commonly the doses of medications required can lead to side effects such as “feeling like a zombie” or being unsteady on your feet.

Surgery is an option in patients with moderate to severe symptoms or medication side effects.

Microvascular Decompression (MVD)

The main surgical procedure is called “microvascular decompression” and involves making a small opening in the skull behind the ear and then moving the offending blood vessel away from the trigeminal nerve, and keeping it tucked out of the way using a teflon patch. This remarkable and elegant operation has an 85% success rate of getting people pain free and off all their medications and is the treatment of choice for most people undergoing surgery. It involves a hospital stay of approximately 3-5 days in most patients and a 6 week recovery period. Note that IF the insulation damage to the nerve is NOT caused by blood vessel compression, but rather by multiple sclerosis or a stroke, then this procedure does not usually provide durable relief and other techniques are recommended.

Percutaneous Rhizotomy (balloon, radiofrequency, glycerol)

Other options for treatment focus on causing a degree of intentional interference with the trigeminal nerve’s function by compressing, heating or exposing the nerve to chemical (each of these 3 methods is called percutaneous trigeminal rhizotomy) or by using pinpoint radiation on the nerve (stereotactic radiosurgery). When these techniques are used they too can be dramatically successful, but there tends to be a trade off in that some numbness in the face will be produced by these treatments.

The percutaneous trigeminal rhizotomy procedure is performed as day surgery and is minimally invasive requiring only a needle through the cheek. Dr Jonker generally uses a balloon technique.

Stereotactic Radiosurgery (SRS)

Stereotactic radiosurgery is the least invasive of the options and consists of a pinpoint dose of radiation applied to the nerve by multiple external beams. No anaesthetic or incision is required. This is delivered in a single session lasting around 45 minutes. It requires a high degree of precision, and accuracy within 1/2 a millimetre (1/20th of a centimetre!) is required in each of the 3 positional planes. This technique can take an average of 2-4 weeks to become effective. Facial numbness occurs in only one quarter of patients, but these patients also have the benefit of the most durable response to this technique- so some numbness is not necessarily a bad thing. A number of modified conventional radiotherapy machines can be used to perform stereotactic radiosurgery, as well as dedicated radiosurgery treatment platforms which include Novalis Tx, Gamma Knife, and CyberKnife.

Duration of effect

Each of the procedures is associated with a recurrence rate over time. With MVD this is very low, however it is more common for the pain to eventually come back with percutaneous rhizotomy and stereotactic radiosurgery. These procedures can be repeated if required.

Complications

A detailed discussion of potential complications will take place if you are considering or are recommended surgery.

Microvascular decompression is not associated with any “expected” complications, however there is a very small risk of serious complications, including hearing loss in the ear on that side, as well as meningitis and a remote risk of stroke.

Percutaneous rhiztomy is a very effective and safe procedure- however a degree of numbness on the face is expected after a successful procedure. Rarely, percutaneous rhizotomy (and possibly radiosurgery) are subject to a particular risk in that if too much numbness is caused (usually after repeating the procedure multiple times) then a constant facial pain associated with numbness can be caused. This is caused anaesthesia dolorosa and is somewhat analagous to the phantom limb pain experienced by amputees. It is thus highly recommended that the person performing these procedures be experienced in knowing how much numbness to produce, and which patients are suitable and which are unsuitable.

Radiosurgery has had very few complications described other than some expected facial numbness in some patients.

 

Neurosurgical Conditions