Trigeminal Neuralgia
Ronald Brisman, M.D.

Trigeminal Neuralgia: Diagnosis and Treatment. Perspective Statement. World Neurosurgery, December 2

Brisman R: Trigeminal Neuralgia: Diagnosis and Treatment. World Neurosurgery Volume 76, Issue 6, December 2011, Pages 533-534
http://dx.doi.org/10.1016/j.wneu.2011.06.028
The following is a revised personal version of the text of the final journal article.

Trigeminal neuralgia (or tic douloureux) is a unique and severe form of face pain that neurosurgeons treat when pain is intractable to medical management.

Trigeminal neuralgia is a clinical syndrome characterized by brief electric-like pains (intense, sharp, superficial or stabbing) that may last up to 2 minutes. Pains are usually triggered by light touch about the mouth or face such as with talking, eating, brushing the teeth or washing the face. The pain is unilateral at any one time and is in the trigeminal distribution, usually the second and third divisions, either alone or in combination, or the second and first divisions and infrequently, the first division alone. Periods of spontaneous remission are characteristic.

The pain almost always responds to carbamazepine (Tegretol) or oxcarbazepine (Trileptal) at least initially. If it does not respond, the diagnosis of trigeminal neuralgia should be questioned.

Criteria for the diagnosis of trigeminal neuralgia, essentially as above described, have been formalized by the International Association for the Study of Pain (7) and the International Headache Society (6).

Patients who in addition to paroxysmal triggered pain of typical trigeminal neuralgia have constant unprovoked pain are often diagnosed as having atypical trigeminal neuralgia. Those with only constant and unprovoked pain, often bilateral and not responsive to carbamazepine or oxcarbazepine do not have trigeminal neuralgia but rather atypical facial pain (now called persistent idiopathic facial pain).

A new classification for facial pain has been proposed and is based on information obtained from the patient’s medical history whereby face pain of spontaneous onset that is more than 50 percent episodic (sharp, shooting) is called TN1 and face pain that is more than 50 percent constant is called TN2 (4).

Unfortunately, without clinical data validating TN1 or TN2, some have mistakenly substituted typical trigeminal neuralgia for TN1 and atypical trigeminal neuralgia for TN2. Many patients with typical trigeminal neuralgia will describe their pain as constant (for more than 50 percent of the time or more than 50 percent of the total pain), especially when it is frequent and severe. If asked to hold completely still, however, their pain will subside dramatically and often disappear. Patients with spontaneous face pain that is really constant and not paroxysmal or triggered and not sensitive to carbamazepine or oxcarbazepine usually do not have any kind of trigeminal neuralgia, but rather have persistent idiopathic facial pain.

The precise diagnosis is important regarding the likelihood that the patient will respond to neurosurgical intervention: those with typical trigeminal neuralgia often respond very well; those with atypical trigeminal neuralgia may respond and this is more likely if most of their symptoms are characteristic of typical trigeminal neuralgia; and those with persistent idiopathic facial pain are unlikely to respond.

The clinical symptoms of trigeminal neuralgia are occasionally caused by multiple sclerosis or a brain tumor. Other patients with clinical symptoms of trigeminal neuralgia have idiopathic trigeminal neuralgia that is often caused by a blood vessel compressing the trigeminal nerve in the trigeminal cistern.

High resolution MRI scans (1 mm or less) T1 weighted images with contrast and T2 images will show the cisternal trigeminal nerve very well and will often show a blood vessel near or in contact with the trigeminal nerve. Blood vessel contact is often seen in patients without trigeminal neuralgia but is seen more often with those who have clinical trigeminal neuralgia. However, the MRI does not make the diagnosis of trigeminal neuralgia, which is clinical and is based on a careful history (obtained from the patient by an experienced clinician) and examination. MRI may be helpful when microvascular decompression (MVD) is being considered in that patients who do not have a vessel in contact with the trigeminal nerve (10-24 percent of those with typical trigeminal neuralgia) are less likely to benefit from a pure MVD that does not denervate the trigeminal nerve. MRI, which should include the entire head (although not necessarily at very thin sections), may also be helpful in diagnosing multiple sclerosis, a condition in which vascular compression is unlikely to be the cause of the trigeminal neuralgia and pure MVD unlikely to be the solution. Persistent idiopathic facial pain with or without vascular contact on MRI is not likely to be helped by any kind of neurosurgery.

The anticonvulsants carbamazepine and oxcarbazepine are very helpful in relieving the symptoms of trigeminal neuralgia. Other anticonvulsants such as gabapentin, pregabalin and lamotrigine may be helpful. Less frequently, baclofen, a muscle relaxer, may also relieve pain.

Many patients become resistant to medicines, which have to be used at higher doses often causing unpleasant side-effects. They then become candidates for neurosurgical intervention with either Gamma Knife Radiosurgery (GKRS), needle rhizotomy (radiofrequency electrocoagulation [RFE], glycerol or balloon), or MVD.

Trigeminal denervation relieves the pain of trigeminal neuralgia. The more denervation the longer lasting is pain relief but the chance of unpleasant side effects is increased. GKRS and needle rhizotomy are primarily denervating procedures although the denervation may be mild and not noticeable. MVD is sometimes denervating, especially if the vessel is deforming the nerve, hard to mobilize or not present and purposeful denervation is carried out. However, for a given degree of denervation, an initial MVD is likely to give longer lasting pain relief, 64 percent excellent results after 10 years (1), than purely denervating procedures. MVD has an additional mechanism of pain relief in that it may remove the vascular compression.

In the present issue of World Neurosurgery, Chen and colleagues present a “Long-term Follow-up of Patients Treated with Percutaneous Balloon Compression for Trigeminal Neuralgia in Taiwan (5).” Of 130 patients who completed the study and were followed, 122 had an initially successful operation. The follow up ranged from 8 to 10.1 years. Forty-one patients had recurrent symptoms (pain that required medicines or another procedure) within 7 years; successful relief from one procedure that persisted for at least 7 years occurred in 62 percent (81 of 130) patients. Those treated with 90 seconds of compression did better than those treated with 70 seconds without apparent added complications.

I personally prefer Gamma Knife radiosurgery (GKRS) for most patients who are to be treated with a minimally invasive technique (3) as it is more precise and less invasive than percutaneous balloon compression (PBC). As with PBC, GKRS is rarely associated with corneal denervation, but unlike PBC, GKRS almost never causes trigeminal motor impairment or diplopia. If I use a percutaneous technique, I prefer RFE and/or glycerol for a modest denervation (2) as there are fewer complications (less motor denervation, cheek hematoma or diplopia) than with PBC and general anesthesia is not required. By having RFE and glycerol available at the time of the procedure, the neurosurgeon can use one or the other or both depending on technical circumstances that may develop during the procedure: return of CSF, final location of the needle, response to stimulation and division of preoperative pain.

Percutaneous techniques for treatment of trigeminal neuralgia remain viable options for patients with medically intractable trigeminal neuralgia. The procedures are effective and minimally invasive. PBC is a low cost, low tech option that is readily available.

MVD is more invasive and has a greater likelihood of complications. Patients with medically intractable trigeminal neuralgia who want to forego MVD can be advised that a minimally invasive procedure (needle rhizotomy with balloon, RFE or glycerol or GKRS), perhaps with a repeat procedure for recurrence can be a very satisfactory alternative and does not preclude a subsequent MVD.

REFERENCES:
  1. Barker FG, Jannetta PJ, Bissonette DJ, Larkins MV, Jho HD: The Long-term outcome of microvascular decompression for trigeminal neuralgia. NEJM 334: 1077-1083, 1996.
  2. Brisman R: Retrogasserian glycerol injection with or without radiofrequency electrocoagulation for trigeminal neuralgia. Neurosurgical and Medical Management of Pain: Kluwer, 51-56, 1988.
  3. Brisman R: Gamma knife surgery with a dose of 75 to 76.8 Gray for trigeminal neuralgia. J Neurosurg 100:848-854, 2004.
  4. Burchiel KJ: A new classification for facial pain. Neurosurgery 53:1164-1167, 2003.
  5. Chen JF, Tu PH, Lee ST: Long-term follow-up of patients treated with percutaneous balloon compression for trigeminal neuralgia in Taiwan. World Neurosurgery.
  6. Headache Classification Subcommittee of the International Headache Society. The International Classification of Headache Disorders: 2nd edition. Cephalgia 24 Suppl 1:9-160, 2004.
  7. Merskey H, Bogduk N: Classification of Chronic Pain. Seattle, IASP Press, 1994, ed 2.
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