What is Craniofacial Pain Syndrome?
The most common craniofacial pain syndrome is trigeminal neuralgia (“TMJ,” jaw joint pain or tic douloureux). Trigeminal neuralgia is a facial pain syndrome that usually develops in individuals over 50 years old. Its incidence is 4/100,000, and it is the most common facial pain sydrome in this age group.
Other neuropathic syndromes affect the trigeminal nerve and warrant different treatments with varied rates of success. Rarely, neuralgias of other cranial nerves mimic trigeminal neuralgia. Finally, it is essential to distinguish atypical facial pains from these neuropathic syndromes to avoid unsuccessful therapies.
Causes are uncertain, but there is considerable evidence that vascular compression of a nerve root is the cause. This may be due to branches of the superior cerebellar artery, basilar artery, or local veins compressing the trigeminal nerve root. In younger patients, trigeminal neuralgia can be caused by tumors in the region of cranial nerve V or (more commonly) by multiple sclerosis. These entities must therefore be ruled out.
Although the diagnosis remains based exclusively on history and symptomatology, modern diagnostic techniques, particularly high-resolution magnetic resonance imaging, provides valuable new insight into the pathophysiology of these cases with additional implications for therapeutic strategies.
Imaging studies, CT or MRI, with and without contrast enhancement, are normally performed on every patient with trigeminal neuralgia. Often, elongated and tortuous vessels can be seen and tumors of the region need to be excluded as a cause for the syndrome.
The character of classical trigeminal neuralgia is “electric-like shocks” lasting a few seconds but of a debilitating, intense nature. They are usually on one side of the face, most often in the area of the upper cheek down to the level of the jaw, the maxillary (V2) and mandibular (V3) branches of the trigeminal nerve.
The ophthalmic division (V1), transmitting sensation from the skin of the forehead and the eye, is less commonly involved. The trigeminal nerve is also known as cranial nerve V. It transmits sensation from the face, eyes and teeth and controls the muscles of mastication (chewing).
Painful attacks may occur spontaneously but are more often associated with a specific stimulus in a “trigger area.” Common trigger points are the eyebrow for ophthalmic division pain, the upper lip for maxillary division involvement, and the lower molar teeth for mandibular division pain.
Sensory stimuli by touch, cold, wind, talking or chewing can precipate the attacks. Pain-free intervals last for minutes to weeks, but long-term spontaneous remission is rare. The attacks cease during sleep but often occur upon arising in the morning. This constellation of symptoms provides the diagnosis.
The primary treatment of trigeminal neuralgia is pharmacological. Most patients obtain relief, at least initially, within 30 minutes of administration of carbamazepine (Tegretol). This drug does have side effects — mostly bone marrow depression and liver damage — and patients should be monitored by their physician. Some individuals may also respond to phenytoin (Dilantin).
After pharmacologic failure, surgical intervention is necessary. Surgical options include blocking the trigger point with local blocks, neurectomy — block of the nerve branches, percutaneous rhizotomy of the trigeminal ganglion (destruction of the site of sensory nerve cell bodies just inside the skull and dura), and microvascular decompression of the nerve root zone.
Decisions on which treatment is best for a given patient must be based on the nature of the pain, the health of the patient, imaging findings and consultation with the neurosurgeon.