Trigeminal neuralgia affects mainly adults, especially the elderly. It is more common among women.
Trigeminal neuralgia is usually caused by:
- Compression by an intracranial artery (eg, anterior inferior cerebellar artery, ectatic basilar artery)
- Less often, a venous loop that compresses the 5th cranial (trigeminal) nerve at its root entry zone into the brain stem
Other less common causes include compression by a tumor and occasionally a multiple sclerosis plaque at the root entry zone (usually in younger patients), but these causes are usually distinguished by accompanying sensory and other deficits.
Other disorders that cause similar symptoms (eg, multiple sclerosis) are sometimes considered to be trigeminal neuralgia and sometimes not. Recognizing the cause is what is important.
The mechanism is unclear. One theory suggests that nerve compression causes local demyelination, which may result in ectopic impulse generation and/or disinhibition of central pain pathways involving the spinal trigeminal nucleus.
Symptoms and Signs
Pain occurs along the distribution of one or more sensory divisions of the trigeminal nerve, most often the maxillary. The pain is paroxysmal, lasting seconds up to 2 min, but attacks may recur rapidly. It is lancinating, excruciating, and sometimes incapacitating. Pain is often precipitated by stimulating a facial trigger point (eg, by chewing, brushing the teeth, or smiling). Sleeping on that side of the face is often intolerable.
Usually, only one side of the face is affected.
Diagnosis / Clinical evaluation
Symptoms of trigeminal neuralgia are almost pathognomonic. Thus, some other disorders that cause facial pain can be differentiated clinically:
- Chronic paroxysmal hemicrania (Sjaastad syndrome) is differentiated by longer (5 to 8 min) attacks of pain and its dramatic response to indomethacin.
- Pain is differentiated by its constant duration (without paroxysms), typical antecedent rash, scarring, and predilection for the ophthalmic division.
- Migraines, which may cause atypical facial pain, is differentiated by pain that is more prolonged and often throbbing.
- Sinusitis and odontogenic pain can usually be differentiated by their associated findings (eg, nasal discharge, fever, positional headache, tooth sensitivity).
Neurologic examination is normal in trigeminal neuralgia. Thus, neurologic deficits (usually loss of facial sensation) suggest that the trigeminal neuralgia–like pain is caused by another disorder (eg, tumor, stroke, multiple sclerosis plaque, vascular malformation, other lesions that compress the trigeminal nerve or disrupt its brain stem pathways).