Anyone who has experienced toothaches, blocked sinuses, earaches, corneal scratches or migraine headaches knows that pain arising from any part of the head can be severe. Head pain is transmitted to the brain through the fifth of twelve pairs of cranial nerves at the base of the brain, named the trigeminal nerves. The worst head pain of all is the result of one or the other of these nerves misfiring, a condition known as trigeminal neuralgia, in which hundreds of episodes a day of lightning like spasms of pain on one side of the face are triggered by trivial touch or movement or by nothing identifiable. The pain is severe enough to bring sufferers to their knees and to cause more than a few to say that if it persisted they would have to commit suicide. The famous painting, The Scream, by Norwegian artist Edvard Munch, has been called a visual representation of the agony caused by trigeminal neuralgia.
Symptoms of trigeminal neuralgia are almost always one-sided. Spasms of facial pain are brief and explosive and described as stabbing, electrical, or like being stuck with an ice pick. Episodes can last for weeks or months, and then disappear not to return, or they may return in similar fashion, without warning, months or years later. Pain bouts may also become chronic and associated with other duller, longer lasting pain in the same area of the face. Because light touch and facial movements such as chewing and talking can trigger pain, patients avoid eating, lose weight, become depressed and socially withdrawn and look disheveled from avoiding skin care and shaving.
Why does it happen?
About 150,000 new cases of trigeminal neuralgia are diagnosed in the US every year, more often in women than men and usually over age 60. The ailment can appear in younger people, most often in conjunction with multiple sclerosis. As long ago as the eleventh century, an Arab physician, Jujani, suggested that a blood vessel in the head, near the nerve that served the face, caused spasmodic facial pain and anxiety, a prescient notion since one of the few risk factors for trigeminal neuralgia is high blood pressure. Chronic high blood pressure distorts and hardens arteries, and one of the most effective treatments of trigeminal neuralgia in modern times has been to pad the nerve, protecting it from the pounding of an overlying artery.
Bolstering Jujani’s theory, pathological examinations of trigeminal nerves have shown evidence of damage and repair to the sheaths surrounding individual nerve fibers, suggesting that pressure from a nearby artery or vein, causes intermittent, reversible damage. The association of trigeminal neuralgia with multiple sclerosis, an inflammatory disease which also causes myelin sheath damage, lends weight to the idea that stripping sensory nerve fibers of their myelin sheaths somehow causes them to be irritable and misfire. There is no specific test for trigeminal neuralgia, which can be diagnosed from the clinical history alone. However, sometimes CT and MRI scans are done to rule out tumors irritating the trigeminal nerve, or to look for evidence of demyelinating diseases like multiple sclerosis or other autoimmune problems. Spinal fluid analysis might be added a search for inflammatory or demyelinating marker proteins and cells.
Other conditions may produce shooting head pains. One is glossopharyngeal neuralgia, coming from irritation of a different cranial nerve and causing pain deep in the throat and ear. It is much rarer than trigeminal neuralgia, but medical treatments are similar. Another is occipital neuralgia which comes from compression of a nerve in the upper neck, at the base of the skull. This painful condition is associated with poor posture, trauma or arthritic changes. Occipital neuralgia presents itself as stabbing or shooting pains, as well as duller aching pain and general headaches in the back and sides of the head, and at times behind the eyes. Temporomandibular joint problems (the joint that hinges the jaw to the skull) may also cause shooting pain in the side of the face, along with jaw pain and locking.
The first effective treatment of trigeminal neuralgia was based on the concept of nerve cell irritability, with the use of drugs that treated seizures, first introduced in the mid-1900s. Though not perfect, these drugs continue to provide significant relief for the majority of trigeminal neuralgia sufferers. In addition, many attempts have been made to change the input of the trigeminal nerve to the brain physically by cutting it or injecting it with chemicals that deaden it. This treatment is called neuro-ablative surgery and the relief obtained is in direct proportion to the amount of numbness in the face caused by deliberately damaging the nerve. The more numbness, the better the pain relief. However, for some people, persistent facial numbness or unpleasant sensations are almost as intolerable as the pain, so numerous variations on such procedures have been tried. There are few controlled studies of outcome. Gamma knife surgery is the latest method. Symptoms recur within three years in 20-60% of patients, in inverse proportion to the amount of numbness produced by this deliberate nerve damage.
Microvascular decompression surgery (MVD), as mentioned above, is the most effective surgical procedure for trigeminal neuralgia. It involves opening the skull and placing a Teflon felt pad between the trigeminal nerve and the blood vessel that lies atop it, just where the nerve enters the brain stem. In experienced hands MVD produces immediate pain relief in over 90% of cases, with relief sustained for a decade or more in over 2/3 of them. Though many patients would rather try this or other surgical procedures than be dependent on anticonvulsant drugs, they must carefully weigh the risks, which are those of general anesthesia and of opening the cranial cavity, infection and damage to delicate neural structures chief among the possibilities. Procedures such as these should be done in centers where experience levels of all involved are demonstrable.
All the pains we suffer are reminders that our exquisitely complicated pain networks exist to guard the body, particularly the head and the brain within, against damage from the environment. Like every other part of the body, the pain systems can go awry, making life very difficult, but this is nature’s trade-off since life without pain is more dangerous. In conditions like trigeminal neuralgia we are left to try to understand the cause and to intervene as best we can without causing harm.