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What is trigeminal neuralgia?
What causes trigeminal neuralgia?
How is trigeminal neuralgia diagnosed?
How is trigeminal neuralgia treated?
Trigeminal neuralgia (also known as tic douloureux or neuropathic facial pain) is a condition that is characterized by episodes of sharp, lancinating, and shock-like stabs of pain in the face which last a few seconds. The pain is generally experienced only on one side of the face, and it may be elicited by a variety of factors such as shaving, chewing, smiling, brushing teeth, or touching the skin of the face. There is usually no associated numbness or weakness of the face with trigeminal neuralgia.
What causes trigeminal neuralgia?
Trigeminal neuralgia is caused by compression of the trigeminal nerve which is the nerve that supplies sensation to the face. The source of compression in 90% of cases is a small normal artery or vein located at the point where the nerve joins the brainstem. Over time, the pulsatile flow of blood within the artery will cause it to bump against the nerve which leads to damage to the covering around the nerve, causing it to fire abnormally which is experienced as painful electric-like shocks. Although very rare, sometimes a small tumor in the vicinity of the nerve can also lead to symptoms due to nerve compression, while other patients may experience this type of facial pain as a result of underlying multiple sclerosis which leads to an inflammatory response within the trigeminal nerve, causing pain.
How is trigeminal neuralgia diagnosed?
The diagnosis is usually made by obtaining a thorough history and performing a complete neurological examination, which will exclude most, if not all, other possible conditions. The neurologic exam should also involve an attempt to reproduce the pain by touching the trigger point. Once the diagnosis of trigeminal neuralgia is made magnetic resonance imaging (MRI) of the brain should be performed in order to rule out a tumor as the cause of the pain. While the offending blood vessel may be seen in the vicinity of the trigeminal nerve on the MRI, this is often not the case.
How is trigeminal neuralgia treated?
There is a variety of treatments available for the management of trigeminal neuralgia which includes medical and surgical options
Anticonvulsant medications, such as carbamazepine, are the first line of treatment for trigeminal neuralgia. This drug can provide complete or satisfactory relief of pain in as many as 70% of patients; and , while other anticonvulsants may be tried, they have not been found to be as effective. Side effects of this medication include drowsiness, dizziness, decreased white blood cell count, and toxicity to the liver toxicity. When oral medication fails to control the pain, several surgical and non-operative methods may be pursued, which are listed below.
Glycerol injection is a procedure where the chemical, glycerol, is injected into a portion of the trigeminal nerve, called the gasserian ganglion, by insertion of a long needle through the skin. This is a simple and effective treatment which only takes a few minutes, and can be done on an outpatient basis. As many as 85% of patients may achieve immediate pain relief; however, the failure rate over time is relatively high and nearly 50% of patients will have recurrence of their symptoms after 3 to 4 years. The procedure may be repeated in such cases, but glycerol become less effective after several injections are performed.
Radiofrequency rhizotomy is a similar procedure to glycerol injection, where a needle is introduced through the skin into the nerve; however, instead of an injection, a high frequency (radiofrequency) current is used to heat the tip of the needle which will selectively destroy pain nerve fibers. Although this procedure tends to preserve the nerve fibers that supply normal sensation to the face, some patient may experience loss of sensation to all or a portion of their face. About 98% of individuals have a good immediate response to this procedure; but about 20% of patients will have a recurrence of symptoms after a few years.
Balloon compression of the gasserian ganglion is another minimally invasive procedure where a small balloon catheter is introduced through a needle into the trigeminal nerve. The balloon is then briefly inflated in order to compress the nerve, after which the balloon is deflated and removed. This procedure leads to initial pain relief in about 93% of patients, but similar to the other two procedures mentioned above, it has a high recurrence rate (about 20% over a few years). Another unfavorable side effect of this procedure is numbness in the face, which may be experienced by as many as 72% of patients.
Stereotactic radiosurgery, unlike the name suggests, is not an actual surgery. Instead, it is a type of radiation treatment where beams of radiation are focused with great accuracy onto the portion of the trigeminal nerve that is closest to the brainstem. This, over time, will lead to excellent pain relief in as many as 58% of patients; another 36% of individuals experience good (but not complete) pain relief; and the remaining 6% will feel no improvement in their pain at all. Transient facial numbness can occur but is generally rare, and the long term recurrence rates are unknown. This treatment is a suitable alternative to anticonvulsant therapy and compares favorably to other treatments.
Microvascular decompression is a surgical procedure where, under general anesthesia, a small window of bone is removed from behind the ear to gain access to the portion of the brainstem where the trigeminal nerve is located. Then, under the microscope, the blood vessel that is pressing on the nerve is identified and moved away from the nerve, after which a soft cushion is placed between the nerve and the blood vessel in order to keep them apart. Initial pain relief is seen in 83% of patients with a 10-year recurrence rate of about 15%. Rare complications of this procedure include facial numbness, deafness, face weakness, and cerebrospinal leak.
