Trigeminal Neuralgia

The exact cause of trigeminal neuralgia is not fully understood; however, hypothesized causes depend on the subtype. For example, it is postulated that the compression of the trigeminal nerve causes classic trigeminal neuralgia by a vascular structure (e.g., vein or artery) where it enters the brainstem. Compression of the nerve leads to  demyelination, or loss of the myelin sheath, of the nerve fibers. Damage to the myelin sheath, which is responsible for insulating nerve cells and fibers, results in increased electrical activity in the trigeminal nerve, thereby triggering pain. Conversely, secondary trigeminal neuralgia may be idiopathic, where the cause is unknown, or due to another underlying medical cause (e.g., multiple sclerosis). It may also occur due to nerve compression by a non-vascular structure, such as a tumor or a cyst.  

Risk factors for the development of trigeminal neuralgia include biological sex, with those born as female more likely to develop the disorder; advanced age, specifically those 50 to 60 years of age; the presence of underlying demyelinating disorders, such as multiple sclerosis; herpes simplex virus infection; acoustic neuroma; saccular aneurysm; and vestibular schwannoma.

The signs and symptoms of trigeminal neuralgia include extreme pain that occurs spontaneously and is exacerbated with touching or moving the tongue, lips, and face. The primary form of trigeminal neuralgia is characterized by severe pain described as intense, sharp, stabbing, and shooting. The individual may report that it feels like a lightning bolt has struck their face or they have suffered an electric shock. The pain is paroxysmal, accompanied by redness and warmth (i.e., flushing), lasts one to several seconds, and is intermittent throughout the day. In between the episodes of sharp pain, the individual may have pain-free periods or dull, constant pain that lasts approximately one to two minutes. In addition to pain, there may be autonomic symptoms, such as lacrimation, conjunctival injection, excessive salivation, and rhinorrhea.  In most cases, the pain and autonomic symptoms are isolated to one side of the face. The pain may worsen with mild tactile stimuli, such as chewing, brushing the teeth, shaving facial hair, blowing one’s nose, and drinking hot or cold drinks. 

The frequency and severity of trigeminal neuralgia can vary among individuals. One individual may have multiple attacks in one day, whereas another may have only one episode every month.  However, the pain tends to worsen with fewer pain-free periods over time. If untreated, trigeminal neuralgia can profoundly affect an individual’s quality of life and has been shown to cause profound psychological effects, such as depression and anxiety.

While trigeminal neuralgia type II is characterized by a less intense pain, typically described as constant, dull, aching, or burning, it can also occur in conjunction with the classic form. Type II trigeminal neuralgia also tends to affect a more widespread portion of the face (e.g., extending across the entire half of the face rather than remaining in the lower jaw). 

Trigeminal neuralgia is diagnosed using physical examination and obtaining a thorough medical history. This involves assessing for signs of neurological deficit, such as extremity weakness, which can make other diagnoses, such as stroke, more likely. Often, trigeminal neuralgia is referred to as a disease of exclusion; therefore, other potential causes are ruled out before diagnosis. Often, trigeminal neuralgia is referred to as a disease of exclusion; therefore, other potential causes are ruled out before diagnosis. Often, trigeminal neuralgia is referred to as a disease of exclusion; therefore, other possible causes are ruled out before diagnosis. 

Suppose there is no clinical evidence of neurological deficit and no better explanation for facial pain. In that case, two criteria may be used to determine if the individual has trigeminal neuralgia. Criteria A states that the pain occurs in one or more trigeminal nerve divisions (V1-V3), and there is no radiation of pain beyond these divisions. Criteria B says that the pain has three or more of the following four characteristics: recurring paroxysmal attacks less than two minutes in duration; the severe intensity of pain; pain is shock-like, shooting, stabbing, and sharp; and stimulating the affected side of the face results in at least two attacks. To successfully diagnose trigeminal neuralgia, the individual must meet criteria A and B on at least three separate occasions. 

Trigeminal neuralgia is treated using medications such as carbamazepine, commonly used as an anticonvulsant drug, but has shown efficacy in treating the pain associated with trigeminal neuralgia. It is most effective when used early in the disease course, and most individuals begin with a low dose that gradually increases until the pain dissipates. Other medications with reported efficacy in trigeminal neuralgia include oxcarbazepine, baclofen, and lamotrigine.

Surgical treatments can also provide long-term pain relief, especially if the pain is refractory to medications. Microvascular decompression, also known as the Janetta procedure, can be used to cure trigeminal neuralgia secondary to blood vessel compression. The surgeon will typically make an incision behind the ear on the side of the symptoms, then create a small hole in the skull. The blood vessels pressing on the trigeminal nerve are then moved away, and a pad is placed between the nerve and arteries to prevent future compression. Another possible treatment is stereotactic surgery, which includes procedures known as gamma knife and cyberknife. A concentrated beam of ionizing radiation is used to destroy the trigeminal ganglion or roots, preventing transmission of pain.