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Atypical trigeminal neuralgia (ATN) is a rare disorder of cranial nerve V (CN V), characterized by facial pain that has a constant or fluctuating timing, with heavy, aching, burning, or boring quality. It is hard to distinguish it from classic trigeminal neuralgia or tic douloureux because the latter is also characterized by intense facial pain in the cranial nerve V or trigeminal distribution. Sometimes, atypical neuralgia is mistaken for migraine, hypochondriasis, or temporomandibular joint disorder. Medications for typical trigeminal neuralgia may provide relief from pain.
Cranial nerve V is the largest nerve in the face that transmits signals for different sensations including pain, heat, and pressure. When the trigeminal nerve becomes irritated a condition called trigeminal neuralgia results, manifesting as intense, electric shock-like, or stabbing pain on one side of the face, particularly on the jaw and the lower face. In classic or typical trigeminal neuralgia, the trigeminal nerve pain comes in spasms or attacks that usually last several seconds and do not radiate. Classic trigeminal pain is stimulated when facial “trigger points” are touched and is characterized by painless periods called remissions. When a person goes to the doctor complaining of facial pain that does not completely correspond to the characteristics of classic trigeminal neuralgia, a diagnosis of atypical trigeminal neuralgia or type 2 trigeminal neuralgia is given.
Atypical trigeminal neuralgia pain may be squeezing or burning, rather than electric shock-like or lancinating. Additionally, the pain from this trigeminal neuralgia variant may be constant or continuous, and the patient rarely has periods of remission. Some people who have atypical trigeminal neuralgia complain of constant migraine or pain in the entire face. This pain is aggravated by facial movements such as chewing, talking, and smiling, and sometimes by cold sensations. The constancy of excruciating pain has driven some people with ATN to commit suicide, thereby giving ATN the moniker “the suicide disease.”
The underlying mechanisms of ATN are inflammation of the nerve, destruction of the myelin sheath, and subsequent increase in the sensitivity of CN V. These mechanisms can result from different conditions including a tumor or a malformed blood vessel compressing the nerve, infection, dental procedures, and demyelinating diseases like multiple sclerosis. Some have hypothesized that ATN is secondary to a compression of a part of CN V called portio minor, but others believe that it is a more severe or progressive form of typical trigeminal neuralgia.
Partial relief for atypical trigeminal neuralgia may be obtained from medications used for its classic counterpart. These medications, which include anticonvulsants such as carbamazepine and lamotrigine, anesthetics such as lidocaine, and antidepressants such as amytriptiline, are deemed useful because they provide relief for neuropathic pain. Surgical decompression of the nerve may be curative. It is important to be able to control the pain using these modalities because atypical trigeminal neuralgia can lead to depression and reduce the affected person’s quality of life.