Trigeminal Neuralgia in Emergency Medicine
- Author: J Stephen Huff, MD; Chief Editor: Rick Kulkarni, MD more...
Background
Trigeminal neuralgia (TN), also known as tic douloureux, is a pain syndrome often recognizable by the patient's history. Trigeminal neuralgia is characterized by facial pain often accompanied by a brief facial spasm or tic. Pain distribution is unilateral and follows the sensory distribution of cranial nerve V, typically radiating to the maxillary (V2) or mandibular (V3) area. At times, both distributions are affected. Physical examination will usually eliminate alternative diagnoses. Signs of cranial nerve dysfunction or other neurologic abnormality exclude the diagnosis of classic trigeminal neuralgia and suggest that pain may be secondary to a structural lesion. Nomenclature is nonintuitive. Classic trigeminal neuralgia includes all cases without established etiology after investigation, as well as those with potential microvascular compression of the fifth cranial nerve. In symptomatic trigeminal neuralgia, the pain syndrome is secondary to tumor, multiple sclerosis, orother structural abnormalities.[1]
Pathophysiology
The mechanism of pain production remains controversial. One theory suggests that peripheral injury or disease of the trigeminal nerve increases afferent firing in the nerve; failure of central inhibitory mechanisms may be involved as well. Pain is perceived when nociceptive neurons in a trigeminal nucleus involve thalamic relay neurons. An abnormal vascular course of the superior cerebellar artery is often cited as the cause, as well as other small arteries or veins compressing the facial nerve. In about 85% of cases, no lesion is identified, even after extensive investigations, and the etiology is labeled idiopathic by default.
Aneurysms, tumors, chronic meningeal inflammation, or other lesions may irritate trigeminal nerve roots along the pons, causing symptomatic trigeminal neuralgia. Uncommonly, an area of demyelination from multiple sclerosis may be the precipitant. Lesions of the entry zone of the trigeminal roots within the pons may cause a similar pain syndrome.
An area of demyelination is shown in the image below.
Microscopic demonstration of demyelination in primary trigeminal neuralgia. A tortuous axon is surrounded by abnormally discontinuous myelin. Electron microscope, 3, 300 X. Infrequently, adjacent dental fillings composed of dissimilar metals may trigger attacks,[2] and an atypical case has been reported following tongue piercing. A case report of trigeminal neuralgia in a patient with spontaneous intracranial hypotension has been reported; both conditions resolved following surgical treatment of a cervical root sleeve dural defect.[3]
Epidemiology
Frequency
International
Trigeminal neuralgia (TN) is uncommon, with an estimated prevalence of 155 cases per million persons.
Mortality/Morbidity
- No mortality is associated with idiopathic trigeminal neuralgia (TN), although secondary depression is common if a chronic pain syndrome evolves. In rare cases, pain may be so frequent that oral nutrition is impaired.
- In symptomatic or secondary trigeminal neuralgia, morbidity or mortality relates to the underlying cause of the pain syndrome.
Sex
The male-to-female ratio is 2:3.
Age
Development of trigeminal neuralgia in a young person suggests the possibility of multiple sclerosis.
- Idiopathic trigeminal neuralgia typically occurs in patients in the sixth decade of life, but it may occur at any age.
- Symptomatic or secondary trigeminal neuralgia tends to occur in younger patients.
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