Approach
Trigeminal neuralgia (TN) is a clinical diagnosis. Distinguishing between classical trigeminal neuralgia, secondary trigeminal neuralgia, and idiopathic trigeminal neuralgia is done through history taking, clinical exam (to identify nontrigeminal neurologic signs), and neuroimaging.
History
Typical history is of stereotyped, unilateral paroxysms of facial pain lasting seconds to minutes in a distribution along ≥1 divisions of the trigeminal nerve. Bilateral or side-alternating pain is rare and should raise suspicion of an underlying disorder.[2] The pain associated with TN is typically described as intense, sharp, superficial, stabbing, or burning in quality. Triggers such as tooth brushing, eating, cold, and touch are common. Although most patients are asymptomatic between episodes and do not complain of neurologic deficit, the intensity of attacks keeps patients continually fearful of repeat attacks. An important component of history taking in these patients involves the attempt to elicit information that supports differential diagnoses, such as a history of prior oropharyngeal or facial trauma, previous herpes zoster infections, or symptoms of rash and facial droop.[19]
Physical exam
Patients with classical TN should have a completely unremarkable physical and neurologic exam. Important components of the physical exam needed to rule out other facial pain syndromes include exam of dentition and oropharynx, assessment of temporomandibular joint function, skin exam, palpation of temporal arteries, and full neurologic exam with particular focus on facial sensory exam. Sensory changes on neurologic exam are suggestive of secondary TN.
Tests
Classical TN is a clinical diagnosis. Some guidelines recommend that magnetic resonance imaging (MRI) should be performed for all patients; no clinical characteristic can reliably exclude secondary TN.[20][21][22] Measuring trigeminal reflexes in a qualified electrophysiological laboratory can be used for distinguishing secondary TN from classical or idiopathic TN if MRI is contraindicated or unavailable.[20][22]
Imaging tests that can be used to exclude other causes of trigeminal distribution pain include intraoral radiographs if pain appears to be of dental origin.
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