Peripheral Lesion with Direction-Fixed Nystagmus

Typical spontaneous nystagmus associated with acute peripheral vestibular lesions is dominantly horizontal in vector and generally beats in one direction regardless of the eye position within the orbits. The nystagmus is usually present in the primary position, increases in gaze toward the direction of the fast phase, and decreases or disappears completely in gaze toward the direction of the slow phase. This pattern of vestibular nystagmus is said to obey "Alexander's law" (Video 2a-direction-fixed left-beating nystagmus in a patient with acute peripheral vestibulopathy). Disease/Diagnosis: Nystagmus.