Period Alternating Nystagmus
Patient looks straight ahead: spontaneous nystagmus, mainly horizontally to the left. 40 seconds: Changing of direction: nystagmus is now beating to the right. Intensity increases when the patient looks to the right (1 minute 5 seconds) and decreases when the patient looks to the left according to Alexander’s law. No significant change of intensity when the patient looks upward and downward (1 minute 30 seconds).