A flowchart approach to nystagmus/intrusions

In tandem with the flowchart, the following added clues should be used to help with etiology: i) vector [horizontal, vertical, torsional]; ii) binocular or monocular; iii) spontaneous or provoked [e.g., BPPV]; iv) change with monocular viewing or gaze direction; v) rest of history, neurologic, and ocular motor exam. For example, peripheral vestibular nystagmus is classically unidirectional, horizontal or horizontal-torsional, and increases with patient looking in the direction of the fast phase (i.e., obeys Alexander's law), though this pattern can also have a central localization. Conversely, pure torsional or pure vertical nystagmus should raise suspicion for a central cause. As an alternate example, latent nystagmus is one of the few kinds of nystagmus that changes with the viewing eye (e.g., left-beating with left eye viewing and right-beating with right eye viewing). Infantile nystagmus and nystagmus due to vision loss can have either a jerk OR a pendular waveform and thus are presented here under both categories. Macro square wave jerks (SWJs) differ from SWJs in that macro-SWJs have amplitude greater than about 50 degrees.