The Heimann-Bielschowsky phenomenon after optic neuritis.

A 32-year-old woman with relapsing-remitting multiple sclerosis and a right optic neuritis with incomplete remission presented with unique neuro-ophthalmologic abnormality consisting of a spontaneous, pendular, vertical movement of the right eye consistent with the Heimann-Bielschowsky phenomenon (HBP). This rare form of dissociated nystagmus probably reflects a "dual abnormality mechanism" comprising the coexistence of an asymmetric conduction delay in the optic nerve and a strategic network disruption in brainstem gaze holding centres. For the clinician it is important to recognize this rare neuro-ophthalmologic syndrome and be aware of its benign nature.