Electrophysiologic study of Fisher syndrome

Electrophysiologic studies were performed on a 6-year-old girl with Fisher syndrome. We recorded several evoked potentials in this patient: visual evoked potentials, auditory brainstem responses, auditory evoked potentials, short-latency somatosensory evoked potentials, blink reflex elicited by photic stimuli (photo-evoked eyelid microvibration), blink reflex elicited by auditory stimuli (auditory evoked eyelid microvibration), and motor nerve conduction velocity. In our study, photo-evoked eyelid microvibration response was not obtainable; laterality was indicated in visual evoked potential and electroencephalographic studies, and the remaining evoked potentials demonstrated normal responses. The results obtained from the brainstem reflex (photo-evoked eyelid microvibration) suggest that the pathologic focus of Fisher syndrome is located in the midbrain, particularly in the pretectum. It is expected that the combined use of these electrophysiologic techniques may facilitate differentiation between Fisher and Guillain-Barré syndromes.