PATHOLOGICAL TORSIONAL EYE DEVIATION DURING VOLUNTARY SACCADES - A VIOLATION OF LISTINGS LAW

Background-Under normal conditions, there are no torsional eye movemen ts during voluntary saccades when the head is stationary (Listing's la w). Methods and results-Using dual search coils for three dimensional eye movement recordings, a patient is reported who had direction speci fic rapid deviations of torsional eye position (up to 10.5 degrees) du ring voluntary saccades followed by a slow exponential torsional drift after the end of the saccade (''blip'') towards the initial torsional eye position. In the absence of spontaneous nystagmus, this transient torsion means a violation of Listing's law for voluntary saccades and was associated with a lesion involving the cerebellar vermis, its dee p nuclei, and the dorsolateral medulla. Amplitudes of the blip were la rger for ipsilesional (hypermetric) than contralesional (hypometric) h orizontal saccades. For comparison transient torsion, during and after saccades was also examined in six normal subjects. Using the same in vivo calibration, there were no blips larger than 1.2 degrees in any o f them. Conclusion-Transient torsion with large amplitudes can be clin ically seen on bedside examination and might thus be a new clinical si gn in the diagnosis of saccadic disorders.