Abstract

Three-dimensional eye rotations were measured using the magnetic search coil technique, in a patient with a right rostral interstitial nucleus of the medial longitudinal fasciculus (RIMLF) lesion and four control subjects. Up to 10 deg contralesional torsional deviations with each voluntary saccade were revealed, which also could be seen during bedside examination. There was no spontaneous nystagmus. Based on MRI criteria the lesion involved RIMLF but spared the interstitial nucleus of Cajal (INC). This deficit has so far not been described in patients. Our results also support the hypothesis that the vertical-torsional saccade generator in humans is organized similarly as in monkeys: each RIMLF encodes torsional saccades in one direction, while both participate in vertical saccades.