Skew deviation following vestibular nerve surgery

Eighteen consecutive patients undergoing vestibular nerve surgery underwent pre‐ and postoperative examination of ocular motility. Five patients developed a skew deviation following surgery, with the lower eye on the operated side and an incomitant pattern of deviation in all cases. Three patients experienced diplopia lasting from 1 day to 6 months. The magnitude of skew deviation was increased by head tilt away from the operated side in only 1 case. The development of skew deviation was not determined by preoperative ocular alignment or binocular function, or any particular type or pattern of vestibular disease. There was an association with large changes in ocular torsion and subjective visual vertical, which correlated with lesser degrees of canal paresis to preoperative caloric testing on the operated side. No patient developed a head tilt postoperatively. There is a gradation of responses to surgical vestibular deafferentation in humans, skew deviation only occurring in patients suffering marked changes in subjective visual vertical and ocular torsion.