Adaptations and deficits in the vestibulo-ocular reflex after third nerve palsy.
OBJECTIVE
To analyze the vestibulo-ocular reflex (VOR) in patients with unilateral peripheral third nerve palsy.


METHODS
Ten patients and 15 healthy subjects were studied using magnetic search coils. Subjects made sinusoidal +/-10 degrees head-on-body rotations in yaw, pitch, and roll in darkness and during monocular viewing in light.


RESULTS
Horizontal VOR and visually enhanced VOR (VVOR) gains of the paretic eye were decreased during both abduction and adduction. Vertical VOR and VVOR gains of the paretic eye were decreased during both elevation and depression. Dynamic and static torsional VOR and VVOR gains of the paretic eye were reduced during both excyclotorsion and incyclotorsion. Horizontal, vertical, and torsional VOR and VVOR gains were normal in the nonparetic eye.


CONCLUSIONS
Adducting VOR gains were reduced as anticipated from medial rectus palsy. Abducting gains were also reduced; the reduction is attributed to an adaptive decrease in innervation to the lateral rectus to achieve symmetry of the horizontal VOR in the paretic eye. Torsional VOR gains were reduced during excyclotorsion from palsy of the inferior oblique muscle. Gains were also reduced during incyclotorsion, which can be explained by an adaptive decrease in innervation to the superior oblique to restore symmetry of the torsional VOR in the paretic eye.


CONCLUSIONS
Monocular adaptation in the VOR of the paretic eye reduces asymmetrical movement of retinal images during head motion, prevents nystagmus, and reduces retinal image disparity.
Wong
Agnes M F
AM
Division of Neurology, University Health Network, EC 5-042, Toronto Western Hospital, 399 Bathurst St, Toronto, Ontario, Canada M5T 2S8.
Sharpe
James A
JA
D000221:Adaptation, Ocular / Q000502:physiology*; D000328:Adult; D000368:Aged; D005133:Eye Movements; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009759:Nystagmus, Pathologic / Q000517:prevention & control; D015840:Oculomotor Nerve Diseases / Q000503:physiopathology*; D012027:Reflex, Vestibulo-Ocular / Q000502:physiology*; D015357:Vision Disparity; D015349:Vision, Monocular