Cervico-ocular reflex in normal subjects and patients with unilateral vestibular hypofunction.
OBJECTIVE
To determine whether the cervico-ocular reflex contributes to gaze stability in patients with unilateral vestibular hypofunction.


METHODS
Prospective study.


METHODS
Tertiary referral center.


METHODS
Patients with unilateral vestibular hypofunction (n = 3) before and after vestibular rehabilitation and healthy subjects (n = 7).


METHODS
Vestibular rehabilitation.


METHODS
We measured the cervico-ocular reflex in patients with unilateral vestibular hypofunction before and after vestibular rehabilitation and in healthy subjects. To measure the cervico-ocular reflex, we recorded eye movements with a scleral search coil while the trunk moved at 0.3, 1.0, and 1.5 Hz beneath a stabilized head. To determine whether the head was truly stabilized, we measured head movement using a search coil.


RESULTS
We found no evidence of cervico-ocular reflex in any of the seven healthy subjects or in two of the patients with unilateral vestibular hypofunction. In one patient with chronic unilateral vestibular hypofunction, the cervico-ocular reflex was present before vestibular rehabilitation only for leftward trunk rotation (relative head rotation toward the intact side). After 5 weeks of placebo exercises, there was no change in the cervico-ocular reflex. After an additional 5 weeks that included vestibular exercises, cervico-ocular reflex gain for leftward trunk rotation had increased threefold. In addition, there was now evidence of a cervico-ocular reflex for rightward trunk rotation, potentially compensating for the vestibular deficit.


CONCLUSIONS
The cervico-ocular reflex appears to be a highly inconsistent mechanism. The change of the cervico-ocular reflex in one patient after vestibular exercises suggests that the cervico-ocular reflex may be adaptable in some patients.
Schubert
Michael C
MC
Laboratory of Vestibular Neurophysiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
Das
Vallabh
V
Tusa
Ronald J
RJ
Herdman
Susan J
SJ
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004584:Electronystagmography; D005133:Eye Movements / Q000502:physiology*; D005260:Female; D019416:Head Movements / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012027:Reflex, Vestibulo-Ocular / Q000502:physiology*; D015837:Vestibular Diseases / Q000503:physiopathology* / Q000534:rehabilitation; D014725:Vestibular Nerve / Q000503:physiopathology