Selective abolition of the vestibular-ocular reflex by sedative drugs.

INTRODUCTION: The vestibulo-ocular reflex (VOR) is an important part of the neurological examination of the patient with coma when determining brainstem function. VOR is tested via the oculocephalic reflex (OCR) and the oculovestibular reflex (OVR), or cold calorics. It has been noted that sedative medications, such as opioids and benzodiazepines, can diminish or abolish the VOR.
METHODS: We performed a chart review on three patients noted to have absent VOR at initial neurological assessment as an isolated finding.
RESULTS: The three patients ranged in age from 45-74 years. Two patients presented with intentional drug overdoses, whereas the third patient had a complicated course postcardiac surgery and received sedative drugs. All three patients initially had absent responses to OCR and cold calorics bilaterally. However, all other brainstem functions were normal at the initial examination. All three patients regained both OCR and OVR within 24 hours after sedative medication had been removed.
CONCLUSION: Sedatives may selectively and transiently abolish the VOR, altering the clinical examination; this is to be considered in the examination of a patient with coma.