Unusual caloric responses in a patient with a fourth ventricular ependymoma.

The caloric test is probably the most widely used clinical test of vestibular function. A unilateral decrease in response to cold and warm water reliably indicates a unilateral peripheral vestibular lesion. Central signs on caloric testing are less common but important to recognize because they are often associated with lesions of the brainstem. We describe a patient with a tumor originating in the floor of the fourth ventricle who presented with premature reversal after cold stimulation on one side and perverted nystagmus after cold stimulation of the other side.