Vestibular stimulation results in a characteristic and stereotyped oculo motor response in INO. Characteristically the abducting eye nystagmus can be increased or decreased by the appropriate vestibular stimulation. The asymmetry of eye movements is increased by a caloric stimulation in which the fast phase of nystagmus is to the same side as the abducting eye. It is decreased by a stimulation in which the slow phase of induced nystagmus is to the side of the abducting eye nystagmus. Consequently, lesser degrees of INO may be more readily observed during appropriate vestibular stimulation response.