BINOCULAR COUNTERROLLING IN HUMANS WITH UNILATERAL LABYRINTHECTOMY AND IN NORMAL CONTROLS

Ocular counterrolling (OCRJ is the reflex torsion of the eyes about their visual axes in the direction opposite to the head as it is rolled about its naso-occipital axis. Considered to be mediated by the otolith receptors in the utricle,’ OCR is an observable behavior that invites inferences on the complex functions of the inner ear. More than 75 years of effort have been devoted to the seemingly simple task of comparing OCR in persons with known unilateral lesions to that of normal persons, focusing on the amplitude of OCR under static tilt. The contradictory results of the several studies, as reviewed below, suggest that this measure is not a productive parameter in detecting unilateral otolith dysfunction. B5rAny is credited with first introducing OCR to the clinic in 1906.4*5 He examined the response in normals and in deaf-mutes, and felt that OCR was regulated by the semicircular canals. In 1925, Kompanejetz examined OCR in 48 deaf-mutes, tilting their heads 30” to the right and looking at both eyes “simultaneously” (actually ~equentially).~ He separated his patients into two groups, one having some response to caloric or rotatory stimulation, and the other group having none. He found the presence and absence of OCR in both groups and therefore concluded that OCR was innervated from a point independent of the semicircular canals. He further observed that OCR may be different in the two eyes, suggesting that “in an asymmetrically injured otolith apparatus, a disturbance of the associated eye movements may occur, manifesting itself in different angles for the two eyes in ~ounterrolling.”~ A few years later, Kompanejetz looked at 100 normal subjects to see i f hoth eyes performed equally.6 He observed that there was more OCR in the right eye when the head was inclined to the right and more in the left eye when the head was inclined to the left. He also found that both eyes showed more OCR on tilt to the right than on tilt to the left. He considered it normal to find differences of 5’ in a given eye when tilted to either side, or of 3-4” between the two eyes when the head was tilted to one side. Unfortunately, this study differed in design and followed his work in the deaf-mute patients, so he was unable to make comparatile observations in persons with labyrinthine defects. He wrote, “It is regrettable that up to now we have not succeeded in commanding such methods [for the otolith apparatus] as may be used for examining the functions of the semicircular canals.”fi Today, more than 50 years later, we may say the same. Many investigators over the years have studied OCR in a variety of experimental designs. In 1936, Gollas studied seven patients with unilateral labyrinthine and cochlear de~truction.~ He held them at 20, 40, 60, and 90” positions on both sides and examined OCR in both eyes. He found that tipping to the side of the lesion resulted in normal OCR, but that tipping to the contralateral side produced much less OCR. He found no difference in the two eyes. In 1963, Miller and Graybiel compared OCR in 9 normal persons to 10