Human ocular torsional position before and after unilateral vestibular neurectomy

Abstract

The static ocular torsional position of both eyes of 23 patients was measured by means of fundus photographs one day before and one week after unilateral vestibular neurectomy for the treatment of acoustic neuroma, Ménière's disease or paroxysmal vertigo. The results showed that in all patients the vestibular neurectomy caused both eyes to tort (i.e. to roll around the visual axis) toward the side of the neurectomy when measured one week after operation. The extent of this torsion was an average of 9.5 degrees one week after operation and there was no statistically significant difference in the average magnitude of the torsion in the two eyes. In 8 of these patients, additional measurements were made at intervals up to one year after operation and it was found that in these patients there is a significant reduction in torsion over time from an average of 10.2 degrees one week after operation to an average of 2.8 degrees by 16 weeks after operation. The change in torsional eye position following the neurectomy was accompanied by a change in the perceived visual orientation of a small (9.5 degrees visual angle) illuminated horizontal line at a straight ahead eye level position in an otherwise completely darkened room. One week after operation when asked to adjust the line to the perceived gravitational horizontal by rotating it in roll (i.e. around an X axis), patients who had had a right vestibular neurectomy consistently set the line so that the right side of the line (from the patient's point of view) was below the true gravitational horizontal. Similarly patients after a left neurectomy consistently set the line so that the left side of the line was below the true gravitational horizontal. There is a high correlation (r = 0.95) between the direction and magnitude of the change in torsional eye position and the direction and magnitude of the change in the perceived visual horizontal one week after operation.(ABSTRACT TRUNCATED AT 250 WORDS)

Spatial orientation in patients with chronic unilateral vestibular hypofunction is ipsilesionally distorted

“…In the literature, acutely after UVH a strong bias of the SVV and the subjective visual horizontal (SVH) towards the lesioned side (up to 25° (Friedmann, 1971, Curthoys et al , 1991, Bergenius et al , 1996, Anastasopoulos et al , 1997, Lopez et al , 2008) has been described consistently. While this bias slowly decreases, not all patients reach normal values after months to years (Friedmann, 1970, Curthoys et al , 1991, Böhmer et al , 1995, Tribukait et al , 1998, Hafström et al , 2004, Hafstrom et al , 2006, Lopez et al , 2008, Toupet et al , 2014, with adjustment errors between -2.0° and 11.7°.…”

“…While this bias slowly decreases, not all patients reach normal values after months to years (Friedmann, 1970, Curthoys et al , 1991, Böhmer et al , 1995, Tribukait et al , 1998, Hafström et al , 2004, Hafstrom et al , 2006, Lopez et al , 2008, Toupet et al , 2014, with adjustment errors between -2.0° and 11.7°. These results are consistent with our observation of a trend (3.7±2.0°, p=0.100) towards an ipsilesional SVV bias when upright.…”

“…The SVV thereby shifts towards the lesioned side when upright (Friedmann, 1971, Curthoys et al , 1991, Bergenius et al , 1996, Anastasopoulos et al , 1997, Lopez et al , 2008. Healthy humans show a distinct pattern of roll-angle dependent SVV errors: while roll over-compensation occurs at small (<60°) and very large (>120-135°) (Tarnutzer et al , 2009a) angles (E-effect) (Mueller, 1916), roll undercompensation is found for medium-sized (60-135°) angles (A-effect) (Aubert, 1861).…”

Clinical implication of ocular torsion in peripheral vestibulopathy

“…Fundus photography is used to evaluate the ocular torsion (OT) resulting from the static imbalance of the roll plane sensed by the otolith receptors in the utricles [1]. The OT abnormality in acute unilateral vestibular loss usually resolves within days or weeks [2,3]. Caloric testing examines the relative status of each horizontal semicircular canal separately and reflects the dynamic vestibular imbalance evoked by caloric stimulation.…”

Cardiovascular Risk Factors in Total or Divisional Vestibular Neuritis

“…[43][44][45] The SVV tilt can be determined bedside using a simple, self-made bucket, 46 or be measured using a computerized program in the laboratory.…”