Affiliations: [a] Department of Audiology, Karolinska Hospital, Stockholm, Sweden | [b] Department of Otorhinolaryngology, University Hospital, Lund, Sweden
Note: [1] Preliminary data were presented at the Bárány Society meeting, Uppsala, Sweden, June 6–8, 1994.
Note: [*] Reprint address: Krister Brantberg, MD, Department of Audiology, Karolinska Hospital, S-171 76 Stockholm, Sweden; Phone: + 46, 8 7294022; Fax: + 46, 8 345431; E-mail: [email protected]
Abstract: The functional status of the velocity storage mechanism was studied in patients at long-term follow-up (2 to 4 years) after unilateral vestibular neurectomy. The time constant of the vestibulo-ocular reflex (VORtc), the effect of head tilt on postrotatory nystagmus, optokinetic after-nystagmus (OKAN), and nystagmus after rapid head shaking were studied in 10 patients. In agreement with previous findings, VORtc was found to be short and most patients manifested OKAN, suggesting that unilateral peripheral vestibular loss is associated with a complete loss of storage within the the VOR but only a partial loss of velocity storage for visual input. However, at postrotatory head tilt the VOR time constant was further shortened, supposedly due to discharge of functioning velocity storage. Moreover, most patients manifested nystagmus after head shaking. These findings on tilt suppression and head-shaking nystagmus suggest that velocity storage within the VOR may function even in patients with complete unilateral vestibular lesions.
