Periodic alternating nystagmus and vestibulo-spinal system facilitating activity

Objective: Periodic alternating nystagmus has been associated with the inst ability of the velocity storage mechanism, which is known to play an import ant role in both the vestibulo-oculomotor and the optokinetic systems. In t he present study we looked for a possible spinal equivalent to PAN. Methods and results: In 3 PAN patients, the H-reflex amplitude proved to be slightly but significantly influenced by nystagmus direction, in that it w as greater when the nystagmus was beating toward the stimulation side. Conclusions: This finding suggests that projections from velocity storage m ay play a role not only in the ocular motor but also in assisting postural stability through the vestibule-spinal system. (C) 2000 Elsevier Science Ir eland Ltd. All rights reserved.