Effect of 4-aminopyridine on gravity dependence and neural integrator function in patients with idiopathic downbeat nystagmus.
Downbeat nystagmus (DBN) is a frequent sign in patients with cerebellar degeneration. It consists of an upward drift of the eye that does not depend on vertical head position (spontaneous drift, SD), a gravity-dependent component (GD), and a gaze-evoked drift reflecting gaze-holding impairment (deficient neural integrator function). The potassium-channel blocker 4-aminopyridine (4-AP) is reported to reduce DBN in patients with cerebellar atrophy but with little or no effect in patients with idiopathic DBN. We prospectively studied the effect of 4-AP on all three components in a large (n = 24) group of the clinically frequent idiopathic DBN. DBN was reduced by 22-31% when the head was off the head erect position. In contrast, there was no effect on vertical gaze-evoked drift. This indicates the therapeutic efficacy of 4-AP not only in patients with cerebellar atrophy but also in idiopathic DBN patients. This beneficial effect, which might be missed when gravity-dependent head positions are not tested, was not related to an improvement of gaze-holding deficit. We suggest it may be related to the restored inhibition of the overacting otolith-ocular reflex.
Department of Neurology, University Luebeck, Ratzeburger Allee 160, 23538 Luebeck, Germany.
T
T
Sander
A
A
Sprenger
S
S
Marti
T
T
Naumann
D
D
Straumann
C
C
Helmchen
D015761:4-Aminopyridine / Q000627:therapeutic use*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D005133:Eye Movements / Q000187:drug effects; D005260:Female; D006112:Gravitation; D019416:Head Movements / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009759:Nystagmus, Pathologic / Q000188:drug therapy / Q000473:pathology / Q000503:physiopathology; D026902:Potassium Channel Blockers / Q000627:therapeutic use*
D026902:Potassium Channel Blockers; D015761:4-Aminopyridine