The effect of the potassium channel blocker 4-aminopyridine(4-AP) on spontan eous upbeat nystagmus (UBN) was investigated with the search coil technique duri ng fixation in different gaze positions and smooth pursuit ...The effect of the potassium channel blocker 4-aminopyridine(4-AP) on spontan eous upbeat nystagmus (UBN) was investigated with the search coil technique duri ng fixation in different gaze positions and smooth pursuit in a patient before a nd after ingestion of 10 mg 4-AP. UBN was reduced from 8.6 deg/s to 2.0 deg/s b y 4-AP causing subjective relief from distressing oscillopsia, and impaired upw ard smooth pursuit was restored(gains: before medication 0.38; after medication 0.86). In the dark, UBN was slightly stronger and not affected by 4-AP. We prop ose that 4-AP improved the function of cerebellar pathways that mediate gaze ho lding and smooth pursuit by intensifying the excitability of cerebellar Purkinje cells.展开更多
Background: In a recent study, the authors found that blinks in healthy volunt eers always triggered ocular torsion quick phases during dynamic roll movements of the head. On the basis of this observation, they hypoth...Background: In a recent study, the authors found that blinks in healthy volunt eers always triggered ocular torsion quick phases during dynamic roll movements of the head. On the basis of this observation, they hypothesized that blinks in patients with a vestibular tone imbalance would also trigger torsional quick pha ses. Methods: Using video oculography with a fixation target, the authors recor ded the ocular torsion position of the left eye of 37 participants while they ma de voluntary blinks once every 6 to 10 seconds. The participants were recruited from four groups: two age groups of healthy volunteers with a mean ±SD age of 3 2 ±4 (n=9) and 65 ±11 y (n=9); patients with a unilateral vestibular disorder in an acute state (n=12, 53 ±17 y); and those in a persisting state in which sp ontaneous nystagmus had already faded (n= 9, 65 ±13 y). Results: In the control groups of healthy volunteers, blinks triggered no or only small quick phases on the order of 0.1 deg. In both patient groups blinks always triggered quick phas es with significantly higher amplitudes of 1.85 ±.1.02 deg and were followed by exponentially decaying slow phases with time constants on the order of 1 to 2 seconds. Patients in the persisting state clearly differed from patients in the acute state in that their torsional spontaneous nystagmus had already vanished d ue to vestibular compensation. But surprisingly, these two groups did not show a large difference in terms of the effect of blinks on ocular torsion. The author s always observed torsional quick phases with the upper pole of the eye beating away from the side of the lesion. Conclusions: Blinks are able to trigger torsio nal quick phases in patients with both acute and persisting vestibular disorders . The side of the impairment can be determined from the direction in which the e ye is rotated after a blink. Thus, ocular torsion recordings during blinks can b e used as a simple clinical test for a vestibular tone imbalance, particularly d uring a persisting failure in which spontaneous nystagmus has resolved and can t herefore no longer be used for diagnosis.展开更多
文摘The effect of the potassium channel blocker 4-aminopyridine(4-AP) on spontan eous upbeat nystagmus (UBN) was investigated with the search coil technique duri ng fixation in different gaze positions and smooth pursuit in a patient before a nd after ingestion of 10 mg 4-AP. UBN was reduced from 8.6 deg/s to 2.0 deg/s b y 4-AP causing subjective relief from distressing oscillopsia, and impaired upw ard smooth pursuit was restored(gains: before medication 0.38; after medication 0.86). In the dark, UBN was slightly stronger and not affected by 4-AP. We prop ose that 4-AP improved the function of cerebellar pathways that mediate gaze ho lding and smooth pursuit by intensifying the excitability of cerebellar Purkinje cells.
文摘Background: In a recent study, the authors found that blinks in healthy volunt eers always triggered ocular torsion quick phases during dynamic roll movements of the head. On the basis of this observation, they hypothesized that blinks in patients with a vestibular tone imbalance would also trigger torsional quick pha ses. Methods: Using video oculography with a fixation target, the authors recor ded the ocular torsion position of the left eye of 37 participants while they ma de voluntary blinks once every 6 to 10 seconds. The participants were recruited from four groups: two age groups of healthy volunteers with a mean ±SD age of 3 2 ±4 (n=9) and 65 ±11 y (n=9); patients with a unilateral vestibular disorder in an acute state (n=12, 53 ±17 y); and those in a persisting state in which sp ontaneous nystagmus had already faded (n= 9, 65 ±13 y). Results: In the control groups of healthy volunteers, blinks triggered no or only small quick phases on the order of 0.1 deg. In both patient groups blinks always triggered quick phas es with significantly higher amplitudes of 1.85 ±.1.02 deg and were followed by exponentially decaying slow phases with time constants on the order of 1 to 2 seconds. Patients in the persisting state clearly differed from patients in the acute state in that their torsional spontaneous nystagmus had already vanished d ue to vestibular compensation. But surprisingly, these two groups did not show a large difference in terms of the effect of blinks on ocular torsion. The author s always observed torsional quick phases with the upper pole of the eye beating away from the side of the lesion. Conclusions: Blinks are able to trigger torsio nal quick phases in patients with both acute and persisting vestibular disorders . The side of the impairment can be determined from the direction in which the e ye is rotated after a blink. Thus, ocular torsion recordings during blinks can b e used as a simple clinical test for a vestibular tone imbalance, particularly d uring a persisting failure in which spontaneous nystagmus has resolved and can t herefore no longer be used for diagnosis.
