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Horizontal and vertical components of spontaneous nystagmus in the dark were assessed in 40 healthy subjects with monocular computerised video-oculography. Five different static head-in-space positions were used: sitting upright, face up, right ear down, left ear down, and face down; the head-on-trunk position being kept the same in each position. In the sitting position, four subjects (10%) had downbeat nystagmus (slow-phase velocity [SPV] 0.7 °/s, SD 0.27) and 12 (30%) had upbeat nystagmus (SPV 2.58 °/s, SD 1.38). In the supine position, three subjects (7.5%) had downbeat nystagmus (SPV 5.60 °/s, SD 6.72) and 25 (62.5%) had upbeat nystagmus (SPV 3.86 °/s, SD 4.54). The direction of nystagmus frequently changed with changes in head position. In 15 subjects, the behaviour of the vertical nystagmus was investigated during a slow 1.2 °/s, 360° revolution in pitch. All subjects had nystagmus at some point and the slow-phase velocity was modulated sinusoidally suggestive of gravitational modulation by otolithic signals with an offset towards upbeat nystagmus. Normal subjects have a physiological spontaneous nystagmus of low velocity in the dark, often upbeating, which is under the modulation of otolith input. [ABSTRACT FROM AUTHOR]

Body sway and vibration perception in the lower limbs were measured in 32 normal subjects and 25 patients with peripheral neuropathies; nerve conduction studies were also performed in the patients with neuropathies. Body sway was measured by means of force-plate posturography, and three methods were used to assess vibration perception: a neurothesiometer, a semiquantitative tuning fork, and the bone vibrator of a conventional audiometer. Body sway and vibration perception were increased in the patients with peripheral neuropathies and there was significant correlation between these measures.d These findings, together with the lack of correlation between sway and muscle strength, indicate that the main source of unsteadiness in these patients is the loss of proprioceptive information. Vibration perception and body sway did not correlate with the electrophysiological variables, indicating that these measures assess different aspects of peripheral nerve function. In all subjects there was close correlation between vibration perception as assessed by the neurothesiometer and the audiometer could be used to screen proprioceptive function in patients with balance disorders. In normal subjects age correlated with vibration perception (measured with the neurothesiometer and audiometer) and also with body sway standing on foam. This suggests that the increased body sway in elderly people may partly be due to redue proprioception in the lower limbs. [ABSTRACT FROM AUTHOR]