To assess the contributions of the vestibular system to whole-body motion discrimination in the dark, we measured direction-recognition thresholds as a function of frequency for yaw rotation, superior-inferior translation (“z-translation”), inter-aural translation (“y-translation”), and roll-tilt for 14 normal subjects and for three patients following total bilateral vestibular ablation. The patients had significantly higher average threshold measurements than normal (p<0.01) for yaw-rotation (depending upon frequency, 5.4× to 15.7× greater), z-translation (8.3× to 56.8× greater), y-translation (1.7× to 4.5× greater), and roll tilt (1.3× to 3.0× greater) – establishing the predominant contributions of the vestibular system for these motions in the dark.
Fatigue in MG is highly prevalent, mainly physical, and influenced by depressive symptoms, disease severity, female sex and sleep debt. Cognitive fatigue in MG may not be a direct disease manifestation, but secondary to depression. The FSS and FIS represent reliable and validated tools, appropriate to discern meaningful clinical aspects of fatigue in MG. Clinical recognition of the complexity of fatigue may foster individualized treatment approaches for affected MG patients.
We measured vestibular perceptual thresholds in patients with idiopathic bilateral vestibulopathy to assess the distribution of peripheral vestibular damage in this disorder. Thresholds were measured with standard psychometric techniques in 4 patients and compared with thresholds in normal subjects and patients with completely absent peripheral vestibular function. Motion paradigms included yaw rotation (testing the lateral canals), interaural translation (testing the utricles), superior-inferior translation (testing the saccules), and roll tilt (testing the vertical semicircular canals and the otolith organs). We found that perceptual thresholds were abnormally elevated in the patients with idiopathic bilateral vestibulopathy for yaw rotation at all frequencies and for interaural translation at only the lower frequencies. Thresholds were normal for the other 2 motion paradigms. The results demonstrate that the distribution of vestibular dysfunction in this disorder is not uniform but, rather, can affect lateral canal and utricular thresholds while relatively sparing vertical canal and saccular function.
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