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Title: Psychophysical and psychological factors affecting recovery from acute balance disorders
Author: Cousins, Sian Emma
ISNI:       0000 0004 2728 8200
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2012
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Patients with acute vestibular neuritis are traditionally investigated with caloric or rotational examination of the vestibular-ocular reflex. However, clinical outcome is poorly predicted by such vestibular reflex assessments. We hypothesised that symptomatic recovery would depend upon higher order visuo-vestibular compensatory mechanisms. Thirty-one patients were studied in the acute and recovery phases of vestibular neuritis (median 2 days and 10 weeks, respectively). Patients underwent examination of vestibulo-ocular and vestibular-perceptual responses, at threshold and supra-threshold levels. Supra-threshold stimuli (90°/s velocity step rotations) allowed quantification of vestibulo-ocular and vestibulo-perceptual time constants. Additional measures of visual dependency (rod-and-disc task), dizziness symptom load (Vertigo Symptom Scale and Dizziness Handicap Inventory) and psychological factors (including - autonomic arousal, anxiety, depression, fear of bodily sensations) were obtained. Vestibulo-perceptual and vestibulo-ocular thresholds were raised and asymmetric acutely and remained slightly elevated and asymmetric at recovery. Acutely, supra-threshold vestibulo-ocular time constants were shortened and asymmetric. In contrast, perceptual responses were reduced but notably symmetrical. At recovery, vestibulo-ocular supra-threshold responses remained abnormal but perceptual supra-threshold responses normalised. Visual dependency was significantly elevated above normals in both acute and recovery stages. Vertigo symptom recovery was significantly predicted by acute levels of visual dependency (p=0.002), autonomic anxiety (p=0.004). A number of measures were associated with vertigo symptoms at recovery, in addition to visual dependency (p=0.012) and autonomic anxiety (p<0.001), including - anxiety and depression (p<0.003), fear of body sensations (p=0.033), vestibular perceptual thresholds (p=0.017) and caloric canal paresis (p=0.001). Factor Analysis revealed a strong association between clinical outcome, visual dependency and psychological factors, all loading on a single component accounting for 59.15% of the variance. The bilateral suppression of supra-threshold vestibular perception observed acutely represents a hitherto unrecognised central adaptive ‘anti-vertiginous’ mechanism. However, poor symptomatic recovery is best predicted by increased visual dependency and psychological factors. The findings show that long term recovery from unilateral vestibular deficit is mediated by central compensatory mechanisms, including multi-sensory integration and psychological processing.
Supervisor: Bronstein, Adolfo Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral