Miner AP, Cortez CM, Maury BM, Sim CA, Allen RJ; University of Puget Sound, Tacoma, WA. rallen@ups.edu.

PURPOSE: Neuroanatomical theory suggests that plantar stimulation may potentially override vestibular organ input to the vestibular nuclei, thus attenuating perceived vertigo. Easily implemented plantar stimulation may yield a much needed treatment for bedridden patients suffering from vertigo of diverse etiologies. The purpose of the present study was to determine the influence of plantar somatosensory input on the duration, intensity, and reported discomfort of induced vertigo. SUBJECTS: Twenty-three volunteers (age range 22-33 years) reporting no dizziness history, cervical spine or head injury, vestibular or oculomotor pathology, peripheral neuropathy, somatosensory loss, or ototoxic or oculomotor altering substance use. METHODS: Medical screening and verification of normal plantar somatosensory via Semmes Weinstein 3.64 monofilament testing preceded subject participation. Vertigo was induced by reclining each participant 30^o to horizontal and irrigating the right external auditory canal for 90 seconds with 20 ml of 5^o C (+ 0.5^o) water, under two experimental conditions. Directly following vertigo induction the plantar stimulation condition brought a 18 kg pressure plate into contact with plantar surfaces of the participants’ feet. The control condition repeated vertigo induction, yet provided no plantar stimulation. The order of conditions randomly varied and participants served as their own controls. To verify that vertigo had subsided prior to administration of the second experimental condition, the Dix-Hallpike maneuver was performed. The influence of plantar stimulation on the experience of vertigo was assessed by subjective reports of vertigo duration and intensity (via visual analog scale) and duration of nystagmus using digital ocular imaging (DOI). Participants’ comments pertaining to qualitative sensations associated with the two experimental conditions were collected. ANALYSES: Differences between responses for each condition on each of the three dependent variables were assessed using paired t-tests. Qualitative findings regarding response differences between conditions were coded as ordinal data ranking vertigo attenuation and analyzed using Chi-square. RESULTS: The plantar stimulation condition resulted in significantly reduced subjectively reported duration (p = 0.019) and intensity (p = 0.012) of vertigo, compared to control. Chi-square analysis of reports ranking condition efficacy for reducing vertigo sensations revealed the plantar stimulation condition significantly reduced discomfort related to vertigo (p = 0.036) compared to control. VAS data collection intermittently interfered with DOI measures, thus compromising the quality of the nystagmus duration data. Nystagmus duration data was therefore not included in the results. CONCLUSION: Plantar somatosensory stimulation appears to reduce the duration, intensity, and discomfort of calorically induced vertigo in normal subjects. FUNDING SOURCE: None.

Copyright 2004 by the American Physical Therapy Association

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