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Vestibular hypersensitivity to sound (Tullio phenomenon): structural and functional assessment
S R Watson1, G M Halmagyi, J G Colebatch
1Institute of Neurological Sciences and School of Medicine, Prince of Wales Hospital, Sydney, Australia.
Neurology
|February 19, 2000
Summary
The Tullio phenomenon involves sound-induced vestibular symptoms. Click testing is crucial for diagnosis, as abnormal sound sensitivity confirms the significance of CT-detected semicircular canal dehiscence.
Area of Science:
- Neuroscience
- Otolaryngology
- Medical Imaging
Background:
- The Tullio phenomenon presents as vestibular activation triggered by acoustic stimuli.
- It is linked to low thresholds for click-evoked vestibulocollic responses and superior semicircular canal dehiscence on CT scans.
Observation:
- Four patients with Tullio phenomenon underwent high-resolution CT and vestibulocollic reflex testing.
- Stimulation included clicks and galvanic currents to assess vestibular responses.
Findings:
- Affected ears showed low click-evoked thresholds (55-65 dB nHL), while unaffected ears had normal thresholds (>70 dB nHL).
- Galvanic-evoked responses were normal and symmetric across all patients.
- CT scans revealed thin or absent bony roofs of the anterior semicircular canal in affected ears, and also in some unaffected ears.
Implications:
- Normal galvanic responses suggest sound sensitivity in Tullio phenomenon originates distal to the vestibular nerve, likely at the receptor level.
- While CT shows canal dehiscence, click hypersensitivity is key for diagnosing functional significance, especially when CT findings are also present in unaffected ears.
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