Symptomatic high frequency/acceleration vestibular loss: consideration of a new clinical syndrome of vestibular dysfunction

CONCLUSION: Symptomatic high frequency/acceleration vestibular loss is a distinct clinical entity that can be missed on conventional ENG with caloric testing. Under certain circumstances, symptomatic patients with a high frequency/acceleration vestibular loss should undergo an MSSC study for confirmation, if required.

OBJECTIVE: To document that normal electronystagmography (ENG) with conventional bithermal caloric testing is inadequate for diagnosing clinically significant high frequency/acceleration vestibular loss.

MATERIAL AND METHODS: Patients with clinical symptoms and signs of persistent peripheral vestibular dysfunction despite normal conventional bithermal caloric testing on ENG underwent high frequency/acceleration horizontal magnetic scleral search coil (MSSC) eye movement studies. The clinical findings and results from audiometric tests, conventional ENG with bithermal caloric tests and MSSC tests were reviewed.

RESULTS: Eleven patients were identified as having an abnormal MSSC study, indicating a high frequency/acceleration vestibular loss consistent with their clinical history despite normal or equivocal bithermal caloric responses on conventional ENG. Although valuable, ENG caloric testing evaluates lateral semicircular canal function and should be considered a non-physiological test primarily of low frequency vestibular function. High frequency/acceleration head thrust testing clinically detected a "high frequency/acceleration vestibular loss" in 8/11(72.7%) cases.