Tapping the head activates the vestibular system: a new use for the clinical reflex hammer.

We investigated the use of skull taps with a modified clinical reflex hammer as a method of vestibular activation. Using recently described EMG techniques to measure vestibulocollic reflexes in response to clicks, we were able to show analogous short-latency potentials to taps. The earliest responses were invariably absent on the side of a previous vestibular nerve section but were preserved in profound sensorineural or conductive hearing loss. We propose that the taps activated the vestibular apparatus directly by a bone-conducted vibration wave.