Head tilt suppression test as a differential diagnostic tool in vertiginous patients.

The head tilt suppression test has been known to be a diagnostic tool to distinguish between centrally originating dizziness and peripheral vertigo, as the latter enhances the natural spontaneous firing rate of the velocity storage system and decreases the time constant; however, the otolith organ is now considered to be a cause of head tilting effect. Therefore we questioned whether the head tilt suppression test is still worth differential diagnostic tool. We measured the time constant and initial eye velocity of pre- and post-rotatory nystagmus in a velocity step test in nine healthy adults. The time constant was significantly affected by head tilting (p = 0.001), pre- and post-rotatory nystagmus (p = 0.020) and the compounding interaction between them (p < 0.000). The initial eye velocity was also significantly affected by pre- and post-rotatory nystagmus (p = 0.016) and the compounding interaction (p < 0.000), but not by head tilting (Wilks' Lambda = 0.054). The head tilt suppression test is a useful method for the differential diagnosis of vertiginous patients. It is affected by pre- and post-rotatory nystagmus and their interaction, however, other central parameters in vestibular function testing should also be considered in order to obtain an exact differential diagnosis.