In a patient with rotational vertigo and nystagmus, where we suspect, or wish to prove a peripheral lesion, this test is of assistance. It relies on the vestibulo-occular reflex, which is responsible for bringing the eyes back to the centre.
In unilateral nystagmus and rotational vertigo, the peripheral lesion is opposite to the direction of the fast nystagmus. When the head is turned towards the lesion, the eyes move with the head, for a brief moment and the vestibular-occular reflex then returns them to the centre. If this occurs it is a positive test indicating a peripheral cause.