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HINTS is an acronym for Head Impulse, Nystgmus, Test of Skew, a three-step bedside examination helpful in distinguishing acute peripheral vestibulopathy from structural disease of the posterior fossa, especially brainstem stroke.(1,2) The [[Head_impulse_test|head impulse test]] is a bedside evaluation of the integrity of the vestibulo-ocular reflex (VOR). The examiner briskly rotates the patient’s head while having the patient fixate on a target, usually the examiner’s nose. When impaired, the VOR cannot match the velocity of head rotation causing the eyes to lag behind and requiring a corrective saccade back to the target. An abnormal HIT indicates peripheral vestibular hypofunction on the side towards which the head was rotated.
One of the characteristics of vestibular nystagmus is consistent in consistency of direction. It may vary in intensity, but the fast phase always beats away from the impaired labyrinth. In contrast, nystagmus of central origin often changes direction. Skew deviation is a comitant vertical ocular malalignment, typically due to a stroke involving the prenuclear brainstem vertical ocular control mechanisms. The deviation remains the same in all directions of gaze. With other causes of vertical malalignment, such as IVth nerve palsy, the deviation changes in various directions of gaze (noncomitant). Skew deviation does not occur with peripheral vestibular lesions.
On HINTS testing, the patient with acute peripheral vestibulopathy, as in acute viral labyrinthitis, has an abnormal HIT, showing a corrective saccade, unidirectional nystagmus and no skew deviation. The patient with acute vertigo due to a brainstem stroke or other structural pathology has a normal HIT, with no corrective saccade, direction changing nystagmus and may have skew deviation. A central finding on any of the three tests suggests a central lesion. The pattern of findings on HINTS testing can thus help distinguish an acute peripheral vestibular disturbance from acute structural pathology of the posterior fossa.
