Abnormal Head Impulse Test in Vestibular Neuritis 1 Week After Onset

This is a 25-year-old woman who experienced the acute vestibular syndrome due to right-sided vestibular neuritis 1 week prior to this video. Left-beating nystagmus (LBN) was only noted in left gaze, but with fixation-removed, there was clear LBN in primary position that increased with head-shaking and vibration. The head impulse test (HIT) was abnormal to the right: when her head was moved quickly to the right (while being asked to fixate on the examiner's nose), due to a deficient vestibulo-ocular reflex on the right, the eyes initially moved to the right with the head. Since the visual target (examiner's nose) moves off the fovea, a refixation or catch-up saccade is necessary to bring the eyes back to the desired target. In this case, since the eyes have moved with the head to the right, the catch-up saccade is directed leftward back to center. This is referred to as an overt saccade, and is usually fairly obvious in the acute setting, occurring after the head movement. However, as compensation occurs over time, it may be more and more difficult to identify an abnormal HIT months or years later. Many patients develop compensatory covert saccades, which occur during the head movement, and these may only be seen with video HIT. Since covert saccades take some time to develop, they are generally not present (or not prominent) in the acute setting, and the bedside HIT is enough to differentiate vestibular neuritis from posterior fossa stroke. An abnormal HIT is a reassuring physical exam sign in that it is suggestive of a peripheral (benign) etiology such as vestibular neuritis. However, ischemia involving the labyrinth (‘peripheral', but dangerous), vestibular nucleus, fascicle of the 8th cranial nerve and other regions may cause an abnormal HIT. However, when paired with the pattern of nystagmus (unidirectional or gaze-evoked?) and test of skew (skew deviation present or absent?), the HINTS exam (Head Impulse, Nystagmus, Test of Skew) outperforms even MR-diffusion weighted imaging in the first 24-48 hours.