Bilaterally Abnormal Head Impulse Test

𝗢𝗿𝗶𝗴𝗶𝗻𝗮𝗹 𝗗𝗲𝘀𝗰𝗿𝗶𝗽𝘁𝗶𝗼𝗻: This video is an example of bilaterally abnormal head impulse test (HIT) due to bilateral vestibular loss (BVL). Typical symptoms in BVL: head movement-induced dizziness and jumping vision for years with visual jumping/bouncing of the visual world while walking Typical signs in BVL: abnormal HIT to the right and left (i.e., a visible corrective saccade is apparent in both directions); gait was wide-based and unsteady; 20/20 vision with both eyes open, but when the head was moved horizontally and vertically at 2-3 Hz, he lost 5 lines of visual acuity (abnormal dynamic visual acuity); he could stand on a foam pad with eyes open for at least 10 seconds, and with eyelid closure, he immediately lost balance. 𝗡𝗲𝘂𝗿𝗼-𝗼𝗽𝗵𝘁𝗵𝗮𝗹𝗺𝗼𝗹𝗼𝗴𝘆 𝗮𝗻𝗱 𝗡𝗲𝘂𝗿𝗼-𝗼𝘁𝗼𝗹𝗼𝗴𝘆 𝗧𝗲𝘅𝘁𝗯𝗼𝗼𝗸 𝗟𝗲𝗴𝗲𝗻𝗱: Bilateral vestibular loss is a common cause of head movement-dependent oscillopsia, and in these patients, evaluating the vestibulo-ocular reflex (VOR) is essential. While the bedside HIT is usually enough to make the diagnosis of unilateral or bilateral vestibular loss, the video HIT has advantages: 1) overt corrective saccades can be identified (occurring after the head movement, visible to the examiner at the bedside, black arrow), 2) covert corrective saccades can be identified (occurring during the head movement, and can be invisible at the bedside, black arrowhead), 3) a gain can be calculated to quantify the VOR (gain = ratio of eye movement velocity to head movement velocity, where typically a value below 0.6-0.7 is considered abnormal). In this case, the gains in the planes of the left and right horizontal (lateral) canals were 0.18 and 0.38, respectively, and consistent with bilateral vestibular loss https://collections.lib.utah.edu/ark:/87278/s6t20cf1. (Video and legend created with the assistance of Justin Bosley)