HINTS Exam and Saccadic Dysmetria in Lateral Medullary Stroke

𝗢𝗿𝗶𝗴𝗶𝗻𝗮𝗹 𝗗𝗲𝘀𝗰𝗿𝗶𝗽𝘁𝗶𝗼𝗻: This is a 50-year-old who experienced the abrupt onset of prolonged vertigo following chiropractic therapy 2 months prior. Initial work-up included an MRI and MR angiogram - MR-diffusion weighted imaging showed an acute left lateral medullary stroke and left vertebral artery occlusion, which was thought to be related to a dissection. The examination seen here was performed 2 months following his stroke, and there was no spontaneous nystagmus with fixation. When fixation was removed with video infrared goggles, right-beating (with a slight torsional component, top poles beating towards the right ear) nystagmus was apparent. Head impulse testing in the planes of the horizontal canals was normal, which is a "central" sign in patients presenting with acute vertigo and spontaneous nystagmus. He also had a skew deviation with a left (ipsilesional) hypotropia. When the utricle-ocular motor fibers are affected caudal to their decussation as in a lateral medullary stroke, the hypotropic eye will be ipsilesional as in this case. Therefore, the HINTS (Head Impulse, Nystagmus, Test of Skew) exam was consistent with a central localization. Additionally, there was saccadic dysmetria, with hypermetric saccades to the (ipsilesional) left side and hypometric saccades to the (contralesional) right side. Although not shown here, there was also leftward ocular lateropulsion, a finding which is usually seen ipsilateral to hypermetric saccades. This is a typical finding in the Wallenberg syndrome, given involvement of the inferior cerebellar peduncle and the climbing fibers that course through it on their way to the ipsilateral dorsal vermis (see normal saccadic pathway https://collections.lib.utah.edu/details?id=1260093, and what happens to saccades with lateral medullary injury https://collections.lib.utah.edu/details?id=1260094). 𝗡𝗲𝘂𝗿𝗼-𝗼𝗽𝗵𝘁𝗵𝗮𝗹𝗺𝗼𝗹𝗼𝗴𝘆 𝗮𝗻𝗱 𝗡𝗲𝘂𝗿𝗼-𝗼𝘁𝗼𝗹𝗼𝗴𝘆 𝗧𝗲𝘅𝘁𝗯𝗼𝗼𝗸 𝗟𝗲𝗴𝗲𝗻𝗱: This patient experienced the acute vestibular syndrome due to left lateral medullary stroke from left vertebral artery dissection. Two months later he was examined and the following ocular motor/ vestibular findings were observed: 1) with fixation-removed, there was right-beating nystagmus (with a slight torsional component, top poles beating towards the right ear), 2) head impulse testing HIT in the planes of the horizontal canals was normal, 3) there was a skew deviation with a left (ipsilesional) hypotropia. Therefore, the HINTS (Head Impulse, Nystagmus, Test of Skew) exam was consistent with a central localization based on the normal HIT and presence of a skew deviation. Additionally, there was saccadic dysmetria, with hypermetric saccades to the (ipsilesional) left side and hypometric saccades to the (contralesional) right side. Although not shown here, there was also leftward ocular lateropulsion, a finding which is usually seen ipsilateral to hypermetric saccades. (Video courtesy of Dr. Tzu-Pu Chang) https:// collections.lib.utah.edu/ark:/87278/s6546m8r