Complete Microvascular 6th Nerve Palsy with Slow Abducting Saccade

𝗢𝗿𝗶𝗴𝗶𝗻𝗮𝗹 𝗗𝗲𝘀𝗰𝗿𝗶𝗽𝘁𝗶𝗼𝗻: This is a 90-year-man with HTN, HLD, DM who woke up with horizontal diplopia. Two years prior, he was diagnosed with a microvascular right 6th nerve palsy that resolved over several months. There was little concern for giant cell arteritis, myasthenia gravis, or a mass lesion in the absence of typical symptoms or accompanying signs, and a new microvascular left 6th nerve palsy was diagnosed. With saccades to the left, not only was abduction severely limited OS, but there was significant slowing of the leftward abducting saccades even when looking from the right to center, which is typical of a paretic process. In contrast, if an abducting saccade were made from the right to center with normal/near normal speed and it stopped abruptly (due to an abduction deficit OS), this should raise suspicion for a restrictive process. 𝗡𝗲𝘂𝗿𝗼-𝗼𝗽𝗵𝘁𝗵𝗮𝗹𝗺𝗼𝗹𝗼𝗴𝘆 𝗮𝗻𝗱 𝗡𝗲𝘂𝗿𝗼-𝗼𝘁𝗼𝗹𝗼𝗴𝘆 𝗧𝗲𝘅𝘁𝗯𝗼𝗼𝗸 𝗟𝗲𝗴𝗲𝗻𝗱: This is a 90 year-man with HTN, HLD, DM who woke up with horizontal diplopia. Two years prior, he was diagnosed with a microvascular right 6th nerve palsy that resolved over several months. There was little concern for giant cell arteritis, myasthenia gravis, or a mass lesion in the absence of typical symptoms or accompanying signs, and a new microvascular left 6th nerve palsy was diagnosed. With saccades to the left, not only was abduction severely limited OS, but there was significant slowing of the leftward abducting saccades even when looking from the right to center, which is typical of a paretic process. In contrast, if an abducting saccade were made from the right to center with normal/near normal speed and it stopped abruptly (due to an abduction deficit OS), this should raise suspicion for a restrictive process such as thyroid eye disease. https://collections.lib. utah.edu/ark:/87278/s62v6km4