Saccadic Intrusions (Square Wave Jerks, SWJ)

𝗢𝗿𝗶𝗴𝗶𝗻𝗮𝗹 𝗗𝗲𝘀𝗰𝗿𝗶𝗽𝘁𝗶𝗼𝗻: Seen here are SWJ, which is the most common example of a saccadic intrusion. Here the patient is fixating on the camera, and all of the sudden a saccade takes the eyes off the fixation target, there's a brief intersaccadic interval, and then the eyes return to the target. Therefore, the saccade is the culprit that initiates the movement, rather than the slow phase (which is the culprit with jerk or pendular nystagmus). The intrusions occur quite frequently (many more than would be expected given his age alone), and these prominent SWJ were related to a progressive cerebellar degeneration in his case. 𝗡𝗲𝘂𝗿𝗼-𝗼𝗽𝗵𝘁𝗵𝗮𝗹𝗺𝗼𝗹𝗼𝗴𝘆 𝗮𝗻𝗱 𝗡𝗲𝘂𝗿𝗼-𝗼𝘁𝗼𝗹𝗼𝗴𝘆 𝗧𝗲𝘅𝘁𝗯𝗼𝗼𝗸 𝗟𝗲𝗴𝗲𝗻𝗱: Seen here are SWJ, which is the most common example of a saccadic intrusion. Here the patient is fixating on the camera, and all of the sudden a saccade takes the eyes off the fixation target, there's a brief intersaccadic interval, and then the eyes return to the target. Therefore, the saccade is the culprit that initiates the movement, rather than the slow phase (which is the culprit with jerk or pendular nystagmus). The intrusions occur quite frequently (many more than would be expected given his age alone), and these prominent SWJ were related to a progressive cerebellar degeneration in his case