Macrosquare-wave jerks are analagous to square-wave jerks, but represent a distinctive entity with an unusually large saccade amplitude of approximately 40 degrees.
Square-wave jerks (SWJs) and macrosquare-wave jerks (MSWJs) have been observed in several disease entities, including multiple sclerosis, infratentorial lesions, and neurodegenerative diseases, with SWJs being more frequent than MSWJs.
Pathogenesis
Macro-square wave jerks result from defective GABA (γ-aminobutyric acid) inhibition of the superior colliculus by the substantia nigra pars reticulata1.
It is presumed that degeneration of omnipause neurons may give rise to MSWJs, as seen in Video 1.
Treatment
Diazepam or phenobarbital1.
Horizontal saccadic eye movements with an amplitude of approximately 40 degrees and frequency of 2 Hz occurred spontaneously (Part 1), and during horizontal smooth pursuit (Part 2)
(vv)Macro Sq Wave 20298.mp4(tt)
From: Klotz L, Klockgether T. Multiple system atrophy with macrosquare-wave jerks. Mov Disord. 2005;20(2):253-254. doi:10.1002/mds.20298
(vv)Macro Swj.mp4(tt)
From: Harrison's Principles of Internal Medicine, 20e. Retrieved from: https://accessmedicine.mhmedical.com/MultimediaPlayer.aspx?MultimediaID=17610957