J Clin Neurol.  2020 Jan;16(1):37-45. 10.3988/jcn.2020.16.1.37.

A Cortical Substrate for Square-Wave Jerks in Progressive Supranuclear Palsy

Affiliations
  • 1Department of Neurology, Eginition Hospital, School of Medicine, National and Kapodistrian University of Athens, Athens, Greece. eanagnost@eginitio.uoa.gr
  • 22nd Department of Radiology, University General Hospital ‘Attikon,’ School of Medicine, National and Kapodistrian University of Athens, Athens, Greece.

Abstract

BACKGROUND AND PURPOSE
Square-wave jerks (SWJs) are the most common saccadic intrusion in progressive supranuclear palsy (PSP), but their genesis is uncertain. We aimed to determine the characteristics of SWJs in PSP (the Richardson subtype) and Parkinson's disease (PD) and to map the brain structures responsible for abnormal SWJ parameters in PSP.
METHODS
Eye movements in 12 patients with PSP, 12 patients with PD, and 12 age-matched healthy controls were recorded using an infrared corneal reflection device. The rate, mean amplitude, and velocity of SWJs were analyzed offline. Voxel-based morphometry using a 3-Tesla MRI scanner was performed to relate changes in brain volume to SWJ parameters.
RESULTS
The SWJ rate was more than threefold higher in PSP patients than in both PD patients and controls (mean rates: 33.5, 10.3, and 4.3 SWJs per minute, respectively). The volumes of neither the midbrain nor other infratentorial brain regions were correlated with the SWJ rate. Instead, highly significant associations were found for atrophy in the superior, middle, and inferior temporal gyri in the PSP group.
CONCLUSIONS
SWJs in PSP are not mediated by midbrain atrophy. Instead, supratentorial cortical structures located mainly in the temporal lobe appear to be deeply involved in the generation of abnormally high SWJ rates in these patients. Known anatomical connections of the temporal lobe to the superior colliculus and the cerebellum might play a role in SWJ genesis.

Keyword

progressive supranuclear palsy; square-wave jerks; eye movements; Parkinson's disease; voxel-based morphometry

MeSH Terms

Atrophy
Brain
Cerebellum
Eye Movements
Humans
Magnetic Resonance Imaging
Mesencephalon
Parkinson Disease
Superior Colliculi
Supranuclear Palsy, Progressive*
Temporal Lobe
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