The ocular motor defects in progressive supranuclear palsy.

Area of Science:

• Ophthalmology
• Neurology
• Neuroscience

Background:

• Progressive supranuclear palsy (PSP) is a neurodegenerative disease impacting eye movements.
• Understanding specific ocular motor deficits in PSP is crucial for diagnosis and management.

Purpose of the Study:

• To quantitatively analyze horizontal eye movement abnormalities in patients with progressive supranuclear palsy using infrared recordings.
• To identify and characterize previously undescribed ocular fixation defects in PSP.

Main Methods:

• Quantitative infrared horizontal eye movement recordings were performed on 8 patients diagnosed with progressive supranuclear palsy.
• Analysis focused on ocular fixation, refixation saccades, pursuit eye movements, and the vestibulo-ocular reflex.

Main Results:

• All patients demonstrated horizontal eye movement capability, though some had vertical gaze paralysis.
• A novel finding was the universal presence of square-wave jerks in all patients, indicating an ocular fixation defect.
• Refixation saccades showed hypometria, reduced velocity/amplitude relationships, and prolonged duration.
• Pursuit eye movements were abnormal, with low gain (0.2-0.5), reflecting an inability to match eye to target velocity.
• Defects in the vestibulo-ocular reflex included impaired gain increase and failure of suppression during head rotation.

Conclusions:

• Patients with progressive supranuclear palsy exhibit a distinct pattern of horizontal eye movement abnormalities, including square-wave jerks, saccadic dysfunction, and pursuit deficits.
• These quantitative findings provide objective measures of ocular motor impairment in PSP.
• The identified ocular motor signs, particularly square-wave jerks, may serve as valuable diagnostic markers for progressive supranuclear palsy.