Pseudonystagmus in progressive supranuclear palsy.

Area of Science:

• Neuro-ophthalmology
• Neurodegenerative Diseases
• Movement Disorders

Background:

• Ocular oscillations are crucial in diagnosing neurodegenerative disorders.
• Nystagmus in parkinsonian syndromes can indicate cerebellar involvement, characteristic of multiple system atrophy.

Purpose of the Study:

• To investigate vertical jerky eye oscillations observed in patients with progressive supranuclear palsy.
• To determine the cause of these oscillations and their relationship to head movements.

Main Methods:

• Oculographic assessments using head-fixed corneal curvature trackers.
• Evaluation of eye oscillations in six patients diagnosed with progressive supranuclear palsy.
• Assessment of the effect of head stabilization on observed oscillations.

Main Results:

• Six patients with progressive supranuclear palsy exhibited vertical jerky eye oscillations.
• These oscillations were eliminated upon adequate head stabilization.
• The eye movements were phase-locked and frequency-matched with subtle, involuntary head oscillations, suggesting a vestibulo-ocular reflex response.

Conclusions:

• The observed jerky eye oscillations in progressive supranuclear palsy patients were interpreted as 'pseudonystagmus', not true nystagmus.
• This phenomenon results from the vestibulo-ocular reflex responding to involuntary head oscillations.
• Head stabilization is critical during clinical and instrumented assessments of gaze holding in neurodegenerative conditions.