Square wave jerks in parkinsonian syndromes

Area of Science:

• Ophthalmology
• Neurology
• Movement Disorders

Background:

• Square wave jerks (SWJ) are abnormal saccadic oscillations.
• Ocular motor abnormalities can aid in differentiating Parkinsonian syndromes.
• Previous research has not fully elucidated the role of SWJ in distinguishing idiopathic Parkinson's disease (PD) from other related disorders.

Purpose of the Study:

• To compare the frequency of SWJ in patients with progressive supranuclear palsy (PSP), multiple system atrophy/Parkinson's disease plus (MSA/PP), and idiopathic Parkinson's disease (PD).
• To investigate the potential of SWJ frequency as a clinical marker for differentiating between these Parkinsonian syndromes.

Main Methods:

• Quantitative assessment of SWJ frequency in patients diagnosed with PSP, MSA/PP, PD, and age-matched healthy controls.
• Defining abnormal ocular fixation based on SWJ frequency exceeding 10/min.
• Correlating SWJ frequency with clinical features such as gait freezing, falls, and instability in PD patients.

Main Results:

• Normal controls exhibited a mean SWJ frequency of 2.3/min.
• Abnormal ocular fixation (SWJ > 10/min) was prevalent in PSP (7/8) and MSA/PP (16/25) patients.
• Abnormal fixation was less common in PD patients (13/85), but when present, was associated with more severe gait freezing, falls, and instability.

Conclusions:

• SWJ frequency analysis can assist in clinically differentiating PD from PSP and MSA/PP.
• Abnormal ocular fixation, indicated by increased SWJ, is a significant finding in PSP and MSA/PP.
• The presence of SWJ in PD patients with abnormal fixation suggests a distinct clinical phenotype, potentially unrelated to nigrostriatal degeneration.