Selective Unidirectional Horizontal Saccadic Paralysis From Acute Ipsilateral Pontine Stroke

Area of Science:

• Neuroscience
• Ophthalmology
• Neurology

Background:

• Unidirectional horizontal saccade impairment with preserved smooth pursuit is linked to dorsomedial pontine lesions.
• Previous lesion studies were too large to precisely localize this deficit to the pontine paramedian reticular formation (PPRF).

Observation:

• A single case report details a patient with impaired rightward saccades and intact rightward smooth pursuit.
• Brain magnetic resonance imaging (MRI) revealed a small, restricted diffusion area within the PPRF in this patient.

Findings:

• The discrete PPRF lesion correlated with the observed selective impairment of horizontal saccades.
• This case supports the hypothesis that the PPRF is critical for generating unidirectional horizontal saccades.

Implications:

• Provides crucial evidence for the specific role of the PPRF in saccade generation.
• Advances understanding of the neural circuitry underlying eye movement control.
• May inform diagnosis and treatment of saccadic disorders.