[Complex eye movement disturbance in thalamic and mesencephalic infarcts]

Area of Science:

• Neuroscience
• Neurology
• Ophthalmology

Background:

• Sudden onset of double vision and gait imbalance can indicate serious neurological events.
• Vertical "one-and-a-half"-syndrome is a rare condition characterized by complex eye movement abnormalities.

Observation:

• A 36-year-old male presented with acute diplopia and ataxia.
• Neurological exam showed vertical gaze paresis and leftward horizontal gaze nystagmus.
• MRI revealed bilateral thalamic and left mesencephalic ischemic lesions.

Findings:

• Optokinetic nystagmus (OKN) testing demonstrated subtle, complex eye movement disorders including hypometric saccades and convergence-retraction nystagmus.
• These oculomotor abnormalities, not apparent on standard examination, were attributed to lesions in the thalamic intralaminar nuclei and mesencephalic structures.
• The ischemic lesions likely resulted from an anomalous arterial supply, possibly involving common branches of the basilar artery.

Implications:

• This case underscores the importance of detailed oculomotor assessments, particularly OKN testing, in diagnosing complex gaze palsies.
• Understanding the vascular anatomy and lesion localization is crucial for diagnosing and managing these rare neurological conditions.
• The study highlights the diagnostic utility of OKN in uncovering subtle eye movement abnormalities indicative of brainstem and thalamic pathology.