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Summary
Acute thalamic and midbrain strokes can cause rare eye movement disorders. This study identifies monocular downbeat nystagmus as a key sign of medial thalamic and upper mesencephalon infarction.
Area of Science:
- Neuroscience
- Ophthalmology
- Neurology
Background:
- Medial thalamic and upper mesencephalon infarctions are uncommon neurological events.
- Ophthalmoparesis, particularly vertical gaze abnormalities, can result from lesions in these brain regions.
Observation:
- Two patients presented with acute unilateral medial thalamic and upper mesencephalon infarction.
- Clinical manifestations included ipsilateral third nerve nuclear palsy, contralateral skew deviation with impaired eye elevation, and monocular downbeat nystagmus.
Findings:
- Monocular downbeat nystagmus, a rare sign, was observed in these patients.
- This nystagmus is hypothesized to result from dysfunction in cerebellar-modulated pathways, integrator neurons, or posterior commissure fibers affecting vertical ocular reflexes.
Implications:
- This finding expands the understanding of neuro-ophthalmological signs associated with specific brainstem and thalamic lesions.
- Recognizing monocular downbeat nystagmus in the context of medial thalamic or upper mesencephalon infarction can aid in diagnosis and localization of the lesion.