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Selective vertical saccadic palsy from unilateral medial thalamic infarction: clinical, neurophysiologic and MRI
1Department of Clinical Neuropharmacology and Neurology, College of Medicine, Sultan Qaboos University, Al-Khod, Muscat-123, Sultanate of Oman.
Background:
Impairment of vertical gaze has been attributed to lesions involving the neural structures at the mesodiencephalic level.
Objective:
Eye movements were studied in a patient with a unilateral paramedian thalamic infarction documented by MRI.
Case Description:
A 63-year-old man presented 3 days after sudden onset vertical diplopia and hypersomnia. Eye movements were studied with electro-oculography and revealed impairment of vertical saccades with sparing of the vertical vestibulo-ocular reflex, vertical pursuit, Bell's phenomenon and vertical optokinetic nystagmus. MRI scan revealed a circular zone of altered signal intensity, suggesting infarction, in the paramedian ventral part of the right thalamus.
Conclusions:
This case demonstrates that a unilateral lesion mainly affecting the dorsomedial nucleus of the thalamus can result in selective impairment of vertical saccades and suggests that the corticofugal fibers mediating vertical saccades traverse in the medial thalamus en route to the rostral midbrain.