Two Cases of Acute Esotropia in Contralateral Thalamic Hemorrhage

ABSTRACT

Monocular gaze palsies which result from a supranuclear cerebral lesion are rare clinical manifestations. The prefrontal cortico-oculomotor pathways travel across the thalamus and mesodiencephalic junction terminating directly in oculomotor complexes. These pathways exist bilaterally and the contralateral oculomotor bundle exerts an inhibitory influence upon the oculomotor neurons, particularly those related to the medial rectus muscle. The acute disinhibition of these neurons by a posterior thalamic lesion results in a sustained but transient discharge of the medial rectus and tonic activation. Impairment of monocular projections in the contralateral posterior thalamus could result in a tonic activation of the medial rectus, analogous to the conjugate gaze deviation observed with a frontal lobe lesion. We describe two patients with an acute onset of esotropia and contralateral supranuclear lesions - thalamic hemorrhages.