Isolated Third Nerve Palsy and Alternate Hemiparesis in Brain Stem Stroke: A Case Report.

A very rare sign of brain stem stroke is Weber's Syndrome. Ipsilateral third nerve palsy and contralateral hemiparesis are the hallmarks of Weber's Syndrome. Midbrain infarction is the most frequent cause of Weber's Syndrome. The perforating branches of the basilar bifurcation or occlusion of the posterior cerebral artery commonly cause the infarction. We report the case of a 58-year-old female diagnosed with Weber's syndrome. The risk factors were hypertension and dyslipidemia. This patient presented with acute right-side motor weakness and left medial gaze palsy (third nerve palsy). A brain Computed Tomography (CT) scan revealed a lesion on the right side of the mesencephalon, which was consistent with an acute brainstem infarction. Subsequent Transcranial Doppler (TCD) and Digital Subtraction Angiography (DSA) revealed severe stenosis of the posterior circulation. We diagnosed and treated this patient as having Weber's syndrome based on the symptoms, signs, and imaging findings.