A 60-year-old man was admitted to our hospital due to progressive aphasia and right hemiparesis. Brain magnetic resonance imaging showed the left thalamus and basal ganglia lesion. Digital subtraction angiography showed the vein of Galen and straight sinus occlusion, suggesting cerebral venous thrombosis. Since his left transverse sinus was hypoplastic, his left deep cerebral lesion was due to the left deep cerebral vein congestion by the asymmetrical venous outflow. After anticoagulant therapy, his symptom and unilateral lesion improved. Clinicians should consider the vein of Galen and straight sinus thrombosis even in unilateral deep cerebral lesions.