Bilateral paramedian thalamic infarct in the presence of an unpaired thalamic perforating artery.

Bilateral paramedian thalamic infarction is rare. The suggested mechanism is occlusion of a central unpaired thalamic perforating artery--an anatomic variant. In the few existing reports of this condition, the diagnosis was based on computed tomography (CT) or magnetic resonance imaging (MRI) findings alone. Other causes of thalamic lesions were not ruled out, and there was no angiographic demonstration of the presumed variant artery. We present a case of a 48-year-old man with a bilateral thalamic infarction seen on CT and MRI. Initial neurological examination revealed lethargy, severe combined motor and sensory aphasia, and a mild upward gaze limitation. The patient had no focal motor deficits. After 24 hours, the patient was more alert and his speech became more fluent, but Korsakoff-type amnesia with poor attention span became apparent. The patient improved slowly over 6 months of rehabilitation. Bilateral thalamic lesions can be caused by several conditions. Among those are thiamine deficiency, cerebral lupus, toxoplasmosis, cysticercosis, cerebral syphilitic gumma, and even tumors and fungal infections. All these were ruled out in our case. Superselective digital subtraction angiography (DSA) demonstrated a single unpaired thalamic perforator. To our knowledge, this is the first time this anatomical variant has been demonstrated in vivo in association with bilateral thalamic infarction.