[Monoparesis of the left leg with bilateral pyramidal signs due to posterior spinal artery syndrome]

A 63-year-old hypertensive and diabetic woman suddenly experienced severe pain in the back and abdomen of the left side. Sensory disturbance and muscle weakness in her left leg and urinary retention followed. Somatosensory evoked potential (SEP) indicated a thoracic cord lesion. Furthermore, MRI showed a focal lesion with a high signal intensity on T2-weighted images in the left posterolateral region of the cord Th4-9. She was diagnosed with posterior spinal artery syndrome (PSAS) due to spinal infarction by clinical presentation and MRI findings. Monoparesis can be caused by PSAS.