A 58-year-old man with no significant medical history presented with difficulty walking and right leg weakness for one year, worsening over the past two months. Neurological examination revealed power in the right leg at 3/5 and 4/5 in the left leg, with exaggerated deep tendon reflexes in both lower limbs and normal findings in the upper limbs.
MRI of the spine showed a small syrinx at the T4 vertebral level on the right side, along with a sharp dorsal indentation of the cord and widening of the subarachnoid space below this level. This appearance resembled a surgical scalpel. Contrast-enhanced images showed no meningeal enhancement, and the brain MRI was normal.