A 23-year-old man presented with a 1-month history of headache and numbness of the left arm and hand. Neurological examination showed hypesthesia in the left arm. Magnetic resonance imaging of the spine showed peg-shaped herniation of tonsils 9 mm below the foramen magnum (fig 1A), with altered signal intensity in the medulla (fig 1B). There was no hydrocephalus. T1W and T2W screening of the whole spine showed holocord syringohydromyelia (fig 2A,B). No focal intraspinal mass was seen. Chiari I malformation with a holocord syrinx was …