arachnoid web

Dorsal

arachnoid web: the ‘scalpel’ sign—a case report and differential diagnosis. MRI of the dorsal spine T2W sagittal (a, b) and axial (c, d) sections show a small syrinx within the cord at D4 vertebral level on right side (black arrow). There was sharp dorsal indentation of the cord (black arrow in a) and widening of the subarachnoid space below this level. This appearance is similar to a surgical scalpel. The anterior subarachnoid space is preserved