The scalpel sign has been recently described in dorsal thoracic arachnoid web on sagittal MRI spine studies. It relates to focal distortion of the thoracic cord, appearing anteriorly displaced. The enlarged dorsal CSF space mimics the profile of a surgical scalpel. It is helpful in distinguishing cases where the thoracic cord is focally anteriorly displaced, a finding seen in a couple of other conditions in addition to dorsal thoracic arachnoid web, namely ventral cord herniation and the presence of a dorsal arachnoid cyst. #scalpel #sign #spinal #spine #thoracic #sagittal #mri #radiology
