Spinal intradural extraarachnoid metastasis.

A case of carcinomatous metastasis at the L2-3 level localized in the intradural extraarachnoid space is presented. The anatomy of the subarachnoid angle where the transition occurs from peripheral nerve to nerve root is reviewed. Anatomic evidence suggests that the spread of the tumor to the potential intradural extraarachnoid space might be via the perineural sheath.