Thoracic Dorsal Spinal Cord Herniation: Brief Report and Review of Literature with an Attempt at Hypothesizing the Possible Pathogenesis.

Spontaneous dorsal cord herniations are very rare, with only 3 reported cases published in the literature. We report a case of a 15-year-old girl, presenting with progressive symptoms of myelopathy, diagnosed with dorsal cord herniation. She was managed surgically. The herniated arachnoid forming the cyst wall was opened to find a dorsally herniated mass of the dorsal spinal cord. The dura was opened above and below the herniation and then around it to free the herniating nodule of the spinal cord. The nodule was not reducible and was partially amputated for biopsy, and to facilitate dural closure. The patient's post-operative course was uneventful with no fresh deficits. Lower limb weakness improved to 5/5 power with normal gait at 3 months follow-up. We speculate, after a literature review, that the dorsal cord herniation is a 'dorsal trans-dural appendage of the spinal cord' possibly resulting from (a) abnormal migration of neural crest cells during formation of dorsal meninges; or (b) abnormal differentiation of neural crest cells; or (c) abnormal signaling by the neural crest cells.