Idiopathic spinal cord herniation: Report of two cases and review of the literature

DIOPATHIC spinal cord herniation is rare. We have report two such cases, in which the patients presented with Brown-Sequard syndrome. We found computer- ized tomography (CT) myelography, magnetic resonance (MR) imaging of the thoracic spine, and especially cere- brospinal fluid (CSF) flow studies, obtained by means of phase-contrast pulse sequence cine MR imaging and en- doscopic inspection, to be useful in the preoperative diag- nosis. We also review the literature and report the clinical, neuroradiological, endoscopic, and operative findings in idiopathic spinal cord herniation. U The authors describe two occurrences of idiopathic spinal cord herniation, an entity that has been reported previ- ously in only 11 cases. The patients described in this report presented in midlife with Brown-Sequard syndrome. Computerized tomography myelography and magnetic resonance (MR) imaging showed ventral displacement of the spinal cord with no apparent dorsal mass. Intraspinal cerebrospinal fluid (CSF) flow studies in which phase-contrast pulse sequence cine MR imaging was used displayed a normal pattern dorsal to the spinal cord. Percutaneous intrathe- cal endoscopic observation did not disclose dorsal intradural cysts, but ventral adhesions were seen between the spinal cord and the dura. Microsurgical intradural exploration revealed ventrolateral herniation of the cord and a ventral root through a dural defect into an epidural arachnoid cyst. The adhesions were released, the cord was repositioned intradu- rally, and the dural defect was patched. The patients showed gradual improvement postsurgery, as did most of the patients in the previously reported cases. The CSF flow and endoscopic studies were found to be particularly infor- mative, and dural patching with surgical membrane is recommended. KEY WORDSidiopathic spinal cord herniationextradural arachnoid cyst • cerebrospinal fluid flow studyendoscopyBrown-Sequard syndrome