The Immunohistochemical Profile of the Normal Conus medullaris and Filum terminale

Abstract

Background: The embryopathy underlying tethering of the filum terminale is poorly understood. Few studies have detailed the normal immunohistochemical profile of the distal spinal cord. Knowledge of normal filum development is the foundation upon which to compare tissues obtained from diseased fila in patients with tethered cord syndrome. Aims: Ten distal spinal cords containing morphologically normal conus medullaris and filum terminale were obtained at autopsy from patients with no clinical evidence of tethered cord syndrome. All were immunostained with caudal neural tube developmental markers H4C4, VIN-IS-53, AC4, FP3 and NOT1, and a panel of mature neuroglial, neural crest, epithelial and mesenchymal markers. Results: H4C4 marked ventral white matter and periventricular gray matter in the conus and showed rare reactivity in neuroglial tissue of the filum. VIN-IS-53 marked ependyma, cell bodies and dorsal white matter in the conus and strongly marked neuroglial tissue in the filum. AC4 marked neuronal cell bodies and white matter in the dorsal conus and strongly marked neuroglial tissue in the filum. FP3 and NOT1 marked neuronal cell bodies of the conus and were typically negative in the filum except for rare neuronal cell bodies. NOT1 also marked ependyma in the conus and filum. Glial fibrillary acidic protein, synaptophysin, neurofilament protein and epithelial membrane antigen showed expected reactivity in neuroglial elements of the filum and conus. No staining was seen in neuroglial tissue for CAM5.2, smooth muscle actin, myoglobin, desmin, HMB45 or HAM56. Conclusions: The immunoprofile of the normal conus medullaris and filum terminale was defined with a panel of developmental caudal neural tube markers and a panel of mature markers specific for neuroglial, epithelial and mesenchymal tissues.