Developmental anomalies of the spinal cord

A review of the literature and a personal collection of human spinal cord anomaly cases revealed a kaleidoscope of malformations and normal variations of this anatomical structure. One of the most frequently found anomalies is dysraphism and, thus, this is clinically one of the most important malformations of the spinal cord. There are different forms of spinal dysraphism combined with brain anomalies. Other forms of spinal malformations should also be discussed in relation to cranial and brain malformations. Certain kinds of neoplasms, such as my‐xopapillary ependymomas and paragangliomas of the medullary conus/filum terminale and sacrococcygeal subcutaneous ependymomas, can be discussed in relation to their embryological aspects. Regarding pathological histogenesis in cases of abnormal course of fibers, fiber tract‐related pathological sulcus formation, neuronal heterotopia etc., many experimental investigations are currently being performed. They include investigations concerned with neural stem cell exploration, target search or crossing of the developing axons and migration of neurons. Senescent changes of survived malformations may also be of interest, such as senile degeneration of the heterotopia. In this review, we propose: (i) a hypothesis on morphogenesis of the ascending course of spinal nerve roots in Chiari anomaly type 2, emphasizing the idea of the ‘craniocervical growth conflict of both neural and mesodermal tissues’(Roth); (ii) at least two possible causes resulting in abnormal longitudinal sulcus formation of the spinal cord surface; (iii) three probable histological types of the filum terminale in the tethered cord; and (iv) a speculation on multipotentiality of the cellular differentiation of ependymal vestiges originating from the embryonal canalization phase.