Studio neuroradiologico della diastematomielia: Correlazioni con l'embriopatogenesi

Diastematomyelia is an uncommon defect of the neural axis and spinal column involving a sagittal cleft in the spinal cord and/or cauda equina, and phylum terminale; a spur of bone, cartilage or fibrous tissue separes two distinct spinal compartments and hemicords.

A true double cord, each with four nerve roots is traditionally defined as diplomyelia.

Associated cutaneous, skeletal or visceral anomalies are very common. Clinical onset occurs most frequently in adulthood, with low back pain, perineal hyperpatia and symptoms of motor and sensory deficit. In infantile onset cases pain is less frequent while neurologic symptoms prevail with orthopedic complications. Symptoms generally resemble tethered cord syndrome.

Several hypotheses have been advanced to explain the embryopathogenesis of diastematomyelia, and they give rise to the current accredited theory, recently proposed by Pang and Coll.

This paper resembles these hypoteses and explanes the actual accepted theory: the formation of an “ectopic or accessory neurenteric canal” abnormally joining the ectodermal and entodermal layers, bisects the notocord in its cranial development from Hensen's node; a regional splitting of the notocord takes place at this level and the maturative outcome is a split spinal cord with spinal dysraphism.

Recently (1992) Pang and Coll. perfected this theory postulating a migration of mesenchymal cells along the accessory neurenteric canal, to form an “endomesenchymal tract”. The presence of displaced mesenchyma other than ectoderm and endoderm, is able to explain the entire complex of associated anomalies in diastematomyelia. Finally, they have by-passed the traditional distinction between diastematomyelia and diplomyelia, proposing a new unified theory of “Split Cord Malformations” (SCM).