Butterfly vertebra with lumbar intervertebral disc herniation

A butterfly vertebra is a rare congenital anomaly that is usually asymptomatic. The authors, however, describe a novel case involving a butterfly vertebra overlapping with disc herniation that presented as radiculopathy. A butterfly vertebra is characterized by a symmetrical fusion defect resulting in a sagittal cleft vertebra. Only a few cases of butterfly vertebrae have been reported as incidental findings. This spinal anomaly may be associated with other congenital conditions such as Pfeiffer, Crouzon, Jarcho-Levin, and Alagille syndromes. Moreover, there is no previous report of a case associated with symptomatic disc herniation from the sagittal cleft. The authors excised the herniated disc fragment. They performed intraoperative discography after exposure of the corresponding intervertebral space via a conventional interlaminar approach. Histological examination of a tissue specimen showed scattered chondrocytes in the myxohyaline stroma, which indicated the nucleus pulposus.

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).

The Human Larynx at the End of the Embryonic Period Proper

The laryngeal cavity was studied in eight serially sectioned embryos of stage 23 and in three early fetuses, and graphic reconstructions were prepared. After the isolation of the tracheal from the pharyngeal cavity during stages 16 through 22, a communication (not necessarily the pharyngotracheal duct) appears again during stage 23. At this time (8 postovulatory weeks) the laryngeal cavity comprises 1) the coronal and parts of the sagittal clefts of the vestibule (uniting later at the laryngeal inlet); 2) the ventricles, which are not yet completely formed; and 3) the subglottic cavity, which appeared already in earlier stages. The characteristic events of stage 23 are the dissolution of the epithelial lamina and the development of the ventricles. The disruption of the epithelial lamina is an active process that comprises rearrangement and growth, but not loss of cells. The ventricles, which begin as solid outgrowths in stage 20, do not represent fifth pharyngeal pouches. They now point toward the middle of the still paired thyroid laminae and are not at the level of the future glottis, which lies more caudally. In the absence of the median part of the soft palate, the nasopharynx communicates widely with the oral cavity. The epithelium of the respiratory tube, including the larynx, resembles that of the pharynx and esophagus in being pseudostratified columnar and showing a clear basement membrane. It is ciliated over that part of the epiglottis that surmounts the arytenoid swellings, and also over the tip and back of the latter. The transitional area between the laryngopharynx and the esophagus is already innervated by the recurrent laryngeal nerve. Nerve fibers have not yet reached the epithelium of the coronal cleft and the ventricles, but fibers are present near the sagittal cleft of the vestibule. The sensory innervation of the pharynx and larynx has been followed and plotted for the first time in an embryo, and previously unrecorded silver-impregnated receptors have been observed.