Segmental spinal dysgenesis: Neuroradiologic findings with clinical and embryologic correlation

BACKGROUND AND PURPOSE: Segmental spinal dysgenesis (SSD) is a rare congeni tal abnormality in which a segment of the spine and spinal cord fails to de velop properly. Our goal was to investigate the neuroradiologic features of this condition in order to correlate our findings with the degree of resid ual spinal cord function, and to provide insight into the embryologic origi n of this disorder. We also aimed to clarify the relationship between SSD a nd other entities, such as multiple vertebral segmentation defects, congeni tal vertebral displacement, and caudal regression syndrome (CRS). METHODS: The records of patients treated at our institutions for congenital spinal anomalies were reviewed, and 10 cases were found to satisfy the inc lusion criteria for SSD. Plain radiographs were available for review in all cases. MR imaging was performed in eight patients, one of whom also underw ent conventional myelography. Two other patients underwent only conventiona l myelography. RESULTS: Segmental vertebral anomalies involved the thoracolumbar, lumbar, or lumbosacral spine. The spinal cord at the level of the abnormality was t hinned or even indiscernible, and a bulky, low-lying cord segment was prese nt caudad to the focal abnormality in most cases. Closed spinal dysraphisms were associated in five cases, and partial sacrococcygeal agenesis in thre e. Renal anomalies were detected in four cases, and dextrocardia in one; al l patients had a neurogenic bladder. CONCLUSION: SSD is an autonomous entity with characteristic clinical and ne uroradiologic features; however, SSD and CRS probably represent two faces o f a single spectrum of segmental malformations of the spine and spinal cord . The neuroradiologic picture depends on the severity of the malformation a nd on its segmental level along the longitudinal embryonic axis. The severi ty of the morphologic derangement correlates with residual spinal cord func tion and with severity of the clinical deficit.