Anomalies of the lumbosacral nerve roots. An anatomic investigation.

Some patients suffering from lumbar disk herniation do not manifest the typical clinical symptoms expected for this disorder. Lumbar disk surgery occasionally reveals anatomic abnormalities in the nerve roots of these individuals. Therefore, to gain greater medical insight into these anomalies, an investigation of the lumbar and sacral nerve roots of 60 fresh cadavers was performed. Anatomic specimens were obtained through postmortem examination within 24 hours of death. Wide deroofing of the T10 to S5 spinal segment exposed the spinal canal for thorough investigation of every lumbar and sacral nerve root, including a detailed examination of their intradural and extradural anastomosis. Findings included a 30% incidence of anomalies of the lumbar and sacral nerve roots. The incidence of anomalies of L4 to sacral nerve roots was 13.3%, comparable to statistics reported elsewhere. Six types of anomalies were classified. Complex anomalies were common.