Conjoined lumbosacral nerve roots. Diagnosis with metrizamide myelography.

The most common anomaly of the lumbosacral nerve roots consists of a composite root sleeve containing the roots for two spinal nerves. Before the advent of water-soluble myelography, this anomaly was rarely diagnosed except at operation. Metrizamide myelography readily demonstrates the anomaly because of improved filling of the root sleeves and greater definition of the nerve roots within the subarachnoid space. However, an underlying disk herniation may not be evident on the myelogram because of the unique anatomic configuration.