Conjoined lumbosacral nerve roots: current aspects of diagnosis

Abstract

Conjoined lumbosacral nerve roots (CLNR) are the most common anomalies involving the lumbar nerve structures which can be one of the origins of failed back syndromes. They can cause sciatica even without the presence of a additional compressive impingement (such as disc herniation, spondylolisthesis or lateral recess stenosis), and often congenital lumbosacral spine anomalies (such as bony defects) are present at the "conjoined sheaths". This congenital anomaly has been reported in 14% of cadaver studies, but myelographic or computed tomographic studies have revealed an incidence of approximately 4% only. Diagnostic methods such as magnetic resonance imaging (MRI) are helpful for determination of the exact anatomical relations in this context. We present five typical cases of conjoined nerve roots observed during a 1 year period, equivalent to 6% of our out-patients without a history of surgical treatment on the lumbar spine. In all cases with suspicious radiological findings MRI or lumbar myelography combined with CT and multiplanar reconstructions is recommended.

Fig. 1

Case 1. Suboptimal CT scan showing a space-occupying process on the left side (arrow); a herniated disc was assumed at level L5/S1

Fig. 2

Case 1. Axial T2-weighted MR image with abnormal dural sac configuration (arrow) on the side of the conjoined nerve roots

Fig. 3

Case 1. Axial T1-weighted MR image with combined passage of the nerve roots L5 and S1 (arrow) through the neuroforamen L5/S1

Fig. 4

Case 2. Myelography with prolapsing disc L4/L5 and associated spinal channel stenosis. Conjoined nerves L4/L5 (arrow) are seen on the left side

Fig. 5

Axial CT scan, bone window. Conjoined nerve anomaly of S2 and S3 on the left side with impression (arrow) of bony structures

Fig. 6

Myelography with conjoined nerves L5/S1 (arrow) on the right side