Classification by position of dorsal root ganglia in the lumbosacral region.

In order to determine the incidence of the proximally placed L5 and S1 dorsal root ganglia, 144 patients with lumbosacral radiculopathy were investigated. All of the patients underwent nerve root infiltration for depicting the nerve root. Using some bony landmarks on the anteroposterior radiculogram, the dorsal root ganglia were classified into three types: intraspinal, intraforaminal, and extraforaminal. The intraspinal type was further subdivided into subarticular and sublaminar types. The intraspinal type is more common in the S1 than in the L5 root, regardless of age and sex. Although the proximally placed dorsal root ganglia may offer a locus minoris resistantiae for neural irritation and compression, its role for symptom production of radiculopathy should be further analyzed.