Dorsal root ganglia morphologic features in patients with herniation of the nucleus pulposus - Assessment using magnetic resonance myelography and clinical correlation

Study Design. Morphologic features of the dorsal root ganglia were investig ated in patients with herniation of the nucleus pulposus by means of magnet ic resonance myelography. Objectives. This study was undertaken to assess morphologic changes of the dorsal root ganglia in patients with herniation of the nucleus pulposus and to determine the relations between the morphologic features of the dorsal root-ganglia and clinical features. Summary of Background Data. It has recently been reported that application of the nucleus pulposus to a nerve root induces edema in the rat dorsal roo t ganglion. Edema in the human dorsal root ganglion resulting from Lumbar d isc herniation has not been discussed in the literature, to the authors' kn owledge. Methods. Eighty-three consecutive patients (average age 42.1 years; range 1 7 to 77 years) with monoradicular symptoms were examined. Dorsal root gangl ion morpho logic features, i.e., indentations and swelling, were evaluated by magnetic resonance myelography. The dorsal root ganglion swelling at eac h level was quantitatively expressed as a ratio of the dorsal root ganglion width on the involved side to that of the contralateral side and was terme d dorsal root ganglion ratio. Eighty-three uninvolved levels were chosen as controls in a randomized manner. Factors possibly contributing to the morp hologic changes in the dorsal root ganglion were investigated. Neurologic s ymptoms, evaluated by the Japan Orthopaedic Association scoring system, wer e correlated to the morphologic changes. The morphologic features were foll owed up for 1 year after treatment in a small group of patients. Results. Dorsal root ganglion indentations were always found in the narrowe d intervertebral foramens. The incidence of indentations was significantly higher at the involved nerve roots (10.8%) than at the uninvolved nerve roo ts (4.0%) (P = 0.026). Patients with dorsal root ganglion indentations were significantly older (P = 0.0008). Leg pain scores in patients with indenta tions were significantly poor (P = 0.007). The dorsal root ganglion ratios significantly higher at the involved levels than at the,uninvolved levels ( P = 0.001); the means +/- SD were 1.19 0.25 and 1.08 +/- 0.13, respectively . Patients with lateral herniated nucleus pulposus had significantly higher dorsal root ganglion ratios than those with central herniated nucleus pulp osus (P = 0.0007); the mean ratios SD were 1.48 +/- 0.32 and 1.10 +/- 0.12, respectively. A moderate positive correlation was found between dorsal roo t ganglion ratio and age (Pearson's correlation coefficient 0.313). There w as moderate negative correlation between the dorsal root ganglion ratio and leg pain, gait motor, and total Japan Orthopaedic Association score (corre lation coefficients were = -0.385, -0.350, -0422, and 0.358 respectively) T he dorsal root ganglion ratios were significantly diminished at 1-year foll ow-up (P = 0.001); the means +/- SD were 1.22 +/- 0.22 and 109 +/- 0.07, re spectively. Indentations observed before treatment disappeared after treatm ent. Conclusions. Swelling and impingement in the involved dorsal root ganglion were clearly visualized by magnetic resonance myelography. The swelling and indentations were well correlated with severity of leg pain. These finding s have important value in understanding the pathophysiology of the nerve ro ots in herniated nucleus pulposus.