The patient, a seventeen-year-old high-school student, had radicular pain in the left lower extremity when he was first seen by us in 1991. He was a rugby player (center prop position number three), and, in early December 1991, he had pain on the left side of the low back during rugby training; the pain was not associated with any specific injury. One week after the onset of this pain, he visited a local orthopaedic clinic because of persistent tingling in the left lower limb. Spondylolysis involving the third lumbar vertebra was diagnosed on the basis of radiographic examination. The patient was treated non-operatively with medication, pelvic traction, and thermotherapy. However, the symptoms worsened, and he was examined with magnetic resonance imaging, which revealed an epidural mass located posterolateral to the dura at the third lumbar level. He was referred to our outpatient clinic on January 17, 1992, and a tumor of the cauda equina was diagnosed.
The patient was admitted to the hospital on January 20, 1992, at which time he had pain on the left side of the low back, tingling in the left lower limb, and radicular pain. He had no history of coagulopathy, a previous lumbar operation, or an epidural puncture. The findings of the general physical examination were normal, with normal function of the bowel and bladder and normal laboratory findings. The patient could walk without limping, and the lumbar spine had normal alignment on visual examination. However, flexion of the spine was restricted, with a finger-to-floor distance of thirty centimeters. There were no abnormal cutaneous findings, such as a dimple, a hairy patch, or unusual pigmentation. The third lumbar spinous process and the left buttock were tender. Straight-leg raising produced radicular pain at 30 degrees of elevation of the left lower extremity. Hypoesthesia was present in the medial aspect of the left lower extremity. The deep tendon reflexes were normal in both knees and in the right ankle but were absent in the left ankle. The muscle strength of the lower extremities was evaluated with manual muscle-testing and was found to be normal.
Radiographs and computerized tomography scans showed spondylolysis at the third lumbar vertebra with normal spinal alignment (Fig. 1). Spina bifida was not found. An anteroposterior myelogram showed a large defect on the left between the third and fourth lumbar vertebrae, and a lateral myelogram showed a posterior epidural mass compressing the thecal sac at this level (Fig. 2). Coronal and sagittal magnetic resonance images, made with a 1.5-tesla system (Gyro Scan T5; Philips Medical Systems International B.V., Veenpluis, The Netherlands), showed a large oval mass, approximately twenty-five by fifteen millimeters in size, occupying the posterior epidural space between the third and fourth lumbar vertebrae. The signal intensity was high but non-homogeneous on T1-weighted images and was high with a low-intensity rim on T2-weighted images. An axial image showed an epidural mass that appeared to be continuous with the left vertebral foramen between the third and fourth lumbar vertebrae. Magnetic resonance images of the intervertebral disc between the third and fourth lumbar vertebrae showed a normal shape and a normal intensity (Figs. 3-A, 3-B, and 3-C).
An operation was performed on January 30, 1992. The unstable third lumbar lamina was removed from the pars interarticularis, and a partial laminectomy was performed at the fourth lumbar vertebra. After removal of the ligamentum flavum, the posterior epidural mass was visualized. The mass severely compressed the dural sac centrally to the left lateral edge in the epidural space. The mass adhered strongly to the dura and both the third and the fourth lumbar nerve root. The fourth lumbar nerve root was compressed more severely than was the third. The mass was completely extirpated under microscopic magnification. The capsule of the mass was hard and elastic and was filled with a dark red-gray solid and liquid material. No vascular abnormality was seen in the epidural space. The third lumbar lamina was replaced with bone grafts in the pars interarticularis bilaterally with use of a modified Scott wiring method15.
Examination of histological sections of the mass revealed organizing hemorrhage with infiltration by surrounding fibrous granulation tissue. There was no evidence of neoplasm or infection (Fig. 4).
The pain in the left lower limb was relieved immediately after the operation. The patient returned to playing rugby six months later. At one year after the resection, bilaterial osseous union at the pars interarticularis was confirmed radiographically and the screws and wires were removed. At six years, a slight narrowing of the intervertebral space between the third and fourth lumbar vertebrae was detected during a follow-up radiographic examination. (Fig. 5). At the time, the patient was working as an engineer and had no low-back pain or neurological deficits.