In symptomatic cases of nerve-root irritation due to a herniated lumbar intervertebral disk without any myelographic findings, lateral lumbar disk herniation is most suspicious. However, when myelography is positive, lateral disk herniation may not be revealed. We report a rare case of intra-spinal canal and extraforaminal lumbar disk herniation. A 61-year-old woman complained of right anterior thigh pain. A right femoral nerve stretch test was positive, and knee reflex was absent. There was marked grade 4/5 weakness of the quadriceps, tibialis anterior and extensor hallucis longus muscles. Sensory disturbance was present on the medial aspect of the right lower leg.
Anteroposterior and right oblique myelography projections revealed amputation of the right L4 nerve root and a major right lateral defect in the dural sac at the L4 level. We suspected that the herniated disk had migrated upward to the L4 nerve root at intracanal. However, CTM at L4/5 level showed extensive foraminal and far lateral disk herniation. The angled coronal MRI view showed that the right L4 root was displaced upward beyond the ganglion by an extraforaminal herniated disk with a intraforaminal component. Discogram depicted two herniatied masses lateral to the L4/5 interspace and at L4 intra-canal. At surgery, the two fragments of herniated disk were removed and nerve root compression was relieved. She had complete postoperative recovery.
