Extraforaminal lumbar disk herniation. Clinical features and computerized tomography.

Disk herniation lateral to the intervertebral foramen is defined as extraforaminal. Its particular anatomical site makes its clinical and neurologic features completely different from those of posteromedial and posterolateral disk herniations. Prior to the advent of computerized tomography, only diskography was capable of preoperatively identifying this rare disease. We present 5 cases of extraforaminal disk herniation, the clinical and tomographic diagnosis of which was confirmed at surgery. All patients had severe motor deficit and reported sciatica as prevalent over low back pain. The herniated disk was L4-5 in 2 cases and L5-S1 in 3 cases. The CT scan suggested disk protrusion in 2 cases, extrusion in 2 cases, and sequestration in 1 case. Four of these findings were confirmed intraoperatively. Diskectomy was done after hemilaminectomy and partial or total facetectomy. The clinical result was excellent in 2 cases and good in 3 cases after an average follow-up of 10 months. The use of CT scan as part of the routine diagnostic procedure in patients with radicular pain has lowered the number of cases which the surgical findings were inexplicably negative for disk herniation without having to resort to more complex and invasive diagnostic techniques such as myelo-CT and disk-CT. Moreover, preliminary tomographic localization of the extraforaminal disk herniation makes it possible to operate on the affected level using more conservative techniques. In any case, thorough clinical examination is essential for both correct interpretation of the CT scan and appropriate choice of treatment.