[Lumbar Foraminal Stenosis: Diagnosis and Microsurgical Decompression]

Lumbar foraminal stenosis is a common problem; however, correct diagnosis and appropriate surgical treatment are difficult. This article describes the author's techniques for imaging diagnosis using thin-slice magnetic resonance imaging(MRI) and the microsurgical technique of foraminal decompression through the intermuscular approach. Thin-slice MRI consists of 1-mm thickness continuous images of the lumbar spine using a T2-weighted-image-based sequence. With multiplanar reconstruction in three planes, all nerve roots are carefully observed from the lateral recess to the extraforaminal area. This technique provides the correct diagnosis of subtle nerve root compression in the foramen. The outlet of the intervertebral foramen is exposed using Wiltse's intermuscular approach. To avoid disorientation, several surgical landmarks and two basic routes to reach the outlet of the foramen are established. The foramen is carefully unroofed by using an ultrasonic bone curette. For complete decompression of the nerve root and ganglion, the inferomedial aspect of the pedicle and its medial and lateral limits should be determined. In addition, the yellow ligament must be completely removed, and the intertransverse ligament lateral to the nerve root should be sufficiently decompressed.