Abstract
Introduction
In degenerative lumbar spine, it seems possible that foraminal stenosis is over-diagnosed as axial scanning is not performed in the plane of the exiting nerve root. We carried out a two-part study to determine the true incidence of foraminal stenosis.
Patients and Methods
Initially we performed a retrospective analysis of radiology reports of conventional Magnetic Resonance Imaging in 100 cases of definite spinal stenosis to determine the incidence of reported ‘foraminal stenosis’. Subsiquently we performed a prospective study of MRI including fine slice T2 and T2 STIR coronal sequences in 100 patients with suspected stenosis. Three surgeons and one radiologist independently compared the diagnoses on conventional axial and sagittal sequences with the coronal scans.
Results
The retrospective analysis found that ‘foraminal stenosis’ was reported by radiologists in 46% using conventional axial and sagittal sequences. In the prospective study of 100 patients suspected of having stenosis, spinal stenosis was reported in 40; degenerative spondylolisthesis in 14; posterolateral disc herniation in 14; normal report in 13; far lateral disc herniation in 7; isthmic (lytic) spondylolisthesis in 6; and degenerative scoliosis in 6. Conventional sequences diagnosed lateral recess stenosis reliably, but also suggested foraminal stenosis in 43%. However, coronal sequences clearly showed no foraminal nerve compression at all. In degenerative spondylolisthesis conventional scans suggested foraminal stenosis in 10 of 14 cases. Coronal imaging again showed no foraminal stenosis. Excellent correlation was found in normal spines and in disc herniation. Foraminal nerve compression was confirmed by conventional and coronal imaging only in isthmic spondylolisthesis, degenerative scoliosis and far lateral disc herniation.
Conclusion
The addition of coronal MRI proves that foraminal stenosis is over-diagnosed. True foraminal stenosis definitely exists in isthmic spondylolisthesis, degenerative scoliosis and far lateral disc herniation, but we question its existence in spinal stenosis and degenerative spondylolisthesis.
