Somatosensory-evoked potentials as an add-on diagnostic procedure to imaging studies in patients with lumbosacral spinal canal stenosis

Abstract Introduction Lumbo-sacral spinal stenosis (LSS) is a frequent cause for chronic low back pain. The diagnosis is primarily radiological. Neural insult is not frequent in every case. Although the degree and type of LSS can exactly be described with the current imaging studies, the extent of neural impairment cannot be expressed by radiological means. Electrophysiological investigations have an important role in determining the extent of neural compromise. The aim of this study was to evaluate the validity of mixed and dermatomal somatosensory-evoked potentials (SEPs) for the diagnosis of neurological compromise in LSS. Subjects Twenty-two patients (11 men and 11 women) with CT and/or MRI-based confirmation of LSS were enrolled. All patients went through thorough neurological and electrophysiological examination. Twenty healthy individuals matching to patients for age and sex were enrolled in the electrophysiologic tests as a control group. Results Classic neurogenic claudication was encountered in 86.4% of cases (19 patients). Examination revealed neurologic deficits in six patients (27.3%). MRI evidence of nerve root compression was found in only 12 patients (54.5%). The incidence of electrophysiological abnormality was the highest using dermatomal SEP (90.9%) followed by mixed SEP of the posterior tibial nerve (81.8 %), H-reflex comes next (59.1%), and finally F-wave, which showed the lowest incidence (18.2%). The correlation analysis between different electrophysiologic items and the patient's complaint of neurogenic claudication was best with dermatomal SEP (77.3%), followed by mixed SEP (68.2%) with a significant fair agreement. Conclusion Dermatomal and mixed SEPs had added to the clinical and radiological assessment of patients with LSS providing evidence for root dysfunction. Their inclusion in routine evaluation of those patients would help detection of functional integrity of the neural structures.