Dermatomal somatosensory evoked potentials in the diagnosis of patients with lumbosacral radiculopathies

Dermatomal somatosensory evoked potentials in the diagnosis of patients with lumbosacral radiculopathies Objective: To assess the association between electrophysiological studies and magnetic resonance imaging (MRI), clinical findings and its contribution to the diagnosis of lumbosacral radiculopathies. Method: 30 patients (9 F, 21 M) with back and leg pain and with root compression detected only at one level on MRI were admitted to the study. All patients were under the care of neurosurgery clinic in our hospital. 21 (11 F, 10 M) healthy volunters were admitted to the study as the control group. Bilaterally tibial and peroneal nerve motor, superficial peroneal and sural nerve sensory conduction studies, tibial F response, soleus H reflex, tibial nerve somatosensory evoked potentials (SEP) and L3, L4, L5 and S1 dermatomal SEP (DSEP) responses were evaluated in all participants. Additionally, needle electromyography (EMG) examinations were performed in the patient group. Results: All of the 30 patients had lumbosacral disc herniation on MRI, 17 (58,8%) of them had radiculopathy by needle EMG consistent with MRI findings. 7 (58,3%) of 12 patients who had L5/S1 disc herniation, had abnormal soleus H reflex responses. Although DSEP responses of 27 (90%) patients showed an abnormality, only 7 (23,3%) patients’ findings were consistent with MRI. Ten patients had tibial SEP abnormalities, however 6 (20%) of these patients’ findings were in concordance with MRI. Conclusions: We suggest that needle EMG is the most sensitive electrophysiological examination to localize the radiculopathy in patients with lumbosacral disc herniation. The sensitivity of soleus H reflex is similar to the needle EMG findings, especially in patients with S1 radiculopathy. Although the sensitivity of DSEP examinations was found to be high, spesifity was found to be low due to the detected subclinical involvement.