Dermatomal somato sensory evoked potentials in cervical spondylosis

Dermatomal somatosensory evoked potentials (DSSEP) from C5-T1 dermatomes were recorded in 20 normal healthy adult volunteers as controls and 61 patients with neck pain. The patients were divided into three groups. Group I : symptomatic patients withclinical signs of C5-T1 radiculopathy and radiological evidence of cervical spondylosis (21 patients). Group II : symptomatic patients without clinical signs of radiculopathy but with radiological evidence of cervical spondylosis (20 patients). Group III: patients with persistent neck pain without any clinical radiculopathy or radiological evidence of cervical spondylosis (20 patients). A complete neurological examination and nerve conduction study of median and ulnar nerves were done to rule out peripheral neuropathy. Normative data was established for DSSEP from C5-T1 dermatomes using the control group and the values obtained were comparable with western normative data. In the group I, DSSEP was abnormal in all the cases. It was possible to preciselylocate the involvement of C5 root in 75 , C6 root in 88.88, C7 root in 92.30 , C8 root in 76.92, and T1 root in 100. The DSSEP was abnormal in 11 patients in Group II, but was normal in all the patients of Gruoup III. DSSEP of C5-T1 dermatomes correlated well with the clinical findings in Group I patients. It was possible to detect subclinical radioculopathy in a significant number of patients in Group II. DSSEP is a simple non invasive method for evaluation of cervical radiculopathy.