Magnetic resonance imaging in the preoperative evaluation of cervical radiculopathy. Forty patients with cervical radiculopathy were examined preoperatively with magnetic resonance imaging (MRI). MRI was used alone in 27 (68%) of the 40 patients; the remainder also had computed tomography in conjunction with myelography. The primary criterion on MRI for a clinically significant lesion was asymmetrical narrowing of the subarachnoid space in the region of the nerve root. Surgical confirmation of the abnormality was obtained in all 40 cases. The operative findings were a herniated nucleus pulposus (32 of 40 patients), spondylosis (2 of 40 patients), or a combination of the two (6 of 40 patients). MRI identified a surgical lesion (herniated nucleus pulposus, spondylosis, or both) in 37 of the 40 (92%) patients. We think MRI is the only preoperative imaging examination necessary in most cases of cervical radiculopathy. 