Neurologic involvement in patients with rheumatoid arthritis with atlantoaxial subluxation--a clinical and neurophysiological study.

Anterior subluxation of the atlantoaxial joint (AAS) is a frequent and potentially serious complication of rheumatoid arthritis (RA). The results of neurological evaluation, obtained in 30 patients with RA with AAS, and of somatosensory evoked potentials (SEP) studies, accomplished in 25 of these patients, were compared with the findings observed in 20 patients with RA without AAS, all of whom underwent neurological evaluation and SEP studies. Abnormal plantar responses were found only in patients with RA with AAS. There were more frequent SEP abnormalities in patients with RA with AAS than in patients without AAS, namely increased latencies of the N13 potentials evoked by stimulation of the median and radial nerves, which correspond to conduction delays at the cervical spinal cord level. A sensitivity of 56% and a specificity of 90% for SEP studies in the diagnosis of AAS in patients with RA were found. On the other hand, the observation that the mean values for the latencies of the N11 and N13 potentials evoked by stimulation of the radial nerves were significantly higher in patients with RA with AAS compared to patients with RA without AAS may suggest the existence of a frequent subclinical involvement of the cervical spinal cord caused by AAS.