Cutaneous sensory impairment in rheumatoid atlanto-axial subluxation assessed quantitatively by electrical stimulation.

Thresholds for cutaneous perception and pain in 27 rheumatoid patients were investigated by electrical stimulation. Patients with atlanto-axial subluxation showed impaired sensibility over the ophthalmic division of the trigeminal nerve. Patients with vertical atlanto-axial subluxation showed in addition to a pronounced decrease in the sensibility over the ophthalmic and maxillary divisions of the trigeminal nerve, also sensory disturbances over cervical, thoracic and lumbar levels. The mandibular division was never affected. The trigeminal sensibility seems to be affected early in the rheumatoid atlanto-axial subluxation and progresses with the severity of the subluxation, possibly due to bony compression of the trigeminal spinal tract at C 1 level.