A subclinical impairment of ventilatory function in cervical spondylotic myelopathy.

Objective: To evaluate the ventilatory function in patients with cervical spondylotic myelopathy (CSM).

Design: Prospective cohort study.

Setting: Medical school in Japan.

Participants: Thirty-seven consecutive patients with CSM.

Interventions: All the patients had surgical intervention for mild to moderate spastic limb paresis.

Main Outcome Measures: Analysis of the maximum voluntary ventilation (MVV) in addition to routine spirometry before and after surgical decompression. Functional assessment was made by using the Japanese Orthopaedic Association (JOA) Scale.

Results: The MVV (% predicted) increased significantly (P<.002) from 77%+/-19% preoperatively to 84%+/-20% postoperatively. None of the other routine spirometric data (ie, vital capacity, forced vital capacity, forced expired volume in 1 second, peak expiratory flow rate) increased significantly. According to the JOA score, tetraparesis improved significantly (P<.0001) from 8.3+/-3.2 preoperatively to 11.4+/-3.0 postoperatively. The ratio of postoperative to preoperative MVV showed a significant correlation (r=.538, P<.002) with that of the JOA score.

Conclusions: MVV provides a useful measure for monitoring ventilatory impairment in patients with myelopathy.