Impaired postural stability in patients with cervical myelopathy - Evaluation by computerized static stabilometry

Study Design. A prospective clinical study. Objective. To quantitatively evaluate impairment of postural stability in patients with cervical myelopathy. Summary of Background Data. Proprioceptive sensation plays an important role in coordinated movement of the lower extremities and postural stability. Nevertheless, although disturbance of proprioceptive information will have an influence on the maintenance of postural stability, there have been few studies dealing with deterioration of postural stability in patients with cervical myelopathy. Methods. We investigated 52 cervical myelopathy patients who could stand without support and compared the results with those of 29 age-matched healthy volunteers. Postural stability was examined using a stabilometer. In the stabilometer, sway of gravity center was measured at upright position with eyes closed for 30 seconds. We used 2 parameters for evaluation: environmental area (EA), which measures degree of sway of the gravity center, and locus length per environmental area (L/EA), which measures fine control of standing posture by proprioceptive reflexes. Results. The mean EA of the patient group was 13.9, whereas that of the control group was 2.74, revealing significantly larger postural instability in the patient group compared to the control group. The L/EA of the patient group was significantly worse than the control group. It was also shown that postural instability was significantly larger in the myelopathy patients with the severe clinical symptoms. Conclusion. The results of the present study demonstrate impairment of postural stability in patients with cervical myelopathy. The stabilometer can objectively evaluate the postural stability, which may reflect the function of the dorsal columns and the corticospinal tracts. Thus, stabilometry is a useful method for measuring a part of proprioceptive function and for objective assessment of the lower limb function of cervical myelopathy.