Stance ataxia and delayed leg muscle responses to postural perturbations in cervical spondylotic myelopathy.

OBJECTIVE We studied balance control in patients with cervical spondylosis, on the hypothesis that ataxia and changes in postural responses occur concurrently as a consequence of structural problems in the cervical cord. SUBJECTS AND PATIENTS Seventeen patients and 17 healthy subjects were recruited. Based on magnetic resonance imaging, the patients were divided into 2 groups, with (n=9) and without (n=8) signs of myelopathy. METHODS Body sway was recorded under quiet stance on a force platform. Postural perturbations evoked early and late responses in soleus and tibialis anterior. RESULTS Most patients showed increased body sway during stance, which was larger in cervical spondylosis with myelopathy than cervical spondylosis. Early postural responses in the soleus were not affected. Late responses in soleus and tibialis anterior were delayed in cervical spondylosis with myelopathy. Across all patients, latency of tibialis anterior late response was correlated with lower limb sensory impairment and amplitude of body sway. CONCLUSION Abnormal transmission through the cervical cord of proprioceptive input to supraspinal centres and of descending commands to caudal cord levels are accountable for ataxia in cervical spondylosis with myelopathy. Stabilometry may be an economic and easy way in a clinical and rehabilitative setting to distinguish severe from mild forms of cervical spondylosis prior to physical treatment and to help the differential diagnosis from other diseases featuring similar signs.