The natural course of pre-clinical spondylotic cervical cordcompression and predictors of its clinical manifestation

In a previous study (Bednarik et al., 1998) we showed the value of somatosensory and motor evoked potential (MEP) parameters in assessment of the clinical relevance of cervical cord compression in clinically silent cases. We felt that a comparison of the predictive value of some other electrophysiological, clinical and radiological variables was indicated, in a larger group of patients over a longer follow-up period. A group of 66 patients (32 women, 34 men, median age 50 years) with magnetic resonance signs of spondylotic cervical cord compression and without clear-cut clinical signs of spondylotic cervical myelopathy (SCM) was prospectively followed for at least 2 years (range: 2-8 years, median follow-up period: 4 years). Primary endpoint was the development of clinical myelopathic signs. Clinical, radiological and electrophysiological parameters were assessed by three independent observers and then correlated with the clinical outcome. Clinical signs of myelopathy were detected in 13 patients (19.7%) during the follow-up period. The only variables significantly associated with the development of clinically symptomatic SCM were the presence of symptomatic cervical radiculopathy (92% of SCM cases), abnormal somatosensory (SEP) and/or motor evoked potentials (84.6%) and EMG signs of multisegmental anterior horn cell lesion (61.5%). In contrast, radiological parameters, such as Pavlovs ratio, spinal cord compression ratio, and spinal cord hyperintensity and area, showed no significant association with the development of symptomatic SCM. Thirty-four patients showed no signs of clinical radiculopathy and normal EP and EMG findings at the beginning: none of them developed clinical signs of clinically symptomatic SCM during the follow-up period. Conclusions. Evoked potentials and EMG signs of subclinical cervical cord lesion together with clinical signs of cervical radiculopathy may predict the development of clinically manifest SCM and could thus serve as valuable tools in its management.