A prospective study of “undiagnosed” isolated myelopathy: II. Value of magnetic resonance imaging, evoked potentials and CSF analysis

Abstract

We aimed to determine the sensitivity of available "diagnostic" tests in detecting subclinical abnormalities characteristic of multiple sclerosis (MS) in patients with unexplained isolated myelopathy, and any relationship between test results and level of disability. The trial investigations were carried out in 69 prospectively selected patients with acute or chronic noncompressive myelopathies. Magnetic resonance scans were the most sensitive individual tests, revealing asymptomatic brain lesions in 51 patients (74%, C.I. 64-84). An abnormal IgG/albumin ratio (IgG/A) was present in 29 (42%, C.I. 30-54), oligoclonal bands (OCB) in 27 (39%, C.I. 17-39) and abnormal evoked potentials (EP) (visual and/or auditory brain stem) in 19 cases (28%, C.I. 17-39). OCB and abnormal EP were found significantly less often than in control patients with clinically definite MS (CDMS) and significantly more often than in patients with myelopathy due to other conditions. The number of anatomical brain areas with lesions on magnetic resonance imaging (MRI) was significantly associated with CSF abnormalities; abnormal EP were correlated with abnormal MRI and elevated CSF immunoglobulins. Clinical classifications, age, symptom duration, disability levels and genetic factors did not appear to influence the prevalence of abnormal MRI or CSF. For the exclusion of compressive and structural diseases of the spinal cord, myelography has been superceded by cervical and thoracic MRI. In addition, MRI of the brain is the investigation of choice in patients with myelopathies that remain unexplained after spinal MRI. However, whether used alone or in combination with other tests, the specificity and predictive value of brain MRI abnormalities for the risk of developing MS, as well as the associated "false positive" rates, remain to be defined by long-term follow-up of prospectively ascertained and representative cases.