Cranial magnetic resonance imaging in the evaluation of myelopathy of undetermined etiology.

The spinal form of MS is a clinical conundrum, the solution of which may yield many answers; to be certain that it is MS and not another disease causing the myelopathy is often difficult. We evaluated 20 patients with myelopathy of undetermined etiology (clinical findings limited to the spinal cord) using T2-weighted cranial magnetic resonance imaging (T2 MRI) and cranial computerized tomography (CT). Some patients were also studied with flash visual evoked responses (FVER) and spinal fluid analysis for myelin basic protein (MBP) and oligoclonal banding (OCB). Thirteen patients had T2 MRIs consistent with demyelinating disease (two or more areas of increased signal intensity, of appropriate size, in periventricular/subcortical white matter), while only one CT showed focal lesions. FVER were abnormal in 8 of 15 patients tested; spinal fluid OCB was present in 12 of 16 patients tested, only 1 of whom had elevated MBP. T2 MRI showed lesions typical of demyelination in the majority of study patients, was much more sensitive than CT, and was well correlated with evidence of demyelination by other tests. Although the specificity of T2 MRI in MS is unknown, it may be very high in this clinical setting.