MRI contributes to the differentiation between MS and HTLV-I associated myelopathy in British Columbian coastal natives.

BACKGROUND Human T-cell lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) in British Columbian Coastal Natives has, to date, been a clinical and laboratory diagnosis. However, magnetic resonance imaging (MRI) abnormalities have been well-described in other populations in which HAM/TSP is endemic. METHODS In order to assess the usefulness of MRI as a diagnostic tool in this population, we compared scans of HAM/TSP patients with those of HTLV-I positive non-HAM/TSP British Columbian Coastal Natives (carriers) and multiple sclerosis patients presenting with progressive paraparesis. RESULTS The typical nonspecific findings of thoracic cord atrophy and increased signal in the periventricular and subcortical white matter on T2-weighted images were confirmed in the HAM/TSP patients. Despite a lack of specificity of the MRI findings between HAM/TSP patients and HTLV-I carriers, criteria that could effectively differentiate HAM/TSP patients from multiple sclerosis patients with similar clinical presentations were determined. CONCLUSIONS Clinical and radiological correlations suggest that longitudinal MRI investigations charting the course of HAM/TSP may reveal the clinical significance of these lesions and further define the role of MRI in the diagnosis of this entity. Magnetic resonance imaging is an important supplement to immunological and clinical data in differentiating multiple sclerosis from HAM/TSP.