Objective: To clarify the incidence and clinical significance of HTLV-I associated myelopathy/tropical spastic paraparesis (HAM/TSP) showing T2 hyperintensity in the spinal cord on magnetic resonance images (MRI).
Patients and methods: We reviewed the spinal cord MRI of 38 HAM/TSP patients and analyzed them in relation to clinical and laboratory findings. Analyzed data were: age at onset, disease duration, disability status, responsiveness to interferon therapy, brain abnormalities on MRI, serum anti-HTLV-I titers, and cerebrospinal fluid (CSF) findings.
Results: MRI findings of the spinal cord were classified into 3 types, "normal" (n=22, 57.9%), "atrophy" (n=13, 34.2%) and "T2-hyperintensity" (n=3, 7.9%). Patients in the normal and atrophy types showed slowly progressive paraparesis. Significant differences were not found between the normal and atrophy types in any clinical or laboratory data, including disease duration, disability status and responsiveness to interferon-alpha therapy. Meanwhile, all patients showing T2-hyperintensity had severe paraparesis of a rapid progressive nature, with CSF IgG elevation.
Conclusion: HAM/TSP with T2-hyperintensity on spinal MRI shows a rapid progressive clinical course with severe motor impairment. The incidence of this malignant form of HAM/TSP is estimated to be around 7.9%.