Radiological Changes in Spinal Cord and Brain of Patients with HTLV-1 Associated Myelopathy/Tropical Spastic Paraparesis (HAM/TSP)

HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a chronic progressive neurological disorder and shares many radiological and clinical features with other more prevalent myelopathies. Here, we quantified spinal cord and brain volumes in adults with HAM/TSP in comparison with healthy volunteers (HVs) and participants diagnosed with multiple sclerosis (MS). Clinical disability and MRI were assessed in 24 HVs, 43 HAM/TSP, and 46 MS participants. Spinal cord cross-sectional area (SCCSA) and brain tissue volumes were measured and compared. HAM/TSP participants had significantly lower SCCSA at C2-3 (54.0±8 mm2), C4-5 (57.8±8 mm2), and T4-9 (22.7±4 mm2) and significantly elevated brain white matter hyperintensity (WMH) fraction (0.004±0.008) was compared to HVs (C2-3: 69.4±8 mm2, C4-5: 75.1±9 mm2, T4-9: 34.1±4 mm2; all p < 0.0001; and WMH: 0.0004±0.0007; p < 0.001). In HAM/TSP, SCCSA at all levels but not WMH showed the significant correlation with clinical disability scores. Brain white matter hyperintensities in HAM/TSP, therefore, may not be related to clinical disability. SCCSA and WMH in our limited MS cohort were higher than the HAM/TSP cohort (67.6±8 mm2, 72.7±9 mm2, 33.4±5 mm2; p < 0.0001). Principal component analysis suggested that SCCSA and WMH may be used to differentiated HAM/TSP from MS. Understanding these differences may help establish early diagnostic criteria for HAM/TSP patients.