In vivo imaging of spinal cord atrophy in neuroinflammatory diseases

Objective: Spinal cord atrophy is prominent in chronic progressive neurologic diseases such as human T-cell lymphotropic virus type 1 (HTLV-1)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and multiple sclerosis (MS). Here we compared the spinal cord cross-sectional area (SCCSA) in HAM/TSP and MS patients to that of healthy volunteers (HVs). Methods: SCCSA and clinical disability scores were measured in 18 HAM/TSP patients, 4 asymptomatic carriers (ACs) of HTLV-1, 18 MS patients, and 10 HVs from a 3T magnetic resonance imaging. SCCSA measured in patients and ACs were compared to that of HVs and correlated with disability scores. Results: The entire spinal cord in HAM/TSP patients was thin compared to HVs, whereas only the cervical cord in MS patients was thinner than in HVs (p < 0.0001). In HAM/TSP patients, SCCSA extensively correlated with Ambulation Index, whereas only the cervical cord correlated with disease duration (p < 0.05). In MS patients, the SCCSA extensively correlated with Scripps Neurologic Rating Score and the Expanded Disability Status Scale (p < 0.05). One of the 4 ACs showed atrophy in a pattern similar to HAM/TSP. Interpretation: These results are in accordance with the findings that whereas over half of all lesions in an MS cord are seen in the upper cervical cord, most of the pathology in HAM/TSP is seen in the thoracolumbar cord, which in turn may be responsible for the more extensive cord atrophy seen in HAM/TSP. An imaging marker such as SCCSA might serve as a surrogate endpoint in clinical trials, especially to assess the neuroprotective impact of various therapies.