Imaging - 2Friday, September 11, 2009, 15:30 - 17:30The relationship of thalamic volume and shape to pain in relapsing-remitting multiple sclerosisK. Sheehan, H. Wishart, R. Roth, L. Shen, J. Wan, J. MacDonald, J. Ford, J. Seville, B. Oliver, L. Kasper (Lebanon, Indiannapolis, US)
Multiple sclerosis is associated with thalamic atrophy, even in the early stages of the disease. Differences in thalamic volume between patients with MS and healthy controls have been demonstrated even after accounting for differences in brain parenchymal fraction. The clinical significance of thalamic atrophy in MS is under active investigation. Given the importance of the thalamus in the brain’s pain circuitry and elevated levels of neuropathic pain experienced by patients with MS, we examined the relationship of thalamic volume and shape to pain self-ratings in patients with MS. Participants were patients with mild to moderate relapsing-remitting MS (n=25; Extended Disability Status Scale = 2.7 + 1.5), evaluated and diagnosed according to standard criteria at our MS Center, and healthy demographically matched controls (n=12). MRI scans included a coronal T1-weighted 3D spoiled gradient recalled (SPGR) acquisition and an axial fluid-attenuated inversion recovery (FLAIR) scan. A single investigator (KS) performed all the thalamic tracings, blind to group membership, using our laboratory’s standardized procedure manual for thalamic segmentation. Inter- and intra-rater reliability, evaluated using intraclass correlation coefficients on a separate set of eight scans, were 0.82 and 0.93 respectively. The thalamic segmentations were reconstructed and registered to the original T1 scans, and submitted to shape analysis using spherical harmonic (SPHARM) surface modeling. Participants completed the Pain Effects Scale, a self-report questionnaire comprised of six items, with a maximum total pain score of 30, that assesses the ways in which pain interferes with mood, ability to walk or move, sleep, work, recreational activities, and enjoyment of life. An overall pain severity self-rating was also obtained using a visual Likert scale. Thalamic volume was lower in patients than controls (t(35)= 2.12, p <.05) and lower thalamic volume was associated with higher self-rated pain (r= 0.47, p<.05). This relationship persisted even after covarying for total lesion volume, total brain tissue volume, and medications for pain, disease and depression (all p<.05). SPHARM modeling revealed regionally specific relations between thalamic volume loss and pain self-ratings (cluster region p < .05). These results suggest a role of the thalamus in MS-related pain symptoms, a finding we are investigating further in work on the neural and genetic basis of pain in MS.
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