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17-06-2015 | Multiple sclerosis | Article

Thoracic cord grey matter atrophy may reflect regional disability in MS

medwireNews: Lower thoracic spinal cord grey matter (GM) area is significantly associated with multiple sclerosis (MS) disability and may be a means of tracking disease progress, in vivo study findings show.

The results showed that 43 patients with progressive MS had more pronounced thoracic cord GM atrophy than 99 patients with relapsing MS, as measured using phase-sensitive inversion recovery magnetic resonance imaging. The findings expand on earlier evidence of a similar association with upper cervical GM atrophy.

The greatest differences in thoracic GM area, of 3.90 mm2 (20.3%) and 3.20 mm2 (19.3%), were seen at disc levels C3/C4 and C2/C3, respectively. But GM area was also significantly reduced by 1.37 mm2 (13.2%) at T9/T10 and by 1.02 mm2 (10.6%) at T8/T9 in patients with progressive MS, compared with those with relapsing MS.

This GM atrophy contributed to total cord areas being significantly reduced at all four disc levels in patients with progressive versus relapsing MS, whereas total cord areas in patients with relapsing MS did not differ significantly from those of 20 healthy patients matched for age and gender. Thoracic GM atrophy was also more selective in patients with relapsing MS compared with controls, being significantly smaller only at disc levels C2/C3, T8/T9 and T9/T10.

The researchers, led by Regina Schlaeger (University of California, San Francisco, USA), note that total cord area, white matter area and GM area all correlated inversely with Expanded Disability Status Scale (EDSS) score. With regard to GM area, cervical GM made the biggest contribution in multivariable regression analyses followed by thoracic GM and then brain GM volume.

Cervical and thoracic GM area measurements contributed independently to EDSS score, leading Schlaeger and team to suggest that, although they reflect a global process of GM degeneration in MS, they also “convey regional information concerning atrophy.”

Such individual variation within the thoracic cord could have direct functional consequences, they say. “We observed a moderate, but significant, association between the thoracic GM area at the disc level T9/T10 and the strength of muscles (ie, iliopsoas) innervated by the corresponding segmental level (L1/L2)”, the team reports in JAMA Neurology.

“In line with this observation, [9-hole peg test] was only correlated with [spinal cord] GM areas at cervical levels, not at the thoracic levels.”

The researchers say that a robust relationship between cord GM atrophy and disability, which is far stronger than those known for measures of cortical GM or white matter, suggests the need for a “reorientation” of current imaging practices.

“Magnetic resonance imaging-based estimations of cord GM that have strong correlations with MS disability may better track the disease process in the context of both clinical trials and longitudinal observational studies”, they conclude.

By Lucy Piper

medwireNews is an independent medical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2015