Cortical atrophy is relevant in multiple sclerosis at clinical onset.

Introduction: Increasing evidence suggests relevant cortical gray matter pathology in patients with Multiple Sclerosis (MS), but how early this pathology begins; its impact on clinical disability and which cortical areas are primarily affected needs to be further elucidated.
Methods: 115 consecutive patients (10 Clinically Isolated Syndrome (CIS), 32 possible MS (p-MS), 42 Relapsing Remitting MS (RR-MS), 31 Secondary Progressive MS (SP-MS)), and 40 age/gender-matched healthy volunteers (HV) underwent a neurological examination and a 1.5 T MRI. Global and regional Cortical Thickness (CTh) measurements, brain parenchyma fraction and T2 lesion load were analyzed.
Results: We found a significant global cortical thinning in p-MS (2.22 +/- 0.09 mm), RR-MS (2.16 +/- 0.10 mm) and SP-MS (1.98 +/- 0.11 mm) compared to CIS (2.51 +/- 0.11 mm) and HV (2.48 +/- 0.08 mm). The correlations between mean CTh and white matter (WM) lesion load was only moderate in MS (r = -0.393, p = 0.03) and absent in p-MS (r = -0.147, p = 0.422). Analysis of regional CTh revealed that the majority of cortical areas were involved not only in MS, but also in p-MS. The type of clinical picture at onset (in particular, pyramidal signs/symptoms and optic neuritis) correlated with atrophy in the corresponding cortical areas.
Discussion: Cortical thinning is a diffuse and early phenomenon in MS already detectable at clinical onset. It correlates with clinical disability and is partially independent from WM inflammatory pathology.