title: Grey matter damage and overall cognitive impairment in primary progressive multiple sclerosis.
abstract: OBJECTIVE
  To identify associations between cognitive impairment and imaging measures in a cross-sectional study of patients with primary progressive multiple sclerosis (PPMS).
  
  
  METHODS
  Neuropsychological tests were administered to 27 patients with PPMS and 31 controls. Patients underwent brain conventional magnetic resonance imaging (MRI) sequences, volumetric scans and magnetization transfer (MT) imaging; MT ratio (MTR) parameters, grey matter (GM) and normal-appearing white matter (NAWM) volumes, and WM T2 lesion load (T2LL) were obtained. In patients, multiple linear regression models identified the imaging measure associated with the abnormal cognitive tests independently from the other imaging variables. Partial correlation coefficients (PCC) were reported.
  
  
  RESULTS
  Patients performed worse on tests of attention/speed of visual information processing, delayed verbal memory, and executive function, and had a worse overall cognitive performance index, when compared with controls. In patients, a lower GM peak location MTR was associated with worse overall cognitive performance (p < 0.001, PCC = 0.77). GM mean and peak height MTR showed the strongest association with the estimated verbal intelligence quotient (IQ) decline (p < 0.001, PCC = -0.62), and executive function (p < 0.001, PCC = 0.79). NAWM volume was associated with attention/speed of visual information processing (p < 0.001, PCC = 0.74), while T2LL was associated with delayed verbal memory (p = 0.007, PCC = -0.55).
  
  
  CONCLUSIONS
  The finding of strong associations between GM MTR, NAWM volume and T2LL and specific cognitive impairments suggests that models that predict cognitive impairment in PPMS should include comprehensive MRI assessments of both GM and WM. However, GM MTR appears to be the main correlate of overall cognitive dysfunction, underlining the role of abnormal GM integrity in determining cognitive impairment in PPMS.
authors.affiliation: Department of Brain Repair and Rehabilitation, UCL Institute of Neurology, London, UK.
authors.forename: C
authors.initials: C
authors.lastname: Tur
authors.forename: S
authors.initials: S
authors.lastname: Penny
authors.forename: Z
authors.initials: Z
authors.lastname: Khaleeli
authors.forename: D R
authors.initials: DR
authors.lastname: Altmann
authors.forename: L
authors.initials: L
authors.lastname: Cipolotti
authors.forename: M
authors.initials: M
authors.lastname: Ron
authors.forename: A J
authors.initials: AJ
authors.lastname: Thompson
authors.forename: O
authors.initials: O
authors.lastname: Ciccarelli
mesh_terms: D000328:Adult; D000368:Aged; D001288:Attention; D001921:Brain / Q000473:pathology* / Q000503:physiopathology; D016022:Case-Control Studies; D016009:Chi-Square Distribution; D003071:Cognition; D003072:Cognition Disorders / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology / Q000523:psychology; D003430:Cross-Sectional Studies; D056344:Executive Function; D005260:Female; D006801:Humans; D016014:Linear Models; D008131:London; D008279:Magnetic Resonance Imaging; D008297:Male; D008568:Memory; D008875:Middle Aged; D020528:Multiple Sclerosis, Chronic Progressive / Q000150:complications* / Q000473:pathology / Q000503:physiopathology / Q000523:psychology; D009483:Neuropsychological Tests; D011237:Predictive Value of Tests; D014705:Verbal Behavior