title: Magnetic resonance study of the influence of tissue damage and cortical reorganization on PASAT performance at the earliest stage of multiple sclerosis.
abstract: We sought to determine the influence of tissue damage and the potential impact of cortical reorganization on the performance to the Paced Auditory Serial Addition Test (PASAT) in patients at the earliest stage of multiple sclerosis (MS). Magnetization transfer ratio (MTR) imaging and functional magnetic resonance imaging (fMRI) experiments using PASAT as paradigm were carried out in 18 patients with clinically isolated syndrome suggestive of MS (CISSMS) compared to 18 controls. MTR histogram analyses showed structural abnormalities in patients involving the normal-appearing white matter (NAWM) but also the gray matter (GM). Mean PASAT scores were significantly lower in the group of patients taken as a whole, and were correlated with the mean NAWM MTR value. No correlation was observed between PASAT scores and GM MTR. However, in the subgroup of patients with normal PASAT performance (n = 9), fMRI showed larger activations in bilateral Brodmann area 45 (BA45) and right BA44 compared to that in controls (n = 18). In these areas with potentially compensatory reorganization, the whole group of patients (n = 18) showed significantly greater activation than controls (n = 18). Activation in the right BA45 was inversely correlated with the mean NAWM MTR and the peak position of GM MTR histograms of patients. This study indicates that even at the earliest stage of MS, cortical reorganization is present inside the executive system of working memory and could tend to limit the determinant functional impact of NAWM injury on the execution of the PASAT.
authors.affiliation: Centre de Résonance Magnétique Biologique et Médicale, (CRMBM), UMR CNRS 6612, Faculté de Médecine, Marseille, France.
authors.forename: Bertrand
authors.initials: B
authors.lastname: Audoin
authors.forename: My Van
authors.initials: MV
authors.lastname: Au Duong
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Ranjeva
authors.forename: Danielle
authors.initials: D
authors.lastname: Ibarrola
authors.forename: Irina
authors.initials: I
authors.lastname: Malikova
authors.forename: Sylviane
authors.initials: S
authors.lastname: Confort-Gouny
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Soulier
authors.forename: Patrick
authors.initials: P
authors.lastname: Viout
authors.forename: André
authors.initials: A
authors.lastname: Ali-Chérif
authors.forename: Jean
authors.initials: J
authors.lastname: Pelletier
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Cozzone
mesh_terms: D000328:Adult; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000000981:diagnostic imaging / Q000473:pathology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D009103:Multiple Sclerosis / Q000000981:diagnostic imaging / Q000473:pathology*; D009483:Neuropsychological Tests; D011859:Radiography