Structure of WM bundles constituting the working memory system in early multiple sclerosis: a quantitative DTI tractography study.
Working memory impairment is frequently observed in patients with early multiple sclerosis (MS). MRI and functional MRI studies have shown that working memory impairment is mostly due to diffuse white matter (WM) damage affecting the connectivity between distant cortical areas. However, working memory deficits in early MS patients can be either completely or partly masked by compensatory functional plasticity. It seems likely that concomitantly with the WM bundle injury resulting from pathological processes, the functional plasticity present in early MS patients may be accompanied by reactive structural WM plasticity. This structural plasticity may effectively compensate for connectivity disturbances and/or contribute to functional brain reorganization. The diffusion characteristics of WM bundles involved in working memory were assessed here by performing quantitative diffusion tensor imaging (DTI) tractography on 24 patients with early relapsing-remitting MS and 15 healthy control subjects. The DTI tractography findings showed that WM connections constituting the executive system of working memory were structurally impaired (the fractional anisotropy was lower than normal and the mean diffusivity, higher than normal). A significantly larger number of connections between the left and right thalami was concurrently observed in the MS patients than in the control subjects, which suggests that the WM is endowed with reactive structural plasticity.
Audoin
Bertrand
B
Centre de Résonance Magnétique Biologique et Médicale, UMR CNRS 6612, Faculté de Médecine, Université de la Méditerranée, 27 boulevard Jean Moulin, 13385 Marseille cedex 05, France.
Guye
Maxime
M
Reuter
Françoise
F
Au Duong
My-Van
MV
Confort-Gouny
Sylviane
S
Malikova
Irina
I
Soulier
Elisabeth
E
Viout
Patrick
P
Chérif
André Ali
AA
Cozzone
Patrick J
PJ
Pelletier
Jean
J
Ranjeva
Jean-Philippe
JP
D000328:Adult; D016880:Anisotropy; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000502:physiology*; D003937:Diagnosis, Differential; D038524:Diffusion Magnetic Resonance Imaging; D004292:Dominance, Cerebral / Q000502:physiology; D005260:Female; D006179:Gyrus Cinguli / Q000503:physiopathology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D009103:Multiple Sclerosis / Q000175:diagnosis / Q000503:physiopathology*; D009413:Nerve Fibers, Myelinated / Q000502:physiology*; D009415:Nerve Net / Q000503:physiopathology*; D009473:Neuronal Plasticity / Q000502:physiology; D012984:Software; D013788:Thalamus / Q000503:physiopathology