title: Anatomical predictors of aphasia recovery: a tractography study of bilateral perisylvian language networks.
abstract: Stroke-induced aphasia is associated with adverse effects on quality of life and the ability to return to work. For patients and clinicians the possibility of relying on valid predictors of recovery is an important asset in the clinical management of stroke-related impairment. Age, level of education, type and severity of initial symptoms are established predictors of recovery. However, anatomical predictors are still poorly understood. In this prospective longitudinal study, we intended to assess anatomical predictors of recovery derived from diffusion tractography of the perisylvian language networks. Our study focused on the arcuate fasciculus, a language pathway composed of three segments connecting Wernicke's to Broca's region (i.e. long segment), Wernicke's to Geschwind's region (i.e. posterior segment) and Broca's to Geschwind's region (i.e. anterior segment). In our study we were particularly interested in understanding how lateralization of the arcuate fasciculus impacts on severity of symptoms and their recovery. Sixteen patients (10 males; mean age 60 ± 17 years, range 28-87 years) underwent post stroke language assessment with the Revised Western Aphasia Battery and neuroimaging scanning within a fortnight from symptoms onset. Language assessment was repeated at 6 months. Backward elimination analysis identified a subset of predictor variables (age, sex, lesion size) to be introduced to further regression analyses. A hierarchical regression was conducted with the longitudinal aphasia severity as the dependent variable. The first model included the subset of variables as previously defined. The second model additionally introduced the left and right arcuate fasciculus (separate analysis for each segment). Lesion size was identified as the only independent predictor of longitudinal aphasia severity in the left hemisphere [beta = -0.630, t(-3.129), P = 0.011]. For the right hemisphere, age [beta = -0.678, t(-3.087), P = 0.010] and volume of the long segment of the arcuate fasciculus [beta = 0.730, t(2.732), P = 0.020] were predictors of longitudinal aphasia severity. Adding the volume of the right long segment to the first-level model increased the overall predictive power of the model from 28% to 57% [F(1,11) = 7.46, P = 0.02]. These findings suggest that different predictors of recovery are at play in the left and right hemisphere. The right hemisphere language network seems to be important in aphasia recovery after left hemispheric stroke.
authors.affiliation: 1 Research Department of Clinical, Educational, and Health Psychology (RDCEHP), Division of Psychology and Language Sciences, Faculty of Brain Sciences, University College London, UK2 Natbrainlab, Department of Neuroimaging, Institute of Psychiatry, King's College London, UK s.forkel@ucl.ac.uk m.catani@iop.kcl.ac.uk.
authors.forename: Stephanie J
authors.initials: SJ
authors.lastname: Forkel
authors.affiliation: 3 Natbrainlab, Department of Forensic and Neurodevelopmental Sciences, Institute of Psychiatry, King's College London, London, UK4 Inserm U1127; UPMC-Paris6, UMR_S 1127; CNRS UMR 7225, Centre de Recherche de l'Institut du Cerveau et de la Moelle épinière, Groupe Hospitalier Pitié-Salpêtrière, 75013 Paris, France.
authors.forename: Michel
authors.initials: M
authors.lastname: Thiebaut de Schotten
authors.affiliation: 2 Natbrainlab, Department of Neuroimaging, Institute of Psychiatry, King's College London, UK5 NIHR Biomedical Research Centre for Mental Health at South London and Maudsley NHS Foundation Trust and King's College London, London, UK.
authors.forename: Flavio
authors.initials: F
authors.lastname: Dell'Acqua
authors.affiliation: 6 Department of Clinical Neuroscience, Institute of Psychiatry, King's College London, London, UK.
authors.forename: Lalit
authors.initials: L
authors.lastname: Kalra
authors.affiliation: 7 Sackler Institute for Translational Neurodevelopment and Department of Forensic and Neurodevelopmental Sciences, Institute of Psychiatry, King's College London, UK.
authors.forename: Declan G M
authors.initials: DG
authors.lastname: Murphy
authors.affiliation: 2 Natbrainlab, Department of Neuroimaging, Institute of Psychiatry, King's College London, UK5 NIHR Biomedical Research Centre for Mental Health at South London and Maudsley NHS Foundation Trust and King's College London, London, UK.
authors.forename: Steven C R
authors.initials: SC
authors.lastname: Williams
authors.affiliation: 3 Natbrainlab, Department of Forensic and Neurodevelopmental Sciences, Institute of Psychiatry, King's College London, London, UK s.forkel@ucl.ac.uk m.catani@iop.kcl.ac.uk.
authors.forename: Marco
authors.initials: M
authors.lastname: Catani
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016880:Anisotropy; D001037:Aphasia / Q000209:etiology / Q000473:pathology*; D001921:Brain / Q000473:pathology*; D001931:Brain Mapping; D056324:Diffusion Tensor Imaging; D005260:Female; D007839:Functional Laterality; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007802:Language; D008297:Male; D008875:Middle Aged; D009434:Neural Pathways / Q000473:pathology; D011237:Predictive Value of Tests; D020127:Recovery of Function / Q000502:physiology*; D012189:Retrospective Studies; D020521:Stroke / Q000150:complications
keywords: aphasia; arcuate network; diffusion tensor imaging tractography; language recovery; stroke