title: The right hemisphere is not unitary in its role in aphasia recovery.
abstract: Neurologists and aphasiologists have debated for over a century whether right hemisphere recruitment facilitates or impedes recovery from aphasia. Here we present a well-characterized patient with sequential left and right hemisphere strokes whose case substantially informs this debate. A 72-year-old woman with chronic nonfluent aphasia was enrolled in a trial of transcranial magnetic stimulation (TMS). She underwent 10 daily sessions of inhibitory TMS to the right pars triangularis. Brain activity was measured during picture naming using functional magnetic resonance imaging (fMRI) prior to TMS exposure and before and after TMS on the first day of treatment. Language and cognition were tested behaviorally three times prior to treatment, and at 2 and 6 months afterward. Inhibitory TMS to the right pars triangularis induced immediate improvement in naming, which was sustained 2 months later. fMRI confirmed a local reduction in activity at the TMS target, without expected increased activity in corresponding left hemisphere areas. Three months after TMS, the patient suffered a right hemisphere ischemic stroke, resulting in worsening of aphasia without other clinical deficits. Behavioral testing 3 months later confirmed that language function was impacted more than other cognitive domains. The paradoxical effects of inhibitory TMS and the stroke to the right hemisphere demonstrate that even within a single patient, involvement of some right hemisphere areas may support recovery, while others interfere. The behavioral evidence confirms that compensatory reorganization occurred within the right hemisphere after the original stroke. No support is found for interhemispheric inhibition, the theoretical framework on which most therapeutic brain stimulation protocols for aphasia are based.
authors.affiliation: Laboratory for Cognition and Neural Stimulation, Department of Neurology, University of Pennsylvania, Philadelphia, PA, USA. turkeltp@georgetown.edu
authors.forename: Peter E
authors.initials: PE
authors.lastname: Turkeltaub
authors.forename: H Branch
authors.initials: HB
authors.lastname: Coslett
authors.forename: Amy L
authors.initials: AL
authors.lastname: Thomas
authors.forename: Olufunsho
authors.initials: O
authors.lastname: Faseyitan
authors.forename: Jennifer
authors.initials: J
authors.lastname: Benson
authors.forename: Catherine
authors.initials: C
authors.lastname: Norise
authors.forename: Roy H
authors.initials: RH
authors.lastname: Hamilton
mesh_terms: D000368:Aged; D001037:Aphasia / Q000503:physiopathology*; D001931:Brain Mapping; D005260:Female; D005625:Frontal Lobe / Q000502:physiology / Q000503:physiopathology; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007802:Language; D008279:Magnetic Resonance Imaging; D009473:Neuronal Plasticity / Q000502:physiology; D020127:Recovery of Function / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation / Q000379:methods