title: No Effect of Anodal Transcranial Direct Current Stimulation on Gamma-Aminobutyric Acid Levels in Patients with Recurrent Mild Traumatic Brain Injury.
abstract: In patients in the chronic phase after recurrent mild traumatic brain injury (mTBI), alterations in gamma-aminobutyric acid (GABA) concentration and receptor activity have been reported, possibly mediating subtle but persistent cognitive deficits and increased rate of dementia in older age. We evaluated whether anodal transcranial direct current stimulation (atDCS) over the primary motor cortex reduces GABA concentration and GABABreceptor activity in patients with recurrent mTBI. Seventeen patients (mean age 25, two women) in the chronic phase after recurrent mTBI and 22 healthy control subjects (mean age 26, two women) were included. All participants received comprehensive cognitive testing and detailed questionnaires on post-concussive symptoms at baseline. Subsequently, they participated in four experimental sessions, consisting of either magnetic resonance spectroscopy (MRS)/atDCS/MRS, transcranial magnetic stimulation (TMS)/atDCS/TMS, MRS/sham/MRS, or TMS/sham/TMS to determine GABA concentration (from MRS) and GABABreceptor activity (from TMS) after atDCS and after sham stimulation. Patients with mTBI scored significantly lower on verbal fluency tasks compared with healthy control subjects. GABA concentration at baseline was associated with the number of mTBI, although no group differences in GABA concentration and GABABreceptor activity were found. Moreover, no effects of atDCS on GABA concentration and receptor activity were seen in patients with mTBI or healthy control subjects. GABA concentration may increase with the number of mTBI, but atDCS did not modulate GABA concentration and receptor activity, as has been reported previously. Specifics of experimental design and analysis, but also characteristics of the respective samples, may account for these differential findings, and should be addressed in future larger studies.
authors.affiliation: 1 Department of Neurology, Charité-University Hospital , Berlin, Germany .
authors.forename: Skadi
authors.initials: S
authors.lastname: Wilke
authors.affiliation: 1 Department of Neurology, Charité-University Hospital , Berlin, Germany .
authors.forename: Jonathan
authors.initials: J
authors.lastname: List
authors.affiliation: 4 Physikalisch-Technische Bundesanstalt (PTB) , Braunschweig und Berlin, Berlin, Germany .
authors.forename: Ralf
authors.initials: R
authors.lastname: Mekle
authors.affiliation: 1 Department of Neurology, Charité-University Hospital , Berlin, Germany .
authors.forename: Robert
authors.initials: R
authors.lastname: Lindenberg
authors.affiliation: 1 Department of Neurology, Charité-University Hospital , Berlin, Germany .
authors.forename: Martin
authors.initials: M
authors.lastname: Bukowski
authors.affiliation: 1 Department of Neurology, Charité-University Hospital , Berlin, Germany .
authors.forename: Stefanie
authors.initials: S
authors.lastname: Ott
authors.affiliation: 4 Physikalisch-Technische Bundesanstalt (PTB) , Braunschweig und Berlin, Berlin, Germany .
authors.forename: Florian
authors.initials: F
authors.lastname: Schubert
authors.affiliation: 4 Physikalisch-Technische Bundesanstalt (PTB) , Braunschweig und Berlin, Berlin, Germany .
authors.forename: Bernd
authors.initials: B
authors.lastname: Ittermann
authors.affiliation: 1 Department of Neurology, Charité-University Hospital , Berlin, Germany .|2 Center for Stroke Research Berlin, Charité-University Hospital , Berlin, Germany .|3 NeuroCure Cluster of Excellence, Charité-University Hospital , Berlin, Germany .
authors.forename: Agnes
authors.initials: A
authors.lastname: Flöel
mesh_terms: D000328:Adult; D001265:Athletic Injuries / Q000150:complications / Q000000981:diagnostic imaging* / Q000628:therapy*; D001924:Brain Concussion / Q000000981:diagnostic imaging* / Q000209:etiology / Q000628:therapy*; D005260:Female; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000000981:diagnostic imaging / Q000378:metabolism; D012008:Recurrence; D057566:Self Report; D065908:Transcranial Direct Current Stimulation / Q000379:methods*; D016896:Treatment Outcome; D055815:Young Adult; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D005680:gamma-Aminobutyric Acid
keywords: GABA; MR spectroscopy; concussion; transcranial magnetic stimulation