High-Definition Transcranial Direct Current Stimulation to Improve Verbal Retrieval Deficits in Chronic Traumatic Brain Injury.

Chronic verbal retrieval deficits have been noted in traumatic brain injury (TBI), but no U.S. Food and Drug Administration-approved interventions are available. The present study investigated whether 10 sessions of 20 min of 1 mA anodal high-definition transcranial direct current stimulation (HD-tDCS) targeting pre-supplementary motor area/dorsal anterior cingulate cortex (preSMA/dACC) compared with sham HD-tDCS would improve verbal retrieval deficits in TBI patients. Improvements in verbal retrieval processes were observed up to 8 weeks post-treatment. Thus, potential dysfunction to verbal retrieval circuitry in TBI appears amenable to remediation through electromodulation with HD tDCS to the preSMA/dACC. Although further studies clarifying mechanisms by which tDCS brought about these improvements will likely inform refinements in the application of this therapeutic technique, the findings suggest the efficacy of using HD-tDCS to target other systems vulnerable to TBI to improve functioning.

Neurodegenerative Dementias After Traumatic Brain Injury.

Traumatic brain injury (TBI) is often considered to be a risk factor for the later development of neurodegenerative conditions, but some findings do not support a link. Differences in research methods, clinical samples, and limitations encountered when assessing and documenting TBI details likely contribute to the mixed reports in the literature. Despite some variability in findings, a review of the literature does provide support for the notion that TBI appears to be associated with earlier onset of some neurodegenerative disorders, although clearly not everyone with a TBI appears to be at an increased risk. Whereas a mechanistic link remains unknown, TBI has been found to initiate an accumulation of pathological processes related to several neurodegenerative disorders. The authors propose a hypothetical model that relates TBI to the development of pathological burden overlapping with some neurodegenerative conditions, in which onset of cognitive/behavioral impairments is hastened in some individuals, but pathological processes stabilize afterward, resulting in a similar course of decline to individuals with dementia who do not have a history of TBI.