Efficacy of Transcranial Direct Current Stimulation in Patients with Primary Progressive Aphasia: A Systematic Review and Updated Meta-analysis
Khaled Alhwaishel1, Aisha Rizwan Ahmed2, Jhon Bocanegra-Becerra3, Mariano Gallo Ruelas4
1Mansoura University, 2Jinnah Medical and Dental College, 3University of Peruana Cayetano Heredia, 4Instituto De Investigación Nutritional
Objective:
Our aim is to evaluate the efficacy of tDCS in improving cognitive and language functions in patients with PPA.
Background:
Primary progressive aphasia (PPA) is a group of dementias characterized by progressive loss of specific language functions with relative sparing of other cognitive domains. Transcranial direct current stimulation (tDCS) has been introduced as a potential therapeutic option for PPA.
Design/Methods:
PubMed, Embase, Cochrane Library, and Web of Science were searched up to June 2024 to identify randomized controlled studies (RCTs) comparing tDCS vs sham procedure in patients with PPA.
Results:
Our analysis encompassed nine RCTs comparing the efficacy of tDCS against sham treatment, with a total of 146 participants. Due to the crossover design implemented in several studies, 94.5% of participants received active tDCS, while 91.1% received the sham intervention. The findings demonstrated significant improvements immediately post-tDCS (SMD 0.43, 95% CI 0.10; 0.76, p = 0.01) and sustained benefits after two months or more (SMD 0.51, 95% CI 0.10; 0.92, p = 0.01) in the untrained naming task. Similarly, for the trained naming tasks, significant improvement was observed more than one day after tDCS (SMD 1.04, 95% CI 0.28; 1.80, p < 0.01), which persisted up to two months (SMD 0.64, 95% CI 0.15; 1.13, p = 0.01). However, no significant improvements were observed in cognitive tasks, either immediately following tDCS (MD 0.27, 95% CI -0.48; 1.01, p = 0.40) or beyond one day but within two months (MD 1.81, 95% CI -1.18; 4.79, p = 0.24).
Conclusions:
Our findings suggest that tDCS may be efficacious in augmenting naming tasks both acutely and over a prolonged period of up to two months. However, its effects on overall cognitive performance remain inconclusive. Further robust trials are warranted to elucidate its impact on cognitive function.
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