Sentence completion in progressive supranuclear palsy following transcranial direct current stimulation

Progressive supranuclear palsy (PSP) is an atypical Parkinsonian disorder which results in deterioration of motor and cognitive skills, including language disorders such as impaired word retrieval. While there is evidence of successful use of tDCS to improve word fluency in PSP, little is known about the effectiveness of brain stimulation for word retrieval in sentence context. Therefore, we investigated whether tDCS reduces sentence completion time in PSP patients. In this sham-controlled, triple-blinded crossover study, anodal tDCS (atDCS) was applied over the left Broca's area at 2 mA for 20 min (n = 23). In contrast to patients with multiple system atrophy (MSA), also an atypical Parkinsonian disorder, and healthy elderlies, sentence completion improved in PSP patients when tDCS was applied. The improvement in word fluency reported in previous studies using other electrode positions was not replicated. By using atDCS of the left Broca's area, we were able to demonstrate a difference between the two movement disorders. The obtained insight could be helpful to improve language therapy of these disorders.