Abstract
Primary progressive aphasia (PPA) is a neurodegenerative condition characterized by gradual deterioration of language function. We investigated whether two weeks of daily transcranial direct current stimulation (tDCS) treatment would improve language abilities in six people with a non-fluent form of PPA. tDCS was applied in an unblinded trial at an intensity of 1.5mA for 20min/day over 10days. At the time of stimulation, patients were engaged in narrating one of several children’s wordless picture stories. A battery of neuropsychological assessments was administered four times: at baseline, immediately following the 2-week stimulation period, and then 6-weeks and 12-weeks following the end of stimulation. We observed improvement in linguistic performance in the domains of speech production and grammatical comprehension. Our encouraging results indicate that larger, sham-controlled studies of tDCS as a potential intervention for PPA are warranted.
Highlights
Autopsy studies demonstrate that most patients with progressive aphasia (PPA) have pathologic changes consistent with frontotemporal lobar degeneration (FTLD); Alzheimer’s Disease and other pathologies have been associated with this syndrome (Grossman, 2010)
Four of the patients had a diagnosis of logopenic variant PPA (lvPPA); the other two were diagnosed with Nonfluent/agrammatic variant PPA (naPPA), according to published criteria (Gorno-Tempini et al, 2011) and confirmation at a local consensus conference. lvPPA patients have lexical retrieval difficulty and repetition deficits; naPPA patients have slowed, effortful speech with deficits in grammatical expression, and a pattern of speech errors known as apraxia of speech
Though it is unclear when best to administer transcranial direct current stimulation (tDCS) for PPA, our results suggest that early treatment may be beneficial
Summary
Linguistic deficits vary between patients, impacting functions such as fluency of conversational speech, single word comprehension, repetition and naming ability. Nonfluent/agrammatic variant PPA (naPPA) is characterized primarily by slowed speech production with grammatical simplifications and errors, and is associated with atrophy of regions of the left frontal lobe (Grossman, 2012). Semantic variant PPA (svPPA) is associated with atrophy of the left anterior and ventral temporal lobe, and produces difficulty with naming and word comprehension that relates to broader deficits in semantic processing (Hodges & Patterson, 2007). Logopenic variant PPA (lvPPA) is marked by atrophy of the left temporal and parietal lobes, which manifests as word-retrieval deficits and difficulty with repetition (Gorno-Tempini et al, 2008). The relentless progression of PPA symptoms eventually leads to a profound impairment in communication ability and, to more generalized deficits of cognition
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