Arcuate fasciculus lesion load predicts speech impairment after stroke
MedWire News: Lesion load of the arcuate fasciculus (AF) is a useful predictor of rate, informativeness of content, efficiency of speech, and naming ability when assessing the severity of speech production impairments in patients with aphasia after stroke.
"Several studies have related speech and language impairment after stroke to the extent of lesion damage within specific cortical and subcortical structures, however… our study is the first to quantitatively relate the extent of lesion damage within white matter tracts to verbal fluency," say Gottfried Schlaug (Harvard Medical School, Boston, Massachusetts, USA) and co-authors.
Studies have suggested that the AF may be involved in the mapping of sounds to articulation, while the uncinate fasciculus (UF) and extreme capsule (EmC) are thought to be more involved in the mapping of sounds to meaning.
To investigate the relationship between lesion size and location and impairment of fluent speech production, 30 patients with chronic stroke (mean age of 58.5 years) showing residual impairments in speech production underwent high-resolution anatomic magnetic resonance imaging (MRI) and a battery of cognitive and language tests.
Speech fluency was assessed using three functional measures of conversational speech and naming ability: rate, informativeness, and overall efficiency. Tract-lesion overlap volumes were calculated using maps of tracts derived from diffusion tensor images of 10 age-matched healthy individuals to assess the relationship between impairment scores and lesion load along each fiber tract.
Regression analysis revealed that rate of speech, naming ability, informativeness, and efficiency of speech were significantly predicted by AF lesion load. However, UF, EmC, and lesion load were nonsignificant predictors of speech production after stroke.
The researchers note that despite lesion size showing a substantial correlation with these lesion load measures, it remained nonsignificant.
"In the future, automation of AF lesion load calculations may allow physicians and researchers to make more accurate prognoses regarding impairment of speech production after stroke and recovery potential, possibly even in the subacute stroke phase, and thus, identify optimal interventions for patients based on their lesion-behavior profiles," conclude the authors in the journal Stroke.
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By Ingrid Grasmo