Poster B10, Tuesday, August 20, 2019, 3:15 – 5:00 pm, Restaurant Hall
Relation between diffusion measures of the arcuate fasciculus and initial severity of aphasia in the acute phase after stroke
Klara Schevenels1, Robin Lemmens3,4,5, Inge Zink1, Bert De Smedt2, Maaike Vandermosten1;1Experimental Oto-Rhino-Laryngology, Department of Neurosciences, KU Leuven, 2Parenting and Special Education Research Unit, Faculty of Psychology and Educational Sciences, KU Leuven, 3Experimental Neurology, Department of Neurosciences, KU Leuven, 4Laboratory of Neurobiology, Center for Brain and Disease Research, VIB, Leuven, 5Department of Neurology, University Hospitals Leuven
The arcuate fasciculus (AF) is a white matter bundle connecting temporal, parietal and frontal regions. The direct long segment connects the inferior frontal and temporal lobes, two indirect shorter segments connect the inferior frontal with the inferior parietal lobe (anterior segment) and the inferior parietal with the temporal lobe (posterior segment) (Catani et al., 2005). The AF has been related to phonological language skills (Yeatman et al., 2011), reading (Vandermosten et al., 2012b) and syntactic skills (Friederici et al. 2011). Therefore, the properties of this tract after stroke might be related to initial aphasia severity, particularly for phonology and syntax. We used diffusion imaging tractography to obtain an estimated reconstruction of the AF in vivo and derived the fractional anisotropy (FA) index to evaluate the tract. We consecutively recruited 15 stroke patients (9 males, 6 females, mean = 71.2 y.o., SD = 9.1 years) with left hemispheric or bilateral lesions and language impairment from the stroke unit at the University hospital of Leuven. Patients were screened for language disorders with the ScreeLing (Doesborgh et al., 2003) on average 4.5 days after stroke (SD = 5.8 days) and underwent a diffusion MRI scan on average 4.5 days after stroke (SD = 2.1 days). The ScreeLing provides a global measure of aphasia severity as well as subtest scores for semantic, phonological and syntactic processing. MRI data for all but one subject were acquired with a 3T scanner equipped with a 32-channel head coil and a single-shot EPI pulse sequence. Diffusion weighting of b=700, 1000 and 2000 s/mm2 in 20, 32 and 60 directions, together with 7 non-diffusion weighted images, lead to the acquisition of 119 images. After deterministic whole brain tractography, 5000 streamlines were propagated from all brain voxels with a step size of 1 mm, FA-values above 0.2 and a maximum angle of 40 degrees (Basser et al., 2000). Tractography dissections were obtained in Trackvis using a region of interest approach in the patients’ native FA-map, following the protocol described in Wakana et al. (2007). We obtained volume and FA-values for the different segments of the AF in both hemispheres and related these measures to the total and subtest scores of the ScreeLing using Holm’s corrected Kendall pairwise correlations. The results indicate a significant positive correlation between the FA in the left posterior AF and the total ScreeLing score (r = 0.54, p = .048), the semantic score (r = 0.56, p = .039) and the syntactic score (r = 0.60, p = .025). Against our expectations, there were no significant correlations with the phonological scores. To further clarify our results, we will look at the relation between the AF and the different tasks for each linguistic component and examine what is explained by the size and location of the lesion. In addition, we will integrate new data to investigate how different diffusion measures are related to language recovery from the acute stage after stroke to the subacute stage after stroke and whether more advanced diffusion models explain our data better.
Themes: Disorders: Acquired, Phonology and Phonological Working Memory
Method: White Matter Imaging (dMRI, DSI, DKI)