Evaluating post-thrombectomy effective connectivity changes in anterior circulation stroke

Abstract

Objective: Granger causal analysis (GCA) and amplitude of low-frequency fluctuation (ALFF) are commonly used to evaluate functional alterations in brain disorders. By combining the GCA and ALFF, this study aimed to investigate the effective connectivity (EC) changes in patients with acute ischemic stroke (AIS) and anterior circulation occlusion after mechanical thrombectomy (MT).

Methods: Resting-state functional magnetic resonance imaging (rs-fMRI) data were collected from 43 AIS patients with anterior circulation occlusion within 1 week post-MT and 37 healthy controls. ALFF and GCA were calculated for each participant. Patients were further divided into groups based on prognosis and perfusion levels. The differences in ALFF and EC were compared between AIS patients and healthy controls and between subgroups of patients. Pearson correlations between EC, ALFF values, and clinical characteristics of patients were calculated.

Results: Compared to healthy controls, post-MT, AIS patients exhibited significant ALFF increases in the left precuneus and decreases in the left fusiform gyrus and right caudate. Increased EC from the contralesional lingual gyrus, contralesional putamen, ipsilesional thalamus, and contralesional thalamus to the contralesional caudate was obsrved, while decrease in EC were found for contralesional caudate to the ipsilesional thalamus and medial superior frontal gyrus. EC differences were particularly notable between perfusion groups, with significantly lower EC in the poorly perfused group. EC values were also positively correlated with National Institutes of Health Stroke Scale (NIHSS) scores pre-MT.

Interpretation: In AIS patients, the caudate nucleus was central to the observed EC changes post-MT, characterized by decreased outputs and increased inputs. These changes indicate functional remodeling within the cortico-basal ganglia-thalamic-cortical pathway.

Figure 1

Lesion maps were obtained by combining the lesion masks of all patients. CL, contralesional hemisphere; IL, ipsilesional hemisphere.

Figure 2

Between‐group differences of ALFF values. Compared with the healthy controls, AIS patients after MT showed significantly increased ALFF (warm color) in PCUN_IL and decreased (cold color) ALFF in FFG_IL and CAU_CL (voxel p < 0.001, cluster p < 0.05, cluster size >19, GRF corrected). AFLL, amplitude of low‐frequency fluctuation; AIS, acute ischemic stroke; CAU, caudate; CL, contralesional hemisphere; FFG, fusiform gyrus; GRF, Gaussian random field; IL, ipsilesional hemisphere; MT, mechanical thrombectomy; PCUN, precuneus.

Figure 3

Between‐group differences of EC of CAU_CL. The arrows represent the directions of the EC: the blue arrow indicates the CAU_CL to the whole brain, while the red arrow indicates the whole brain to CAU_CL. Compared with the healthy controls, AIS patients after MT exhibited significantly increased (warm color) EC from LING_CL, PUT_CL, THA_IL, and THA_CL to CAU_CL, and decreased (cold color) EC from CAU_CL to THA_IL and SFGmed_IL (voxel p < 0.001, cluster p < 0.05, cluster size >15, GRF corrected). AIS, acute ischemic stroke; CAU, caudate; CL, contralesional hemisphere; EC, effective connectivity; GRF, Gaussian random field; IL, ipsilesional hemisphere; LING, lingual gyrus; MT, mechanical thrombectomy; PUT, putamen; SFGmed, medial superior frontal gyrus; THA, thalamus.

Figure 4

Correlation between EC from the PUT_CL to the CAU_CL and NIHSS scores before MT. CAU, caudate; CL, contralesional hemisphere; EC, effective connectivity; MT, mechanical thrombectomy; NIHSS, National Institutes of Health Stroke Scale; PUT, putamen.