Relationship between Visual Perception and Microstructural Change of the Superior Longitudinal Fasciculus in Patients with Brain Injury in the Right Hemisphere: A Preliminary Diffusion Tensor Tractography Study

Abstract

Right hemisphere brain damage often results in visual-spatial deficits. Because various microstructural changes of the superior longitudinal fasciculus (SLF) after a stroke in the right hemisphere affect visual perception, including neglect, the present study investigates the relationship between both microstructural change and lateralization of SLF and visual perception, using diffusion tensor imaging (DTI) in patients with lesions in the right hemisphere. Eight patients with strokes (five patients with intracranial hemorrhage, and three patients with infarction; mean age of 52.5 years) and 16 mean-age-matched healthy control subjects were involved in this study. The visual perception of all eight patients was assessed with the motor-free visual perception test (MVPT), and their SLFs were reconstructed using DTI. The results showed that there was a significant difference between the DTI parameters of the patients and the control subjects. Moreover, patients with microstructural damage to the right SLF showed impairment of visual perception. In patients with damage to both the dorsal and ventral pathways of the right SLF, spatial neglect was present. However, although a leftward SLF asymmetry was revealed in our patients, this lateralization did not show a relationship with visual perception. In conclusion, the microstructural changes of the right SLF play an important role in visual perception, and both pathways contribute to spatial neglect, but leftward lateralization of the right SFL activity after a stroke does not contribute to general visual perception.

Keywords: diffusion tensor imaging; lateralization; neglect; superior longitudinal fasciculus; visual perception.

Figure 1

T2-weighted brain magnetic resonance images of all of the patients with stokes in the right hemisphere within four or five weeks after onset. In patients 1, 2, 4, 5, and 6, intracranial hemorrhage (ICH) in the right hemisphere is visible. Patients 3, 7, and 8 have a cerebral infarction in the right hemisphere. Patient 1: ICH in the right thalamus and posterior limb of the internal capsule. Patient 2: ICH in the right parietal lobe. Patient 3: cerebral infarction in the right frontal lobe, insular cortex, and basal ganglia. Patient 4: ICH in the right thalamus, posterior basal ganglia, and parietal lobe. Patient 5: ICH in the right basal ganglia. Patient 6: ICH in the right basal ganglia, right thalamus, right insula, and right front-parietal lobe. Patient 7: cerebral infarction in the right frontal lobe, insular cortex, and parietal lobe. Patient 8: cerebral infarction in the right basal ganglia and frontotemporal lobe. Note: ICH, intracranial hemorrhage; R, right; A, anterior. “R” and “A” in patient 1 are reflected throughout the patient’s image.

Figure 2

(A) “OR” region of interest (ROI) of the superior longitudinal fasciculus (SLF). (B) “AND” ROI of the SLF. (C) Reconstruction of the right SLF using diffusion tensor imaging (DTI) in a control subject (55 years, female). Note: yellow part; the right SLF, R, right; A, anterior; blue circle, ROI; blue line, dorsal pathway; blue arrow, ventral pathway.

Figure 3

Diffusion tensor images for the bilateral SLFs of eight patients. Patients 2, 4, 6, 7, and 8 show an injury of both the dorsal and ventral pathways of the right SLF. Patients 1 and 3 show injuries in the ventral pathway of the SLF, and the SLF of patient 5 reveals damage in the dorsal pathway. Note: SLF, superior longitudinal fasciculus; yellow part; the right SLF, red part; the left SLF, R, right; A, anterior; orange arrow, injury site; “R” and “A” in patient 8 are reflected throughout the patient’s image.

Figure 4

Summary of the pathway based on our finding. Note: SLF, superior longitudinal fasciculus. “?” means the requirement of further study. +; the right SLF with microstructural damage, −; the right SLF without microstructural damage.