# The impact of radiation-induced temporal lobe injury on cognition and structure across the whole brain in nasopharyngeal carcinoma patients

## TL;DR

Radiation-induced temporal lobe injury in nasopharyngeal cancer patients leads to cognitive decline and structural brain changes, which could help identify and monitor this condition.

## Contribution

This study identifies specific brain regions and structural changes linked to cognitive impairment in patients with radiation-induced temporal lobe injury.

## Key findings

- RI-TLI patients showed lower attention, memory, and overall cognitive scores compared to nRI-TLI patients.
- RI-TLI was associated with reduced gray and white matter in key brain regions like the temporal lobe and prefrontal cortex.
- Structural brain changes correlated with cognitive deficits and could serve as potential neuroimaging markers for RI-TLI.

## Abstract

Radiation-induced temporal lobe injury (RI-TLI) is one of the most common late-stage complications after radiotherapy for nasopharyngeal carcinoma (NPC), which seriously affects patients’ cognitive function and quality of life. However, the mechanism by which RI-TLI affects the gray matter (GM) and white matter (WM) across the whole brain, leading to cognitive impairment, is currently unclear in NPC patients.

One year after the end of radiotherapy, 32 NPC patients with RI-TLI (RI-TLI group) and 38 NPC patients without RI-TLI (nRI-TLI group) were included in this study. The Montreal Cognitive Assessment (MoCA) was applied to evaluate the differences of cognitive function between RI-TLI and nRI-TLI groups. In addition, T1 structural magnetic resonance imaging data were acquired, and then the whole-brain voxel-based morphometry was employed to compare the differences of GM and WM between groups. The relationships between GM and WM of abnormal brain regions and MoCA scores were explored. Finally, receiver operating characteristic (ROC) curve was performed to determine the suitability of altered brain structure for distinguishing RI-TLI from nRI-TLI.

Compared with nRI-TLI group, RI-TLI group exhibited decreased attention, delayed recall scores and total scores of MoCA. In addition, RI-TLI group exhibited decreased GM volume in the right middle temporal gyrus, left hippocampus, right superior temporal gyrus, right superior frontal gyrus and decreased GM density in the left superior frontal gyrus, right superior frontal gyrus, right supplementary motor area. Moreover, RI-TLI group demonstrated decreased WM volume in the right inferior temporal gyrus, left hippocampus, right superior temporal gyrus, right medial superior frontal gyrus and decreased WM density in the left superior frontal gyrus, right superior frontal gyrus. The attention scores of MoCA were positively associated with GM volume of the right superior temporal gyrus, right superior frontal gyrus, GM density of the left superior frontal gyrus, right superior frontal gyrus, WM density of the left superior frontal gyrus. The delayed recall scores of MoCA were positively related to GM volume of the left hippocampus, WM density of the left superior frontal gyrus. The total scores of MoCA were positively associated with GM volume of the left hippocampus, WM volume of the left hippocampus, right superior temporal gyrus, WM density of the left superior frontal gyrus. ROC analysis demonstrated that altered GM and WM might be helpful for distinguishing RI-TLI from nRI-TLI.

Compared to nRI-TLI patients, RI-TLI patients exhibit more severe cognitive impairment alongside decreased GM and WM in both the temporal lobe and prefrontal regions. The observed structural alterations are associated with the severity of cognitive deficits and may serve as potential neuroimaging markers for RI-TLI.