Grading scale based on arcuate fasciculus segmentation to predict postoperative language outcomes of brain arteriovenous malformations

Abstract

Objective: The long-term postoperative language outcomes for brain arteriovenous malformations (bAVMs) have not been well characterised. With fibres scattered in the Broca's, Wernicke's and Geschwind's area, the arcuate fasciculus (AF) is considered as a crucial structure of language function. This study aimed to observe the language outcomes, determine the risk factors and construct a grading system for long-term postoperative language deficits (LDs) in patients with bAVMs involving the AF (AF-bAVMs).

Methods: We retrospectively reviewed 135 patients with AF-bAVMs. Based on the course of the AF and our clinical experience, three boundary lines were drawn to divide the AF into segments I, II, III and IV in spatial order from the frontal lobe to the temporal lobe. Surgery-related LD evaluations were performed 1 week (short term) and at the last follow-up (long term) after surgery. Finally, based on multivariable logistic regression analysis, a grading system was constructed to predict long-term postoperative LD. The predictive accuracy was assessed using the area under the receiver operating characteristic curve (AUC).

Results: Sixty-two (45.9%) patients experienced short-term postoperative LD. After a mean follow-up of 50.2±24.9 months, long-term LD was found in 14 (10.4%) patients. Nidus size (p=0.007), LD history (p=0.009) and segment II involvement (p=0.030) were independent risk factors for short-term LD. Furthermore, segment II involvement (p=0.002), anterior choroidal artery (AChA) feeding (p=0.001), patient age (p=0.023) and LD history (p=0.001) were independent risk factors for long-term LD. A grading system was developed by combining the risk factors for long-term LD; its predictive accuracy was 0.921.

Conclusions: The involvement of the trunk of the AF between Broca's area and the inferior parietal lobule, a nidus supplied by the AChA, older patient age and history of LD were associated with long-term postoperative LD. The grading system combining these factors demonstrated favourable predictive accuracy for long-term language outcomes.

Keywords: Arteriovenous Malformations.

Figure 1

Based on the characteristics of the AF course and our clinical experience, we defined three boundary lines (dashed lines). The first line was located where the last fibre of the AF in Broca’s area merged into the trunk of the AF. The second line was located where the first branch of AF extended from the trunk to the inferior parietal lobule. The third line was located at the anterior border of Wernicke’s area. These three boundary lines divided the AF into four segments, which were designated I, II, III and IV in spatial order from the frontal lobe to the temporal lobe. AF, arcuate fasciculus.

Figure 2

Violin graph showing the difference in postoperative LD recovery time according to the AF segment where the nidus was located. The language function of patients with bAVMs located in segment II required a significantly longer time to recover than those with the involvement of segments I and III (segment I involvement vs II, p=0.024; segment III involvement vs II, p=0.044) (^*p<0.05 based on Wilcoxon rank-sum tests). AF, arcuate fasciculus; bAVMs, brain arteriovenous malformations; LD, language deficit.

Figure 3

ROC analyses of the grading system for predicting long-term postoperative LD in all patient cohorts. The AUC was 0.921 (95% CI 0.836 to 1.000), and the cut-off point was 4. AUC, area under the receiver operating curve; LD, language deficit; ROC, receiver operating curve.

Figure 4

Stacked bar chart showing the proportions of patients with or without long-term postoperative LD in low-grade and high-grade groups. In the high-grade group, 73.3% of patients suffered from long-term postoperative LD; however, only 2.5% of patients had long-term LD in the low-grade group. LD, language deficit.