White and gray matter contributions to executive function recovery after traumatic brain injury

Abstract

Objective: We investigated the association between regional white and gray matter volume loss and performance on executive functions (EFs) in patients with penetrating traumatic brain injury (pTBI). Methods:We studied 164 pTBI patients and 43 healthy controls from the Vietnam Head Injury Study. We acquired CT scans for pTBI patients and divided them according to lesion localization (left and right prefrontal cortex [PFC]). We administered EF tests (Verbal Fluency, Trail Making, Twenty Questions) and used voxel-based lesion symptom mapping (VLSM) and group-based correlational and multiple regression analyses to examine the relative influence of gray and white matter lesions on EF recovery. Results:The VLSM analysis revealed that white and gray white matter lesions were associated with impaired EFs. In the left PFC lesion group, damage to the PFC gray matter, anterior corona radiata, and superior longitudinal fasciculus (SLF) were most correlated with functional recovery. Verbal Fluency, which involves a broad fronto-temporo-parietal network, was best predicted by SLF lesion volume. Trail Making and Twenty Questions, which is associated with more focal left frontal damage, was better predicted by PFC lesions. Conclusions:Our results indicated that white matter volume loss can be a superior predictor of recovery and a crucial factor driving clinical outcome in functions involving a broad network such as Verbal Fluency. White matter damage may place additional burden on recovery by deteriorating signal transmission between cortical areas within a functional network. Neurology ® 2015;84:1394-1401 GLOSSARY ACR 5 anterior corona radiata; ANOVA 5 analysis of variance; D-KEFS 5 Delis-Kaplan Executive Function System; EF 5 executive function; HC 5 healthy control; IFG 5 inferior frontal gyrus; IPG 5 inferior parietal gyrus; LACR 5 left anterior corona radiata; LPFC 5 left prefrontal cortex lesions; LSLF 5 left superior longitudinal fasciculus; MFG 5 middle frontal gyrus; PFC 5 prefrontal cortex; pTBI 5 penetrating traumatic brain injury; RPFC 5 right prefrontal cortex lesions; SCR 5 superior corona radiata; SFG 5 superior frontal gyrus; SLF 5 superior longitudinal fasciculus; SPG 5 superior parietal gyrus; TBI 5 traumatic brain injury; VLSM 5 voxel-based lesion system mapping. Traumatic brain injury (TBI) is a major public health problem worldwide.1 While physical deficits following TBI generally improve over time, cognitive impairments can persist 2,3 and cause permanent disability. 1,4 Some of the most persistent deficits after TBI involve executive functions (EFs), resulting in impaired mental flexibility and planning. 5,6 Extensive functional neuroimaging and lesionmapping evidence indicates that the prefrontal cortex (PFC) plays a central role in EFs. [6][7][8] EFs also involve interactions between frontal and posterior brain regions. 9,10 To date, the majority of lesion-mapping studies have focused on the cortical gray matter correlates of functional impairment, yet white matter involvement has rarely been q...

White matter tracts lesions and decline of verbal fluency after deep brain stimulation in Parkinson's disease

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Texture analysis of early cerebral tissue damage in magnetic resonance imaging of patients with lung cancer

“…Gray matter is mainly composed of the cell bodies of neurons, but white matter is principally surrounded by the myelin sheaths of neurons. In regard to functionality, the former contains nerve centers, which play a major role in generating neural activity; the latter, on the other hand, represents the main transmission pathways carrying the neural signals generated by the brain and the gray matter of the spinal cord (40,41). The results of the present study show that the texture parameters were not significantly different between the 2 hemispheres, but 4 of 6 texture parameters were significantly different between gray and white matter.…”

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