Brain infarctions after glioma surgery: prevalence, radiological characteristics and risk factors.

BACKGROUND: Prevalence, radiological characteristics, and risk factors for peritumoral infarctions after glioma surgery are not much studied. In this study, we assessed shape, volume, and prevalence of peritumoral infarctions and investigated possible associated factors. METHODS: In a prospective single-center cohort study, we included all adult patients operated for diffuse gliomas from January 2007 to December 2018. Postoperative infarctions were segmented using early postoperative MRI images, and volume, shape, and location of postoperative infarctions were assessed. Heatmaps of the distribution of tumors and infarctions were created. RESULTS: MRIs from 238 (44%) of 539 operations showed restricted diffusion in relation to the operation cavity, interpreted as postoperative infarctions. Of these, 86 (36%) were rim-shaped, 103 (43%) were sector-shaped, 40 (17%) were a combination of rim- and sector-shaped, and six (3%) were remote infarctions. Median infarction volume was 1.7 cm3 (IQR 0.7-4.3, range 0.1-67.1). Infarctions were more common if the tumor was in the temporal lobe, and the map shows more infarctions in the periventricular watershed areas. Sector-shaped infarctions were more often seen in patients with known cerebrovascular disease (47.6% vs. 25.5%, p = 0.024). There was a positive correlation between infarction volume and tumor volume (r = 0.267, p < 0.001) and infarction volume and perioperative bleeding (r = 0.176, p = 0.014). Moreover, there was a significant positive association between age and larger infarction volumes (r = 0.193, p = 0.003). Infarction rates and infarction volumes varied across individual surgeons, p = 0.037 (range 32-72%) and p = 0.026. CONCLUSIONS: In the present study, peritumoral infarctions occurred in 44% after diffuse glioma operations. Infarctions were more common in patients operated for tumors in the temporal lobe but were not more common following recurrent surgeries. Sector-shaped infarctions were more common in patients with known cerebrovascular disease. Increasing age, larger tumors, and more perioperative bleeding were factors associated with infarction volumes. The risk of infarctions and infarction volumes may also be surgeon-dependent.

Surgically acquired deficits and diffusion weighted MRI changes after glioma resection--a matched case-control study with blinded neuroradiological assessment.

BACKGROUND: Acquired deficits following glioma resection may not only occur due to accidental resection of normal brain tissue. The possible importance of ischemic injuries in causing neurological deficits after brain tumor surgery is not much studied. We aimed to study the volume and frequency of early postoperative circulatory changes (i.e. infarctions) detected by diffusion weighted resonance imaging (DWI) in patients with surgically acquired neurological deficits compared to controls. METHODS: We designed a 1 ∶ 1 matched case-control study in patients with diffuse gliomas (WHO grade II-IV) operated with 3D ultrasound guided resection. 42 consecutive patients with acquired postoperative dysphasia and/or new motor deficits were compared to 42 matched controls without acquired deficits. Controls were matched with respect to histopathology, preoperative tumor volumes, and eloquence of location. Two independent radiologists blinded for clinical status assessed the postoperative DWI findings. RESULTS: Postoperative peri-tumoral infarctions were more often seen in patients with acquired deficits (63% versus 41%, p = 0.046) and volumes of DWI abnormalities were larger in cases than in controls with median 1.08 cm3 (IQR 0-2.39) versus median 0 cm3 (IQR 0-1.67), p = 0.047. Inter-rater agreement was substantial (67/82, κ = 0.64, p<0.001) for diagnosing radiological significant DWI abnormalities. CONCLUSION: Peri-tumoral infarctions were more common and were larger in patients with acquired deficits after glioma surgery compared to glioma patients without deficits when assessed by early postoperative DWI. Infarctions may be a frequent and underestimated cause of acquired deficits after glioma resection. DWI changes may be an attractive endpoint in brain tumor surgery with both good inter-rater reliability among radiologists and clinical relevance.

Reduced fractional anisotropy does not change the shape of the hemodynamic response in survivors of severe traumatic brain injury.

The hemodynamic response (HDR) function is the basis for standard functional magnetic resonance imaging (fMRI) analysis. HDR is influenced by white matter inflammation. Traumatic brain injury (TBI) is frequently accompanied by diffuse white matter injury, but the effect of this on the HDR has not been investigated. The aims of the present study were to describe the HDR in visual cortex and examine its relationship with the microstructure of the optic radiation in severe TBI survivors and controls. Ten severe TBI survivors without visual impairments, but with known diffuse axonal injury, and 9 matched controls underwent diffusion tensor imaging (DTI) and fMRI. From the fMRI time series obtained during brief randomized visual stimuli, blood oxygenation level-dependent (BOLD) signal changes for each subject were estimated in V1, and group HDR curves were produced. Standard between-group analysis of BOLD activation in V1 + V2 was performed. For each individual the optic radiations were identified and fractional anisotropy (FA) plus mean apparent diffusion coefficient (ADC(mean)) values for these tracts were calculated. Group HDR curves from the visual cortex were fully transposable between TBI survivors and controls, despite a significant reduction in FA in the optic radiation in TBI survivors. A significant correlation between BOLD signal in the visual cortex and FA values in the optical tract was present in controls, but not in TBI survivors. Between-group comparisons showed that TBI survivors had increased areas of activation in V1 and V2. The HDR appears to be intact in traumatic white matter damage, supporting the validity of using standard fMRI methodology to study neuroplasticity in TBI.

Simple dual tasking recruits prefrontal cortices in chronic severe traumatic brain injury patients, but not in controls.

The ability to carry out two tasks simultaneously, dual tasking, is specifically impaired after traumatic brain injury (TBI). The aim of the present study was to investigate the neuronal correlates to this increased dual cost in chronic severe TBI patients (n = 10) compared to healthy controls (n = 11) using functional magnetic resonance imaging (fMRI) at 3 Tesla (T). The tasks were a visual search and a simple two-fingers button press motor task. Performance data demonstrated similar and significant dual task interference in both TBI patients and controls using a linear mixed model. However, principal component analysis showed that TBI patients and controls could be classified into different categories based on motor activity in the single compared to the dual task condition, thus reflecting the increased variability in the performance in the TBI group. Random effects between-group analysis demonstrated significantly reduced activation in the TBI group in both single task conditions in the occipital and posterior cingulate cortices, and for the visual task also in the thalami. This pattern was reversed in the dual task condition with significantly increased activation of a predominantly left lateralized prefrontal-anterior midline-parietal network in the TBI group compared to the controls. The increase in activation occurred within regions described to be engaged in healthy volunteers as dual task cost increases. This finding points to substitution, functional reorganization within the primary network subserving the task, following TBI, and demonstrates more effortful processing. Recruitment of these additional prefrontal resources may be connected to serial rather than parallel processing in low level dual tasking in TBI. Thus, in severe TBI, low level dual task performance depends on increased attentional and executive guidance.