Changes in Intranetwork Functional Connectivity of Resting State Networks Between Sessions Under Anesthesia in Neurosurgical Patients.

BACKGROUND: In this study, we evaluated the changes in resting-state networks (RSNs) under anesthesia in neurosurgical patients. METHODS: RSNs were analyzed in 12 patients with pituitary adenoma presented by chiasma compression operated via standard transsphenoidal approach under propofol anesthesia before and after tumor resection. All the patients had suprasellar tumor extension with compression of the optic chiasma. We investigated second-level effects by contrasting dummy-encoded covariates representing the effects of the sessions (first vs. second) on RSNs. We corrected for multiple comparisons using a false discovery rate of 0.05 (2-sided). RESULTS: Connectivity between the right and left precentral gyri (motor network) decreased significantly from the first to the second session (P = 0.0002), as did the connectivity between the postcentral gyri (P = 0.009). The same was valid for connectivity between the visual cortices (P = 0.0002). The salience network showed a significant decrease in the connectivity of the anterior part of the cingulate gyrus and insular cortex (P = 0.0001). The default mode network showed a decrease in the connectivity between the posterior part of the cingulate gyrus, parietal, and frontal cortices (P = 0.0002). There was no significant correlation between the reduction in connectivity and dose or duration of anesthesia. CONCLUSIONS: Different RSNs could be identified under anesthesia and used for intraoperative brain mapping and remapping during tumor resection. However, RSNs showed a significant decrease in connectivity with the continuation of anesthesia.

The Fluctuations of Blood Oxygen Level-Dependent Signals as a Method of Brain Tumor Characterization: A Preliminary Report.

OBJECTIVE: In this study we present the nature and characteristic of the fluctuation of blood oxygen level-dependent (BOLD) signals measured from brain tumors. METHODS: Supratentorial astrocytomas, which were neither operated nor previously managed with chemotherapy or radiotherapy, were segmented, and the time series of the BOLD signal fluctuations were extracted. The mean (across patients) power spectra were plotted for the different World Health Organization tumor grades. One-way analysis of variance (ANOVA) was performed to identify significant differences between the power spectra of different tumor grades. Results were considered significant at P < 0.05. RESULTS: A total of 58 patients were included in the study. This group of patients included 1 patient with grade I glioma; 15 with grade II; 12 with grade III; and 30 with grade IV. The power spectra of the tumor time series were individually inspected, and all tumors exhibited high peaks at the lower frequency signals, but these were more pronounced in high-grade tumors. ANOVA showed a significant difference in power spectra between groups (P = 0.000). Post hoc analysis with Bonferroni correction showed a significant difference between grade II and grade III (P = 0.012) and grade IV (P = 0.000). There was no significant power spectra difference between grade III and IV tumors (P = 1). CONCLUSIONS: The power spectra of BOLD signals from tumor tissue showed fluctuations in the low-frequency signals and were significantly correlated with tumor grade. These signals could have a misleading effect when analyzing resting state functional magnetic resonance imaging and could be also viewed as a potential method of tumor characterization.

Inter-Network Functional Connectivity Changes in Patients With Brain Tumors: A Resting-State Functional Magnetic Resonance Imaging Study.

OBJECTIVE: Measuring functional connectivity (FC) and resting state networks (RSNs) using resting state functional magnetic resonance imaging is a method of preoperative planning in patients with brain tumors. However, the baseline FC and RSNs are altered in patients with brain tumors. In this study, we examined changes in inter-network FC in patients with brain tumors. METHODS: We performed region of interest (ROI) analysis of FC in 34 patients with supratentorial gliomas and 14 healthy subjects. We performed bivariate correlation analyses at the level of each subject. Resulting correlations were Fischer Z-transformed. The used nodes included 132 ROIs from the automated anatomical labeling atlas in addition to 32 ROIs representing the different functional brain networks. We investigated second-level effects by contrasting dummy encoded covariates representing the effects of group membership on functional connectivity. The significant 2-sided P value with corrected false discovery rate was set to 0.05. We set the t contrast between the group of patients with brain tumors and the group of healthy subjects to detect the effects of tumors on inter-network connectivity. RESULTS: Overall, the inter-network FC was significantly higher in patients with brain tumors compared with healthy subjects. The anterior and posterior cerebellar networks, as well as the supratentorial network, showed significantly higher connectivity in patients with brain tumors than in healthy subjects. CONCLUSION: Although brain tumors affect the FC and RSNs, the current study showed higher baseline inter-network connectivity in patients with brain tumors, which could indicate an intrinsic neural compensatory mechanism.

Intraoperative Resting-State Functional Connectivity and Resting-State Networks in Patients with Intracerebral Lesions: Detectability and Variations Between Sessions.

OBJECTIVE: To evaluate the functional connectivity (FC) and resting-state networks (RSNs) in patients under anesthesia operated for resection of intracerebral lesions. METHODS: We performed intraoperative resting-state functional magnetic resonance imaging (irs-fMRI) in 24 patients under anesthesia before and after lesion resection. Correlation matrices were established for each session (a total 48 of sessions). We analyzed the changes in overall FC and in FC of the healthy and operated hemispheres between the first and second sessions. We tested the correlation between changes in FC and clinical outcomes and the duration, rate, and total dosage of anesthesia. We also performed a group analysis to detect topographic changes in RSNs in patients under anesthesia. A single-subject analysis was performed to detect clinically relevant RSNs in each patient. RESULTS: FC decreased significantly in the second session, as did interhemispheric connectivity. The decrease in the pathological hemisphere was significant and significantly greater than the decrease in the intrahemispheric connectivity of the healthy hemisphere. The change in FC was not correlated with clinical outcome or with the duration, rate, or dosage of anesthesia. Group analysis showed topographic changes in RSNs, especially in high-level networks such as default mode and salience networks. Identification of clinically relevant networks was also possible. CONCLUSIONS: FC and RSNs could be identified under anesthesia and used for extended brain mapping. Further studies are needed to optimize the depth of hypnosis to stabilize FC between sessions.

Resting-State Functional Connectivity in Neurosurgical Patients Under Propofol Anesthesia: Detectability and Variability Between Patients and Between Sessions.

BACKGROUND: Intraoperative assessment of functional connectivity (FC) provides a new possibility for mapping the eloquent brain region before, during, and after tumor resection. The aim of this study was to perform a systematic analysis of detectability of FC and its variation between subjects and sessions. METHODS: FC was analyzed in 10 patients with pituitary adenoma under propofol anesthesia before and after tumor resection. FC of each session (20 sessions total) was correlated to a reference matrix of a group of healthy subjects to evaluate variations of overall, interhemispheric, and intrahemispheric FC between sessions. RESULTS: Resting-state patterns could be detected during anesthesia (F1,9 = 112.14, P < 0.001). There was a significant effect of session (F1,9 = 19.401, P = 0.002), which included a reduction in resting state from the first to second session. There was no effect of connection type (F2,8 = 1.498, P = 0.280), and there was no interaction between connection type and session (F2,8 = 0.187, P = 0.833). The correlation between the observed reduction in resting-state activity between the sessions and the time span between sessions was not significant (r = 0.25, P = 0.29). FC of the first session showed a significant correlation to the initial dose of anesthesia (r = 0.7, P = 0.007). However, there was no significant correlation between the total dose of propofol and FC of the second session (r = 1.7, P = 0.6). CONCLUSIONS: Significant FC could be detected under anesthesia but showed a significant decrease in the second session. To implement FC intraoperative brain mapping, further studies are required to optimize the depth sedation to obtain stable FC between sessions.

Reliability of Functional Magnetic Resonance Imaging in Patients with Brain Tumors: A Critical Review and Meta-Analysis.

BACKGROUND: Formal studies that validated functional magnetic resonance imaging (fMRI) against direct cortical stimulation (DCS) have shown inconsistencies. METHODS: We reviewed the reported data and performed a meta-analysis of studies that had validated fMRI using DCS and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We performed the meta-analysis of the studies that had met our inclusion criteria. The positive predictive values (PPVs), negative predictive values (NPVs), false omission rates (FORs), false discovery rates (FDRs), sensitivity, and specificity were calculated. We also identified the factors that could influence the fMRI findings. RESULTS: Six studies of language activation and two of motor activation were eligible for the present meta-analysis. The PPV of fMRI for the detection of eloquent motor cortex was 59.5%, and the FDR was 40.5%. The NPV was 96% and the FOR was 3.9%. The sensitivity and specificity of fMRI for the detection of the eloquent motor cortex was 91% and 76%, respectively. For language activation, the PPV was 71.7%, the NPV was 80%, the FDR was 28.2%, and the FOR was 19.5%. The sensitivity and specificity was 80% and 71.5%, respectively. The factors that could have caused a mismatch or affected the reliability were analyzed. CONCLUSION: The results from the present analysis of the available reported evidence suggest that fMRI itself (due to neurovascular uncoupling) or analysis of the findings have limitations regarding reliability when validated against DCS. From the existing studies, our results indicate that using fMRI alone for surgical planning could lead to undesirable outcomes.

Inter-hemispheric language functional reorganization in low-grade glioma patients after tumour surgery.

Despite many claims of functional reorganization following tumour surgery, empirical studies that investigate changes in functional activation patterns are rare. This study investigates whether functional recovery following surgical treatment in patients with a low-grade glioma in the left hemisphere is linked to inter-hemispheric reorganization. Based on literature, we hypothesized that reorganization would induce changes in the spatial pattern of activation specifically in tumour homologue brain areas in the healthy right hemisphere. An experimental group (EG) of 14 patients with a glioma in the left hemisphere near language related brain areas, and a control group of 6 patients with a glioma in the right, non-language dominant hemisphere were scanned before and after resection. In addition, an age and gender matched second control group of 18 healthy volunteers was scanned twice. A verb generation task was used to map language related areas and a novel technique was used for data analysis. Contrary to our hypothesis, we found that functional recovery following surgery of low-grade gliomas cannot be linked to functional reorganization in language homologue brain areas in the healthy, right hemisphere. Although elevated changes in the activation pattern were found in patients after surgery, these were largest in brain areas in proximity to the surgical resection, and were very similar to the spatial pattern of the brain shift following surgery. This suggests that the apparent perilesional functional reorganization is mostly caused by the brain shift as a consequence of surgery. Perilesional functional reorganization can however not be excluded. The study suggests that language recovery after transient post-surgical language deficits involves recovery of functioning of the presurgical language system.

Saccadic abnormalities in psychotropic-naive obsessive-compulsive disorder without co-morbidity.

BACKGROUND: Oculomotor studies have found saccadic abnormalities in obsessive-compulsive disorder (OCD), lending support for models postulating a central role for inhibition in OCD. Saccadic abnormalities in OCD may also be potential candidates for a biological marker, important for more endophenotype-oriented research. Saccadic abnormalities have not been examined in psychotropic-naive patients with OCD without co-morbidity. METHOD: We compared the error rates and latencies of 14 carefully selected adult psychotropic-naive patients with OCD with no co-morbid diagnosis and 14 pairwise matched healthy controls on a fixation task, on a prosaccade task and on an antisaccade task. RESULTS: Patients with OCD showed normal error rates on all tasks, but latencies on the antisaccade task were significantly increased. CONCLUSIONS: Our results indicate that patients with OCD have no gross impairment of oculomotor inhibitory capacities, but may have a disturbed capacity to deliberately initiate a saccade to an imagined target.