Search

Background:Individuals with traumatic brain injury (TBI) often suffer from a number of enduring cognitive impairments such as in attention, memory, speed of processing information and dual-task performance.Objective:The aim of this study was to assess the patterns of regional brain activation in response to the Tower of London (ToL) task in a group of patients suffering from chronic TBI using functional magnetic resonance imaging (fMRI).Methods:fMRI was performed during performance of the ToL planning task in 10 patients suffering from severe TBI and in 10 age- and sex-matched controls using a 3 T magnetic resonance scanner.Results:Performance data showed no difference in response accuracy between the TBI group and the healthy control group. Statistical parametric brain maps showed that the TBI group activates larger and additional areas of the cerebral cortex than the healthy control group both for tasks and for a subtraction contrast between the tasks.Conclusions:The results of this study are interpreted as a cortical reorganization inside the executive system of vigilance and working memory in patients with TBI. Both parietal and frontal areas are recruited to compensate for damaged brain tissue.

The aim of this study was to establish a robust set of motor tasks that could be used to functionally delineate the motor cortex with blood oxygenation level dependent functional magnetic resonance imaging (BOLD fMRI) at 3 T and produce precise functional maps for pre-operative planning and functional neuronavigation.Twelve male and four female control subjects were recruited for this study which examined six different motor tasks. Finger-, tongue-, lip- and toe-movements, as well as isometric upper arm- and thigh-contraction tasks were conducted during separate scans on a 3 T MRI scanner. Furthermore, patients that previously had undergone similar motor tasks were reviewed, to evaluate whether this set of tasks was able to be adopted for use in a population of patients with brain lesions.The results of this study indicated that the finger-, toe- and tongue-motor tasks were the most robust in identifying their respective primary motor area. Moreover, all three tasks activated regions at regular intervals along the convexity of the hemisphere, making it possible to functionally delineate the primary motor cortex in both healthy subjects and patients.The motor tasks described in this study (toe, finger and tongue) were effective at localizing the primary motor cortex for the purposes of neurosurgical planning. These three tasks produced the highest success rate and resulted in activations at regular intervals along the convexity of the hemisphere, allowing the delineation of the entire motor strip even in the presence of edema and anatomical distortions.

The fractal dimension (FD) was used to reveal brain structure irregularities in patients with schizophrenia. FD provides a unique way of quantifying the shape complexity of cortical folding of the human brain. MR images were obtained from seven patients with schizophrenia that were compared with six healthy control subjects. The MR images were first segmented, and the FD was calculated for the grey/white matter boundary for the whole brain and the hemispheres separately, using the box-counting and Minkowski-Bouligand methods. The results showed that the patients had larger FD values than the controls, for the whole brain volume and right hemisphere.

Traumatic brain injury (TBI) is the most common cause of death and disability in young people. The functional outcome in patients with TBI cannot be explained by focal pathology alone, and diffuse axonal injury (DAI) is considered a major contributor to the neurocognitive deficits experienced by this group. The aim of the present study was to investigate whether diffusion tensor imaging (DTI) offers additional information as to the extent of damage not visualized with standard magnetic resonance imaging (MRI) in patients with severe TBI. Nine chronic male TBI patients and 11 matched healthy controls were recruited. Results of the voxel-based analysis of fractional anisotropy (FA) maps and apparent diffusion coefficient (ADC) maps revealed significant differences in anisotropy in major white matter tracts, including the corpus callosum (CC), internal and external capsule, superior and inferior longitudinal fascicles, and the fornix in the TBI group. The FA and ADC measurements offered superior sensitivity compared to conventional MRI diagnosis of DAI. Region-of-interest (ROI) analyses confirmed these results in the investigated regions. The findings of this study support the hypothesis that severe TBI is accompanied by DAI. The DTI changes were more prominent on the right side that contained the focal pathology in most of the patients and accurately reflected differences in both hemispheres. In conclusion, DTI holds great promise as a diagnostic tool to identify and quantify the degree of white matter injury in TBI patients.

Objective: This case report suggests that screening of patients with psychiatric symptoms using modern neuroimaging can help identify organic causes of mental illness. Method: A single case study was reported. Results: We report the case of a 25-year-old woman with a recent diagnosis of bipolar II disorder having an magnetic resonance imaging (MRI) scan as part of a research project that reveals an intraventricular brain tumour. The latter is most likely the cause of her irritability and ‘hypomanic’ symptoms and is defined anatomically using diffusion tensor imaging and structural and functional imaging using MRI and positron emission tomography. Conclusion: The lesion in this individual case most probably produces mood symptoms by impinging upon the fornix, a component of the limbic system. However, more generally, the increase in diagnosis of bipolar disorder has to be tempered against alternate causes of similar symptoms and necessitates vigilance of potential organic mechanisms.

Objective. The aims of this study were: 1) To develop protocols for, integration and assessment of the usefulness of high quality fMRI (functional magnetic resonance imaging) and DTI (diffusion tensor imaging) data in an ultrasound-based neuronavigation system. 2) To develop and demonstrate a co-registration method for automatic brain-shift correction of pre-operative MR data using intra-operative 3D ultrasound. Methods. Twelve patients undergoing brain surgery were scanned to obtain structural and fMRI data before the operation. In six of these patients, DTI data was also obtained. The preoperative data was imported into a commercial ultrasound-based navigation system and used for surgical planning and guidance. Intra-operative ultrasound volumes were acquired when needed during surgery and the multimodal data was used for guidance and resection control. The use of the available image information during planning and surgery was recorded. An automatic voxel-based registration method between preoperative MRA and intra-operative 3D ultrasound angiography (Power Doppler) was developed and tested postoperatively. Results. The study showed that it is possible to implement robust, high-quality protocols for fMRI and DTI and that the acquired data could be seamlessly integrated in an ultrasound-based neuronavigation system. Navigation based on fMRI data was found to be important for pre-operative planning in all twelve procedures. In five out of eleven cases the data was also found useful during the resection. DTI data was found to be useful for planning in all five cases where these data were imported into the navigation system. In two out of four cases DTI data was also considered important during the resection (in one case DTI data were acquired but not imported and in another case fMRI and DTI data could only be used for planning). Information regarding the location of important functional areas (fMRI) was more beneficial during the planning phase while DTI data was more helpful during the resection. Furthermore, the surgeon found it more user-friendly and efficient to interpret fMRI and DTI information when shown in a navigation system as compared to the traditional display on a light board or monitor. Updating MRI data for brain-shift using automatic co-registration of preoperative MRI with intra-operative ultrasound was feasible. Conclusion. In the present study we have demonstrated how both fMRI and DTI data can be acquired and integrated into a neuronavigation system for improved surgical planning and guidance. The surgeons reported that the integration of fMRI and DTI data in the navigation system represented valuable additional information presented in a user-friendly way and functional neuronavigation is now in routine use at our hospital. Furthermore, the present study showed that automatic ultrasound-based updates of important pre-operative MRI data are feasible and hence can be used to compensate for brain shift.

Blood-Oxygenation-Level-Dependent functional Magnetic-Resonance-Imaging (BOLD fMRI) and Diffusion Tensor Imaging (DTI) are specialized MRI-techniques for imaging of eloquent cortices and neural tracts in gray and white matter, respectively. By processing of the BOLD fMRI images, it is possible to map eloquent cortices and visualize them as statistical parametric color coded maps to be overlain on for instance anatomical MRI-images. Processing of the DTI images using a technique called Diffusion Tensor Tractography (DTT), makes it possible to map important neural tracts and visualize them as fiber bundles. The results from these examinations may be helpful during planning and resection of brain lesions, by providing information on functional eloquent cortices and important white matter tracts in close proximity to the lesion, as the goal of surgery is to maximize resection without inflicting new neurological deficits. This functional information may also be incorporated into neuronavigation systems and utilized during surgery. The overall aim of this thesis was to develop, implement, and evaluate BOLD fMRI and DTT at 3 Tesla for routine use in preoperative planning and 3D ultrasound-guided functional neuronavigation combined with minimal invasive neurosurgery. Obtaining normative functional data in healthy subjects is a first step in the development of clinical useful tasks. Thus, we investigated different motor tasks in a group of healthy subjects to evaluate which combination was best suited for functional mapping and delineation of the primary motor cortex. Movement of fingers, toes, and tongue yielded the highest success rates in healthy subjects and proved equally successful in patients with brain lesions. We also investigated a set of language tasks and the reproducibility of the activation size and location for these. We found that a word-generation task and a responsive naming task should be preferred for mapping of the frontal and temporal language area, respectively. A novel language task with the potential to map both the frontal and temporal language areas was also established. This task has the advantage of being more engaging, which may help the subjects to maintain concentration and stay motivated throughout the scanning session. We have also evaluated the use of BOLD fMRI and DTT in 3D ultrasound-guided functional neuronavigation by retrospectively reviewing patients operated during a threeyear period. We found that surgery gave an overall significant improvement in clinical status compared to preoperatively, and for gliomas we found a median residual tumor volume of 11%. We also found a significant correlation between decreasing lesion-toeloquent- area distance and increasing residual tumor percentage in gliomas, indicating that the resections were performed as a compromise between removing as much tumor tissue as possible without jeopardizing eloquent areas. Furthermore, some glioma patients with lesion-to-eloquent-area distance less than 2 mm also had radical resections without post-operative neurological deficits. Thus indicating that guided functional neuronavigation with updated anatomical information using 3D ultrasound gives the surgeon an advantage when resecting brain lesions, as well as facilitates maximal tumor resection with minimal deficit. The challenges ahead lie in establishing standardized tasks and analysis for processing of these investigations, as well as carrying out prospective outcome studies or clinical randomized trials in order to produce evidence for effect of presurgical BOLD fMRI and DTT on morbidity and mortality in patients with brain lesions.

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.