Lars Jönsson

Intersubject variability in the anterior extent of the optic radiation assessed by tractography.

INTRODUCTION Temporal lobe resection for epilepsy involves a risk of damaging the anterior part of the optic radiation, Meyers loop, causing a contralateral upper quadrant visual field defect. This study aims to assess the intersubject variability in the course of Meyers loop in vivo by diffusion tensor imaging and tractography. METHODS Seven healthy volunteers and two patients with previous temporal lobe resection were recruited. Diffusion tensor imaging and tractography were used to visualize the optic radiation. The distances from the anterior edge of Meyers loop to landmarks in the temporal lobe were calculated. RESULTS In the healthy subjects, the mean distance between the most anterior part of Meyers loop and the temporal pole was 44 mm (range 34-51 mm). Meyers loop did not reach the tip of the temporal horn in any subject. A disruption in Meyers loop could be demonstrated in the patient with quadrantanopia after temporal lobe resection. CONCLUSIONS Meyers loop has a considerable variability in its anterior extent. Tractography may be a useful method to visualize Meyers loop, and assess the risk of a visual field defect, prior to temporal lobe resection.

Surgical treatment of epilepsy ‐ clinical, radiological and histopathological findings in 139 children and adults

The present study relates clinical and radiological data to histopathological diagnoses in the first 139 patients (children and adults) in the Göteborg Epilepsy Surgery series. Temporal lobe resections were most common (54.0%) followed by frontal lobe (18.0%) and multilobar resections (11.5%). All histopathological specimens were re‐evaluated in connection with this study. Parenchymal malformations and atrophic‐gliotic lesions were the most common histopathological findings. Microdysgenesis was more common than major malformations (24.5% versus 11.5%). When the MRI scans were blindly re‐evaluated the MRI findings correlated with histopathological diagnosis in all of the vascular malformations, in 77.8% of the tumours, in 76.5% of the cases with hippocampal sclerosis but only in 28.6% of the major cortical development malformations. Hemispherectomies carried the best seizure outcome prognosis followed by temporal lobe resections (75.0% versus 57.3% seizure free 2 years after surgery). Vascular malformations carried the best, and microdysgenesis the worst prognosis (76.9% versus 39.4% seizure free).

Long-Term Follow-up of a Patient with Traumatic Brain Injury Using Diffusion Tensor Imaging

This case report describes a patient who sustained severe head trauma with diffuse axonal injury (DAI). Examination with magnetic resonance diffusion tensor imaging (MR-DTI), 6 days post-injury, showed a severe reduction in fractional anisotropy (FA) in the rostral pons containing the corticospinal tract, which correlated to the patients severe hemiparesis. By 18 months post-accident, the patient had recovered completely and conventional MRI showed no pathology. However, although her FA values in the rostral pons had increased, they were still not normalized. It seems that a complete normalization of the FA values is not required to achieve clinical recovery, and that MR-DTI seems to be more sensitive to DAI compared to conventional MRI.

Guidelines for the use of magnetic resonance imaging in diagnosing and monitoring the treatment of multiple sclerosis: recommendations of the Swedish Multiple Sclerosis Association and the Swedish Neuroradiological Society.

Multiple sclerosis (MS) is associated with inflammatory lesions in the brain and spinal cord. The detection of such inflammatory lesions using magnetic resonance imaging (MRI) is important in the consideration of the diagnosis and differential diagnoses of MS, as well as in the monitoring of disease activity and predicting treatment efficacy. Although there is strong evidence supporting the use of MRI for both the diagnosis and monitoring of disease activity, there is a lack of evidence regarding which MRI protocols to use, the frequency of examinations, and in what clinical situations to consider MRI examination. A national workshop to discuss these issues was held in Stockholm, Sweden, in August 2015, which resulted in a Swedish consensus statement regarding the use of MRI in the care of individuals with MS. The aim of this consensus statement is to provide practical advice for the use of MRI in this setting. The recommendations are based on a review of relevant literature and the clinical experience of workshop attendees. It is our hope that these recommendations will benefit individuals with MS and guide healthcare professionals responsible for their care.

Lateralisation with magnetic resonance spectroscopic imaging in temporal lobe epilepsy: an evaluation of visual and region-of-interest analysis of metabolite concentration images

Abstract We carried out spectroscopic imaging (MRSI) on nine consecutive patients with temporal lobe epilepsy being assessed for epilepsy surgery, and nine neurologically healthy, age-matched volunteers. A volume of interest (VOI) was angled along the temporal horns on axial and sagittal images, and symmetrically over the temporal lobes on coronal images. Images showing the concentrations of N-acetylaspartate (NAA) and of choline-containing compounds plus creatine and phosphocreatine (Cho + Cr) were used for lateralisation. We compared assessment by visual inspection and by signal analysis from regions of interest (ROI) in different positions, where side-to-side differences in NAA/(Cho + Cr) ratio were used for lateralisation. The NAA/(Cho + Cr) ratio from the different ROI was also compared with that in the brain stem to assess if the latter could be used as an internal reference, e. g., for identification of bilateral changes. The metabolite concentration images were found useful for lateralisation of temporal lobe abnormalities related to epilepsy. Visual analysis can, with high accuracy, be used routinely. ROI analysis is useful for quantifying changes, giving more quantitative information about spatial distribution and the degree of signal loss. There was a large variation in NAA/(Cho + Cr) values in both patients and volunteers. The brain stem may be used as a reference for identification of bilateral changes.

Different stages of white matter changes in the original HDLS family revealed by advanced MRI techniques.

The temporal evolution of white matter (WM) changes on MR examinations in hereditary diffuse leukoencephalopathy with spheroids (HDLS) is largely unknown. Our purpose was to investigate the evolution of these WM changes with diffusion weighted/tensor imaging (DWI/DTI) and MR Spectroscopy (MRS).

Update of the original HDLS kindred: divergent clinical courses.

Sundal C, Ekholm S, Nordborg C, Jönsson L, Börjesson‐Hanson A, Lindén T, Zetterberg H, Viitanen M, Andersen O. Update of the original HDLS kindred: divergent clinical courses.
Acta Neurol Scand: 2012: 126: 67–75.
© 2011 John Wiley & Sons A/S.

Performance of 2D 1H spectroscopic imaging of the brain: some practical considerations regarding the measurement procedure

This paper deals with some of the practical considerations in the planning and performance of chemical shift imaging (MRSI or CSI) of the brain. It contains some aspects of 1) the imaging procedure (MRI), i.e., suggestions of an imaging protocol useful for the spectroscopic planning, 2) the planning of the spectroscopic volume, i.e., size and position, 3) evaluation and judgment of the preparation results, and 4) evaluation of the MRSI images. The paper also contains suggestions of developmental work and quality assessment to be done before patient studies are begun. Examples are given for MRSI studies of temporal lobe epilepsy. Several of the aspects described are obvious for the experienced spectroscopist but may be useful in the initiation of MRSI. The goal of this paper was to share our experiences of how to achieve high quality MRSI, experiences that we would had been grateful for in our prelude of MRSI experiments.

Cortical reorganization of sensory, motor and language functions due to early cortical damage

During evaluation of a 22-year-old man for epilepsy surgery it was demonstrated that reorganisation of sensory, motor and language functions had occurred. Restricted perinatal lesions in the left frontal opercular region and in the hand primary sensory area had resulted in severe partial epilepsy and minor neuropsychological deficits, but no neurological deficits. The dominance for language and handedness was shifted to the right hemisphere but some language representation was still found in the left hemisphere. Threshold electrical stimulation via subdurally placed cortical electrodes revealed reorganisation of the hand sensory area in the left hemisphere. Hand sensory responses were electrically evoked close to the opercular region where also face sensory responses were recorded. Some of the sensory responses were located in the frontal lobe in the premotor cortex. The locations of the sensory representation areas differed from those expected neuroanatomically. The cortical motor responses were located around the presumed location of the precentral gyrus. These findings are considered to represent a functional intra- and interhemispherical reorganisation of cortical areas as a result of early cortical lesions, anatomically close to the somatosensory and language areas. A possible mechanism discussed is reorganisation of the thalamocortical projections.

Anterior to posterior hippocampal MRS metabolite difference is mainly a partial volume effect

Background: The concentration of N-acetylaspartate (NAA) in hippocampus, as measured with magnetic resonance spectroscopy (MRS), and the ratio of NAA/(choline (Cho) + creatine (Cr)) are valuable tools in the lateralization of temporal lobe epilepsy (TLE). MRS of hippocampus is also increasingly used to study certain psychiatric and degenerative diseases. However, the reliability of such measurements of hippocampus has been questioned. Purpose: To re-evaluate MRS imaging data from prior control subjects with regard to variation of metabolite concentrations in hippocampus from anterior to posterior and the partial volume ®contribution to the measurements from adjacent tissue. Material and Methods: Twelve healthy subjects, mean age 33 years, were studied with MRS imaging. The measurement volume was angled along the temporal horns and metabolite concentration images were reconstructed at the MR system. Regions of interest (ROIs) in the anterior, medial, and posterior parts of both hippocampi were evaluated. Signal normalization to the total MRS signal from all ROIs permitted pooling of individual data with different and unknown signal scaling. One subject was re-examined with a high resolution three-dimensional (3D) volume of the brain for evaluation of partial volumes in the MRS examination. Results: Overall, there were significantly lower concentrations of NAA in the anterior parts, and of (Cho+Cr) in the posterior parts, while the NAA/(Cho+Cr) ratio in the posterior parts of the mesial temporal lobes was significantly higher. Hippocampus accounted for one-half, one-third, and one-quarter of the anterior, middle, and posterior ROIs, respectively. The NAA/(Cho+Cr) ratio thus showed a reverse relationship to the relative volume of hippocampal tissue within the ROI. Conclusion: Metabolite concentrations in the mesial temporal lobe obtained with MRS imaging represent the mean value of hippocampus and a considerable amount of adjacent tissue. To assess the hippocampus alone, an actual voxel well below 1 cm3 and a sub-centimeter slice thickness are required.