Identifying the affected hemisphere by 1H-MR spectroscopy in patients with temporal lobe epilepsy and no pathological findings in high resolution MRI

Up to 30% of patients with temporal lobe epilepsy (TLE) remain without remarkable changes in MRI. In this study we investigated the role of (1)H-MR spectroscopy ((1)H-MRS) in lateralizing the affected hemisphere in the mentioned patient group. Twenty-two consecutive patients diagnosed with TLE were investigated by high resolution MRI and (1)H-MRS. We examined the incidence and diagnostic accuracy of temporal metabolite alterations determined by Linear Combination of Model Spectra (L C Model) via water reference. Metabolite values of each hemisphere of TLE patients were compared with healthy controls. Results of metabolite alterations were related to intensive video EEG focus localization. Reduction of N-acetylaspartate + N-acetylaspartyl-glutamate (tNAA) in the affected hemisphere revealed identification in six of nine patients (66%) with unilateral TLE. Group comparison revealed a significant reduction of tNAA (6.1+/-0.8*) in the involved temporal lobe compared with controls (6.67+/-0.4*, P=0.026). Choline levels were significantly increased in the affected hemisphere (1.42+/-0.17*) compared with healthy controls (1.22+/-0.17*, P=0.035). The results of our study show that (1)H-MRS is able to identify the affected hemisphere of MRI negative TLE patients and can be used as an additive tool in multimodal focus localization.     

Low-field magnetic resonance imaging for intraoperative use in neurosurgery: a 5-year experience

The aim of this study was to evaluate the feasibility and point out the indications of intraoperative MR imaging in neurosurgical procedures. The MR imaging was performed using a 0.2-T scanner which was located in a radiofrequency-shielded operating theater. Three major setups for intraoperative imaging were possible: inside the scanner; at the 5-Gauss line; or in an adjacent operating theater. Additionally, in lesions adjacent to eloquent brain areas microscope- and pointer-based neuronavigation with integrated functional data was applied. Three hundred ten patients were investigated in the previous 5 years, among them gliomas (n=95), pituitary tumors (n=81), and 39 non-lesional cases in whom resective or disconnective epilepsy surgery was carried out. We did not observe any adverse effects due to intraoperative MR imaging. Image quality was sufficient to evaluate the extent of the tumor resection in the majority of cases. The main indications for intraoperative MR imaging were the evaluation of the extent of a resection in glioma, ventricular tumor, pituitary tumor, and in epilepsy surgery. Intraoperative MR imaging offers the possibility of further tumor removal during the same surgical procedure in case of tumor remnants, increasing the rate of complete tumor removal. Furthermore, the effects of brain shift, which would lead to inaccurate neuronavigation, can be compensated for by an update of the neuronavigation system with intraoperative MR image data. Electronic Publication     

Intraoperative Magnetresonanztomographie Erfahrungen beim Einsatz in der Neurochirurgie

Intraoperative magnetic resonance imaging using a 0.2 Tesla, open-configured scanner was applied in a total of 243 patients. The aim of this study was to evaluate the feasibility, clinical application, and indications of this method. No adverse effects of the intraoperative imaging could be observed. The extent of tumor resection could be evaluated in the majority of cases. Resection control in glioma, ventricular tumor, pituitary tumor, and epilepsy surgery were the main indications for the intraoperative application. Especially when combined with functional neuronavigation, intraoperative magnetic resonance imaging allowed more radical resectioning with lower morbidity. Second looks to complete tumor removal during the same surgical procedure were possible to determine tumor remnants. Brain shift, which reduces the accuracy of neuronavigational systems, could be compensated for by intraoperative updates.     

Comparing 0.2 tesla with 1.5 tesla intraoperative magnetic resonance imaging analysis of setup, workflow, and efficiency

RATIONALE AND OBJECTIVES: To compare low-field with high-field intraoperative magnetic resonance imaging (MRI) in respect to setup, workflow, and efficiency. MATERIALS AND METHODS: A total of 750 patients were investigated either with a 0.2 T (March 1996-July 2001) or a 1.5 T (April 2002-August 2004) MRI system adapted for intraoperative use. RESULTS: With the low-field setup, 330 patients were examined in 65 months; with the high-field setup, 420 patients were examined in 29 months, which is a 2.8-fold increase in cases per month (14.5 versus 5.1) reflecting improved ease of use. Concerning intraoperative workflow, the time for preparation to start intraoperative imaging decreased fivefold (2 minutes instead of 10 minutes); navigation was applied more often with 57% versus 51% (240/420 versus 167/330), whereas functional data were integrated in 35% versus 39% (84/240 versus 65/167). Application of navigation updates was doubled (22% versus 11%; 53/240 versus 18/167). Image acquisition time was reduced by a factor of two, allowing a more detailed imaging protocol, whereas the image quality is clearly improved in the high-field setup, where there was no difference between the standard preoperative image quality compared with the intraoperative quality. This contributed to an increased detection of tumor remnants and extended resections in pituitary (36% versus 29%; 47/129 versus 17/59) and glioma surgery (41% versus 26%; 38/93 versus 28/106). CONCLUSION: Compared with the low-field setup, the high-field setup results not only in clearly superior image quality and increased imaging armamentarium, contributing to increased rates of detected tumor remnants, but also in a distinct improvement of intraoperative workflow. Furthermore, intraoperative high-field MRI offers various modalities beyond standard anatomic imaging, such as magnetic resonance spectroscopy, diffusion tensor imaging, and functional MRI.     

Anesthesia during high-field intraoperative magnetic resonance imaging experience with 80 consecutive cases

Intraoperative magnetic resonance imaging (MRI) has been used for years to update neuronavigation and for intraoperative resection control. For this purpose, low-field (0.1-0.2 T) MR scanners have been installed in the operating room, which, in contrast to machines using higher magnetic field strength, allowed the use of standard anesthetic and surgical equipment. However, these low-field MR systems provided only minor image quality and a limited battery of MR sequences, excluding functional MRI, diffusion-weighted MRI, or MR angiography and spectroscopy. Based on these advantages, a concept using high-field MRI (1.5 T) with intraoperative functional neuronavigational guidance has been developed that required adaptation of the anesthetic regimen to working in the close vicinity to the strong magnetic field. In this paper the authors present their experience with the first 80 consecutive patients who received anesthesia in a specially designed radio frequency-shielded operating room equipped with a high-field (1.5 T) MR scanner. We describe the MR-compatible anesthesia equipment used including ventilator, monitoring, and syringe pumps, which allow standard neuroanesthesia in this new and challenging environment. This equipment provides the use of total intravenous anesthesia with propofol and remifentanil allowing rapid extubation and neurologic examination following surgery. In addition, extended intraoperative monitoring including EEG monitoring required for intracranial surgery is possible. Moreover, problems and dangers related to the effects of the strong magnetic field are discussed.     

Simple invasive fixation device for fractionated stereotactic LINAC based radiotherapy

Summary.  Background: The aim of this study was to develop a relocatable fixation device for linear accelerator (LINAC) based fractionated stereotactic radiotherapy.  Method: The device consists of a CT- and MRI-compatible stereotactic frame, monocortical titan bone screws, four frame-posts with a lock for the fixation pins and a modified head clamp with additional arms that allows the exact and rigid placement of the frame in the desired final position prior to the final placement of the bone screws. By simply disconnecting the lock from the posts, the frame can be dismounted after treatment planning and after each treatment session. The accuracy of reposition was assessed prospectively, using phantom studies and also by comparison of isocenter movements during fractionated radiotherapy in 10 patients with an intracranial lesion.  Findings: No adverse events were seen after the surgical procedure and the screws were well tolerated throughout the course of treatment. The mean isocenter shifts observed during phantom reposition studies were x=0.05 mm, y=−0.32 mm, z=0.18 mm and the mean isocenter shifts during fractionated treatment were x=0.67 mm, y=0.65 mm, z=0.44 mm.  Interpretation: This new fixation device provides excellent accuracy of reposition during stereotactic radiotherapy. It appears superior to non-invasive, mask fixation techniques. Safety margins as small as 1–1.5 mm may therefore be sufficient for this method of stereotactic radiotherapy. Published online April 28, 2003  Correspondence: Dr. Oliver Ganslandt, Department of Neurosurgery, Schwabachanlage 6, D-91054 Erlangen, Germany.     

The patients’ view: impact of the extent of resection,intraoperative imaging,and awake surgery on health-related quality of life in high-grade glioma patients—results of a multicenter cross-sectional study

Neurosurgical Review - The objective of the present study is to assess the influence of extent of resection (EoR), use of intraoperative imaging, and awake surgery on health-related quality of life...     

Flat panel detector angiographic CT for stent-assisted coil embolization of broad-based cerebral aneurysms

BACKGROUND AND PURPOSE: The purpose of this work was to evaluate angiographic CT (ACT) in the combined application of a self-expanding neurovascular stent and detachable platinum coils in the management of broad-based and fusiform intracranial aneurysms. MATERIALS AND METHODS: Eleven patients harboring wide-necked intracranial aneurysms were treated with a flexible self-expanding neurovascular stent and subsequent aneurysm embolization with platinum microcoils. ACT was performed after the interventional procedure to analyze stent position and the relationship of coils to the stent. Postprocessing included multiplanar reconstructions (MPRs) and maximum intensity projections (MIPs). ACT volume datasets were postprocessed for soft tissue visualization. RESULTS: Accurate stent placement with subsequent coil occlusion of the aneurysms was feasible in all of the patients. Similar to nonsubtracted digital subtraction angiography (DSA) images, radiopaque platinum stent markers showed excellent visibility in ACT as well. The stent struts themselves, hardly visible in nonsubtracted DSA, were visible in MPRs and MIPs of ACT in all of the patients. In aneurysms larger than 10 mm in diameter, accurate stent assessment at the level of the coils was limited due to beam hardening artifacts. Postprocedural ACT in all of the patients did not reveal any evidence of procedure-related intracranial hemorrhage. CONCLUSION: ACT provides cross-sectional, 3D visualization of endovascular stents otherwise hardly visible with plain fluoroscopy. ACT enables us to accurately determine stent position, which may be helpful in complex stent-assisted aneurysm coiling procedures. However, in aneurysms larger than 10 mm in diameter, beam hardening artifacts caused by the endoaneurysmal coil package impair visibility of the stent. Further data are necessary to evaluate the usefulness of ACT in stent-assisted aneurysm coiling.     

(1)H-MRS profile in MRI positive- versus MRI negative patients with temporal lobe epilepsy.

INTRODUCTION: The objective of this study was to quantitate and compare ipsilateral total N-acetyl aspartate (tNAA), creatine (Cr), choline (Cho), myo-inositol (m-Ins) and glutamate plus glutamine (Glx) levels in the hippocampi of patients with temporal lobe epilepsy (TLE) with and without magnetic resonance imaging (MRI) evidence for mesial temporal sclerosis (MRI positive/negative). PATIENTS AND METHODS: Twenty-three age matched healthy controls and 26 consecutive patients with unilateral TLE, based on intensive 24h video-EEG, were investigated with proton magnetic resonance spectroscopy ((1)H-MRS) (17 with unilateral hippocampal sclerosis (HS) in MRI-MRI positive; 9 MRI negative). For statistical analysis one-way analysis of variance (ANOVA) with post hoc multiple comparisons and Bonferroni correction was applied. The significance level was based on p<0.05. RESULTS: The mean tNAA level ipsilateral to the seizure focus was significantly decreased in MRI negative, respectively MRI positive patients in comparison to healthy controls (p<0.001). The lowest tNAA level was noticed in the MRI positive group (p<0.001). Statistical analysis highlighted a clear "tNAA cut-off" (95% confidence interval) between MRI positive- and MRI negative patients and healthy controls. Mean level of Glx and m-Ins was not significantly elevated or reduced. However, in individual cases a significant elevation was noticed for Glx in MRI negative patients, respectively for m-Ins in MRI positive patients. CONCLUSION: MRI negative TLE patients have a different MRS profile than MRI positive patients (HS) with marginal but significant decrease of tNAA. Our results reveal a clear "tNAA cut-off" between the groups. The value of m-Ins and Glx in focus detection in TLE patients remains controversy.