Jean Sabatier

Usefulness of Motor Functional MRI Correlated to Cortical Mapping in Rolandic Low-Grade Astrocytomas

Summary The indications for surgery of slow growing tumours like low grade astrocytomas in eloquent areas are difficult. The timing and the benefit/risk ratio of the surgery must be evaluated, taking into account the potential post operative deficit. The purpose of this study was: a) to validate the data obtained with functional MRI (FMRI) by direct cortical stimulation in patients who are candidate for surgery; b) to demonstrate the usefulness of FMRI coupled with cortical brain mapping and 3D reconstructions of the surfaces of the brain in low grade astrocytoma. FMRI of the hand-motor cortex was performed in 8 patients with low grade astrocytomas. They subsenquently underwent direct cortical mapping to correlate the results of FMRI and resective surgery sparing the functional area. In the 8 cases, the results of direct cortical mapping in the precentral region matched accurately those obtained from FMRI. When surgical resection of low grade astrocytoma in the motor areas is considered, FMRI used with intra-operative cortical mapping can help the surgeon to spare functional areas during tumour removal.

CORTICAL INTRAOPERATIVE STIMULATION IN BRAIN TUMORS AS A TOOL TO EVALUATE SPATIAL DATA FROM MOTOR FUNCTIONAL MRI

RATIONALE AND OBJECTIVE The purpose of this prospective, double-blind study was to correlate motor functional MRI (fMRI) with cortical brain mapping by intraoperative stimulation using 3D reconstructed images of the surface of the brain, and to validate the spatial data of fMRI in patients with brain tumors. METHODS Fourteen patients with tumors of the rolandic region underwent functional MR mapping of the hand region and subsequently cortical mapping before tumor resection. Data obtained with fMRI and brain mapping were not known previously by the neurosurgeon and by the neuroradiologist, respectively (double-blind study). RESULTS In each case, the results of direct cortical mapping matched those obtained with fMRI, both positively and negatively, although the extent of the functional activations was larger than the area required to elicit the corresponding movement during intraoperative brain mapping. CONCLUSION fMRI can be used before surgery to assess motor functional area in patients with rolandic tumors. More studies are needed to validate during surgery the real extent of fMRI activations.

Characterization of choline compounds with in vitro 1H magnetic resonance spectroscopy for the discrimination of primary brain tumors.

RATIONALE AND OBJECTIVES The authors sought to compare 1H magnetic resonance spectroscopy (MRS) spectra from extracts of low-grade and high-grade gliomas, especially with respect to the signals of choline-containing compounds. METHODS Perchloric acid extracts of six high-grade and six low-grade gliomas were analyzed by 1H MRS at 9.4 Tesla. RESULTS The signals of glycerophosphocholine (GPC) at 3.23 ppm, phosphocholine (PC) at 3.22 ppm, and choline (Cho) at 3.21 ppm were identified in both types of tumors. The absolute concentrations of all Cho-containing compounds (GPC + PC + Cho) in high-grade and low-grade gliomas were significantly different. The relative contributions of each of the Cho-containing compounds to the total choline signal were also statistically different. For high-grade gliomas, the choline signal is composed of GPC, PC, and Cho in a well-balanced contribution, whereas in low-grade gliomas, the signal is largely due to GPC with a small involvement of PC and Cho. CONCLUSIONS The differences in the concentration and the repartition of Cho-containing compounds seem to be a marker of high-grade gliomas. They could also help to discriminate between high- and low-grade gliomas in some difficult cases, especially if there is histologic uncertainty between anaplastic astrocytomas and low-grade oligodendrogliomas.

Motor functional MRI for presurgical evaluation of cerebral tumors.

OBJECTIVE To evaluate the capabilities and the limitations of motor functional magnetic resonance imaging (fMRI) in the presurgical evaluation of the cerebral tumors located in or near the motor homunculus. To correlate each type of activation with the histologic characteristics of each tumor. MATERIALS AND METHODS fMRI was performed in 17 patients (14 adults and 3 children), without any motor deficit, presenting with various intracerebral tumors. Three fMRI activation paradigms were used: contralateral to the lesion: ballistic opposition of the fingers, flexion-extension of the foot and click of the tongue. Four patients, without motor deficit, with cerebral tumors far from the motor homunculus were used as control group to look for nonspecific activations. In all cases, the histopathology of the tumor was known accurately. RESULTS In 11 patients with infiltrating tumors, the activated areas were clearly displaced. They were often intratumoral and scattered in correlation with the degree of infiltration. Two patients with noninfiltrating tumors (meningioma) showed extratumoral shift of the activated areas. Four patients presenting cerebral tumors far from the homunculus motor did not show intratumoral activation. The supplementary motor area and the ipsilateral primary motor cortex were also reproducibly activated during the motor tasks. The task of the tongue was often artifacted, probably because of the head motion. CONCLUSIONS These preliminary results suggest that the histopathologic characteristics of a tumor, and especially its microscopic structure, play a role in the organization of the motor functional area. In a small number of cases, fMRI could be used intraoperatively with a neuronavigation system.

Deep Brain Stimulation for Parkinson’s Disease: Correlation between Intraoperative Subthalamic Nucleus Neurophysiology and Most Effective Contacts

Though intraoperative neurophysiology is essential to precisely define the definitive target, little is known regarding its predictive value in defining the most effective contact for chronic deep brain stimulation. In this retrospective study, we reviewed the correlation between intraoperative neurophysiology and contacts selected for chronic stimulation. Twenty consecutive patients implanted for subthalamic nucleus (STN) stimulation were reviewed. There was no significant correlation between the electrophysiologically defined STN and the most effective contact for chronic stimulation at 3 months or at 6 months. Furthermore, there was a discrepancy between the most effective contact for rigidity versus akinesia or tremor at 3 months. Interestingly, at 3 months, the same electrode contact was maximally efficient for rigidity, akinesia and tremor in only 13 of the 39 cases. This lack of correlation did not affect the global improvement.

Evaluation of O-(2-[18F]-Fluoroethyl)-L-Tyrosine in the Diagnosis of Glioblastoma

OBJECTIVE To assess the feasibility of synthesis of O-(2-[(18)F]-fluoroethyl)-l-tyrosine (FET), a new positron emission tomographic (PET) tracer described in several studies but not yet considered standard in management of glioma, in routine practice and to determine FET uptake in a homogeneous group of patients with suspected high-grade glioma. DESIGN Prospective nonrandomized trial. PATIENTS Twelve patients with suspicion of high-grade glioma. RESULTS The mean (SD) FET uptake ratio was 3.15 (0.72) for the 12 patients and 3.16 (0.75) for the 11 patients with glioblastoma. CONCLUSION The initial results are promising and indicate that FET PET is a valuable and applicable tool for the imaging of high-grade glioma.

Contribution of in vivo 1H spectroscopy to the diagnosis of deep-seated brain abscess.

Brain abscesses are associated with high mortality and morbidity even in the antibiotic era and with complex imaging techniques, mainly because of delayed diagnosis. Several reasons can be identified: (1) the incidence of abscesses is low, about 1.1/100 000 person-year1; (2) clinical features may be non-specific without evidence of infection and with neurological signs similar to tumours, which are 50 times more frequent; (3) neuroradiological imaging may be confusing specially in the early stages. The only way to improve the outcome of this pathology is to consider an abscess when faced with a space occupying lesion and to perform a stereotactic biopsy even in elderly or severely deteriorated patients. Recently, in vivo 1H MR spectroscopy (MRS) was reported to give metabolic information on brain abscesses very different from that of brain tumours, permitting a non-invasive differential diagnosis between these two diseases.2 (A) T2 weighted MRI in the axial plane. (B) In vivo1H MRS spectrum from abscess (echo time=135 ms)

Usefulness of in vitro 1H Magnetic Resonance Spectroscopy for the Characterization of Primary Brain Tumors: Report of Two Cases

Pathological diagnosis of brain tumors provides an index of brain disease severity and guides clinical practice in their treatment. Diagnoses are often made from biopsy material obtained using stereotactic techniques with the difficulty of making a histological diagnosis in small samples. In our experience, the estimation of the degree of malignancy on the basis of in vitro1H magnetic resonance spectroscopy (1H MRS) appears to well correlate with histology and clinical evolution. We report two cases with a discordance between the diagnoses on the basis of histology examination and in vitro 1H MRS whose evolution seems to correlate better with the data of1H MRS.

Dedicated linear accelerator radiosurgery for classical trigeminal neuralgia: a single-center experience with long term follow-up

BACKGROUND During the past decades, stereotactic radiosurgery, and Gamma Knife in particular, has proved its safety and efficacy for drug-resistant classic trigeminal neuralgia. However, few large series exist using linear accelerator (LINAC) reporting long-term follow-up. METHODS Between 2006 and 2015, 301 patients were treated by LINAC at our institution. The prescribed radiation dose was 90 Gy at the far anterior target. Clinical response was defined using the Barrow Neurological Institute scale. We considered grades I and IIIa as a successful response. Mean duration of follow-up was 54.6 months (range, 12-132 months). RESULTS Two hundred and seventy-three patients (90.7%) were initially pain free, and 28 patients (9.3%) were unchanged. The actuarial probabilities of maintaining pain relief with or without medication (Barrow Neurological Institute grade I and IIIa) at 0.5, 1, 2, 4, 5, and 10 years were 88.7%, 85.0%, 76.1%, 68.8%, 65.8%, and 48.1%, respectively. Hypesthesia was present in only 26.2% of patients (very bothersome, 0.3%). No anesthesia dolorosa was reported. The actuarial probabilities of maintaining pain relief without further surgery at 0.5, 1, 2, 4, and 5 years were 99.3%, 98.3%, 95.8%, 91.0%, and 89.7%, respectively. Among all treated patients, 86.5% were satisfied by the procedure and would undergo stereotactic radiosurgery again. CONCLUSIONS Stereotactic radiosurgery with dedicated LINAC is associated with high rates of long-term pain relief, with minimal invasiveness and rare complications. LINAC is a possible therapeutic alternative for drug-resistant trigeminal neuralgia and could be proposed to selected patients as the first intention therapy, among other surgical solutions.