Primary thumb sensory cortex located at the lateral shoulder of the inverted omega-shape on the axial images of the central sulcus

Useful landmarks on magnetic resonance (MR) images were identified for preoperative prediction of the relationship of a tumor to the primary sensory cortex of the thumb. Functional MR (fMR) imaging and magnetoencephalography were used to retrospectively localize the hand-digit sensorimotor area in four patients who underwent tumor resection around the central sulcus with intraoperative neurophysiological mapping. fMR imaging revealed the hand-digit motor cortex in the so-called "precentral knob" inside the characteristic inverted-omega on axial MR images. Equivalent current dipoles of the N20 m response in somatosensory evoked fields (SEFs) of the thumb, median nerve, and ulnar nerve stimuli were localized at the lateral portion of the inverted omega-shape from the lateral to medial directions. The SEF-based thumb sensory cortex was verified by intraoperative functional mapping with a neuronavigation system. The hand-digit somatosensory cortices were localized at the lateral shoulder of the inverted-omega, in the lateral anterior inferior position to the hand-digit motor cortices in the precentral knob. Axial MR imaging can provide useful preoperative planning information for the surgical treatment of tumors within or adjacent to the motor-somatosensory cortex.     

Language localization with activation positron emission tomography scanning.

We report the first instance of the use of 3-dimensional magnetic resonance imaging anatomically correlated to positron emission tomography (PET) scanning to identify language areas in a patient with an arteriovenous malformation (AVM) in the posterior speech region. The patient was a 24-year-old right-handed woman with an angiographically proven AVM (3-4 cm) in the left mid-posterior second temporal convolution in whom a left intracarotid injection of sodium Amytal produced significant language disruption. A baseline PET cerebral blood flow study identified the AVM, and an activation PET scan performed during the reading and speaking of simple words showed increased activity in the left parastriate cortex (the second visual area), in the left posterior third frontal convolution (Broca's area), and in the left inferior and midtemporal gyri (Wernicke's area). Increased activity was also noted in the right and left transverse temporal (Heschl's) gyri, in the left precentral gyrus, in the left medial superior frontal gyrus (the supplementary motor area), and in the right cerebellum. We conclude that activation PET scanning is useful in the preoperative assessment of patients who harbor cerebral AVMs in classically described speech regions.     

Preoperative assessment of motor cortex and pyramidal tracts in central cavernoma employing functional and diffusion-weighted magnetic resonance imaging

BACKGROUND: Functional MRI (fMRI) combines anatomic with functional information and has therefore been widely used for preoperative planning of patients with mass lesions affecting functionally important brain regions. However, the courses of functionally important fiber tracts are not visualized. We therefore propose to combine fMRI with diffusion-weighted MRI (DWI) that allows visualization of large fiber tracts and to implement this data in a neuronavigation system. METHODS: DWI was successfully performed at a field strength of 1.5 Tesla, employing a spin-echo sequence with gradient sensitivity in six noncollinear directions to visualize the course of the pyramidal tracts, and was combined with echo-planar T2* fMRI during a hand motor task in a patient with central cavernoma. RESULTS: Fusion of both data sets allowed visualization of the displacement of both the primary sensorimotor area (M1) and its large descending fiber tracts. Intraoperatively, these data were used to aid in neuronavigation. Confirmation was obtained by intraoperative electrical stimulation. Postoperative MRI revealed an undisrupted pyramidal tract in the neurologically intact patient. CONCLUSION: The combination of fMRI with DWI allows for assessment of functionally important cortical areas and additional visualization of large fiber tracts. Information about the orientation of fiber tracts in normal appearing white matter in patients with tumors within the cortical motor system cannot be obtained by other functional or conventional imaging methods and is vital for reducing operative morbidity as the information about functional cortex. This technique might, therefore, have the prospect of guiding neurosurgical interventions, especially when linked to a neuronavigation system.     

Preliminary results of PET activation study in cerebral arteriovenous malformation (AVM), using C15O2 and 18F-FDG

The authors applied PET activation study to two patients with arteriovenous malformation (AVM) to localize primary motor cortex before surgery or embolization. The change in regional cerebral blood flow (rCBF) was measured during foot movements in Case 1 who had a 2-cm AVM located in the post-central gyrus. Superimposed PET/MRI images revealed that the rCBF increase was located in the pre-central gyrus. Its validity was confirmed by intraoperative cortical mapping using electrical median nerve stimulation. The patient safely underwent total removal of AVM. The change in regional cerebral metabolic rate for glucose (rCMRglc) was measured during hand movements in Case 2 who had a huge AVM over the central sulcus. Superimposed PET/MRI images revealed that hand movements significantly increased rCMRglc in the frontal cortex, which was separated from the original primary motor area. The patient safely underwent partial embolization, although he suffered transient weakness of the face after embolization. The preliminary results strongly suggest that PET activation study is useful to localize precisely cortical functions of the patients with AVM, thus reducing morbidity after treatment. The results also suggest that cortical functions may undergo translocation when huge AVM involves the eloquent area.     

Presurgical mapping with functional MRI: comparative study with transcranial magnetic stimulation and intraoperative mapping]

PURPOSE: The accuracy of preoperative mappings in patients with brain tumors near the central sulcus using functional magnetic resonance imaging (fMRI) or transcranical magnetic stimulation (TCS) was evaluated by comparative reference to intraoperative mapping. METHODS: The thumb movement was evoked by TCS for the mapping of the motor cortex. After the placement of the marker determined by TCS on the scalp, fMRI under motor tasks consisting of repetitive grasping was performed. For motor cortex activation, an axial oblique plane to maximize gray matter sampling in the rolandic cortex was employed in order to compare these different mapping techniques more precisely. Sixteen patients with brain tumors were included in this study. RESULTS: In nine patients, fMRI disclosed activation in one restricted gyrus or in the localized area around one restricted sulcus. Of these nine patients, preoperative TCS mapping corresponded closely with fMRI in six, while in the remaining three, the TCS marker fell between 1 and 2 cm apart from the fMRI-activated area. However, in these three patients, intraoperative electrocortical stimulation corresponded with the preoperative mapping with fMRI. In six patients, contigucus two gyri were activated by motor tasks. The TCS marker was disclosed on one of the two activated gyri. Of these six patients, the position of the TCS marker and fMRI-activated site corresponded with each other in four cases. They were found on the same gyrus but there was 1.0-2.0 cm distance between them in two cases. Intraoperative somatosensory evoked potential was monitored in two of these six cases. They corresponded well with the mapping by fMRI and TCS together. In only one patient, no significant activation area was obtained by fMRI because of excessive head motion during motor tasks. The TCS marker in this patient was identical with intraoperative electro-cortical stimulation mapping. CONCLUSION: For presurgical planning in patients with brain tumor near the central sulcus, comparative evaluation with fMRI and TCS is applicable and provides accurate functional mapping.     

Brain surgery in motor areas: the invaluable assistance of intraoperative neurophysiological monitoring

AIM: Surgery for tumors in the central and precentral region, as much as for insular tumors, places at risk the functional integrity of the motor cortex and the subcortical motor pathways. These procedures may therefore benefit from the assistance of intraoperative neurophysiological monitoring (INM). INM consists of "mapping" and true "monitoring" (the continuous "on-line" assessment of the functional integrity of neural pathways) techniques. In spite of the large interest in mapping techniques, monitoring techniques have received less attention. We describe our experience with intraoperative neurophysiological mapping and monitoring of motor tracts during surgery for brain gliomas in or near motor areas, in order to support the feasibility and reliability of monitoring as an essential adjunct to mapping during surgery in these areas. METHODS: Between September 2000 and January 2002, 51 patients were surgically treated for brain gliomas located in the precentral gyrus (45.1%), the postcentral gyrus (23.5%), anterior to the precentral gyrus (15.6%), or in the insula (15.6%). INM of the motor system consisted of monitoring muscle motor evoked potentials (mMEPs) recorded via needle electrodes inserted into the controlateral upper and lower extremity muscles and elicited by transcranial multipulse electrical stimulation (TES). Once the dura was open and the central sulcus was identified using the phase reversal technique, mMEPs were elicited by direct stimulation of the motor cortex (DCS). Motor mapping was performed with a monopolar electrode using the same stimulation parameters as used for monitoring except for much lower intensity (up to 20 mA). RESULTS: Ninety-eight percent of the patients exhibited recordable baseline mMEPs. The success rate of the phase reversal technique was 95.8%. Eight patients presented disappearance of mMEPs during tumor removal. Using corrective measures, all intraoperative changes in mMEPs were reversed in time to prevent an irreversible complete injury to the motor system and no patient lost mMEPs at the end of the operation. At discharge, 66% of the patients remained at their preoperative status, 4% improved, and 24% had a mild worsening as compared to the preoperative status assessed using the Medical Research Council scale; 6% of the patients presented a moderate to severe supplementary motor area syndrome. CONCLUSION: Monitoring techniques significantly implement the reliability and effectiveness of INM since these provide: 1) continuous "on-line" assessment of the functional integrity of motor pathways with higher chance to early detect a progressive mechanical or vascular injury to the neural tissue, as compared to mapping techniques; 2) lower risk to induce intraoperative seizures and strong muscular twitches as compared to the single pulse mapping technique; 3) possibility to monitor motor pathways using TES also when there is no direct access to the motor cortex.     

Surgery of intrinsic cerebral neoplasms in eloquent areas under local anesthesia.

28 patients with a mean age of 43.6 years were operated on for a cerebral neoplasm situated in close proximity to an eloquent area (24 speech area, 4 motor cortex) from 1996 to 1999. Preoperatively, all patients had undergone a detailed neuropsychological examination. In 10 patients aphasic disturbances could be detected. All patients underwent preoperative PET studies (methionine and (15)O-labeled water with activation during speech or finger tapping). These were performed and co-registered with MRI data to demonstrate the topographical relationship between motor or language function and the tumor borders. Anesthesia was induced with i.v. administration of propofol (150-250 mg/h). Craniotomy was performed under local infiltration anesthesia. After opening of the dura, sedation was stopped and operation was continued with the patient being alert and co-operative. With close clinical observation during electrical cortex stimulation, a speech arrest could be triggered or avoided. The motor cortex was identified by recording the phase reversal of the contralateral SEP of the median nerve and by direct cortical stimulation. As soon as aphasic or motor disturbances appeared, the tumor removal was continued with the goal of avoiding these specific regions. In 27 patients, preexisting neuropsychological and neurological deficits did not worsen. Only one patient was left postoperatively with a major permanent aphasic deficit that was present preoperatively to a minor degree. The use of local anesthesia in craniotomy for surgery of intrinsic cerebral neoplasms in eloquent areas allows for a continuous and repetitive monitoring of speech and motor function during the removal of even those tumors that were previously considered inoperable.     

Surgical resection of grade II astrocytomas in the superior frontal gyrus

OBJECTIVE: Surgery in the superior frontal gyrus partially involving the supplementary motor area (SMA) may be followed by contralateral transient weakness and aphasia initially indistinguishable from damage to the primary motor cortex. However, recovery is different, and SMA deficits may resolve completely within days to weeks. No study has assessed the distinct postoperative deficits after tumor resection in the SMA on a homogeneous patient group. METHODS: Twenty-four patients with World Health Organization Grade II astrocytomas in the superior frontal gyrus consecutively treated by surgery were studied. Degree and duration of postoperative deficits were evaluated according to tumor location and boundaries via magnetic resonance imaging scans, intraoperative neuromonitoring results, and extent of tumor resection. RESULTS: Postoperatively, motor deficits were evident in 21 of 24 and speech deficits in 9 of 12 patients. Motor function quickly recovered in 11 and speech function in 3 patients. None of the 12 patients in whom the posterior tumor resection line was at a distance of more than 0.5 cm from the precentral sulcus experienced persistent motor deficits. Eight of these patients developed typical SMA syndrome with transient initiation difficulties. Seven of 12 patients in whom the tumor extended to the precentral sulcus still had motor deficits at the 12-month follow-up assessment. CONCLUSION: Surgery for Grade II gliomas in the superior frontal gyrus is more likely to result in permanent morbidity when the resection is performed at a distance of less than 0.5 cm from the precentral gyrus or positive stimulation points. Therefore, cortical mapping of motor and speech function, in critical cases under local anesthesia with the patient as his or her own monitor, is recommended; resection should be tailored to obtain good functional outcome and maintain quality of life.     

Localization of hand motor activation in Broca's pli de passage moyen

OBJECT: The object of this study was to identify a reliable surface landmark for the hand motor area and to demonstrate that it corresponds to a specific structural component of the precentral gyrus. METHODS: Positron emission tomography (PET) activation studies for hand motor function were reviewed in 12 patients in whom magnetic resonance imaging results were normal. Each patient performed a hand opening and closing task. Using a computer-assisted three-dimensional reconstruction of the surface of each hemisphere studied, the relationship of the hand motor area with cortical surface landmarks was evaluated. CONCLUSIONS: The region of hand motor activation can be reliably identified on the surface of the brain by assessing anatomical relationships to nearby structures. After identification of the central sulcus, the superior and middle frontal gyrus can be seen to arise from the precentral gyrus at a perpendicular angle. A bend or genu in the precentral gyrus is constantly seen between the superior and middle frontal gyrus, which points posteriorly (posteriorly convex). The location of hand motor function, identified using PET activation studies, is within the central sulcus at the apex of this posteriorly pointing genu. The apex of the genu of the precentral gyrus leads to a deep cortical fold connecting the pre- and postcentral gyri and elevating the floor of the central sulcus. This deep fold was described by Paul Broca as the pli de passage fronto-parietal moyen, and the precentral bank of the pli de passage represents the anatomical substratum of hand motor function. Observers blinded to the results of the activation studies were able to identify the hand motor area reliably after instruction in using these surface landmarks.     

功能磁共振成像定位皮质运动区与术中电刺激运动诱发电位的前瞻对照研究

目的以术中电刺激运动诱发电位（MEP）监测为对照,评价中央区脑肿瘤术前运用血液氧饱和水平检测（BOLD）技术的功能磁共振成像（fMRI）定位皮质运动区的准确性。方法此项前瞻性研究选取了16例中央区脑肿瘤。开颅手术前分别执行手运动激发程式,运用BOLD技术的fMRI定位皮质运动区。将fMRI影像与磁共振导航序列影像融合。以术中MEP监测作为皮质运动区定位的标准技术。在神经导航下定位fMRI的各个激活区,单独或联合运用短串经颅电刺激（TCES）和直接皮质电刺激（DCES）,在前臂及手部记录复合肌肉动作电位。比较两种技术的吻合度,以评价fMRI定位的皮质运动区的准确性。结果fMRI与MEP的吻合率为92．3％,其中与TCES的吻合率为100．0％,与DCES的吻合率为66．7％。结论运用BOLD技术的fMRI敏感度高,可实现中央区脑肿瘤术前皮质运动区的准确定位。     

功能和纤维成像在脑功能区胶质瘤中的应用

目的研究功能磁共振成像（fMRI）定位脑运动功能区和弥散张量纤维束示踪成像（diffusion tensor tractography,DTT）显示锥体束与肿瘤位置关系在脑胶质瘤行直接皮质电刺激手术的指导作用。方法对28例邻近或累及脑运动功能区的患者,术前在常规成像基础上,分别行双手握拳刺激策略的血氧水平依赖性功能磁共振成像（BOLD-fMRI）和弥散张量成像（DTI）,经工作站提供的BOLD．fMRI和DTI图像分析软件包获得脑运动功能区的激活图像、二维的部分各向异性伪彩图（fractional anisotropy,FA Color）和三维的白质纤维束示踪图。提供脑肿瘤与脑运动皮质区和运动传导束即锥体束的位置关系信息,制定手术方案。所有患者均行术中皮质直接电刺激定位运动区。术前、术后均行Karnofsky生活状态（KPS）评分,判断患者的状态。结果28例患者的fMRI和DTI获得良好的脑双手握拳运动功能区激活图像和锥体束纤维束走形图像,显示初级运动皮质区、运动前皮质区、辅助运动皮质区等手运动相关的脑功能区和运动传导束——锥体束与肿瘤的位置关系。在术前脑功能磁共振图像指导下,直接皮质电刺激快捷、准确定位初级运动皮质区,发现两者具有良好的一致性。术后患者KPS评分结果较术前提高。结论术前BOLD-fMRI和DTT可于活体、无创地描绘脑运动功能区和锥体束与肿瘤的功能解剖位置关系,优化手术方案,在唤醒麻醉下指导直接皮质电刺激定位运动区的手术,实现最大程度保护患者重要的功能,并最大程度地切除肿瘤。     

Combining MEG and MRI with neuronavigation for treatment of an epileptiform spike focus in the precentral region: a technical case report

BACKGROUND: Epileptic foci are often located in the vicinity but not necessarily within the boundaries of intra-axial brain tumors. Resection of these tumors is based on two major goals: first, maximizing tumor removal without provoking new neurologic deficits, and second, minimizing epileptic seizure activity. Magnetic source imaging (MSI) depicts the generators of magnetic fields overlaid on individual magnetic resonance (MR) images. Established application areas are lesions located adjacent to or partly within the sensory and motor cortex, or in the depth of the brain, necessitating a surgical approach through functionally highly relevant cortical regions. Magnetoencephalography (MEG) is also applicable for epileptiform spike foci recording during interictal activity. CASE DESCRIPTION: A patient with a recurrent glioma close to the Rolandic cortex scheduled for epilepsy and tumor surgery was investigated with MSI. The MSI data showed an epileptiform spike focus outside the tumor boundaries. The resulting MSI images were integrated into our neuronavigation system. This procedure allowed for the preoperative identification of the sensory and motor cortex, the precise localization of the epileptiform spike focus, and careful planning of the surgical procedure. In this case, we were able to safely resect the recurrent tumor and the epileptiform spike focus under general anesthesia using MSI-based neuronavigational guidance but no conventional intraoperative mapping techniques. CONCLUSION: Magnetic source imaging can be a valuable, noninvasive method for planning and performing tumor resections in high-risk brain regions, especially if an epileptiform spike focus has to be localized and included into the resection strategy.     

Multimodal cranial neuronavigation: direct integration of functional magnetic resonance imaging and positron emission tomography data: technical note

OBJECTIVE: This is the first report of the direct integration of functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) data into cranial neuronavigation. METHODS: In a patient with a left precentral oligodendroglioma (World Health Organization Grade III), the Zeiss MKM system (Carl Zeiss Co., Oberkochen, Germany) was used for navigation based on thin-slice, T1-weighted, contrast-enhanced magnetic resonance imaging (MRI) scans. fMRI and methionine PET data were integrated by landmark matching, with reference to skin fiducials. RESULTS: The inaccuracy of the image fusion between fMRI and T1-weighted MRI data was 1.7 mm, that between PET and T1-weighted MRI data was 4.3 mm, and that for the subsequent registration of the navigation was 1.2 mm. The correct fMRI localization of the precentral gyrus was intraoperatively verified by cortical somatosensory evoked potential (phase-reversal) monitoring. Although the tumor was not clearly defined in the MRI scans, [11C]methionine PET demonstrated a clear tumor border, enabling us to achieve gross total tumor removal without postoperative functional deficits. CONCLUSION: Functional neuronavigation permits observation and preservation of relevant brain areas. Other functional areas (such as short-term memory areas) that can be detected only by fMRI might also warrant future monitoring. The simultaneous integration of fMRI and PET data adds a new dimension to cranial neuronavigation, enabling the observation of tumors in relation to functional cortical areas (in our case, the motor strip).     

Functional magnetic resonance imaging in a low-field intraoperative scanner

BACKGROUND: Functional magnetic resonance imaging (fMRI) has been used for preoperative planning and intraoperative surgical navigation. However, most experience to date has been with preoperative images acquired on high-field echoplanar MRI units. We explored the feasibility of acquiring fMRI of the motor cortex with a dedicated low-field intraoperative MRI (iMRI). METHODS: Five healthy volunteers were scanned with the 0.12-tesla PoleStar N-10 iMRI (Odin Medical Technologies, Israel). A finger-tapping motor paradigm was performed with sequential scans, acquired alternately at rest and during activity. In addition, scans were obtained during breath holding alternating with normal breathing. The same paradigms were repeated using a 3-tesla MRI (Siemens Corp., Allandale, N.J., USA). Statistical analysis was performed offline using cross-correlation and cluster techniques. Data were resampled using the 'jackknife' process. The location, number of activated voxels and degrees of statistical significance between the two scanners were compared. RESULTS: With both the 0.12- and 3-tesla imagers, motor cortex activation was seen in all subjects to a significance of p < 0.02 or greater. No clustered pixels were seen outside the sensorimotor cortex. The resampled correlation coefficients were normally distributed, with a mean of 0.56 for both the 0.12- and 3-tesla scanners (standard deviations 0.11 and 0.08, respectively). The breath holding paradigm confirmed that the expected diffuse activation was seen on 0.12- and 3-tesla scans. CONCLUSIONS: Accurate fMRI with a low-field iMRI is feasible. Such data could be acquired immediately before or even during surgery. This would increase the utility of iMRI and allow for updated intraoperative functional imaging, free of the limitations of brain shift.     

Predicting the location of mouth motor cortex in patients with brain tumors by using somatosensory evoked field measurements

OBJECT: Before resective brain surgery, localization of the functional regions is necessary to minimize postoperative deficits. The face area has been relatively difficult to map noninvasively by using functional imaging techniques. Preoperative localization of face somatosensory cortex with magnetoencephalography (MEG) may allow the surgeon to predict the location of mouth motor areas. METHODS: The authors compared the location of face somatosensory cortex obtained with somatosensory evoked fields during preoperative MEG with the mouth motor areas identified during intraoperative electrocortical stimulation (ECS) mapping in 13 patients undergoing resection of brain tumor. RESULTS: In this group of patients, ECS mouth motor sites were usually anterior and lateral to MEG localizations of lip somatosensory cortex. The consistent quantitative relationship between results of these two mapping procedures allows the practitioner to predict the location of mouth motor cortex based on noninvasive preoperative MEG measurements. CONCLUSIONS: Based on this result, the authors suggest that somatosensory mapping using MEG can be used to guide intraoperative mapping and neurosurgical planning.     

Comparison of navigated transcranial magnetic stimulation and functional magnetic resonance imaging for preoperative mapping in rolandic tumor surgery

Navigated transcranial magnetic stimulation (nTMS) is a novel tool for preoperative functional mapping. It detects eloquent cortical areas directly, comparable to intraoperative direct cortical stimulation (DCS). The aim of this study was to evaluate the advantage of nTMS in comparison with functional magnetic resonance imaging (fMRI) in the clinical setting. Special focus was placed on accuracy of motor cortex localization in patients with rolandic lesions. Thirty consecutive patients were enrolled in the study. All patients received an fMRI and nTMS examination preoperatively. Feasibility of the technique and spatial resolution of upper and lower extremity cortical mapping were compared with fMRI. Consistency of preoperative mapping with intraoperative DCS was assessed via the neuronavigation system. nTMS was feasible in all 30 patients. fMRI was impossible in 7 out of 30 patients with special clinical conditions, pediatric patients, central vascular lesions, or compliance issues. The mean accuracy to localize motor cortex of nTMS was higher than in fMRI. In the subgroup of intrinsic tumors, nTMS produced statistically significant higher accuracy scores of the lower extremity localization than fMRI. fMRI failed to localize hand or leg areas in 6 out of 23 cases. Using nTMS, a preoperative localization of the central sulcus was possible in all patients. Verification of nTMS motor cortex localization with DCS was achieved in all cases. The fMRI localization of the hand area proved to be postcentral in one case. nTMS has fewer restrictions for preoperative functional mapping than fMRI and requires only a limited level of compliance. nTMS scores higher on the accuracy scale than fMRI. nTMS represents a highly valuable supplement for the preoperative functional planning in the clinical routine.     

Demonstration of Cerebral Plasticity by Intra-Operative Neurophysiological Monitoring: Report of an Uncommon Case

Summary  It has been postulated long ago that “eloquent” areas shift their location in patients with arteriovenous malformations (AVM). Obviously the “motor region” in not located in the precentral gyrus in a patient with an AVM in the “motor region”.  We report on the case of a 15-year old boy with an AVM in the left sensorimotor cortex, in whom intra-operative mapping showed an inexcitability of the precentral gyrus, while stimulation of the cortex anterior to the primary motor cortex elicited motor responses. This indicates that motor function was translocated from the primary to the supplementary motor cortex. Surgery was performed under general anaesthesia. Neurophysiological monitoring was performed throughout surgery. The central sulcus was identified by phase reversal of the somatosensory evoked potentials. The motor cortex was mapped by direct high-frequency (500 Hz) monopolar anodal stimulation.  In the patient herein reported, stimulation of the “anatomically” defined primary motor cortex induced no motor response, as expected. Motor response was elicited only by stimulation of the cortex anterior to the precentral gyrus. There was no postoperative deterioration of motor function. These observations indicate that the precentral gyrus was functionally “useless”. The motor region was relocated into more rostral areas in the supplementary motor cortex. This translocation of function in the presence of an AVM indicates cerebral plasticity.     

Image-guided motor cortex stimulation in patients with central pain.

According to recent clinical data, motor cortex stimulation (MCS) is an alternative treatment for central pain syndromes. We present our minimally invasive technique of image guidance for the placement of the motor cortex-stimulating electrode and assess the clinical usefulness of both neuronavigation and vacuum headrest. Five patients suffering from central pain underwent MCS with the guidance of a frameless stereotactic system (BrainLab AG, Munich, Germany). The neuronavigation was used for identification of the precentral gyrus and accurate planning of the single burr hole. The exact location was reconfirmed by an intraoperative stimulation test. Postoperative clinical and neuroradiological evaluations were performed in each patient. The navigation system worked properly in all 5 neurosurgical cases. Determination of the placement of stimulating electrode was possible in every case. All patients obtained postoperative pain relief. No surgical complication occurred, and the postoperative course was uneventful in all patients. This preliminary experience may confirm image guidance as a useful tool for the surgery of MCS. Additionally, minimal and safe exposure can be achieved using a single burr hole and vacuum headrest.     

Intraoperative cortical mapping has low sensitivity for the detection of motor function in proximity to a tumor in the primary motor area

Six patients with brain tumors within or near the primary motor cortex underwent preoperative functional magnetic resonance imaging (fMRI) and intraoperative cortical mapping, and the accuracy of those techniques for localization of the primary motor cortex and motor function beside the tumor were determined by comparison against neuroanatomical correlates from pre-, intra- and postoperative neurological observations. The location of the primary motor cortex was detected by intraoperative cortical mapping in 5 of 6 cases and by fMRI in all 6 cases. Brain mapping provided equivocal information on the cortical representation of motor territories, and with the technique used in close proximity to the tumor, the motor territories were not detected in all but 1 case. In contrast, the areas controlling motor function in close proximity to the tumor were detected by fMRI in 4 of 6 cases.These data indicate that intraoperative cortical mapping has a low sensitivity for the detection of motor function in the area beside the tumor. Therefore, this technique may not be sufficient to prevent compromise of motor areas during tumor resection.     

Resection of intrinsic tumors from nondominant face motor cortex using stimulation mapping: report of two cases

We report two right-handed patients who underwent resection of intrinsic glial tumors from the nondominant hemisphere, face motor cortex. Both patients underwent preoperative assessment with computed tomography and magnetic resonance imaging localizing the tumor in the inferior region of the Rolandic cortex. With the patients under general anesthesia and without muscular paralysis, the tumor volume was determined by intraoperative ultrasound and resective surgery accomplished with the aid of cortical and subcortical stimulation mapping techniques. Radical resection of the tumor from the face motor cortex was achieved in both patients. A transient contralateral facial weakness and apraxia were noted in each patient, and this resolved within 6 to 8 weeks following surgery. Removal of intrinsic tumors involving the nondominant face motor cortex may be safely achieved using brain mapping techniques to localize inferior Rolandic cortex and avoid resection of the hand motor cortex and descending subcortical motor pathways. Permanent disability will be prevented due to the bilateral representation of face motor function at the neocortical level. However, due to language localization in cortical zones contiguous with the dominant hemisphere, face motor cortex, we do not recommend resection of this region.