Surgical strategies for supra- and infratentorially grown occipital meningeomas.

BACKGROUND: Extensive tentorial meningeomas which are growing supra- and infratentorially are a surgical challenge, and a distinct surgical strategy is required for good results. PATIENTS: 3 patients, 2 with asymptomatic tumor and 1 with signs of increased intracranial pressure and visual disorder underwent microsurgery. RESULTS: In 2 patients, the semi-sitting position was taken. A lateralized occipital/suboccipital craniotomy with exposure of the confluens sinuum, transverse and superior sagittal sinus was performed. First, the dura was opened infratentorially allowing good cerebrospinal fluid (CSF) release. In a second step the dura was opened supratentorially sparing the sinus. The tumor was then removed completely without brain swelling or significant venous bleeding. One patient underwent surgery in prone position. A unilateral occipital/suboccipital craniotomy with exposure of the confluens sinuum and the ipsilateral transverse sinus was made. The dura was opened supratentorially. A resulting occipital lobe swelling made enlargement of the craniotomy and additional infratentorial dura opening necessary. All patients recovered well without postoperative morbidity. Complete tumor resection was confirmed by early postoperative MRI. CONCLUSION: The authors recommend a semi-sitting position (less venous bleeding, less brain swelling) and a lateralized occipital and suboccipital craniotomy for optimal control of the venous sinuses. Opening of the dura should start infratentorially to allow for CSF drainage and brain relaxation but should be combined with a sinus sparing supratentorial dura opening for adequate visualization and total meningioma removal.

[Modern skull base surgery from the perspective of neurosurgeons]. / Moderne Schädelbasischirurgie aus Sicht des Neurochirurgen.

At present, modern skull base surgery is a highly sophisticated interdisciplinary collaboration of various diagnostic and therapeutic disciplines. The overall goal is the treatment of complex tumorous, traumatic, vascular and inflammatory processes or developmental disorders of the skull base with preservation of function. The paper presents modern concepts, procedures and minimally invasive strategies in skull base surgery and also critically discusses the current trend to endoscopic and robot-assisted surgical techniques.

[Information assisted surgery as a transdisciplinary surgical procedure]. / Informations-assistierte Chirurgie als ein transdisziplinäres Operationsverfahren.

BACKGROUND: Information assisted surgery (IAS) is a further development of the computer assisted surgery (CAS) exclusively for intraoperative localization serving as basis for future technologies such as mechatronic and robotic. It requires of the surgeon a turnaround from traditional surgical proviso as well as transdisciplinary knowledge in the areas of surgical medicine, radiological imaging and information. The advantage of IAS is the predictability of the surgical procedure according to the specifications of modern quality assessment. METHOD: We analyzed the possibilities for the application of IAS in interdisciplinary transfacial surgery of the frontobasis in 9 patients with different pathologies of the central skull base and the cranio-cervical junction and compared this to conventional CAS. RESULTS: We determined retrospectively with a quality assessment analysis that surgery planning is too time consuming in the moment, and that the necessary transdisciplinary knowledge for IAS cannot be taken for granted yet. IAS has not been consequently applied for the entire surgery process in any of the 9 cases. This was due to technical difficulties as well as large intraoperative accuracy deviations of more than 5 mm. CONCLUSION: Even though the highly-developed technology of IIAS -- intelligent information assisted surgery -- is available, with the possibility of half or fully automatic implementation of IIAS including a automatic re-referencing, this technology will not be used in medical navigation for strategic reasons.

[Paralyzed face. Ansa-cervicalis-nervi-hypoglossi]. / Lähmungen der mimischen Gesichtsmuskulatur Ansa-cervicalis-nervi-hypoglossi-Fazialis-Anastomose alternativ zur Hypoglossus-Fazialis-Anastomose?

INTRODUCTION: For 100 years hypoglossal-facial nerve anastomosis (HFA) has been a common surgical procedure for reanimation of paralyzed mimic muscles of the face after axotomy of the facial nerve. However, the denervation and subsequent scarred degeneration of the target muscles of the hypoglossal nerve often results in unfavorable late effects for speech and swallowing. Therefore, the ansa cervicalis nervi hypoglossi-facial nerve anastomosis (ACHFA) can be an alternative to avoid such late effects. As a branch of the hypoglossal nerve the ansa cervicalis innervates the infrahyoidal muscles. Neck dissection surgery proved that resection of the ansa cervicalis causes no side effects for swallowing because of several nerve anastomoses to the cervical plexus. PATIENTS AND METHOD: We compared our clinical results of eight cases following a delayed ACHFA with our own experiences after HFA and results from the literature. RESULTS: We found a reanimation rate lower than usually seen after HFA only in the target muscles of the forehead. This may be caused by a reduced neuronal plasticity of the ansa cervicalis. However, in the target muscles of the other two facial nerve branches we observed the same good results one would expect after HFA. There were no late side effects for swallowing and speech though.

[Neurophysiologic intraoperative monitoring to preserve cranial nerve function in base of skull surgery]. / Neuromonitoring--Funktionssicherung und -erhalt bei schädelbasischirurgischen Eingriffen?

BACKGROUND: Neurophysiologic intraoperative monitoring (NIM) has gone through a renaissance since the advent of computer technology. Currently, both motor and sensory cranial nerves, including the IInd and VIIIth cranial nerves, can be intraoperatively controlled by means of small and mobile systems. PATIENTS AND METHODS: In order to estimate the value of NIM using the new generation of computer systems, we analyzed the records of 379 patients who underwent skull base surgery since 1996. These comprised NIM of the IInd, VIIth, VIIIth cranial nerves in most cases and of the IXth, Xth, XIth, and XIIth cranial nerves in selected cases. RESULTS: Whereas 72% of these cases demonstrated changes in the recorded intraoperative NIM signals, only 29% of them gave evidence of either clinical or electrophysiological neural function alterations during the postoperative follow-up. CONCLUSIONS: NIM is the only available system capable of providing the surgeon with instant intraoperative neural status-related feedback.

[The anterosigmoidal approach. A function-preserving surgical method for petroclival tumors]. / Der anterosigmoidale Zugang. Funktionsschonender Operationskorridor bei petroklivalen Tumoren.

BACKGROUND AND OBJECTIVE: The antero- or persigmoid approach preserves all functional structures of the petrous bone and, therefore, is an alternative to the classic laterobasal approaches for exploring the petroclival region. As high morbidity is assumed and it is a time consuming procedure, this approach is not well known. METHODS AND PATIENTS: Initially, a cadaver study using computer assisted surgery was used to determine the surgical workflow before we optimized our surgical procedures. RESULTS: In a series of 7 patients with benign tumors growing from the petrous apex to the petroclival region, we were able to resect all tumors completely via the anterosigmoidal surgical corridor using computer assisted surgery. CONCLUSIONS: The navigation-guided anterosigmoidal approach is an excellent method, allowing a good overview of the petroclival region. In patients suffering from complex petroclival tumors, it offers a real chance to achieve complete microsurgical tumor resection without functional defects by an interdisciplinary neuro-oto-surgical session.

Individual prefabricated titanium implants and titanium mesh in skull base reconstructive surgery. A report of cases.

Titanium implants can be shaped by traditional hand forming, press shaping, modular construction by welding, construction on full-size models shaped from CT coordinates and, most recently, by computer-assisted design and computer-assisted manufacturing (CAD/CAM) that consist in the direct prefabrication of individual implants by milling them out of a solid block of titanium. The aim of our study was to present a set of preliminary cases of an ongoing program of reconstructive procedures of the skull base using titanium implants. The subjects underwent ablative procedures of the skull base with reconstruction either by titanium mesh or individual prefabricated CAD/CAM implants. Six patients have been operated on successfully since 2000: two received prefabricated CAD/CAM titanium plates and four others underwent reconstruction with titanium mesh. The stability of CAD/CAM plates is superior to that of mesh, thus it is more useful in reconstructing large lesions of the frontal skull base and the temporal and occipital bones. Titanium mesh was successfully used for defects smaller than 100 cm(2) or where selected viscerocranial defects are complicated in design and less reproducible by CAD/CAM. The intraoperative design, shaping and adjustment characteristic of titanium mesh can be dispensed with when CAD/CAM implants are used. The 3-D data set used in the CAD/CAM process also operates in the navigated simulation and planning of the ablation contours, the latter being of great assistance in establishing the optimal future defect. As a disadvantage, CAD/CAM technology is more expensive than titanium mesh, and the process is time-consuming as it is carried out in advance of surgery.

[Microsurgical resection of jugular foramen tumors with hearing preservation and without facial nerve palsy]. / Resektion von Foramen-jugulare-Tumoren mit vollständigem Hörerhalt. Mikrochirurgie ohne Transposition des N. facialis.

BACKGROUND: The juxtacondylar microsurgical approach is an adequate alternative to the classical infratemporal approach for the resection of tumors of the jugular foramen. PATIENTS AND METHODS: Retrospectively, we report on our experience with eight patients suffering from tumors of the jugular foramen with different etiologies, who were treated successfully via the juxtacondylar approach with interdisciplinary cooperation. RESULTS: The advantage of the juxtacondylar approach is that there is no need to expose and transpose the facial nerve. Additionally, reduction or translocation of the posterior wall of the auditory canal and removal of the ossicular chain are not necessary. CONCLUSIONS: Tumors of the jugular foramen can be safely removed without damaging the facial nerve or auditory capacity, with a comparatively much better overview over the vascular and neural structures of the jugular foramen. This more neurosurgically orientated skull base approach is not very well known in the ENT surgical literature.

Preoperative motor system brain mapping using positron emission tomography and statistical parametric mapping: hints on cortical reorganisation.

OBJECTIVES: This study investigated the applicability of statistical parametric mapping (SPM) for analysing individual preoperative brain mapping studies in patients with cerebral mass lesions for neurosurgical planning. The study further investigated if hints on functional reorganisation processes can be found. METHODS: Nine adult patients with cerebral mass lesions underwent activation [(15)O]water-PET under stimulation by finger (n=9) and foot (n=4) movement. Individual SPM-t-maps were computed without anatomical normalisation and coregistered to the individual magnetic resonance imaging. Relative cerebral blood flow change maps were calculated for comparison. RESULTS: The spatial relation between the sensorimotor cortex and the lesion could be determined in all cases. Additional activations covered the ipsilateral sensorimotor cortex and the bilateral cerebellum, premotor cortices and supplementary motor areas. Patients with motor symptoms of the stimulated hand (paresis, focal seizures) activated the ipsilateral premotor cortices and contralateral cerebellum more often than patients without motor symptoms. The SPM results for p<0.005 and cerebral blood flow change maps showed considerably overlapping motor area activations. For p<0.001, SPM missed three sensorimotor cortex activations depicted by cerebral blood flow change maps and by SPM for p<0.005 in typical localisation. SPM analyses showed less activations probably unrelated to task performance. CONCLUSION: It is concluded that SPM provides an efficient method for analysing individual preoperative PET activation studies. Activations of the ipsilateral premotor cortices and contralateral cerebellum may indicate an enhanced recruitment of ipsilateral motor pathways evoked by functional reorganisation processes. However, this changed activation pattern was not necessarily associated with a better neurological status.

Functional MRI and 18F FDG-positron emission tomography for presurgical planning: comparison with electrical cortical stimulation.

BACKGROUND: In patients with mass lesions near "eloquent" cortical areas different preoperative mapping techniques can be used. Two of the most widely used approaches include positron emission tomography (PET) and functional MRI (fMRI). We employed both methods in the same patients undergoing presurgical evaluation and compared the results to those obtained by direct electrical cortical stimulation (DECS). METHOD: 22 patients with tumours of different aetiology near the central region were investigated. FMRI was performed using a T2(*)-weighted gradient-echo BOLD sequence at 1.5 T, PET was performed after injection of 122-301 MBq (18)F-Fluorodeoxyglucose (18-FDG) under rest and activation conditions. DECS was performed in all patients with recordings of muscles primarily involved in the investigated tasks. FINDINGS: In 19 patients all three modalities could be compared, 1 patient demonstrated discordance between fMRI and PET with DECS speaking in favour of fMRI, 6 patients had neighbouring results of PET and fMRI (between 1-2 cm distance), 12 patients had overlapping results. INTERPRETATION: The high incidence of neighbouring results is presumably related to fMRI specific artefacts. Advantages of fMRI are: Higher spatial and temporal resolution, more and different functional runs, shorter examination time, wider availability, longitudinal examinations, non-invasiveness and cost-effectiveness, easy registration to anatomical images. Advantages of PET are: higher signal-to-noise ratio, lesser susceptibility to artefacts (motion, draining veins), evaluation of tumour metabolism. It is our opinion that the neurosurgeon has to decide on a case-by-case basis which study suits his specific needs in the presurgical evaluation of his patient.

Error analysis in cranial neuronavigation.

Neuronavigation systems are now an important component of many modern neurosurgical treatment strategies. Their support facilities intraoperative orientation and makes neurosurgical operations more precise and less traumatic. Computer-aided neurosurgery is definitively not a temporary fashionable phenomenon, the concept of neuronavigation is here to stay. This report summarizes a ten-years-long experience and presents an error analysis of 108 failures (12.4 %) in a total of 874 image-guided cranial neurosurgical procedures with an arm-linked (mechanical) system and two different infrared-light emitting (optical) systems. The application of neuronavigation incurs multiple reasons for pitfalls because of the complex man-machine interface. Principally, we have to differentiate two types of errors: "machine made errors" due to soft- or hardware failure and "man made errors" generally, due to inadequate handling of the navigation system. The error analysis demonstrated that the so-called human interface plays the main role causing a high error rate.

Metabolic and electrophysiological validation of functional MRI.

OBJECTIVES: Although functional MRI is widely used for preoperative planning and intraoperative neuronavigation, its accuracy to depict the site of neuronal activity is not exactly known. Experience with methods that may validate fMRI data and the results obtained when coregistering fMRI with different preoperative and intraoperative mapping modalities including metabolically based (18)F-fluorodeoxyglucose PET, electrophysiologcally based transcranial magnetic stimulation (TMS), and direct electrical cortical stimulation (DECS) are described. METHODS: Fifty patients were included. PET was performed in 30, TMS in 10, and DECS in 41 patients. After coregistration using a frameless stereotactic system, results were grouped into overlapping (<1 cm distance), neighbouring (<2 cm), or contradictory (>2 cm). RESULTS: Comparing fMRI with PET, 18 overlapping, seven neighbouring, and one contradictory result were obtained. In four patients no comparison was possible (because of motion artefacts, low signal to noise ratio, and unusual high tumour metabolism in PET). The comparison of TMS and fMRI showed seven overlapping and three neighbouring results. In three patients no DECS results could be obtained. Of the remaining 38 patients, fMRI hand motor tasks were compared with DECS results of the upper limb muscles in 36 patients, and fMRI foot motor tasks were compared with DECS results of the lower limb on 13 occasions. Of those 49 studies, overlapping results were obtained in 31 patients, and neighbouring in 14. On four occasions fMRI did not show functional information (because of motion artefacts and low signal to noise). CONCLUSIONS: All validation techniques have intrinsic limitations that restrict their spatial resolution. However, of 50 investigated patients, there was only one in whom results contradictory to fMRI were obtained. Although it is not thought that fMRI can replace the intraoperatively updated functional information (DECS), it is concluded that fMRI is an important adjunct in the preoperative assessment of patients with tumours in the vicinity of the central region.

Localisation of motor areas in brain tumour patients: a comparison of preoperative [18F]FDG-PET and intraoperative cortical electrostimulation.

Assessment of the exact spatial relation between tumour and adjacent functionally relevant brain areas is a primary tool in the presurgical planning in brain tumour patients. The purpose of this study was to compare a preoperative fluorine-18 fluorodeoxyglucose positron emission tomography ([18F]FDG PET) activation protocol in patients with tumours near the central area with the results of intraoperative direct cortical electrostimulation, and to determine whether non-invasive preoperative PET imaging can provide results equivalent to those achieved with the invasive neurosurgical "gold standard". In this prospective study, we examined 20 patients with various tumours of the central area, performing two PET scans (each 30 min after i.v. injection of 134-341 MBq [18F]FDG) in each patient: (1) a resting baseline scan and (2) an activation scan using a standardised motor task (finger tapping, foot stretching). Following PET/MRI realignment and normalisation to the whole brain counts, parametric images of the activation versus the rest study were calculated and pixels above categorical threshold values were projected to the individual MRI for bimodal assessment of morphology and function (PET/MRI overlay). Intraoperative direct cortical electrostimulation was performed using a Viking IV probe (5 pulses, each of 100 micros) and documented using a dedicated neuro navigation system. Results were compared with the preoperative PET findings. PET revealed significant activation of the contralateral primary motor cortex in 95% (19/20) of the brain tumour patients (hand activation 13/13, foot activation 6/7), showing a mean increase in normalised [18F]FDG uptake of 20.5% +/- 5.2% (hand activation task) and 17.2% +/- 2.5% (foot activation task). Additionally detected activation of the ipsilateral primary motor cortex was interpreted as a metabolic indication for interhemispheric compensational processes. Evaluation of the PET findings by cortical stimulation yielded a 94% sensitivity and a 95% specificity for identification of motor-associated brain areas. In conclusion, the findings indicate that a relatively simple and clinically available [18F]FDG PET activation protocol enables a sufficiently precise assessment of the local relation between the intracranial tumour and the adjacent motor cortex areas and may facilitate the presurgical planning of tumour resection.

Diagnostic and therapeutic management of spinal arachnoid cysts.

BACKGROUND: The wide variety of intraspinal cystic lesions necessitates different elaborate diagnostic procedures to choose the right therapeutic management in symptomatic patients. Based on the case reports of seven patients with symptomatic spinal arachnoid cysts we discuss the aetiology, diagnostic procedures and therapeutic management of extra- and intradural spinal cysts. METHOD: All patients underwent MRI, Myelography and CT-Myelography during diagnostic evaluation. During surgery the cyst was resected and the communication between the cyst and the subarachnoid space was closed. FINDINGS: Two patients were identified with intradural, five with extradural spinal arachnoid cysts. Postoperative outcome was favourable in those patients without preoperative cord damage. INTERPRETATION: MRI is the diagnostic procedure of first choice because of its potential to demonstrate the exact localisation, extent and relationship of the arachnoid cyst to the spinal cord. Cord atrophy secondary to compression can be visualised and used for prediction of neurological outcome. Myelography and CT-Myelography (CTM) are still of diagnostic value since they might demonstrate the communication between the subarachnoid space and the cyst, which is important for surgical planning. The aim of surgical treatment is neural decompression and prevention of refilling of the cyst which is best accomplished by complete resection of the cyst and closure of the communication between cyst and subarachnoid space.

Functional MRI for presurgical planning: problems, artefacts, and solution strategies.

OBJECTIVES: Presurgical mapping of motor function is a widely used clinical application of functional (f) MRI, employing the blood oxygenation level dependent contrast. The aim of this study was to report on 3 years experience of 194 fMRI studies on the representation of motor function in 103 patients and to describe the problems and artefacts that were typically present. METHODS: An evaluation was carried out to determine whether the patients' age, type or location of the tumourous lesion, severity of the paresis, or the tasks used during the investigation have an effect on artefacts of fMRI studies and how these artefacts are best overcome. RESULTS: Functional MRI identified the motor regions in 85% of all investigated paradigms. In 11% of the investigated patients no information at all on functional localisation was obtained. A draining vein within the central sulcus was present in all patients that showed activation within the parenchyma of the precentral gyrus but also in three patients in whom no parenchymal activation was present. Head movement artefacts were the most frequent cause for fMRI failure, followed by low signal to noise ratio. Motion artefacts were correlated with the degree of paresis and with the functional task. Tasks involving more proximal muscles led to significantly more motion artefacts when compared with tasks that primarily involved distal muscles. Mean MR signal change during task performance was 2.5%. CONCLUSIONS: Most of the artefacts of functional MRI can be reliably detected and at least in part be reduced or eliminated with the help of mathematical algorithms, appropriate pulse sequences and tasks, and-probably most important-by evaluating the fMRI raw data-that is, the MR signal time courses.

Comparison of visual and ROI-based brain tumour grading using 18F-FDG PET: ROC analyses.

Several studies have suggested that the use of simple visual interpretation criteria for the investigation of brain tumours by positron emission tomography with fluorine-18 fluorodeoxyglucose (FDG-PET) might be similarly or even more accurate than quantitative or semi-quantitative approaches. We investigated this hypothesis by comparing the accuracy of FDG-PET brain tumour grading using a proposed six-step visual grading scale (VGS; applied by three independent observers unaware of the clinical history and the results of histopathology) and three different region of interest (ROI) ratios (maximal tumour uptake compared with contralateral tissue [Tu/Tis], grey matter [Tu/GM] and white matter [Tu/WM]). The patient population comprised 47 patients suffering from 17 benign (7 gliomas of grade II, 10 non-gliomatous tumours) and 30 malignant (23 gliomas of grade III-IV, 7 non-gliomatous tumours) tumours. The VGS results were highly correlated with the different ROI ratios (R=0.91 for Tu/GM, R=0.82 for Tu/WM, and R=0.79 for Tu/Tis), and high inter-observer agreement was achieved (kappa=0.63, 0.76 and 0.81 for the three observers). The mean ROI ratios and VGS readings of gliomatous and non-gliomatous lesions were not significantly different. For all measures, high-grade lesions showed significantly higher FDG uptake than low-grade lesions (P<0.005 to P<0.0001, depending on the measure used). Nominal logistic regressions and receiver operating characteristic (ROC) analyses were used to calculate cut-off values to differentiate low- from high-grade lesions. The predicted (by ROC) diagnostic sensitivity/specificity of the different tests (cut-off ratios shown in parentheses) were: Tu/GM: 0.87/0.85 (0.7), Tu/WM: 0.93/0.80 (1.3). Tu/Tis: 0.80/0.80 (0.8) and VGS: 0.84/0.95 (uptake < GM, but >> WM). The VGS yielded the highest Az (+/-SE) value (i.e. area under the ROC curve as a measure of predicted accuracy), 0.97+/-0.03, which showed a strong tendency towards being significantly greater than the Az of Tu/Tis (0.88+/-0.06; P=0.06). Tu/GM (0.92+/-0.04) and Tu/WM (0.91+/-0.05) reached intermediate Az values (not significantly different from any other value). We conclude that the VGS represents a measure at least as accurate as the Tu/GM and Tu/WM ratios. The Tu/Tis ratio is less valid owing to the high dependence on the location of the lesion. Depending on the investigator's experience and the structure of the lesions, the easily used VGS might be the most favourable grading criterion.

Navigated transcranial magnetic stimulation for presurgical planning--correlation with functional MRI.

PURPOSE: This paper describes the potential of navigated transcranial magnetic stimulation to map the motor cortex in patients with mass lesions near the primary motor cortex by comparing the results of this technique to those of functional MRI. MATERIAL AND METHODS: Ten patients with mass lesions near the central sulcus were studied preoperatively using a figure-of-eight transcranial magnetic stimulator attached to a neuronavigation system to allow for direct visualization of the stimulated brain region. Subsequently, in all patients a blood oxygenation level dependent 2D multislice multishot T2*-weighted gradient echo EPI sequence on a 1.5 T Philips Gyroscan during motor activation was performed. Results of both methods were coregistered and compared. RESULTS: The distances between the peak parenchymal fMRI activation and the cortical area where TMS elicited the maximum MEPs ranged between 0 and 1.2 cm (mean 0.6 cm, SD 0.4 cm). CONCLUSION: We conclude that navigated TMS is a reliable alternative for localizing the motor-related areas in the human brain preoperatively and therefore may be a useful adjunct or, in selected patients, even a helpful alternative to functional MRI.

Removal of adherent ventricular catheters by a modified sheath introducer system: technical note.

BACKGROUND/PURPOSE: A series of technical notes has been dedicated to the removal of retained intracranial shunt catheters, among which the intraluminal cautery proved to be the most accepted technique. However, several reports showed that these techniques still harbor potentially serious complications. METHODS: In this technique, a modified plastic sheath introducer system is passed over the retained ventricular catheter. While advancing the tube along the longitudinal axis of the catheter, circular movements of the tube around the longitudinal axis of the catheter are performed, allowing the tube to act as a spherical knife cutting the ingrown choroid plexus or ependymal adhesions. RESULTS: There were no procedure-related complications in any of the 9 patients treated by the technique described. The procedure proved to be easy and effective in all cases. In addition, in case a new ventricular catheter was needed at the same site, it could be placed via the same tube. CONCLUSIONS: The technique described seems to be an easy, safe, and effective alternative to other techniques for removal of retained ventricular catheters. However, considering the limited number of patients treated with the technique described and the great number of patients treated by the widely accepted intraluminal cautery, one cannot claim the one technique as superior to the other at this stage.

High F-18 FDG uptake in a low-grade supratentorial ganglioma: a positron emission tomography case report.

PURPOSE: Positron emission tomography (PET) with fluorine-18 fluorodeoxyglucose (F-18 FDG) is used for the noninvasive monitoring and grading of primary brain tumors. Here the FDG uptake is positively correlated with the malignant extent of the lesion and thereby negatively correlated with patient survival. Little is known about the FDG PET features of primary brain tumors in children, such as mixed neuronal-glial tumors. METHODS: The authors describe a 13-year-old boy who had partial complex seizures since early childhood caused by a brain tumor in the left temporal lobe. RESULTS: Magnetic resonance and computed tomographic examinations yielded uncharacteristic results: mixed density, marked calcifications, little contrast enhancement, a nearly absent mass effect, and no edema. The FDG PET scan revealed a large hypermetabolic tumor, with a tumor: contralateral gray matter FDG uptake ratio of 1.45. In contrast to this intense hypermetabolism, the pathologic analysis after gross total resection revealed a low-grade ganglioglioma (WHO grade 1), which is usually associated with an excellent prognosis. CONCLUSIONS: Mixed neuronal-glial tumors such as gangliogliomas must be considered in making differential diagnoses by judging hypermetabolic FDG PET scans in young patients with brain tumors in the presence of uncharacteristic imaging features.