Transient cortical abnormalities on magnetic resonance imaging after status epilepticus: case report

INTRODUCTION: Transient neuroimaging findings associated with seizure activity have received relatively little attention in the neurosurgical literature. These abnormalities may mimick neoplastic or ischemic changes on magnetic resonance imaging (MRI), possibly leading to additional studies and surgical treatment. CASE DESCRIPTION: A 17-year-old right-handed male was transferred to emergency room in status epilepticus. A MRI obtained 5 months before admission was negative. On the day of admission, he had multiple intermittent upper-left extremity partial seizures and prolonged secondary generalized seizures. An electroencephalogram (EEG) showed frequent epileptiform discharges over the right hemisphere posteriorly. A MRI study performed 2 days after admission revealed non-hemorrhagic abnormalities involving the right occipital region that were hyperintense on fluid-attenuated inversion recovery (FLAIR) and T2 weighted sequences. The apparent diffusion coefficient map was unremarkable. Follow-up MRIs, 3 and 11 months after admission, showed complete resolution of these lesions. CONCLUSION: Imaging findings after status epilepticus may raise suspicion of ischemic or neoplastic lesions. These findings may be reversible. Further follow-up imaging may prevent unnecessary intervention.     

Fusiform gyrus epilepsy: the use of ictal magnetoencephalography. Case report

The authors report successful presurgical identification of an epileptic focus in the fusiform gyrus by using ictal magnetoencephalography (MEG), which was performed with the aid of an advanced whole-brain neuromagnetometer. A 22-year-old man had suffered from medically refractory complex partial seizures since he was 10 years of age. Seizure symptoms, magnetic resonance imaging, and ictal single-photon emission computerized tomography examinations indicated right temporal lobe epilepsy; however, ictal electroencephalography, including sphenoidal recordings, failed even to lateralize the seizure focus. The MEG studies revealed that equivalent current dipoles of interictal activities were scattered bilaterally around the medial temporal structures, but those of ictal onset and postictal activities formed a cluster in the left fusiform gyrus. After confirmation of each ictal and interictal MEG finding by using long-term electrocorticography recordings, focal cortical resection of the left inferior temporal and fusiform gyri was performed. The histopathological diagnosis was cortical dysplasia, and the patient has achieved a good seizure outcome, now 15 months after the operation. Ictal and also postictal MEG may be more specific than interictal MEG for identifying the ictal onset zone.     

Cerebral ganglioglioma with epilepsy: neuroimaging features and treatment

Gangliogliomas are an increasingly recognized cause of epilepsy in children. In this study the clinical, neuroimaging, and neurophysiological data of five patients with cerebral ganglioglioma and epilepsy are reviewed retrospectively. The average age of these patients was 4.4 years at onset and the average duration of seizures before diagnosis was 11 months. Tumors were located in the frontal (3), parietal (1), and occipital (1) lobes. While one cystic and four solid tumors showed various densities on CT and MRI, one frontal lesion was not demonstrated by CT scan but clearly shown by MRI. Scalp electroencephalography (EEG) showed neither localized nor epileptiform abnormalities in three patients, while the remaining two had these abnormalities. In one patient, invasive chronic electrocorticography (ECoG) recordings with subdural electrodes revealed an ictal onset zone located in the hand motor area. In all patients, intraoperative ECoG failed to reveal any epileptiform activities, and tumor removal alone was performed. For a mean of 3.4 years after surgery, all patients are alive and seizure-free, with stable imaging findings. Tumor resection may be the most important factor for optimal seizure control and prevention of tumor recurrence despite the fact that EEG and ECoG findings may conflict on tumor location. Received: 27 December 1999 / Accepted: 29 March 2000     

A Surgical Case of Frontal Lobe Epilepsy Due to Focal Cortical Dysplasia Accompanied by Olfactory Nerve Enlargement: Case Report

A 45-year-old man came to our clinic due to refractory general tonic seizure and an attack of unintended yelling. Magnetic resonance imaging (MRI) demonstrated mild cortical hyperintensity on fluid attenuated inversion recovery (FLAIR) image in the left basal frontal area. Enlargement of the left olfactory nerve was also detected below the affected gyrus. Subtotal resection of the MRI-visible epileptogenic lesion was performed without any neurological deficit. The final pathological diagnosis was focal cortical dysplasia (FCD) type IIa. Seizures and yelling attacks subsided after surgery. Extracerebral abnormalities, including cranial nerve enlargement, are common in patients with hemimegalencephaly. However, such abnormalities are rare with FCD.     

Case of symptomatic epilepsy presenting with focal high intensity on diffusion-weighted image prior to initial convulsive seizure

It has been reported that high intensity on diffusion-weighted image (DWI) in magnetic reasonance imaging (MRI) accompanying a reduction of the apparent diffusion coefficient (ADC) can be detected at the ictal or postictal stage of epileptic seizure. However, it remains unclear whether such a change results from persisting systemic convulsive seizure or from certain physiological changes such as recurrent epileptic discharge prior to the occurrence of obvious convulsion. We report here a case of symptomatic epilepsy displaying a high intensity area on DWI in MRI before convulsive seizure was initiated. A 64-year-old man was admitted to our hospital due to complaints of dizziness and motor weakness. CT and conventional MRI scans failed to reveal any new lesions except for the scar of a ventricular tube in the right parietal lobe, which had been removed due to shunt infection. The DWI, however, demonstrated an apparent high intensity in the right parietal cortex, and the ADC was significantly reduced as compared to that on the contralateral side. Five days after admission, the patient showed convulsive seizures beginning from the right face and upper extremity which subsequently developed to status epilepticus. Following recovery from the convulsions with administration of anticonvulsants, the high intensity of the right parietal lobe on DWI appeared to be diminished. The present case indicates that the manifestation of a high intensity on DWI concomitant with ADC reduction at the epileptic focus can be readily induced by the occurrence of epileptic discharges before convulsive seizure is evident.     

Functional neurosurgery for epilepsy

Introduced at the end of the last century, epilepsy surgery is indicated in patients with intractable partial seizures and based on the resection of the epileptogenic cerebral tissue from which ictal discharges originate. Palliative procedures include seizure spread pathways interruption (callosotomy, multiple subpial transections) and chronic stimulation of the vagus nerve. Complete preoperative investigations including seizure observation, clinical tests, video-EEG, MRI and functional MRI, and PET-scan are performed in order to identify the epileptogenic zone. In difficult cases, invasive seizure monitoring through depth electrode implantation (SEEG) is performed. Resections for temporal lobe seizures are associated with favorable outcome: 60 to 90% of patients will be seizure-free after surgery. A less favorable outcome is observed after extra-temporal resections: 40 to 60% seizure-free patients. A better outcome is observed after surgery for epilepsy associated with an image-defined lesion, most often a tumor, rather than for cryptogenic epilepsy. Tumors associated with chronic partial epilepsy are indolent, most of them are dysembryoplastic neuroepithelial tumors (DNET). Outcome after palliative procedures are more variable, depending on the etiology of epilepsy.     

New-onset psychogenic seizures after intracranial neurosurgery

Summary.  Background: Patients with physical brain abnormalities have an increased risk of developing psychogenic nonepileptic seizures (PNES). Here we describe patients who developed PNES after intracranial neurosurgery for indications other than the control of refractory epileptic seizures and explore whether neurosurgical intervention is at risk factor for PNES.  Method: We searched the database of 372 patients diagnosed with PNES at our department over the last 10 years and identified 17 patients (4.6%) in whom PNES first started after intracranial neurosurgery. Surgical procedures included the complete or partial resection of a meningioma, AV malformation, cavernoma, plexus papilloma, neurinoma, astrocytoma, oligodendroglioma, dysontogenetic cyst, the drainage of a brain abscess and removal of a subdural hematoma. PNES were documented by ictal video-EEG, ictal EEG, or ictal observation and examination in all cases. The diagnosis of additional epileptic seizures were confirmed by ictal EEG/video-EEG, or made on the basis of a clinical assessment by an experienced epileptologist.  Findings: Five patients had purely psychogenic postoperative seizure disorders, twelve had epileptic and psychogenic attacks. Median age at neurosurgery was 32 years (range 5–54), median latency between surgery and onset of PNES was 1 year (range 0–17 years).  Interpretation: PNES may develop after intracranial neurosurgery undertaken for other indications than the control of refractory epileptic seizures. Younger patients with a history of pre-operative psychiatric problems or epileptic seizures and surgical complications may be at higher risk. A diagnosis of PNES should be considered in patients who develop refractory seizures after neurosurgery. Published online September 2, 2002 Correspondence: Markus Reuber M.D. MRCP, Department of Neurology, St James's University Hospital, Beckett Street, Leeds, LS9 7TF, United Kingdom.     

Cryptococcal meningoencephalitis presenting with an unusual magnetic resonance imaging appearance--case report.

A 61-year-old female with a past history of gastric cancer presented with altered mental status, a few seizures, and low-grade fever. Lumbar puncture revealed elevated cerebrospinal fluid (CSF) pressure, lymphocytic pleocytosis, elevated protein level, remarkably decreased glucose level, and presence of cryptococcal antigen. Cryptococcus neoformans was identified by India ink staining and culture of CSF. The patient was given antifungal agents intravenously and intrathecally. CSF findings improved and C. neoformans could not be detected in CSF one month after the onset. Cerebral sulcal hyperintensity was identified in the bilateral frontal and parietal lobes on fluid-attenuated inversion recovery (FLAIR) magnetic resonance (MR) imaging one month after the onset, but no leptomeningeal enhancement was detected in the affected sulci on T1-weighted MR imaging. The sulcal hyperintensity on FLAIR imaging developed in the bilateral temporal and occipital lobes 2 months after the onset. CSF findings obtained by lumbar puncture were within the normal range except for pressure. However, neurological deterioration and reconfirmation of C. neoformans in CSF indicated recurrent cryptococcal inflammation. The sulcal hyperintensity on FLAIR imaging may indicate a high CSF protein concentration in the subarachnoid space. Such cerebral sulcal hyperintensity is an unusual MR imaging finding of cryptococcal meningoencephalitis, and may be an early sign of procrastinating process or recurrent inflammation even if the findings of CSF obtained by lumbar puncture are normal.     

Epilepsy surgery for focal cortical dysplasia and dysembryoplastic neuroepithelial tumor

We studied six patients with focal cortical dysplasia (CD) and four patients with dysembryoplastic neuroepithelial tumor (DNT) who had surgical resection for medically intractable epilepsy. In all CD patients, ictal single photon emission computed tomography (SPECT) using 99mTc-ECD revealed hyperperfusion in the regions where magnetic resonance (MR) imaging showed CD abnormalities. Interictal epileptiform activity and ictal seizure onset on electrocorticography using subdural strip or grid electrodes were demonstrated in the CD itself. In contrast, in all DNT patients, interictal SPECT disclosed hypoperfusion in the area of the lesions. Ictal SPECT in one DNT patient disclosed hyperperfusion in the superior area of the region where MR imaging showed cystic abnormalities. Interictal spiking in all DNT patients and ictal seizure onset in two DNT patients were demonstrated not in the lesions themselves but in the distinct zone from the region of the tumor-involved brain. All CD patients who underwent lesionectomy became seizure-free with a mean follow-up period of 33.5 months. All DNT patients who underwent lesionectomy and resection of the epileptogenic cortex became seizure-free or had their seizure significantly reduced a mean follow-up period of 41.5 months. We conclude that CDs have intrinsic epileptogenicity, while DNTs have epileptogenicity not intrinsically but in encompassed cortical surface areas.     

Consistency of interictal and ictal onset localization using magnetoencephalography in patients with partial epilepsy

OBJECT: The aim of this study was to evaluate the spatial accuracy of interictal magnetoencephalography (MEG) in localizing the primary epileptogenic focus in comparison with alternative MEG-derived estimates such as ictal onset recording or sensory mapping of the periphery where seizures manifest. METHODS: During this retrospective study of 12 patients with epilepsy who had undergone successful magnetic source (MS) imaging with the aid of a dual 37-channel biomagnetometer as well as simultaneous MEG/electroencephalography (EEG) recordings, ictal events were observed in five patients and quantitative comparisons of interictal spike and ictal seizure onset source localizations were made. In the eight patients who had presented with sensorimotor seizure, source localization of cortical sites concordant with seizure foci was determined using somatosensory functional mapping, and the results were quantitatively compared with interictal spike source localizations. Interictal spike sources demonstrated on MEG localized to the same region as the corresponding ictal event or somatosensory source localizations. The mean distance between the ictal foci and interictal spike sources was 1.1 +/- 0.3 cm. Results of functional somatosensory mapping in patients with sensorimotor seizures demonstrated that seizure sources consistently colocalized with interictal MEG spike sources, with a mean distance of 1.5 +/- 0.4 cm. No systematic directional bias was observed. Interictal sources tended to be tightly clustered, and the mean ellipsoid volume, defined by one standard deviation of the source spatial coordinates, was 1 cm3. CONCLUSIONS: Interictal spike localizations on MEG were concordant with ictal and, where relevant, functional somatosensory mapping localizations. These findings support the interpretation of interictal spikes on MEG as a useful and effective noninvasive method for localizing primary seizure foci.     

Predictors of Seizure Outcome after Repeat Pediatric Epilepsy Surgery: Reasons for Failure,Sex, Electrophysiology,and Temporal Lobe Surgery

Considering that seizure freedom is one of the most important goals in the treatment of epilepsy, repeat epilepsy surgery could be considered for patients who continue to experience drug-resistant seizures after epilepsy surgery. However, the chance of seizure freedom is reported to be below 50% after reoperation for failed epilepsy surgery. This study aimed to elucidate the predictive factors for seizure outcomes after repeat pediatric epilepsy surgery. In all, 39 pediatric patients who underwent repeat curative epilepsy surgery between 2008 and 2020 at our institution were retrospectively studied. The relationship between preoperative clinical factors and postoperative seizure freedom at the last follow-up was statistically evaluated. The mean age at the first surgery was 5.5 years (0–16). The etiology of epilepsy was malformation of cortical development in 33 patients. The average time to seizure recurrence after the first surgery was 6.4 months (range, 0–26 months). In all, 16 patients (41.0%) achieved seizure freedom after the second surgery. Seven patients underwent a third surgery, and three (42.9%) achieved seizure freedom. Overall, 19 patients achieved seizure freedom after repeat epilepsy surgery (48.7%). Female sex, surgical failure due to technical limitations, congruent electroencephalography (EEG) findings, lesional magnetic resonance imaging (MRI) and Rt-sided surgery were predictive of seizure freedom, and surgery limited to the temporal lobe was predictive of residual seizures, as determined in the multivariate analysis. The reoperation of failed epilepsy surgery is challenging. Consideration of the above predictive factors can be helpful in deciding whether to reoperate on pediatric patients whose initial surgical intervention failed.     

Tract identification by novel MRI signal changes following stereotactic anterior capsulotomy

BACKGROUND: Five patients underwent magnetic resonance imaging (MRI) following MRI-guided stereotactic bilateral anterior capsulotomy to detect lesion-related anatomic changes. METHODS: Five disabled and treatment-resistant patients with major depression (n = 4) and obsessive-compulsive disorder (n = 1) underwent stereotactic bilateral anterior capsulotomy. All patients had postoperative MRI at 2 months and at 1-4 years after surgery. An additional patient who had a pure motor deficit following a spontaneous basal ganglia hemorrhagic stroke was imaged as a comparator. RESULTS: The 2-month postcapsulotomy MRI showed a previously undescribed increase in T1-weighted signal within similar neural pathways for each patient. These pathways showed no changes in T2-weighted or fluid-attenuated inversion recovery sequences. The signal changes are different from the expected changes associated with anterograde Wallerian degeneration and identify retrograde changes in the proximal segment of the interrupted axon. CONCLUSION: Previously undescribed T1-weighted signal alterations following stereotactic surgery identify retrograde non-Wallerian changes in interrupted axons and provide a new method in identifying and tracing lesioned pathways.     

Validation of ictal single photon emission computed tomography with depth encephalography and epilepsy surgery

Many centers have reported that ictal single photon emission computed tomography (SPECT) localizes regions of seizure onset with greater sensitivity and specificity than interictal SPECT. Here we report interictal and ictal SPECT scan results in both lesional and nonlesional cases. Using technetium hexamethyl propylamenamine oxide (HMPAO) or ethyl cysteinate dimer (ECD), these scans were done in 52 patients with partial and secondarily generalized seizures. Twenty-five had normal MRI and 27 showed structural lesions. None had mesial temporal sclerosis clearly identified on MRI. All 52 subsequently had interictal and ictal intracranial EEG studies that appeared to localize the seizure focus. Thirty-nine patients had surgery and have been followed for 2 or more years. Interictal SPECT scans showed focal hypoperfusion consistent with intracranial EEG localization of the seizure focus in 29% of patients. In another 13%, there was correct lateralization but not localization. Ictal SPECT scans showed focal hyperperfusion consistent with intracranial EEG localization of the seizure focus in 52% of patients. In another 25%, there was correct lateralization but not localization. The presence or absence of structural lesions on MRI did not affect ictal hyperperfusion or its correlation with intracranial EEG. Thirty-nine patients had resective surgery, of whom 62% had class I outcomes. There was a trend towards better outcome when ictal SPECT data were concordant with intracranial EEG data. The presence or absence of structural lesions on MRI did not affect the likelihood of class I outcome. Ictal SPECT is superior to interictal SPECT in localizing and lateralizing seizure foci. Its results correlate well with intracranial EEG, but in more than one third of cases, the latter shows focal seizure onset in areas that do not show focal hyperperfusion. Surgical outcome tends to be better when the two modalities give concordant results.     

Risk of seizure and its clinical implication in the patients with cerebral metastasis from lung cancer

Background

The prevalence, risk factors, and clinical implication of seizure development were investigated in patients with metastatic brain tumors.

Methods

Medical records and radiological findings were analyzed retrospectively in 258 patients with brain metastasis from lung cancer who underwent Gamma Knife radiosurgery (GKS) between January 2008 and December 2009.

Results

During the follow-up period 32 patients (12.4 %) experienced seizure episodes. Coexistence of leptomeningeal seeding was a significant risk factor related to development of seizure (p?<?0.001). Prophylactic use of anticonvulsants was not correlated with reduction of seizure incidence (p?=?0.818). Continued use of anticonvulsants was necessary in nine of the 258 patients (3.5 %) because of recurrent seizures. Imaging studies performed immediately after seizure attacks in the patients with known metastatic brain lesions revealed tumor progression or complications related to treatment in 35 of 42 episodes of seizure (77.8 %).

Conclusions

Patients with metastatic lesions have a substantial risk of developing seizure. Seizure in known metastatic brain tumor patients are usually related to disease progression or complications of treatment. Follow-up imaging should be considered for each seizure episode and adequate multimodal treatment needs to be added to antiepileptic medication.     

Diffuse axonal injury in mild traumatic brain injury: a diffusion tensor imaging study

OBJECT: Diffuse axonal injury (DAI) is a major complication of traumatic brain injury (TBI) that leads to functional and psychological deficits. Although DAI is frequently underdiagnosed by conventional imaging modalities, it can be demonstrated using diffusion tensor imaging. The aim of this study was to assess the presence and extent of DAI in patients with mild TBI. METHODS: Forty-six patients with mild TBI and 29 healthy volunteers underwent a magnetic resonance (MR) imaging protocol including: dual-spin echo, fluid-attenuated inversion recovery, T2-weighted gradient echo, and diffusion tensor imaging sequences. In 20 of the patients, MR imaging was performed at a mean of 4.05 days after injury. In the remaining 26, MR imaging was performed at a mean of 5.7 years after injury. In each case, mean diffusivity and fractional anisotropy were measured using both whole-brain histograms and regions of interest analysis. No differences in any of the histogram-derived measures were found between patients and control volunteers. Compared with controls, a significant reduction of fractional anisotropy was observed in patients' corpus callosum, internal capsule, and centrum semiovale, and there were significant increases of mean diffusivity in the corpus callosum and internal capsule. Neither histogram-derived nor regional diffusion tensor imaging metrics differed between the two groups. CONCLUSIONS: Although mean diffusivity and fractional anisotropy abnormalities in these patients with TBI were too subtle to be detected with the whole-brain histogram analysis, they are present in brain areas that are frequent sites of DAI. Because diffusion tensor imaging changes are present at both early and late time points following injury, they may represent an early indicator and a prognostic measure of subsequent brain damage.     

Single-dose caudal anaesthesia for two infants undergoing diagnostic brain magnetic resonance imaging: high risk and nonhigh risk

We present a case report of two infants given a bupivacaine caudal anaesthetic as a means of achieving sedation for a diagnostic brain magnetic resonance imaging (MRI). Patient 1 was born at 27 weeks of gestation and presented to our hospital at 39 weeks postconception with a history of bronchopulmonary dysplasia and apnoea/bradycardia spells. He was undergoing a brain MRI for the work up of persistent apnoea and craniofacial abnormalities. Patient 2 was a term infant at 42 weeks postconception undergoing a MRI for the work up of a seizure disorder. Both infants fell asleep shortly after placement of the caudal blocks and the studies were completed successfully without complications. Utilizing this technique, we avoided dealing with a potentially difficult airway (patient 1), exacerbating postoperative apnoea and the negative implications of intravenous sedation during a study where there is limited access to the patient's airway.     

Persistence of mild parkinsonism 4 months after liver transplantation in patients with preoperative minimal hepatic encephalopathy: a study on neuroradiological and blood manganese changes

Pallidal hyperintensity at magnetic resonance imaging (MRI) correlates to blood manganese (Mn) levels and parkinsonian signs in patients with cirrhosis. Similarly, metabolite changes in the basal ganglia (BG) at proton spectroscopy are related to these neurological signs. The evolution of these abnormalities after liver transplantation (OLT) is incompletely described. We evaluated 14 unselected consecutive patients with cirrhosis (minimal hepatic encephalopathy [HE] n=8, no HE n=6) before and 4 months after successful OLT for the evolution of parkinsonism using a validated scale (the United Parkinson's Disease Rating Scale, or UPDRS). Pallidal intensity at MRI, spectroscopic changes in the BG at magnetic resonance spectroscopy (MRS), and whole blood manganese concentrations were measured. After OLT in patients with preoperative minimal HE, the UPDRS scores improved, but mild parkinsonism persisted (16.1+/-3.6 to 6.2+/-4.8, P<0.05). Pallidal hyperintensity remained abnormal in 5/8 of cases, but spectroscopic changes normalized in all patients. Blood Mn remained elevated in 4/6 patients. In patients without HE, UPDRS values remained negligible (2.42+/-1.5 to 2.5+/-1.4). Pallidal hyperintensity normalized in 7/8 patients and spectroscopic changes normalized in all patients. Blood Mn remained elevated in 5/6 patients. Four months after successful OLT, patients with preoperative minimal HE and severe pallidal hyperintensity showed persistent mild parkinsonism. The role of blood manganese determination appears limited in the monitoring of MRI and parkinsonian signs changes after OLT.     

Three cases demonstrating the characteristic neuroimaging of reversible posterior leukoencephalopathy syndrome

Revisible posterior leukoencephalopathy syndrome (RPLS) is a syndrome defined predominantly by a characteristic pattern of MR images but heterogeneity and reversibility of the abnormalities is unclear. Three patients with characteristic neuroimaging of RPLS are described. Case 1. A 29-year-old woman underwent cesarean section 3 days before developing headache, visual disturbance, mild conscious deterioration and increased blood pressure. MRI on admission showed predominantly white matter edema bilaterally affecting the occipital, temporal and posterior parietal lobes. Lesions were iso-, hypointense on T1 weighted and hyperintense on T2 weighted and fluid-attenuated inversion recovery (FLAIR) images. Diffusion-weighted image (DWI) did not demonstrate hyperintensity in the same regions. She responded well to initial treatment and showed complete recovery. Case 2. A 67-year-old man had headache and visual disturbance after thromboendarterectomy of the left femoral artery. Initial DWI demonstrated hyperintensity in the occipital lobe. The patient had visual abnormality at discharge. Case 3. A 40-year-old woman with early gastric cancer had headache immediately after the injection of contrast material during abdominal computed tomography (CT) examination followed by generalized convulsion. On the third day, she had severe headache and vomiting. Her consciousness deteriorated to lethargy. CT showed marked brain edema, intracerebral hemorrhage, thin subdural hematoma and midline shift. External decompression and hematoma evacuation was performed. She had left hemianopia and left hemiplegia 1 month later. This report has important implications concerning the accurate early diagnosis of RPLS using MRI including DWI and its utility in prompting initial treatment. It should be noted that some cases demonstrating the characteristic neuroimaging pattern of RPLS do not attain full recovery and that surgical intervention is required in some cases.     

Advances in neuroimaging: management of partial epileptic syndromes

Structural and functional neuroimaging studies are essential in the evaluation of individuals with partial epilepsy syndromes. Magnetic resonance imaging (MRI) is important to delineate structural abnormalities underlying seizure disorders, commonly including hippocampal sclerosis or cortical dysplasias. Identification of a structural lesion is often a reliable indicator of the site of seizure onset. Magnetic resonance spectroscopy (MRS) allows us to investigate cerebral metabolites and some neurotransmitters. Reduction in various metabolite concentrations has proven to be prognostically valuable when no structural abnormality is identified. Positron emission tomography (PET) using deoxyglucose demonstrates areas of reduced glucose metabolism, which are the hallmark of epileptogenic zones and usually extend beyond the underlying anatomical region. It is useful in temporal lobe epilepsy for lateralization; however, results in extratemporal lobe epilepsy have been less favorable. More promising is the use of benzodiazepine receptor ligands, which are reduced in the epileptogenic zone in a more restricted distribution. This appears to be helpful in the localization of extratemporal seizure foci. Peri-ictal single photon emission computed tomography measures increased blood flow during the ictal event and is beneficial in patients with normal MRI studies to determine lateralization and localization of the ictal onset zone. All imaging modalities should be correlated with clinical and neurophysiological data.Commentaries on this paper are available at and     

Neurofunctional tests in presurgical strategies for partial epilepsies

The presurgical evaluation of drug-resistant partial epilepsies primarily relies on two major investigations, including a long term video-EEG monitoring which aimed at recording the patient's typical seizures, and a specifically designed high quality magnetic resonance imaging (MRI). The latter demonstrates an abnormality within the epileptogenic lobe in the majority of cases, which might not, however, necessarily match the epileptogenic zone. Numerous functional neuro-imaging techniques have been progressively added to the pre-surgical evaluation of refractory partial epilepsies, such as the study of cerebral glucose metabolism, benzodiazepine receptor availability, and methionine incorporation using positron emission tomography (PET), the evaluation of ictal cerebral blood flow changes using single photon emission computerized tomography (SPECT), the measurement of N-acetyl-aspartate concentration with magnetic resonance spectroscopy, and the mapping of eloquent areas using functional MRI. These investigations can help to confirm the origin of seizure onset previously suggested by MRI and electro-clinical data, and provide independent prognostic information regarding the chance of a successful surgical treatment. Moreover, functional neuro-imaging data can have a critical diagnostic value when MRI is strictly normal or shows multifocal abnormalities. However, the variety and rapid evolution of functional neuro-imaging techniques makes it difficult to propose a standard protocol. Finally, it remains mandatory to proceed to an intracranial EEG investigation in a substantial number of patients, including the majority of those suffering from an extra-temporal epilepsy.