The role of SEEG in the presurgical decision-making process in MRI-normal mesial temporal lobe epilepsy.

OBJECTIVES: In patients with mesial temporal lobe epilepsy (mTLE) and normal MRI, anterior temporal lobectomy sparing the hippocampus might be considered because of the risk of post-operative memory deficit. However, it is unclear whether some patients with normal MRI and non-invasive EEG and semiological pattern highly suggestive of mesial temporal seizures demonstrate a seizure onset network sparing the hippocampus, potentially warranting surgery. METHODS: A retrospective study of 17 patients with mTLE epilepsy and normal MRI who underwent SEEG. Only patients whose non-invasive presurgical data suggested an unilateral mesial temporal epileptogenic zone (EZ), as defined by combination of ictal semiology and ictal EEG during scalp video-EEG, were included. SEEG data were analyzed using both visual and quantitative approaches. Two EZ organization were defined: (i) EZ involved the hippocampus at the onset of the ictal discharge (HIP group): (ii) patients in whom a delay>1sec was observed between the seizure onset and the involvement of the hippocampus (nHIP group). Non-invasive clinical and functional imaging data, as well as post-operative outcomes, were compared across groups. RESULTS: Eleven patients were included in HIP group and 6 in the nHIP group. In the nHIP group, the maximal epileptogenicity was in the amygdala in five patients and in the entorhinal cortex in one. The hippocampus normalized interictal spiking activity was not different between groups. None of the patients characteristics collected during the non-invasive presurgical workup was associated with the SEEG-based organization of the EZ. Twelve patients underwent a surgical resection, including temporal cortectomy sparing hippocampus in six. Seizure and neuropsychological post-operative outcomes were similar. CONCLUSION: In patients with MRI-normal mTLE, SEEG should be included in the surgical decision-making process because seizure organization cannot be predicted from non-invasive investigations. When hippocampus is not included in the EZ, temporal resection sparing the hippocampus can be considered.

Early Detection of Underlying Cavernomas in Patients with Spontaneous Acute Intracerebral Hematomas.

BACKGROUND AND PURPOSE: Early identification of the etiology of spontaneous acute intracerebral hemorrhage is essential for appropriate management. This study aimed to develop an imaging model to identify cavernoma-related hematomas. MATERIALS AND METHODS: Patients 1-55 years of age with acute (≤7 days) spontaneous intracerebral hemorrhage were included. Two neuroradiologists reviewed CT and MR imaging data and assessed the characteristics of hematomas, including their shape (spherical/ovoid or not), their regular or irregular margins, and associated abnormalities including extralesional hemorrhage and peripheral rim enhancement. Imaging findings were correlated with etiology. The study population was randomly split to provide a training sample (50%) and a validation sample (50%). From the training sample, univariate and multivariate logistic regression was performed to identify factors predictive of cavernomas, and a decision tree was built. Its performance was assessed using the validation sample. RESULTS: Four hundred seventy-eight patients were included, of whom 85 had hemorrhagic cavernomas. In multivariate analysis, cavernoma-related hematomas were associated with spherical/ovoid shape (P < .001), regular margins (P = .009), absence of extralesional hemorrhage (P = .01), and absence of peripheral rim enhancement (P = .002). These criteria were included in the decision tree model. The validation sample (n = 239) had the following performance: diagnostic accuracy of 96.1% (95% CI, 92.2%-98.4%), sensitivity of 97.95% (95% CI, 95.8%-98.9%), specificity of 89.5% (95% CI, 75.2%-97.0%), positive predictive value of 97.7% (95% CI, 94.3%-99.1%), and negative predictive value of 94.4% (95% CI, 81.0%-98.5%). CONCLUSIONS: An imaging model including ovoid/spherical shape, regular margins, absence of extralesional hemorrhage, and absence of peripheral rim enhancement accurately identifies cavernoma-related acute spontaneous cerebral hematomas in young patients.

Comparison of magnetic resonance angiography techniques to brain digital subtraction arteriography in the setting of mechanical thrombectomy: A non-inferiority study.

INTRODUCTION: We performed a non-inferiority study comparing magnetic resonance angiography (MRA) techniques including contrast-enhanced (CE) and time-of-flight (TOF) with brain digital subtraction arteriography (DSA) in localizing occlusion sites in acute ischemic stroke (AIS) with a prespecified inferiority margin taking into account thrombus migration. MATERIALS AND METHODS: HIBISCUS-STROKE (CoHort of Patients to Identify Biological and Imaging markerS of CardiovascUlar Outcomes in Stroke) includes large-vessel-occlusion (LVO) AIS treated with mechanical thrombectomy (MT) following brain magnetic resonance imaging (MRI) including both CE-MRA and TOF-MRA. Locations of arterial occlusions were assessed independently for both MRA techniques and compared to brain DSA findings. Number of patients needed was 48 patients to exclude a difference of more than 20%. Discrepancy factors were assessed using univariate general linear models analysis. RESULTS: The study included 151 patients with a mean age of 67.6±15.9years. In all included patients, TOF-MRA and CE-MRA detected arterial occlusions, which were confirmed by brain DSA. For CE-MRA, 38 (25.17%) patients had discordant findings compared with brain DSA and 50 patients (33.11%) with TOF-MRA. The discordance factors were identical for both MRA techniques namely, tandem occlusions (OR=1.29, P=0.004 for CE-MRA and OR=1.61, P<0.001 for TOF-MRA), proximal internal carotid artery occlusions (OR=1.30, P=0.002 for CE-MRA and OR=1.47, P<0.001 for TOF-MRA) and time from MRI to MT (OR=1.01, P=0.01 for CE-MRA and OR=1.01, P=0.02 for TOF-MRA). CONCLUSION: Both MRA techniques are inferior to brain DSA in localizing arterial occlusions in LVO-AIS patients despite addressing the migratory nature of the thrombus.

Multifocal arterial wall contrast - enhancement in ischemic stroke: A mirror of systemic inflammatory response in acute stroke.

PURPOSE: Intracranial plaque gadolinium enhancement revealed by high-resolution MRI imaging (HR MRI) is considered as a marker of plaque inflammation, a contributing factor of plaque unstability. The aim of the present study was to assess the distribution of gadolinium enhancement in intracranial atherosclerosis. METHODS: Single center analysis of ischemic stroke patients with intracranial atherosclerotic stenosis of M1 or M2 segments of middle cerebral artery, or terminal internal carotid artery (ICA) based on CT-angio or MR-angio. High-resolution MRI imaging (HRMRI) was performed within 6 first weeks following the index event, with 3DT2 BB (black-blood) and 3D T1 BB MR sequences pre and post-contrast administration. RESULTS: We identified 8 patients with 14 plaques, 4 were deemed non-culprit and 10 culprit. All culprit plaques (10/10 plaques) and 3 out of 4 non-culprit plaques showed a gadolinium enhancement. CONCLUSION: At the acute/subacute stage of stroke, a gadolinium enhancement may affect multiple asymptomatic intracranial plaques and may reflect a global inflammatory state.

Combined analysis of MGMT methylation and dynamic-susceptibility-contrast MRI for the distinction between early and pseudo-progression in glioblastoma patients.

INTRODUCTION: Currently, no single diagnostic modality allows the distinction between early progression (EP) and pseudo-progression (Psp) in glioblastoma patients. Herein we aimed to identify the characteristics associated with EP and Psp, and to analyze their diagnostic value alone and in combination. MATERIAL AND METHODS: We reviewed the clinical, conventional magnetic resonance imaging (MRI), and molecular characteristics (MGMT promoter methylation, IDH mutation, and EGFR amplification) of glioblastoma patients who presented an EP (n=59) or a Psp (n=24) within six months after temozolomide radiochemotherapy. We analyzed relative cerebral blood volume (rCBV) and relative vessel permeability on K2 maps (rK2) in a subset of 33 patients using dynamic-susceptibility-contrast MRI. RESULTS: In univariate analysis, EP was associated with neurological deterioration, higher doses of dexamethasone, appearance of a new enhanced lesion, subependymal enhancement, higher rCBV and rK2 values. Psp occurred earlier after radiotherapy completion and was associated with IDH1 R132H mutation, and MGMT methylation. In multivariate analysis, rCBV, rK2, and MGMT methylation status were independently associated with EP and Psp. All patients with a methylated MGMT promoter and a low rCBV (<1.75) were classified as Psp while all patients with an unmethylated MGMT promoter and a high rCBV (≥1.75) were classified as EP. Among patients with discordant MGMT methylation and rCBV characteristics, higher rK2 values tended to be associated with EP. CONCLUSION: Combined analysis of MGMT methylation, rCBV and vessel permeability on K2 maps seems helpful to distinguish EP from Psp. A prospective study is warranted to confirm these results.

Imaging of hemifacial spasm.

Almost all primary hemifacial spasms are associated with one or more neurovascular conflicts, most often at the root exit zone in the immediate vicinity of the brainstem. Imaging has first to exclude a secondary hemifacial spasm and secondly to search for and characterize the responsible neurovascular conflict(s). Magnetic resonance imaging should include high-resolution anatomical hyper T2-weighted sequences and magnetic resonance angiography by using 1.5 or even better 3 Tesla magnets. The most frequent vascular compressions are from the anterior-inferior cerebellar artery, the posterior-inferior cerebellar artery and the vertebrobasilar artery; venous conflicts are very rare. Conflicts are often multiple; also, the same vessel may compress the facial nerve in two places. Also, conflicts may be aided by particular anatomical circumstances, including arterial dolichoectasia, posterior fossa with a small volume or bony malformations.

Imagery of pineal tumors.

Pineal tumors are rare and include a large variety of entities. Germ cell tumors are relatively frequent and often secreting lesions. Pineal parenchymal tumors include pineocytomas, pineal parenchymal tumor of intermediate differentiation, pineoblastomas and papillary tumors of the pineal region. Other lesions including astrocytomas and meningiomas as well as congenital malformations i.e. benign cysts, lipomas, epidermoid and dermoid cysts, which can also arise from the pineal region. Imagery is often non-specific but detailed analysis of the images compared with the hormone profile can narrow the spectrum of possible diagnosis.

Tectal plate tumours. Our experience with a paediatric surgical series.

INTRODUCTION: Exophytic tectal plate tumours are a particular kind of brain stem tumour that can be treated with microsurgical resection. This paper reports our surgical experience with a paediatric series stressing and underlines the fact that this surgery can be possible because the rate of surgical mortality is low in experienced hands with acceptable morbidity. MATERIAL AND METHODS: From 1997 to 2010, 27 patients were treated for exophytic tectal plate tumours. The clinical symptomatology was characterized by an intracranial hypertensive syndrome in 77% of cases, visual disorders in 36% of cases and a Parinaud's syndrome in 12% of cases. All patients were studied using a pre-operative cranio-spinal MRI with and without gadolinium. Hydrocephalus was present in 20 cases treated with a VP shunt in 6 cases and an ETV in the other cases. The surgical removal was total in 60% of cases, partial in 28% of cases and only a large biopsy in 12% of cases. From an histological point of view benign gliomas were diagnosed in 84% of cases and in 16% of cases were classified as WHO grade II and III. Eight patients needed complementary treatment, four with chemotherapy and four with chemotherapy associated to radiotherapy. As a surgical complication two patients had hydrocephalus, one patient had a sub-dural acute haematoma, two patients had an infectious complication requiring surgical treatment and antibiotic therapy, and 5 patients a mechanical shunt dysfunction. No post-surgical mortality was observed. RESULTS: The most recent results after a median survival of 4.3 years show that 22 patients are still alive while 5 patients died of a progressive disease. Twenty patients in school age continue to follow a normal school programme but 10 patients need assistance. CONCLUSION: Exophytic tectal plate tumours can be treated based on a microsurgical approach in paediatric patients. In experienced hands surgery can be performed with an acceptable morbidity and with zero percent mortality. In our experience, the sub-occipital transtentorial approach permits a wide view of the region and safe surgical removal.

Tacrolimus-related cerebral microbleeds after lung transplantation.

Posterior reversible encephalopathy syndrome is a well-known complication of treatment by tacrolimus. We report 2 cases of lung transplant recipients treated with tacrolimus who developed cerebral microbleeds on T2∗-weighted sequences in the acute setting of posterior reversible encephalopathy syndrome. Cerebral microbleeds may be a marker of tacrolimus-induced vasculopathy that may be detected earlier by neuropsychological and magnetic resonance imaging monitoring in transplant recipients treated with tacrolimus.

Treatment of Chiari type I malformation in children: the experience of Lyon.

The Chiari I malformation represents a complex disease and its pathophysiology is not completely understood and consequently different surgical procedures have been proposed in the literature. The use of MRI have increased the diagnosis of Chiari I malformation but generally the Chiari I is characterized by the herniation of tonsils at 5 mm below the plane of the occipital hole. The consequent disturbance of the CSF circulation at the level of the cranio-vertebral junction favors the occurrence of the syrinx between 20 and 70% of cases in pediatric series. Different surgical techniques have been proposed. We report two series of patients treated with the same surgical procedure except for the use of a Goretex dural patch in the second group with better clinical results. Our experience seems to confirm that the Chiari I malformation is a complex disease in which the impairment of the CSF circulation plays an important role to explain the severity of the clinical picture. The bone decompression and the restauration of the CSF circulation with a dural patch with Goretex seems to be effective for improving the clinical picture with good results.

[Idiopathic vasospastic angiopathy of the internal carotid arteries: A rarely recognized cause of ischemic stroke in young individuals]. / Angiopathie vasospastique idiopathique de l'artère carotide interne : une cause peu connue d'accident vasculaire du sujet jeune.

INTRODUCTION: Idiopathic vasospastic angiopathy of the internal carotid arteries is a rare and largely unknown cause of ischemic stroke. METHODS: We report the case of a 39-year-old man with migraine treated by beta-blockers, who had been suffering from progressive right visual impairment and headache for one week. He then experienced a seizure and left hemiparesis. Ophthalmological examination revealed right retinal ischemia and partial left homonymous hemianopia. MRI revealed a long stenosis of both carotid arteries and a recent ischemic stroke in the territory of the right middle cerebral artery. The diagnosis of vasospastic angiopathy of the internal carotid arteries was made based on a second MRI and colored duplex sonography which showed a decrease in the stenosis and no intraparietal hematoma confirming the vasospasm mechanism for stenosis. The clinical course was favorable with calcium channel blockers and aspirin. Use of vasoconstrictor treatments was contraindicated. DISCUSSION/CONCLUSION: Idiopathic vasospastic angiopathy of the internal carotid arteries has been rarely documented. Association with migraine has been mentioned but remains unclear in the literature. This etiology for stroke is probably under-diagnosed due to lack of rapid and repeated examinations of the cervical arteries (angio-MR and colored duplex sonography) to confirm the vasospasm mechanism. Recurrences have been reported justifying a specific secondary preventive treatment to induce vasodilatation. Vasoconstrictor treatments should be contraindicated.

Primary angiitis of the central nervous system: response to mycophenolate mofetil.

Primary angiitis of the central nervous system (PACNS) is a rare inflammatory disease restricted to the CNS of unknown cause. Clinical presentation and evolution are highly variable with potentially fluctuating signs and symptoms. Brain imaging often shows supratentorial ischaemic lesions. Definite diagnosis is established by brain biopsy. Treatment usually combines glucocorticosteroids and cyclophosphamide. A case of PACNS is reported here, which was proved by a brain biopsy and characterised by unusually prominent involvement of the posterior cerebral fossa. Successful treatment with mycophenolate mofetil in combination with steroids is described.

[Imaging anatomy of cranial nerves]. / Imagerie anatomique des nerfs crâniens.

Knowledge of the anatomy of the cranial nerves is mandatory for optimal radiological exploration and interpretation of the images in normal and pathological conditions. CT is the method of choice for the study of the skull base and its foramina. MRI explores the cranial nerves and their vascular relationships precisely. Because of their small size, it is essential to obtain images with high spatial resolution. The MRI sequences optimize contrast between nerves and surrounding structures (cerebrospinal fluid, fat, bone structures and vessels). This chapter discusses the radiological anatomy of the cranial nerves.

Brain stem diffusion-weighted imaging lesion score: a potential marker of outcome in acute basilar artery occlusion.

BACKGROUND AND PURPOSE: The benefit of recanalization in basilar artery occlusion (BAO) has been established. The baseline extent of brain stem damage may also influence the outcome. We investigated whether a baseline diffusion-weighted imaging (DWI) score may provide additional prognostic value in BAO. MATERIALS AND METHODS: We analyzed baseline clinical and DWI parameters in consecutive patients treated with endovascular procedures for acute BAO. Brain stem DWI lesions were assessed by using a semiquantitative score based on arterial territory segmentation. Outcome at 3 months was dichotomized according to the modified Rankin Scale (mRS) as favorable (mRS, 0-2) or unfavorable (mRS, 3-6). Spearman rank correlation tests assessed the correlation between DWI and clinical variables. Univariate and multivariate logistic regression analyses were used to identify clinical and MR imaging predictors of outcome. RESULTS: Twenty-nine patients were included. The brain stem DWI score (median, 3; range, 0-14) was correlated with the baseline National Institutes of Health Stroke Scale (NIHSS) score and the presence and length of coma (r = 0.67, 0.49, and 0.53, respectively; P < .01). Recanalization was achieved in 76%. A higher baseline NIHSS score (P = .02) and brain stem DWI score (P = .03), a lower Glasgow Coma Scale score (P = .04), and the presence of coma (P = .05) were associated with poor outcome in univariate analysis. Multivariate analysis showed that the brain stem DWI score was the only independent baseline predictor for clinical outcome (P = .026). CONCLUSIONS: Baseline brain stem DWI lesion score is an independent marker of outcome in BAO.

A distinct [18F]MPPF PET profile in amnestic mild cognitive impairment compared to mild Alzheimer's disease.

To date, two positron emission tomography (PET) studies have explored 5-HT(1A) receptor density in the hippocampus of Alzheimer's disease (AD) patients. They showed early changes of 5-HT(1A) receptors in this brain region, known to have a dense serotonergic innervation. These studies only reported measurements in hippocampus. In the present PET study, we used an antagonist of 5-HT(1A) receptors, the [(18)F]MPPF (1) to explore 5-HT(1A) receptor density in the whole brain of AD patients at a mild stage of dementia and amnestic mild cognitive impairment (aMCI) patients compared to a control population; (2) to explore more precisely the 5-HT(1A) receptor density in the limbic brain regions of AD patients and aMCI patients compared to controls. Voxel-based analyses were performed to assess differences in the [(18)F]MPPF binding potential (BP) between AD patients and aMCI patients compared to controls. Analyses of whole-brain [(18)F]MPPF BP showed a global decrease in AD brains in contrast with a global increase in aMCI brains. In AD brains, a significant decrease of BP was detected in hippocampus and parahippocampal gyrus, whereas a significant increase of BP was observed in the inferior occipital gyrus in aMCI brains. These whole brain results are in accordance to hippocampal data reported in a previous study, showing an increase of [(18)F]MPPF binding in the aMCI group contrasting with a decrease in the AD group. Altogether, these results suggest the implication of a compensatory mechanism illustrated by an up regulation of serotonergic metabolism at the aMCI stage before a breakdown of this mechanism at the AD stage. This difference of serotonergic receptor labeling allows to distinguish the groups of aMCI patients from mild AD patients with specific [(18)F]MPPF PET profiles for each patient group.

Up-regulation of hippocampal serotonin metabolism in mild cognitive impairment.

OBJECTIVE: Recent studies have suggested modifications of serotonin cerebral metabolism and of 5-HT(1A) receptors density in Alzheimer disease (AD). This study aims at exploring hippocampus 5-HT(1A) receptor density in patients at the amnesic mild cognitive impairment (aMCI) and mild AD dementia stages. METHODS: With use of PET with a selective 5-HT(1A) antagonist, 2'-methoxyphenyl-(N-2'-pyridinyl)-p-[(18)F]fluoro-benzamidoethylpiperazine ([(18)F]MPPF), the hippocampus 5-HT(1A) binding potential (BP) was quantified in 10 patients with mild AD, in 11 patients with aMCI, and in 21 aged paired control subjects. To take into account hippocampal atrophy, a partial volume correction was applied to the [(18)F]MPPF data, leading to the calculation of a corrected BP (BP(c)). Comparison of hippocampus BP over populations was performed using Kruskal-Wallis rank analysis. RESULTS: Hippocampus serotonergic receptor binding distinguishes patients from controls and patients with aMCI from patients with AD. In aMCI patients, the mean hippocampus BP(c) was 59% higher than the controls' (p < 0.005), and it was conversely 35% lower in patients with mild AD (p < 0.01). The difference in BP(c) values between patients with aMCI and mild AD was large, resulting in a p value of <0.0005. These differences were not related to hippocampus atrophy. CONCLUSION: A compensatory mechanism illustrated by an up-regulation of serotonergic metabolism has been shown at the stage of amnesic mild cognitive impairment (aMCI) in contrast with a dramatic decrease at later stages of Alzheimer disease (AD). This difference of hippocampus serotonergic receptor labeling allows distinguishing of patients with aMCI from those with mild AD. Exploring 5-HT(1A) receptors with 2'-methoxyphenyl-(N-2'-pyridinyl)-p-(18)F-fluoro-benzamidoethylpiperazine PET seems to be of interest for better understanding pathophysiologic changes at early stages of AD.

[Cerebral amyloid angiopathy]. / L'angiopathie amyloïde cérébrale.

Cerebral amyloid angiopathy (CAA) is characterized by deposition of cerebrovascular amyloid protein in the media of leptomeningeal vessels. (amyloid B protein, cystatin C, transthyretin, gelsolin, and prion protein). It is a cause of cerebrovascular disorders including cerebral hemorrhage, cognitive impairment and unusually transient neurological symptoms. It is the main contributing factor to cerebral hemorrhage after hypertension in the elderly. We aimed to review epidemiological, pathophysiological and clinical and MRI imaging data in CAA.