Heat Pre-Treatment Modified Host and Non-Host Interactions of Powdery Mildew with Barley Brassinosteroid Mutants and Wild Types

High temperatures associated with climate change may increase the severity of plant diseases. This study investigated the effect of heat shock treatment on host and non-host barley powdery mildew interactions using brassinosteroid (BR) mutants of barley. Brassinosteroids are plant steroid hormones, but so far little is known about their role in plant-fungal interactions. Wild type barley cultivar Bowman and its near-isogenic lines with disturbances in BR biosynthesis or signalling showed high compatibility to barley powdery mildew race A6, while cultivar Delisa and its BR-deficient mutants 522DK and 527DK were fully incompatible with this pathogen (host plant-pathogen interactions). On the other hand, Bowman and its mutants were highly resistant to wheat powdery mildew, representing non-host plant-pathogen interactions. Heat pre-treatment induced shifts in these plant-pathogen interactions towards higher susceptibility. In agreement with the more severe disease symptoms, light microscopy showed a decrease in papillae formation and hypersensitive response, characteristic of incompatible interactions, when heat pre-treatment was applied. Mutant 527DK, but not 522DK, maintained high resistance to barley powdery mildew race A6 despite heat pre-treatment. By 10 days after heat treatment and infection, a noticeable shift became apparent in the chlorophyll a fluorescence and in various leaf reflectance parameters at all genotypes.

Transcriptome profiling of pepper leaves by RNA-Seq during an incompatible and a compatible pepper-tobamovirus interaction

Upon virus infections, the rapid and comprehensive transcriptional reprogramming in host plant cells is critical to ward off virus attack. To uncover genes and defense pathways that are associated with virus resistance, we carried out the transcriptome-wide Illumina RNA-Seq analysis of pepper leaves harboring the L3 resistance gene at 4, 8, 24 and 48 h post-inoculation (hpi) with two tobamoviruses. Obuda pepper virus (ObPV) inoculation led to hypersensitive reaction (incompatible interaction), while Pepper mild mottle virus (PMMoV) inoculation resulted in a systemic infection without visible symptoms (compatible interaction). ObPV induced robust changes in the pepper transcriptome, whereas PMMoV showed much weaker effects. ObPV markedly suppressed genes related to photosynthesis, carbon fixation and photorespiration. On the other hand, genes associated with energy producing pathways, immune receptors, signaling cascades, transcription factors, pathogenesis-related proteins, enzymes of terpenoid biosynthesis and ethylene metabolism as well as glutathione S-transferases were markedly activated by ObPV. Genes related to photosynthesis and carbon fixation were slightly suppressed also by PMMoV. However, PMMoV did not influence significantly the disease signaling and defense pathways. RNA-Seq results were validated by real-time qPCR for ten pepper genes. Our findings provide a deeper insight into defense mechanisms underlying tobamovirus resistance in pepper.

The expression of several pepper fatty acid desaturase genes is robustly activated in an incompatible pepper-tobamovirus interaction, but only weakly in a compatible interaction

The replication of positive strand RNA viruses in plant cells is markedly influenced by the desaturation status of fatty acid chains in lipids of intracellular plant membranes. At present, little is known about the role of lipid desaturation in the replication of tobamoviruses. Therefore, we investigated the expression of fatty acid desaturase (FAD) genes and the fatty acid composition of pepper leaves inoculated with two different tobamoviruses. Obuda pepper virus (ObPV) inoculation induced a hypersensitive reaction (incompatible interaction) while Pepper mild mottle virus (PMMoV) inoculation caused a systemic infection (compatible interaction). Changes in the expression of 16 FADs were monitored in pepper leaves following ObPV and PMMoV inoculations. ObPV inoculation rapidly and markedly upregulated seven Δ12-FADs that encode enzymes putatively located in the endoplasmic reticulum membrane. In contrast, PMMoV inoculation resulted in a weaker but rapid upregulation of two Δ12-FADs and a Δ15-FAD. The expression of genes encoding plastidial FADs was not influenced neither by ObPV nor by PMMoV. In accordance with gene expression results, a significant accumulation of linoleic acid was observed by gas chromatography-mass spectrometry in ObPV-, but not in PMMoV-inoculated leaves. ObPV inoculation led to a marked accumulation of H₂O₂ in the inoculated leaves. Therefore, the effect of H₂O₂ treatments on the expression of six tobamovirus-inducible FADs was also studied. The expression of these FADs was upregulated to different degrees by H₂O₂ that correlated with ObPV-inducibility of these FADs. These results underline the importance of further studies on the role of pepper FADs in pepper-tobamovirus interactions.

Reactions of tobacco genotypes with different antioxidant capacities to powdery mildew and Tobacco mosaic virus infections

The interactions of powdery mildew (Golovinomyces orontii) and Tobacco mosaic virus (TMV) with tobacco lines having down or upregulated antioxidants were investigated. Xanthi-nc, its salicylic acid-deficient NahG mutant, a paraquat-sensitive Samsun (PS) and its paraquat tolerant (PT) mutant were used. Cell membrane damage caused by H2O2 was significantly higher in NahG than Xanthi, whereas it was lower in PT than in PS. Leakage of ions from PT was reduced by the powdery mildew infection. On the other hand TMV inoculation led to a 6-fold and 2-fold elevation of ion leakage from hypersensitive resistant NahG and Xanthi leaves, respectively, whereas ion leakage increased slightly from susceptible PS leaves. G. orontii infection induced ribonuclease (RNase) enzyme activity in extracts from Xanthi and NahG (about 200-250% increase) and weakly (about 20-30% increase) from PS and PT lines. Pre-treatment with protein kinase inhibitor staurosporine or protein phosphatase inhibitor okadaic acid very strongly inhibited mildew development on tobacco lines. Our experiments suggest that protein kinases inhibited by staurosporine seem to be important factors, while protein phosphatases inhibited by okadaic acid play less significant role in TMV-induced lesion development. Both powdery mildew and TMV infections up-regulated the expression of PR-1b, PR-1c and WRKY12 genes in all tobacco lines to various extents.

Local and systemic hormonal responses in pepper leaves during compatible and incompatible pepper-tobamovirus interactions

Phytohormone levels and the expression of genes encoding key enzymes participating in hormone biosynthetic pathways were investigated in pepper leaves inoculated with two different tobamoviruses. Obuda pepper virus (ObPV) inoculation led to the development of hypersensitive reaction (incompatible interaction), while Pepper mild mottle virus (PMMoV) inoculation resulted in a systemic, compatible interaction. ObPV-inoculation markedly increased not only the levels of salicylic acid (SA) (73-fold) and jasmonic acid (8-fold) but also those of abscisic acid, indole-3-acetic acid, indole-3-butyric acid, cis-zeatin, cis-zeatin-9-riboside and trans-zeatin-9-riboside in the inoculated pepper leaves 3 days post inoculation. PMMoV infection increased only the contents of gibberellic acid and SA. Hormone contents did not change significantly after ObPV or PMMoV infection in non-infected upper leaves 20 days post inoculation. Concentrations of some brassinosteroids (BRs) and progesterone increased both in ObPV- and PMMoV inoculated leaves. ObPV inoculation markedly induced the expression of three phenylalanine ammonia-lyase (PAL) and a 1-aminocyclopropane-1-carboxylate oxidase (ACO) genes, while that of an isochorismate synthase (ICS) gene was not modified. PMMoV inoculation did not alter the expression of PAL and ICS genes but induced the transcript abundance of ACO although later than ObPV. Pre-treatment of pepper leaves with exogenous 24-epi-brassinolide (24-epi-BR) prior to ObPV-inoculation strongly mitigated the visible symptoms caused by ObPV. In addition, 24-epi-BR pre-treatment markedly altered the level of several hormones in pepper leaves following ObPV-inoculation. These data indicate that ObPV- and PMMoV-inoculations lead to intricate but well harmonized hormonal responses that are largely determined by the incompatible or compatible nature of plant-virus interactions.

Comparison of a compatible and an incompatible pepper-tobamovirus interaction by biochemical and non-invasive techniques: chlorophyll a fluorescence, isothermal calorimetry and FT-Raman spectroscopy

Leaves of a pepper cultivar harboring the L(3) resistance gene were inoculated with Obuda pepper virus (ObPV), which led to the appearance of hypersensitive necrotic lesions approx. 72 h post-inoculation (hpi) (incompatible interaction), or with Pepper mild mottle virus (PMMoV) that caused no visible symptoms on the inoculated leaves (compatible interaction). ObPV inoculation of leaves resulted in ion leakage already 18 hpi, up-regulation of a pepper carotenoid cleavage dioxygenase (CCD) gene from 24 hpi, heat emission and declining chlorophyll a content from 48 hpi, and partial desiccation from 72 hpi. After the appearance of necrotic lesions a strong inhibition of photochemical energy conversion was observed, which led to photochemically inactive leaf areas 96 hpi. However, leaf tissues adjacent to these inactive areas showed elevated ΦPSII and Fv/Fm values proving the advantage of chlorophyll a imaging technique. PMMoV inoculation also led to a significant rise of ion leakage and heat emission, to the up-regulation of the pepper CCD gene as well as to decreased PSII efficiency, but these responses were much weaker than in the case of ObPV inoculation. Chlorophyll b and total carotenoid contents as measured by spectrophotometric methods were not significantly influenced by any virus inoculations when these pigment contents were calculated on leaf surface basis. On the other hand, near-infrared FT-Raman spectroscopy showed an increase of carotenoid content in ObPV-inoculated leaves suggesting that the two techniques detect different sets of compounds.

Sturge-Weber syndrome

Sturge-Weber syndrome (SWS) is a rare sporadic neurocutaneous syndrome defined by the association of a facial capillary malformation in the ophthalmic distribution of the trigeminal nerve, with ipsilateral vascular glaucoma and vascular malformation of the eye, and a leptomeningeal angioma. SWS is suspected at birth in the presence of facial angioma in the trigeminal nerve area. MRI with gadolinium enhancement and pondered T1, T2, FLAIR and diffusion sequences is today the technique of choice to visualize the leptomeningeal angioma or to suspect it by indirect signs, even before the development of neurological signs, from the first months of life. The prognosis of SWS with leptomeningeal angioma is related to the severity of neurological signs that are absent at birth and develop later in life (epilepsy, hemiparesis, and mental delay). Seizures are usually the presenting neurological symptom. Status epilepticus might inaugurate the epilepsy and remains frequent in infancy. Repetitive seizures are thought to increase the atrophy of brain tissue in regard to the leptomeningeal angioma. Preventive presymptomatic treatment with antiepileptic drugs is often recommended, and parents are trained to use rescue benzodiazepines in case of seizures. After epilepsy onset, in patients intractable to antiepileptic drugs, surgery should be considered.

Sulfate supply influences compartment specific glutathione metabolism and confers enhanced resistance to Tobacco mosaic virus during a hypersensitive response

Sufficient sulfate supply has been linked to the development of sulfur induced resistance or sulfur enhanced defense (SIR/SED) in plants. In this study we investigated the effects of sulfate (S) supply on the response of genetically resistant tobacco (Nicotiana tabacum cv. Samsun NN) to Tobacco mosaic virus (TMV). Plants grown with sufficient sulfate (+S plants) developed significantly less necrotic lesions during a hypersensitive response (HR) when compared to plants grown without sulfate (-S plants). In +S plants reduced TMV accumulation was evident on the level of viral RNA. Enhanced virus resistance correlated with elevated levels of cysteine and glutathione and early induction of a Tau class glutathione S-transferase and a salicylic acid-binding catalase gene. These data indicate that the elevated antioxidant capacity of +S plants was able to reduce the effects of HR, leading to enhanced virus resistance. Expression of pathogenesis-related genes was also markedly up-regulated in +S plants after TMV-inoculation. On the subcellular level, comparison of TMV-inoculated +S and -S plants revealed that +S plants contained 55-132 % higher glutathione levels in mitochondria, chloroplasts, nuclei, peroxisomes and the cytosol than -S plants. Interestingly, mitochondria were the only organelles where TMV-inoculation resulted in a decrease of glutathione levels when compared to mock-inoculated plants. This was particularly obvious in -S plants, where the development of necrotic lesions was more pronounced. In summary, the overall higher antioxidative capacity and elevated activation of defense genes in +S plants indicate that sufficient sulfate supply enhances a preexisting plant defense reaction resulting in reduced symptom development and virus accumulation.

Clinical correlates of white matter blood flow perfusion changes in Sturge-Weber syndrome: a dynamic MR perfusion-weighted imaging study

BACKGROUND AND PURPOSE

Low brain tissue perfusion due to abnormal venous drainage is thought to be a central mechanism of brain damage in SWS. Here, HR-PWI was used to quantify WM perfusion abnormalities and to correlate these with brain atrophy and clinical variables.

MATERIALS AND METHODS

Fourteen children (age range, 0.8-10.0 years) with unilateral SWS underwent MR imaging examinations, including HR-PWI. rCBV, rCBF, and MTT in the affected WM and in contralateral homotopic WM were measured. AI for each perfusion parameter was correlated with age, brain atrophy, and motor and seizure variables as well as IQ.

RESULTS

Increased perfusion was seen in the affected hemisphere in 5 children and decreased perfusion in 9 children. Brain atrophy was more severe in the low-perfusion group (P = .01) and was related to both CBF-AI and CBV-AI (r = -0.69, P = .007; r = -0.64, P = .014, respectively). Older children had lower CBV values on the affected side (r = -0.62, P = .02). Longer duration of epilepsy was related to lower CBF (more negative CBF-AI, r = -0.58, P = .03) and low CBV (r = -0.55, P = .04) on the affected side. Lower perfusion was associated with more frequent seizures (rCBF-AI: r = -0.56, P = .04; rCBV-AI: r = -0.63, P = .02).

CONCLUSIONS

Increased perfusion in the affected cerebral WM may indicate an early stage of SWS without severe brain atrophy. Decreased perfusion is associated with frequent seizures, long duration of epilepsy, and brain atrophy.

Thalamocortical connectivity in healthy children: asymmetries and robust developmental changes between ages 8 and 17 years

BACKGROUND AND PURPOSE

Thalamocortical connections play a crucial role in complex cognitive functioning, and several neuropsychiatric disorders may involve aberrant thalamocortical circuitry. Here, we quantified the cortical pattern and age-related changes of thalamocortical connections by using probabilistic tractography in children and adolescents. We hypothesized that detectable asymmetry (left>right) exists in thalamocortical fiber connections and the connectivity increases with age during maturation.

MATERIALS AND METHODS

Diffusion tensor imaging was acquired in 15 normally developing children (age range, 8.3-17.3 years; 11 males), and fiber tracking was initiated from the thalami. The cortical distribution of ipsilateral thalamocortical fibers was quantified by using a landmark-constrained conformal mapping technique. Furthermore, hemispheric asymmetries and potential age-related changes in regional thalamocortical connections were assessed.

RESULTS

The left thalamus had significantly higher overall cortical connectivity than the right thalamus (P < .001). Left prefrontal cortical areas showed significantly higher thalamic connectivity compared with homotopic regions of the right hemisphere (P < .001), regardless of the applied parameters. There was an increase of overall thalamocortical connectivity with age, with the most pronounced age-related increases in bilateral prefrontal areas (P < .002). However, thalamic connectivity of some other cortical regions (right sensorimotor, left inferior temporal) showed a decrease with age.

CONCLUSIONS

Our results indicate a region-specific left>right asymmetry and robust developmental changes in thalamocortical (particularly thalamo-prefrontal) connectivity during late childhood and adolescence. These data further add to our knowledge about structural lateralizations and their development in the maturing brain.

Cerebellar developmental venous anomalies with associated vascular pathology

Cerebellar developmental venous anomalies (CDVA) are benign conditions, although sometimes they are associated with haemorrhages and reported to be symptomatic. This is the largest follow-up study to investigate the symptomatology of CDVAs and their association with other malformations. Thirty-two patients were followed for 2 - 9 years. Twenty-eight had isolated asymptomatic CDVA without any neurological condition during follow-up, which might be linked to the CDVA. Four patients had CDVA and an associated vascular pathology: two pontine cavernomas, one asymptomatic arteriovenous malformation (this is the first published case in the literature) and one cerebellar infarct with a developmental variation of the posterior fossa venous circulation. One patient had two CDVAs, while another had a unique draining vein from the upper part of the brainstem too. In conclusion, CDVAs are benign, asymptomatic conditions, but they are sometimes associated with pathogenic malformations requiring detailed neuroradiological investigations.

Multimodality imaging of cortical and white matter abnormalities in Sturge-Weber syndrome

BACKGROUND AND PURPOSE

Impaired cortical venous outflow and abnormal deep venous collaterals are common in Sturge-Weber syndrome (SWS), but their relation to brain metabolism and function is poorly understood. In this study, advanced MR imaging techniques, such as susceptibility-weighted imaging (SWI) and diffusion tensor imaging (DTI), were applied in conjunction with positron-emission tomography (PET), to assess cortical and white matter structural abnormalities and their relation to cortical glucose metabolism and cognitive functions in children with unilateral SWS.

MATERIALS AND METHODS

Thirteen children (age, 1.5-10.3 years) with unilateral SWS underwent MR imaging with SWI and DTI, glucose metabolism PET, and comprehensive neuropsychologic assessment prospectively. The MR imaging and PET images were coregistered and cortical regions showing decreased glucose metabolism were compared with locations of SWI signal intensity abnormalities, changes in white matter water diffusion, and cognitive functions.

RESULTS

SWI detected both cortical abnormalities (n=8) and deep transmedullary veins (n=9), including those in young children with no cortical SWI signal intensity changes. These veins were often located under cortex adjacent to hypometabolic regions. DTI showed abnormal water diffusion both under hypometabolic cortex and in adjacent white matter with collateral veins. Cognitive dysfunction was associated with abnormal water diffusion in the posterior white matter.

CONCLUSIONS

Transmedullary venous collaterals can be detected early by SWI and persist in white matter adjacent to damaged cortex in children with SWS. Microstructural white matter damage extends beyond cortical abnormalities and may contribute to cognitive impairment. SWI and DTI can be incorporated into clinical MR imaging acquisitions to objectively assess microstructural abnormalities at different stages of SWS.

Rasmussen encephalitis associated with Parry-Romberg syndrome

Parry-Romberg syndrome is a rare disorder associated with unilateral facial atrophy involving skin, subcutaneous tissue, skeletal muscle, and bone. Occasionally, there is CNS involvement with epilepsy being the most common CNS manifestation. The authors report a child with Parry-Romberg syndrome with a course strongly suggestive of Rasmussen encephalitis. The boy underwent hemispherectomy, and pathology showed the typical findings of Rasmussen encephalitis, suggesting that these two conditions may share common etiologic factors.

Alpha-methyl-L-tryptophan PET detects epileptogenic cortex in children with intractable epilepsy

BACKGROUND

In children with tuberous sclerosis, the PET tracer alpha[11C]methyl-L-tryptophan (AMT) has been shown to be selectively taken up by epileptogenic tubers, thus allowing differentiation from nonepileptogenic tubers in the interictal state.

OBJECTIVE

To determine whether cortical areas showing increased AMT uptake in children without tuberous sclerosis complex with intractable neocortical epilepsy indicate the epileptogenic zone, and to assess the relative contributions of AMT and 2-deoxy-2[18F]fluoro-D-glucose (FDG) PET abnormalities to the localization of epileptogenic cortical regions.

METHODS

Areas of increased AMT and decreased FDG uptake were marked objectively as regions with abnormal asymmetry using an in-house written software in 27 children who underwent comprehensive evaluation for resective epilepsy surgery. The marked PET abnormalities were compared to the locations of scalp and subdural EEG epileptiform abnormalities, as well as histology and surgical outcome.

RESULTS

Focal cortical increases of AMT uptake were found in 15 patients. The lobar sensitivity (39.0%) of AMT PET for seizure onset was lower, but its specificity (100%) was higher (p < 0.0001) than that of hypometabolism on FDG PET (sensitivity 73.2%, specificity 62.7%). AMT PET abnormalities were smaller than corresponding FDG PET hypometabolic regions (p = 0.002), and increased AMT uptake occurred in two patients with nonlocalizing FDG PET. Histologically verified cortical developmental malformations were associated with increased AMT uptake (p = 0.044). Subdural electrodes adjacent to the area of increased AMT uptake were most often involved in seizure onset.

CONCLUSIONS

Focal increase of cortical AMT uptake in children is less sensitive but more specific for the lobe of seizure onset than corresponding FDG PET hypometabolism, and it is often associated with epileptogenic cortical developmental malformations. AMT PET can assist placement of subdural electrodes even when MRI and FDG PET fail to provide adequate localizing information. Cortical areas adjacent to increased AMT uptake should be carefully addressed by intracranial EEG because these regions often show a high degree of epileptogenicity.

Local brain functional activity following early deprivation: a study of postinstitutionalized Romanian orphans

Early global deprivation of institutionalized children may result in persistent specific cognitive and behavioral deficits. In order to examine brain dysfunction underlying these deficits, we have applied positron emission tomography using 2-deoxy-2-[(18)F]fluoro-D-glucose in 10 children (6 males, 4 females, mean age 8.8 years) adopted from Romanian orphanages. Using statistical parametric mapping (SPM), the pattern of brain glucose metabolism in the orphans was compared to the patterns obtained from two control groups: (i) a group of 17 normal adults (9 males, 8 females, mean age 27.6 years) and (ii) a group of 7 children (5 males and 2 females, mean age 10.7 years) with medically refractory focal epilepsy, but normal glucose metabolism pattern in the contralateral hemisphere. Consistent with previous studies of children adopted from Romanian orphanages, neuropsychological assessment of Romanian orphans in the present study showed mild neurocognitive impairment, impulsivity, and attention and social deficits. Comparing the normalized glucose metabolic rates to those of normal adults, the Romanian orphans showed significantly decreased metabolism bilaterally in the orbital frontal gyrus, the infralimbic prefrontal cortex, the medial temporal structures (amygdala and head of hippocampus), the lateral temporal cortex, and the brain stem. These findings were confirmed using a region-of-interest approach. SPM analysis showed significantly decreased glucose metabolism in the same brain regions comparing the orphans to the nonepileptic hemisphere of the childhood epilepsy controls. Dysfunction of these brain regions may result from the stress of early global deprivation and may be involved in the long-term cognitive and behavioral deficits displayed by some Romanian orphans.

Neuroradiological assessment of brain structure and function and its implication in the pathogenesis of West syndrome

Neuroimaging studies with magnetic resonance imaging (MRI) and positron emission tomography (PET) scanning have contributed significantly to our understanding of West syndrome. Cortical dysplastic lesions are the most common abnormalities seen with MRI in infants with spasms, but other structural lesions are also detected occasionally. An underlying cortical dysplasia may not be apparent until myelination has advanced in the brain and poor gray-white matter differentiation becomes observable. Many cortical dysplastic lesions can only be detected using PET scanning of glucose metabolism or gamma-aminobutyric acid(A) (GABA(A)) receptor binding. The MRI and PET findings, together with neurophysiological observations, strongly suggest that infantile spasms are initiated as cortical epileptic discharges that, during a 'critical' developmental period, may undergo secondary generalization in an age-dependent mechanism to emerge as spasms. The onset of spasms often coincides with the functional maturation of cerebral cortex. Based on data from glucose metabolism PET scanning as well as electrophysiological and neurochemical findings on infants with spasms, we have postulated that the offending lesion is a focal or diffuse cortical abnormality which, at a critical stage of maturation, causes abnormal functional interactions with brainstem raphe nuclei which project widely throughout the brain. Raphe-cortical projections could mediate the hypsarrhythmic changes seen on EEG. The prominent serotonergic raphe-striatal pathway and descending spinal pathways may be responsible for secondary generalization of the cortical discharges to result in the relatively symmetric spasms. It is likely that additional factors (e.g. genetic) play a role in the manifestation of the age-specific electroclinical features of West syndrome. Recently developed PET tracers can be used to detect epileptogenic brain regions and also to investigate developmental abnormalities of serotonergic (using the tracer alpha[(11)C]methyl-L-tryptophan) and GABAergic (using [(11)C]flumazenil) neurotransmitter systems. These systems are implicated in epileptogenesis, and their involvement in the pathophysiology of West syndrome can be further addressed by future functional neuroimaging studies.

Surgical treatment of West syndrome

The discovery of focal or multifocal cortical lesions using magnetic resonance imaging (MRI) and positron emission tomography (PET) scanning in the majority of infants with West syndrome has led to a surgical approach in the treatment of some patients with intractable infantile spasms. The locations of these lesions should be concordant with localization of focal ictal and/or interictal electroencephalographic (EEG) abnormalities prior to proceeding with cortical resection. When a single lesion is present on the MRI or PET, and there is good correlation with EEG localization, surgical treatment is generally quite favorable in terms of both seizure control and cognitive development. Interictal glucose metabolism PET scans in children with intractable cryptogenic infantile spasms show unifocal cortical hypometabolism in about 20% of cases. In the majority, however, multifocal asymmetric hypometabolism is suggestive of multifocal underlying lesions, possibly multifocal cortical dysplasia. When the pattern of glucose hypometabolism is symmetric, a lesional etiology is less likely, thus neurometabolic or neurogenetic disorders should be considered. Therefore, the pattern of glucose hypometabolism on PET in infants with intractable cryptogenic spasms is a useful guide to decide whether a medical or surgical approach should be undertaken. In order to achieve the best cognitive outcome with surgery, it is important to resect the entire 'nociferous' area rather than just the seizure focus. Our research with new PET imaging probes has attempted to provide a comprehensive evaluation of the epileptogenic zone including the 'nociferous' cortex. We have used [(11)C]flumazenil (FMZ), which labels gamma aminobutyric acid(A) (GABA(A)) receptors, and have found this to be particularly useful in showing: (i) decreased receptor binding with medial temporal involvement thus indicating resection of medial temporal structures, (ii) the peri-lesional epileptogenic zone surrounding MRI lesions, (iii) the seizure onset zone in MRI-negative cases, and (iv) potential secondary epileptic foci. Another recently developed PET probe, alpha[(11)C]methyl-L-tryptophan (AMT) which is a precursor for the serotonin and the kynurenine metabolism pathways, is capable of differentiating between epileptogenic and non-epileptogenic tubers in patients with tuberous sclerosis complex and intractable epilepsy (including infantile spasms). Subsequently, we have applied AMT PET in patients with multifocal cortical dysplasia to determine the predominant seizure focus, and the results have been promising with regard to seizure control but not cognitive development. Thus, the introduction of newer more specific PET probes for epilepsy has led to improved and more accurate localization of seizure foci that should ultimately improve outcome of epilepsy surgery in West syndrome.

Patterns of cerebral glucose metabolism in early and late stages of Rasmussen's syndrome

Rasmussen's syndrome is a chronic encephalitis characterized by intractable focal epilepsy and progressive neurologic deterioration with lateralized brain destruction. In the early stages of the disease, the diagnosis can be difficult to make, and brain biopsy is often performed. We evaluated the patterns of cerebral glucose metabolism using 2-deoxy-2-[18F]-fluoro-D-glucose positron emission tomography (PET) in 15 children (age range 2.9-15.4 years, mean age 8.7 +/- 4.3 years) with Rasmussen's syndrome. In 6 patients evaluated early (< or = 1 year of onset of seizures), the PET scan showed areas of abnormal metabolism restricted mostly to the frontal and temporal regions, whereas the posterior cortex was preserved. Pathologic changes seen in the resected cortex were more pronounced in cortical areas of abnormal metabolism than in regions showing normal metabolism. In 9 patients evaluated later (>1 year after onset of seizures), the PET scan showed more diffuse hemispheric metabolic abnormalities including the occipital cortex, but the abnormalities remained highly lateralized. These patterns of glucose metabolic abnormalities in the early and late stages of the disease may facilitate the diagnosis of Rasmussen's syndrome and assist guidance of biopsy in early cases, when structural neuroimaging is still normal.

Prolonged vigabatrin treatment modifies developmental changes of GABA(A)-receptor binding in young children with epilepsy

PURPOSE

To determine whether prolonged treatment with vigabatrin (VGB), an antiepileptic drug (AED) that acts by elevating brain gamma-aminobutyric acid (GABA) levels, interferes with age-related changes of in vivo GABA(A)-receptor binding in children with epilepsy.

METHODS

Using [11C]flumazenil (FMZ)-positron emission tomography (PET) imaging, 15 children (aged 1-8 years) with medically intractable epilepsy were studied. Seven of these children were treated with VGB (1,000-2,500 mg/day) for > or =3 months before the FMZ-PET study. The remaining eight patients were medicated with other drugs that are known not to act directly on the GABAergic system. Absolute quantification of PET data was performed by using the volume of distribution (VD) of FMZ in brain tissue representing FMZ ligand binding.

RESULTS

After controlling for age, hemispheric FMZ VD values were significantly lower in children treated with VGB as compared with the non-VGB group (p = 0.012). Regional FMZ VD values of the VGB-treated patients were significantly lower in all cortical regions and the cerebellum, whereas the difference was not significant in the thalamus and basal ganglia. No significant drug effect or drug-by-region interaction could be determined when the patients were separated according to treatment with carbamazepine (p = 0.97) or valproate (p = 0.55).

CONCLUSIONS

VGB induces a decrease in GABA(A)-receptor binding in the cortex and cerebellum of the developing epileptic brain. A similar effect of other drugs and substances of abuse targeting the GABAergic system may be hypothesized. Because of the important role of the GABAergic system in developmental plasticity, the reversibility and functional consequences of this age-specific drug effect should be further studied.

Bilateral medial prefrontal and temporal neocortical hypometabolism in children with epilepsy and aggression

PURPOSE

To identify brain regions with abnormal function in children with intractable partial epilepsy and aggressive behavior by using 2-deoxy-2-[18F]fluoro-D-glucose (FDG) positron emission tomography (PET).

METHODS

Six children (mean age, 9.9 years) with intractable partial epilepsy and aggressive behavior underwent detailed psychodevelopmental assessment and FDG-PET scanning. The objective technique of statistical parametric mapping (SPM) was applied to define focal abnormalities of glucose metabolism, and compared those with those of a group of normal adult subjects (n = 17) as well as age-matched children with epilepsy with similar seizure characteristics but without aggression (n = 7). The findings were analyzed further by using a region-of-interest (ROI) approach.

RESULTS

The aggressive children all showed developmental delay, and four of them also manifested autistic symptoms. SPM analysis demonstrated extensive glucose hypometabolism in the aggressive group bilaterally in the temporal and prefrontal cortex compared with that in normal adult controls. A focal area of medial prefrontal glucose hypometabolism was defined in the aggressive children as compared with the nonaggressive pediatric group with SPM, whereas ROI comparison of these groups confirmed prefrontal hypometabolism and also showed glucose hypometabolism of the temporal neocortex in the aggressive children. Severity of aggression correlated inversely with glucose metabolism of the left temporal as well as bilateral medial prefrontal cortex.

CONCLUSIONS

Bilateral prefrontal and temporal neocortical brain glucose hypometabolism in children with epilepsy and aggressive behavior may indicate a widespread dysfunction of cortical regions, which normally exert an inhibitory effect on subcortical aggressive impulses. PET studies may be used to elucidate the neurobiologic basis of aggressive behavior in children.

Sturge-Weber syndrome: correlation between clinical course and FDG PET findings

OBJECTIVE

To determine whether the extent and degree of glucose hypometabolism defined by PET correlate with seizure characteristics, cognitive function, and interictal EEG abnormalities in children with unilateral cerebral involvement of Sturge-Weber syndrome (SWS).

METHODS

2-Deoxy-2[18F]fluoro-D-glucose (FDG) PET was performed in 13 children (age range 0.7 to 15.1 years; five boys, eight girls) with unilateral SWS. Based on asymmetries between homologous cortical areas in FDG PET images, cortical areas of mildly (10% to 20% decrease), and severely (>20% decrease) asymmetric cortical metabolism were defined. These areas were normalized to the size of the ipsilateral hemisphere and correlated with clinical seizure characteristics, full-scale IQ, and interictal EEG abnormalities.

RESULTS

Both seizure frequency (p = 0.027) and lifetime number of seizures (p = 0.017) showed a positive correlation with the area (expressed as the percentage of cortical area of ipsilateral hemisphere) of mildly asymmetric cortical metabolism. Patients with higher IQ had a shorter duration of epilepsy (p = 0.044) and a larger area of severely asymmetric cortical metabolism (p = 0.044). Patients with bilateral interictal EEG abnormalities had larger lifetime number of seizures (p = 0.042), lower IQ (p = 0.024), and smaller area of severely asymmetric cortical metabolism (p = 0.019) than those with only ipsilateral EEG abnormalities.

CONCLUSIONS

Association of severely asymmetric cortical metabolism with relatively preserved cognitive function in SWS suggests that functional reorganization occurs more readily when cortex is severely rather than mildly damaged. Therefore, the area of mildly asymmetric cortical metabolism may exert a nociferous effect on the remaining of the brain. Thus, the extent and degree of glucose asymmetry detected by PET are sensitive markers of seizure severity and cognitive decline in SWS.

Relationship of flumazenil and glucose PET abnormalities to neocortical epilepsy surgery outcome

BACKGROUND

Cortical areas showing abnormal glucose metabolism and [(11)C]flumazenil (FMZ) binding are commonly seen on PET scans of patients with intractable partial epilepsy, but it is unclear whether these must be totally resected to achieve seizure control.

OBJECTIVE

To analyze whether the extent of cortex showing 2-deoxy-2-[(18)F]fluoro-D-glucose (FDG) or FMZ PET abnormalities correlates with the outcome of resective epilepsy surgery.

METHODS

Cortical FDG and FMZ PET abnormalities in 15 young patients (mean age, 12.2 +/- 7.0 years) with intractable partial epilepsy of neocortical origin were marked as regions with abnormal asymmetry using an objective semiautomated software package. These marked regions were then projected and measured on the brain surface reconstructed from the coregistered high-resolution MRI. Following cortical resection, the size of nonresected cortex with preoperative PET abnormalities was also measured (calculated separately for marked areas in the lobe of seizure onset as defined by long-term video EEG monitoring, and in remote cortical areas). Extent of preoperative PET abnormalities and postoperative nonresected cortex abnormalities on PET were correlated with outcome scores.

RESULTS

Large preoperative FMZ PET abnormalities were associated with poor outcome (r = 0.57; p = 0.025). Larger areas of nonresected cortex with preoperative FMZ PET abnormalities in the lobe of seizure onset were also associated with worse outcome in the whole group (r = 0.66; p = 0.007) as well as in patients with extratemporal resection (r = 0.73; p = 0.007), and in those with no lesion on MRI (r = 0.60; p = 0.049). Patients with seizure-free outcome had significantly smaller nonresected cortex with preoperative FMZ PET abnormalities than those who continued to have seizures (p = 0.022). No significant correlations between nonresected FDG PET abnormalities and surgical outcome were found.

CONCLUSIONS

Extensive cortical abnormalities on FMZ PET predict poor outcome in neocortical epilepsy surgery. Resection of FMZ abnormalities in the lobe of seizure onset is associated with excellent outcome even in the absence of a structural lesion. In contrast, although FDG PET abnormalities regionalized the epileptogenic area, their size was not related to the extent of epileptogenic tissue to be removed.

Postnatal maturation of human GABAA receptors measured with positron emission tomography

During brain development in nonhuman primates, there are large changes in GABAA receptor binding and subunit expression. An understanding of human GABAA receptor ontogeny is highly relevant in elucidating the pathophysiology of neurodevelopmental disorders in which GABAergic mechanisms play a role as well as in understanding differences that occur during development in the pharmacology of drugs acting on this system. We have measured age-related changes in the brain distribution of the GABAA receptor complex in vivo using positron emission tomography (PET) in epileptic children under evaluation for surgical treatment. PET imaging was performed using the tracer [11C]flumazenil (FMZ), a ligand that binds to alpha subunits of the GABAA receptor. FMZ binding was quantified using a two-compartment model yielding values for the volume of distribution (VD) of the tracer in tissue. All brain regions studied showed the highest value for FMZ VD at the youngest age measured (2 years), and the values then decreased exponentially with age. Medial temporal lobe structures, primary visual cortex, and thalamus showed larger differences between values for age 2 years and adults (approximately 50% decrease) than did basal ganglia, cerebellum, and other cortical regions (25-40% decreases). Furthermore, subcortical regions reached adult values earlier (14-17.5 years) than did cortical regions (18-22 years). The ontogeny data of FMZ VD from children may contribute to understanding regional differences in synaptic plasticity as well as improve rational therapeutic use of drugs acting at the GABAA receptor in the pediatric population.

Lissencephaly: fetal pattern of glucose metabolism on positron emission tomography?

BACKGROUND

In classical lissencephaly, the cerebral cortex is four-layered, containing neurons that have failed to complete their migration between 12 and 16 weeks of gestation.

METHODS

The authors studied the functional activity of lissencephalic cortex using 2-deoxy-2[(18)F]fluoro-D-glucose PET (FDG PET) in eight patients (six girls and two boys, mean age 7.5 years) with isolated lissencephaly sequence.

RESULTS

The PET scans revealed a remarkably similar and bilaterally symmetric pattern of glucose metabolism in all eight patients. The cerebral cortex of lissencephaly showed two layers that could be differentiated based on metabolic activity. The inner layer, which probably corresponds to the inner cellular layer of lissencephalic cortex, showed 8 to 63% higher glucose utilization rate than the outer layer, which probably represents a composite of the molecular, outer cellular, and cell-sparse layers. Patients with a higher metabolic ratio between the cortical layers (inner/outer) showed greater delay in communication (p = 0.007) and socialization (p = 0.03).

CONCLUSIONS

These findings are consistent with [(14)C]-2-deoxyglucose autoradiography studies in fetal sheep that have shown that before the development of significant numbers of axons, dendrites, and synapses, glucose metabolism appears to be highest in regions with the highest density of cell bodies, compared to the more mature state when glucose metabolism is highest in areas of greatest dendritic arborization. FDG PET studies of classical lissencephaly provide a different perspective in the analysis of brain gyral anomalies than those with traditional neuroanatomic imaging techniques.

Statistical parametric mapping: assessment of application in children

SPM is a powerful technique for the comparison of functional imaging data sets among groups of patients. While this technique has been widely applied in studies of adults, it has rarely been applied to studies of children, due in part to the lack of validation of the spatial normalization procedure in children of different ages. In order to determine if spatial normalization of FDG PET images using SPM96 to an adult template can be successfully applied in children, we applied PET-derived transformation parameters to coregistered MRI images. We then compared contours of spatially normalized MRI images obtained from 13 children with epilepsy (ages 2-14 years, mean 7.6 +/- 3.9 years) with those derived from 17 adult controls (mean age 27.6 +/- 4.5 years). Contours of spatially normalized MRI image volumes derived from the pediatric group were more variable than those obtained from adult controls. The average deviation from the mean adult contour was age-dependent and decreased with age (average deviation (mm) = 2.22 (mm) - 0.021 (mm/year) x years, r = 0.70, P < 0.001). Separate SPM analyses were performed for children less than 6 years (N1 = 6) and for children between 6 and 14 years of age (N2 = 7). SPM analyses performed in both pediatric groups showed significant regions of hypometabolism in locations consistent with their epileptic foci. SPM analyses in the younger group also showed significant artifacts. Therefore, the error associated with spatial normalization of pediatric brains to an adult template in children less than 6 years of age precludes the application of statistical parametric mapping in this age group. Although the error in the spatial normalization procedure for children ages 6 to 14 years is higher than in adults, it appears that this error does not result in artifacts in the SPM analysis. Furthermore, in contrast our previous studies showing large age-related changes in the absolute glucose metabolic rate at puberty, the SPM analysis showed children over 6 years of age appear to display the same pattern of glucose utilization as adults. However, small differences in the pattern of glucose utilization which might occur during late childhood and adolescence may not have been detected due to the sample size.

Electroclinical correlates of flumazenil and fluorodeoxyglucose PET abnormalities in lesional epilepsy

OBJECTIVE

To analyze the clinical utility of [11C]flumazenil (FMZ) PET to detect perilesional and remote cortical areas of abnormal benzodiazepine receptor binding in relation to MRI, 2-deoxy-2-[18F]fluoro-d-glucose (FDG) PET, and electrocorticographic (ECoG) findings as well as clinical characteristics of the epilepsy in epileptic patients with brain lesion.

BACKGROUND

The success of resective surgery in patients with medically intractable epilepsy and brain lesion depends not only on removal of the lesion itself but also on the reliable presurgical delineation of the epileptic cortex that commonly extends beyond it. PET could provide a noninvasive identification of such epileptogenic areas.

METHODS

Seventeen patients underwent high resolution MRI, FDG and FMZ PET, and presurgical EEG evaluation, including chronic intracranial ECoG monitoring or intraoperative ECoG. Regional cortical FDG/FMZ PET abnormalities were defined on partial volume-corrected PET images using an objective method based on a semiautomated definition of areas with abnormal asymmetry. Structural lesions were defined on coregistered MRI. The marked PET abnormalities visualized on three-dimensional cortical surface were compared with each other, to the extent of MRI-defined lesion, as well as to ECoG findings.

RESULTS

The mean surface extent of FMZ PET abnormalities was significantly larger than the corresponding structural lesions, but it was significantly smaller than areas of glucose hypometabolism. The size of perilesional FDG PET abnormalities showed a correlation with the lifetime number of seizures (r = 0.93, p = 0.001). The extent of perilesional FMZ PET abnormalities was independent of the seizure number and showed an excellent correspondence with spiking cortex, the resection of which resulted in seizure-free outcome in all but one operated patient. Remote FMZ PET abnormalities (n = 6) were associated with early age at seizure onset (p = 0.048) and appeared in ipsilateral synaptically connected regions from the lesion area.

CONCLUSIONS

Three-dimensional surface-rendered FMZ PET is able to delineate perilesional epileptic cortex, and it may be especially useful to localize such areas in patients with extensive perilesional glucose hypometabolism associated with a large number of seizures. Remote FMZ PET abnormalities in patients with early onset and long duration of epilepsy might represent secondary epileptogenesis, but this requires further study.

Is epileptogenic cortex truly hypometabolic on interictal positron emission tomography?

Positron emission tomography (PET) of glucose metabolism is often applied for the localization of epileptogenic brain regions, but hypometabolic areas are often larger than or can miss epileptogenic cortex in nonlesional neocortical epilepsy. The present study is a three-dimensional brain surface analysis designed to demonstrate the functional relation between glucose PET abnormalities and epileptogenic cortical regions. Twelve young patients (mean age, 10.8 years) with intractable epilepsy of neocortical origin underwent chronic intracranial electroencephalographic monitoring. The exact location of the subdural electrodes was determined on high-resolution three-dimensional reconstructed magnetic resonance imaging scan volumes. The electrodes were classified according to their locations over cortical areas, which were defined as hypometabolic, normometabolic, or at the border between hypometabolic and normal cortex (metabolic "border zones") based on interictal glucose PET. Electrodes with seizure onset were located over metabolic border zones significantly more frequently than over hypometabolic or normometabolic regions. Seizure spread electrodes also more frequently overlay metabolic border zones than hypometabolic regions. These findings suggest that cortical areas with hypometabolism should be interpreted as regions mostly not involved in seizure activity, although epileptic activity commonly occurs in the surrounding cortex. This feature of hypometabolic cortex is remarkably similar to that of structural brain lesions surrounded by epileptogenic cortex. Cortical areas bordering hypometabolic regions can be highly epileptogenic and should be carefully assessed in presurgical evaluations.

Multimodality imaging for improved detection of epileptogenic foci in tuberous sclerosis complex

OBJECTIVE

Using interictal alpha-[11C]methyl-l-tryptophan ([11C]AMT) PET scan, the authors have undertaken a quantitative analysis of all tubers visible on MRI or 2-deoxy-2-[18F]fluoro-d-glucose ([18F]FDG) PET, to determine the relationship between [11C]AMT uptake and epileptic activity on EEG.

BACKGROUND

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder, often associated with cortical tubers and intractable epilepsy. The authors have shown previously that [11C]AMT PET scans show high tracer uptake in some epileptogenic tubers and low uptake in the remaining tubers.

METHODS

Eighteen children, age 7 months to 16 years, were studied. Patients underwent video-EEG monitoring, PET scans of [11C]AMT and [18F]FDG, and T2-weighted or fluid-attenuated inversion recovery (FLAIR) MRI. [11C]AMT uptake values were measured in 258 cortical tubers delineated with coregistered MRI or [18F]FDG scans. Uptake ratios were calculated between the [11C]AMT uptake in tubers and those for normal cortex (tuber/normal cortex). Using the region of epileptiform activity, the authors performed receiver operator characteristics (ROC) analysis and determined the optimal uptake ratio for detecting presumed epileptogenic tubers.

RESULTS

Tuber uptake ratios ranged from 0.6 to 2.0. Tuber uptake ratios in the epileptic lobes were higher than those in the nonepileptic lobes (p < 0.0001). All 15 patients with focal seizure activity showed one or more lesions with uptake ratio above 0.98 in the epileptic lobe. ROC analysis showed that a tuber uptake ratio of 0.98 resulted in a specificity of 0.91.

CONCLUSIONS

Cortical tubers with [11C]AMT uptake greater than or equal to normal cortex are significantly related to epileptiform activity in that lobe. Together, interictal [11C]AMT PET and FLAIR MRI improve the detection of potentially epileptogenic tubers in patients with TSC being evaluated for epilepsy surgery.

Evidence for coupling between glucose metabolism and glutamate cycling using FDG PET and 1H magnetic resonance spectroscopy in patients with epilepsy

The purpose of this study was to examine the relation between glucose metabolism and glutamate concentration in the human brain, in both the normal and diseased state. Regional values of glucose metabolism measured with 2-deoxy-2[F-18]fluoro-D-glucose positron emission tomography (FDG PET) studies and single-voxel proton magnetic resonance spectroscopy (1H MRS) measurements of the glutamate/ glutamine/gamma-aminobutyric acid (Glx) tissue concentration were determined in multiple brain regions in 11 patients (5 girls and 6 boys, mean age 7.5 years) with medically intractable partial epilepsy. FDG PET and 1H MRS studies were performed in the interictal state in seven patients and in the ictal/periictal state in four patients. Regions of interest were identified in epileptic cortex (determined by intracranial and/or scalp electroencephalography) and in contralateral normal brain regions. Lower glucose metabolism and lower Glx concentrations were found in the epileptic focus than in the contralateral normal cortex in all seven patients examined in the interictal state, whereas higher glucose metabolism and higher Glx concentrations were observed in the epileptic focus in the four patients who had ictal/periictal studies. Significant correlations were found between the values of cerebral glucose utilization and Glx concentration in epileptic brain region, in nonepileptic brain regions, and in epileptic and nonepileptic regions combined. These results demonstrate a significant relation between glucose metabolism and glutamate/glutamine concentration in normal and epileptic cerebral cortex. This relation is maintained in both the interictal and ictal states.

Relationship between EEG and positron emission tomography abnormalities in clinical epilepsy

Positron emission tomography (PET) is a relatively noninvasive neuroimaging method by means of which a large variety of human brain functions can be assessed. Localized neurochemical abnormalities detected by PET were found in patients with partial epilepsy and suggested the use of this modality for localizing epileptogenic regions of the brain. The clinical usefulness of PET is determined by its sensitivity and specificity for identifying epileptogenic areas as defined by ictal surface and intracranial EEG recordings. The findings obtained from comparative EEG and glucose PET data are reviewed with special emphasis on patients undergoing presurgical evaluation because of medically intractable temporal and extratemporal lobe epilepsy. The utility of glucose PET studies for identifying regions of seizure onset is presented, and the limited specificity of glucose metabolic abnormalities for the detection of various EEG patterns in clinical epilepsy is discussed. The authors review the available intracranial EEG and PET comparisons using [11C]flumazenil (FMZ) PET, a tracer for the assessment of tau-amino-butyric acid/benzodiazepine receptor function. They also summarize their experience with [11C]flumazenil PET in identifying cortical regions that show various ictal and interictal cortical EEG abnormalities in patients with extratemporal seizure origin. Finally, the authors demonstrate that further development of new PET tracers, such as alpha-[11C]methyl-L-tryptophan, is feasible and clinically useful and may increase the number of patients in whom PET studies can replace invasive EEG monitoring.

Glucose and [11C]flumazenil positron emission tomography abnormalities of thalamic nuclei in temporal lobe epilepsy

OBJECTIVES

To analyze interictal patterns of thalamic nuclei glucose metabolism and benzodiazepine receptor binding in patients with medically intractable temporal lobe epilepsy (TLE) using high-resolution 2-deoxy-2-[18F]fluoro-D-glucose (FDG) and [11C]flumazenil (FMZ) PET.

BACKGROUND

Structural and glucose metabolic abnormalities of the thalamus are considered important in the pathophysiology of TLE. The differential involvement of various thalamic nuclei in humans is not known.

METHODS

Twelve patients with TLE underwent volumetric MRI, FDG and FMZ PET, and prolonged video-EEG monitoring. Normalized values and asymmetries of glucose metabolism and FMZ binding were obtained in three thalamic regions (dorsomedial nucleus [DMN], pulvinar, and lateral thalamus [LAT]) defined on MRI and copied to coregistered, partial-volume-corrected FDG and FMZ PET images. Hippocampal and amygdaloid FMZ binding asymmetries and thalamic volumes also were measured.

RESULTS

The DMN showed significantly lower glucose metabolism and FMZ binding on the side of the epileptic focus. The LAT showed bilateral hypermetabolism and increased FMZ binding. There was a significant correlation between the FMZ binding asymmetries of the DMN and amygdala. The PET abnormalities were associated with a significant volume loss of the thalamus ipsilateral to the seizure focus.

CONCLUSIONS

Decreased [11C]flumazenil (FMZ) binding and glucose metabolism of the dorsomedial nucleus (DMN) are common and have strong lateralization value for the seizure focus in human temporal lobe epilepsy. Decreased benzodiazepine receptor binding can be due to neuronal loss, as suggested by volume loss, but also may indicate impaired gamma-aminobutyric acid (GABA)ergic transmission in the DMN, which has strong reciprocal connections with other parts of the limbic system. Increased glucose metabolism and FMZ binding in the lateral thalamus could represent an upregulation of GABA-mediated inhibitory circuits.

Altered in vitro and in vivo flumazenil binding in human epileptogenic neocortex

In vitro and in vivo parameters of flumazenil (FMZ) binding were measured in spiking and nonspiking neocortex identified by intraoperative electrocorticography in epileptic patients who underwent cortical resection for seizure control. In vitro measures of receptor affinity (K(D)), number (Bmax) and laminar distribution for [3H]-FMZ binding in the epileptic focus (n = 38) were compared to nonspiking cortex from a subgroup of the patients (n = 12) and to tissue obtained from trauma patients (n = 5). The in vitro binding parameters were compared to in vivo [11C]-FMZ binding measured with positron emission tomography (PET) (n = 19). The Bmax was higher in the 38 spiking tissues as compared to the 12 nonspiking tissues (P = .012). Paired comparison of spiking versus nonspiking binding in the 12 patients from whom nonspiking tissue was available showed increases in both K(D) (P = .037) and Bmax (P = .0047) in spiking cortex. A positive correlation was found between K(D) and Bmax values for 38 patients (r = 0.55, P < .0001), the magnitude of the K(D) increase being twice that of the Bmax increase. In addition, there was a significant correlation between the asymmetry indices of the in vivo FMZ binding on PET and in vitro K(D) of spiking cortex (n = 19, r = 0.52, P = .02). The laminar distribution of [3H]-FMZ showed increased FMZ binding in cortical layers V-VI in spiking cortex compared to nonspiking and control cortex. The increased receptor number in spiking cortical layers V-VI may be a compensatory mechanism to decreased GABAergic input. The increased Bmax in spiking cortex was accompanied by a larger decrease in the affinity of FMZ for the receptor suggesting that decreased FMZ binding in the epileptic focus measured with PET is due to a decrease in the affinity of the tracer for the receptor.

[Analysis of the activity of neurologic intensive care units]

The authors analysed six-year activity of the intensive Care Unit of Department of Neurology, Medical University of Pécs (POTEI), and two-year activity of the Intensive Care Unit of Department of Neurology, Semmelweis University of Medicine, Budapest (SOTEI). Mortality at POTEI and SOTEI was 33.9% and 32.2%, respectively. Mean duration of stay of survivors at POTEI was 10 +/- 12.8 days, and 7 +/- 6.8 days at SOTEI; mean duration of care of the deceased patients at POTEI was 6.3 +/- 10.5 days, and 10 +/- 13.7 days at SOTEI. At POTEI 60.7%, at SOTEI 63% of the patients was admitted because of cerebrovascular insult. Mortality of patients with brain haemorrhage at POTEI and SOTEI was 53.4% and 57.7% respectively. Mortality of the ischaemic group was 40.6% (POTEI) and 35.3% (SOTEI). In the group of intracranial tumours 44.4% mortality was recorded at POTEI and 47.6% at SOTEI. At POTEI 240 patients (15.9%), while at SOTEI 94 patients (21%) were admitted to treat epileptic seizures. Among the 510 patients, who died within one month 284 patients (55.6%) were unconscious at admission. From those with coma due to severe structural lesion of the brain (brain ischaemia, bleeding, meningitis) only 15 patients survived. Among the 184 patients, who were comatose and survived, the most frequent diagnosis was suicidal attempt with hypnotics (n = 67), metabolic encephalopathy (n = 19) and epilepsy (n = 12). At SOTEI among the 144 deceased patients 102 (70.8%) were unconscious at admission. Coma at admission proved to be a strong predictor of mortality. Mortality of the ventilated patients was 83% at POTEI and of those having subclavian catheter (n = 592) was 47.1%. In the acute phase of brain ischaemia at POTEI 39%, at SOTEI 10.7% of the patients received heparin. At SOTEI the cost of medication of patients who died after two weeks of care was 65.2% higher than that of the survived patients.

[11C]Flumazenil PET in patients with epilepsy with dual pathology

PURPOSE

Coexistence of hippocampal sclerosis and a potentially epileptogenic cortical lesion is referred to as dual pathology and can be responsible for poor surgical outcome in patients with medically intractable partial epilepsy. [11C]Flumazenil (FMZ) positron emission tomography (PET) is a sensitive method for visualizing epileptogenic foci. In this study of 12 patients with dual pathology, we addressed the sensitivity of FMZ PET to detect hippocampal abnormalities and compared magnetic resonance imaging (MRI) with visual as well as quantitative FMZ PET findings.

METHODS

All patients underwent volumetric MRI, prolonged video-EEG monitoring, and glucose metabolism PET before the FMZ PET. MRI-coregistered partial volume-corrected PET images were used to measure FMZ-binding asymmetries by using asymmetry indices (AIs) in the whole hippocampus and in three (anterior, middle, and posterior) hippocampal subregions. Cortical sites of decreased FMZ binding also were evaluated by using AIs for regions with MRI-verified cortical lesions as well as for non-lesional areas with visually detected asymmetry.

RESULTS

Abnormally decreased FMZ binding could be detected by quantitative analysis in the atrophic hippocampus of all 12 patients, including three patients with discordant or inconclusive EEG findings. Decreased FMZ binding was restricted to only one subregion of the hippocampus in three patients. Areas of decreased cortical FMZ binding were obvious visually in all patients. Decreased FMZ binding was detected visually in nonlesional cortical areas in four patients. The AIs for these nonlesional regions with visual asymmetry were significantly lower than those for regions showing MRI lesions (paired t test, p = 0.0075).

CONCLUSIONS

Visual as well as quantitative analyses of FMZ-binding asymmetry are sensitive methods to detect decreased benzodiazepine-receptor binding in the hippocampus and neocortex of patients with dual pathology. MRI-defined hippocampal atrophy is always associated with decreased FMZ binding, although the latter may be localized to only one sub-region within the hippocampus. FMZ PET abnormalities can occur in areas with normal appearance on MRI, but FMZ-binding asymmetry of these regions is lower when compared with that of lesional areas. FMZ PET can be especially helpful when MRI and EEG findings of patients with intractable epilepsy are discordant.

Reversible focal MRI abnormalities due to status epilepticus. An EEG, single photon emission computed tomography, transcranial Doppler follow-up study

We demonstrate clinical data and findings of MRI, transcranial Doppler (TCD), single photon emission computed tomography (SPECT) and electroencephalography (EEG) in an 8 month follow-up study of a 15 year old girl who developed focal status epilepticus with sensory and visual illusions. EEG showed right temporal and occipital seizure activity and attenuation of the alpha activity with right predominance. MRI showed a right temporo-parietal hyper signal on the T2 weighted images involving the cortex with sulcal effacement. MRI-angiography suggested insufficient flow in the right transverse sinus. TCD detected an elevated flow velocity in the ipsilateral middle cerebral artery during status epilepticus, corresponding to an increased perfusion of the epileptic area revealed by SPECT. After normalization of the TCD finding, the MRI detected persistent cortical abnormality beyond the 70th day after admission. MRI normalized on the 103rd day of follow-up. Serial EEG frequency analysis demonstrated the recovery of alpha peak frequency on the left side, but the attenuation of rhythmic signals remained persistent on the right. In our case, the restitution of postictal EEG lag behind the consolidation of MRI signal abnormality.

Early detection of vasospasm after acute subarachnoid hemorrhage using continuous EEG ICU monitoring

The neurologic morbidity of delayed ischemic deficits from vasospasm following aneurysmal subarachnoid hemorrhage (SAH) continues to be the most debilitating complication from this devastating illness. Neurologic critical care is focused on recognition and treatment of these secondary insults but often the treatment is withheld until an irreversible deficit becomes manifest. Continuous EEG (cEEG) monitoring provides a unique potential to recognize early secondary insults and offers an opportunity for early intervention. We studied 32 SAH patients using cEEG and trending of the quantitative measure, relative alpha (RA), to determine if reductions in RA variability occurred with documented vasospasm. In 19/19 patients with angiographically documented vasospasm, we found that RA variability was decreased by a mean of two grades and improved with resolution of vasospasm. In 10/19 this reduction in RA variability preceded the diagnosis of vasospasm by a mean of 2.9 days (SD 1.73). The positive predictive and negative predictive values are 76% and 100%, respectively. Non-diagnostic clinical signs at the time of RA variability reduction and vasospasm were present in 12/19 patients. Thus decreased RA variability is able to provide early detection of neurologic complications such as vasospasm in patients before clear clinical symptoms and signs occur.

Spectral EEG analysis following hemispheric stroke: evidences of transhemispheric diaschisis

Quantitative EEG frequency analysis was performed within the acute stage and after the recovery in 40 patients with hemispheric stroke in order to analyze ipsi- and contralateral alpha peak frequency (APF) and band power changes. Localization of hemispheric lesion was determined by computer tomography. Changes of clinical scores were compared with the alpha asymmetries. In the cases of small subcortical infarcts good improvement of alpha activity was observed over the affected hemisphere; contralateral APF was relatively preserved. Bilateral symmetric reduction of APF was found in territorial middle cerebral artery infarcts, with poor tendency of recovery of alpha power and neurologic status. These findings suggest transitory derangement of alpha generators in the contralateral hemisphere evidenced by APF and power asymmetries. EEG signs of contralateral alpha reduction may be due to the remote effect of primary ischemic lesion indicating an electrical diaschisis phenomenon in the acute phase of stroke. EEG signs of diaschisis may anticipate a poor recovery of alpha activity and clinical status in the post-stroke period.

Relation of laboratory and clinical variables to the grade of carotid atherosclerosis

BACKGROUND AND PURPOSE

To clarify diagnostic entities in ischemic stroke we analyzed the relation between the severity of carotid atherosclerosis, coagulation parameters, lipoproteins, neurological status, and risk factors in 232 patients.

METHODS

Duplex ultrasonography, computed tomography scan, and laboratory investigations were performed between the third and tenth days after stroke. Based on carotid ultrasound scores, we categorized the patients into four groups (A, B, C, and D) according to severity of atherosclerosis. Corresponding laboratory variables and clinical data were statistically analyzed.

RESULTS

Ultrasound scores were significantly (P < .05) higher in the male (n = 126) versus female (n = 106) patients. The hematocrit was significantly higher and thrombin time was significantly shorter in the male group compared with the female group. Severe atherosclerosis (group C) and occlusion (group D) of the internal carotid artery was associated with smoking (C = 56%; D = 78%), hypertension (C = 43%; D = 35%), claudication (C = 13%; D = 5%), and antecedent myocardial infarction (C = 9%; D = 13%). There was no statistical correlation between ultrasound scores and the patients' neurological condition. Cholesterol and plasma fibrinogen levels were significantly higher and high-density lipoprotein cholesterol was significantly lower in groups with severe atherosclerosis compared with patients with slight intimal damage. The presence of multiple plaques or thrombosis of the internal carotid artery was concordant with the prevalence of single cerebral infarcts.

CONCLUSIONS

Severity of carotid atherosclerosis corresponded well with the following factors: age, smoking, and low concentration of high-density lipoprotein cholesterol. Elevation of plasma fibrinogen combined with a loss of high-density lipoprotein cholesterol is strongly associated with severe atherosclerosis and results in brain infarction.

Spectral EEG parameters in patients with tick-borne encephalitis: a follow-up study

Follow-up of spectral EEG parameters were reported for five patients with serologically verified tick-borne encephalitis. Comparisons were made for clinical data and findings of EEG analysis (power probability mapping, peak-power frequencies, and alpha/theta power ratios) were compared. A prominent feature of the EEG abnormality was the marked attenuation of background alpha activity. The peak-power frequency and absolute power analysis of three patients showed significant hemispheric asymmetry in the alpha and theta bands respectively. EEG topograms demonstrated persistent theta power fields in one patient. Alpha/theta power ratio was a reliable indicator for the recovery of rhythmic EEG activity during the convalescence. Reorganization of alpha activity appeared to lag behind the clinical improvement, its course was different from patient to patient. Because of the discrepancy of bioelectric and clinical findings the authors recommend long-term EEG monitoring in patients with tick-borne encephalitis.