Correlation of interictal spike-wave with thalamic glucose metabolism in juvenile myoclonic epilepsy

[18F]FDG PET in conditions associated with hyperkinetic movement disorders and ataxia: a systematic review

PURPOSE

To give a comprehensive literature overview of alterations in regional cerebral glucose metabolism, measured using [18F]FDG PET, in conditions associated with hyperkinetic movement disorders and ataxia. In addition, correlations between glucose metabolism and clinical variables as well as the effect of treatment on glucose metabolism are discussed.

METHODS

A systematic literature search was performed according to PRISMA guidelines. Studies concerning tremors, tics, dystonia, ataxia, chorea, myoclonus, functional movement disorders, or mixed movement disorders due to autoimmune or metabolic aetiologies were eligible for inclusion. A PubMed search was performed up to November 2021.

RESULTS

Of 1240 studies retrieved in the original search, 104 articles were included. Most articles concerned patients with chorea (n = 27), followed by ataxia (n = 25), dystonia (n = 20), tremor (n = 8), metabolic disease (n = 7), myoclonus (n = 6), tics (n = 6), and autoimmune disorders (n = 5). No papers on functional movement disorders were included. Altered glucose metabolism was detected in various brain regions in all movement disorders, with dystonia-related hypermetabolism of the lentiform nuclei and both hyper- and hypometabolism of the cerebellum; pronounced cerebellar hypometabolism in ataxia; and striatal hypometabolism in chorea (dominated by Huntington disease). Correlations between clinical characteristics and glucose metabolism were often described. [18F]FDG PET-showed normalization of metabolic alterations after treatment in tremors, ataxia, and chorea.

CONCLUSION

In all conditions with hyperkinetic movement disorders, hypo- or hypermetabolism was found in multiple, partly overlapping brain regions, and clinical characteristics often correlated with glucose metabolism. For some movement disorders, [18F]FDG PET metabolic changes reflected the effect of treatment.

FDG-PET findings and alcohol-responsive myoclonus in a patient with Unverricht-Lundborg disease

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Alcohol ameliorated myoclonus in this patient with Unverricht-Lundborg disease.

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FDG-PET showed frontoparietal, posterior brainstem, and thalamic hypometabolism.

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FDG-PET thalamic hypometabolism was previously described in Lafora disease.

The aim of this report is to describe clinical, EEG, and neuroimaging findings in a patient with Unverricht-Lundborg disease (ULD), the most common form of progressive myoclonus epilepsy (PME). A 23-year-old male with genetically confirmed ULD had a phenotype consisting of myoclonus, generalized seizures, intellectual disability, ataxia, and dysarthria. Myoclonus and gait disturbance were strongly ameliorated by alcohol consumption. EEG revealed a posterior dominant rhythm with alpha variant, mild bilateral slowing, and anterior-predominant epileptiform abnormalities. Brain MRI showed mild cerebellar atrophy. FDG-PET revealed hypometabolism more prominent in the posterior brainstem, thalami, frontal and parietal lobes.

This report confirms that alcohol may ameliorate myoclonus in a subset of patients with PME, including genetically confirmed ULD. In addition, the presence of FDG-PET hypometabolism predominant in the frontoparietal region and thalami has not been previously described in ULD, yet is consistent with previous brain morphometry studies showing motor cortex and thalamic atrophy in ULD, and brings into question the possibility of a shared metabolic pattern with other PMEs, notably Lafora disease.

Probabilistic mapping of thalamic nuclei and thalamocortical functional connectivity in idiopathic generalised epilepsy

It is well established that abnormal thalamocortical systems play an important role in the generation and maintenance of primary generalised seizures. However, it is currently unknown which thalamic nuclei and how nuclear‐specific thalamocortical functional connectivity are differentially impacted in patients with medically refractory and non‐refractory idiopathic generalised epilepsy (IGE). In the present study, we performed structural and resting‐state functional magnetic resonance imaging (MRI) in patients with refractory and non‐refractory IGE, segmented the thalamus into constituent nuclear regions using a probabilistic MRI segmentation method and determined thalamocortical functional connectivity using seed‐to‐voxel connectivity analyses. We report significant volume reduction of the left and right anterior thalamic nuclei only in patients with refractory IGE. Compared to healthy controls, patients with refractory and non‐refractory IGE had significant alterations of functional connectivity between the centromedian nucleus and cortex, but only patients with refractory IGE had altered cortical connectivity with the ventral lateral nuclear group. Patients with refractory IGE had significantly increased functional connectivity between the left and right ventral lateral posterior nuclei and cortical regions compared to patients with non‐refractory IGE. Cortical effects were predominantly located in the frontal lobe. Atrophy of the anterior thalamic nuclei and resting‐state functional hyperconnectivity between ventral lateral nuclei and cerebral cortex may be imaging markers of pharmacoresistance in patients with IGE. These structural and functional abnormalities fit well with the known importance of thalamocortical systems in the generation and maintenance of primary generalised seizures, and the increasing recognition of the importance of limbic pathways in IGE.

A systematic review of resting-state and task-based fmri in juvenile myoclonic epilepsy

Functional neuroimaging modalities have enhanced our understanding of juvenile myoclonic epilepsy (JME) underlying neural mechanisms. Due to its non-invasive, sensitive and analytical nature, functional magnetic resonance imaging (fMRI) provides valuable insights into relevant functional brain networks and their segregation and integration properties. We systematically reviewed the contribution of resting-state and task-based fMRI to the current understanding of the pathophysiology and the patterns of seizure propagation in JME Altogether, despite some discrepancies, functional findings suggest that corticothalamo-striato-cerebellar network along with default-mode network and salience network are the most affected networks in patients with JME. However, further studies are required to investigate the association between JME's main deficiencies, e.g., motor and cognitive deficiencies and fMRI findings. Moreover, simultaneous electroencephalography-fMRI (EEG-fMRI) studies indicate that alterations of these networks play a role in seizure modulation but fall short of identifying a causal relationship between altered functional properties and seizure propagation. This review highlights the complex pathophysiology of JME, which necessitates the design of more personalized diagnostic and therapeutic strategies in this group.

FDG-PET assessment and metabolic patterns in Lafora disease

PURPOSE

To describe cerebral glucose metabolism pattern as assessed by ¹⁸F-fluorodeoxyglucose positron emission tomography (FDG-PET) in Lafora disease (LD), a rare, lethal form of progressive myoclonus epilepsy caused by biallelic mutations in EPM2A or NHLRC1.

METHODS

We retrospectively included patients with genetically confirmed LD who underwent FDG-PET scan referred to three Italian epilepsy centers. FDG-PET images were evaluated both visually and using SPM12 software. Subgroup analysis was performed on the basis of genetic and clinical features employing SPM. Moreover, we performed a systematic literature review of LD cases that underwent FDG-PET assessment.

RESULTS

Eight Italian patients (3M/5F, 3 EPM2A/5 NHLRC1) underwent FDG-PET examination after a mean of 6 years from disease onset (range 1-12 years). All patients showed bilateral hypometabolic areas, more diffuse and pronounced in advanced disease stages. Most frequently, the hypometabolic regions were the temporal (8/8), parietal (7/8), and frontal lobes (7/8), as well as the thalamus (6/8). In three cases, the FDG-PET repeated after a mean of 17 months (range 7-36 months) showed a metabolic worsening compared with the baseline examination. The SPM subgroup analysis found no significant differences based on genetics, whereas it showed a more significant temporoparietal hypometabolism in patients with visual symptoms compared with those without. In nine additional cases identified from eight publications, FDG-PET showed heterogeneous findings, ranging from diffusely decreased cerebral glucose metabolism to unremarkable examinations in two cases.

CONCLUSIONS

FDG-PET seems highly sensitive to evaluate LD at any stage and may correlate with disease progression. Areas of decreased glucose metabolism in LD are extensive, often involving multiple cortical and subcortical regions, with thalamus, temporal, frontal, and parietal lobes being the most severely affected. Prospective longitudinal collaborative studies are needed to validate our findings.

Subtle Brain Developmental Abnormalities in the Pathogenesis of Juvenile Myoclonic Epilepsy

Juvenile myoclonic epilepsy (JME), a lifelong disorder that starts during adolescence, is the most common of genetic generalized epilepsy syndromes. JME is characterized by awakening myoclonic jerks and myoclonic-tonic-clonic (m-t-c) grand mal convulsions. Unfortunately, one third of JME patients have drug refractory m-t-c convulsions and these recur in 70-80% who attempt to stop antiepileptic drugs (AEDs). Behavioral studies documented impulsivity, but also impairment of executive functions relying on organization and feedback, which points to prefrontal lobe dysfunction. Quantitative voxel-based morphometry (VBM) revealed abnormalities of gray matter (GM) volumes in cortical (frontal and parietal) and subcortical structures (thalamus, putamen, and hippocampus). Proton magnetic resonance spectroscopy (MRS) found evidence of dysfunction of thalamic neurons. White matter (WM) integrity was disrupted in corpus callosum and frontal WM tracts. Magnetic resonance imaging (MRI) further unveiled anomalies in both GM and WM structures that were already present at the time of seizure onset. Aberrant growth trajectories of brain development occurred during the first 2 years of JME diagnosis. Because of genetic origin, disease causing variants were sought, first by positional cloning, and most recently, by next generation sequencing. To date, only six genes harboring pathogenic variants (GABRA1, GABRD, EFHC1, BRD2, CASR, and ICK) with Mendelian and complex inheritance and covering a limited proportion of the world population, are considered as major susceptibility alleles for JME. Evidence on the cellular role, developmental and cell-type expression profiles of these six diverse JME genes, point to their pathogenic variants driving the first steps of brain development when cell division, expansion, axial, and tangential migration of progenitor cells (including interneuron cortical progenitors) sculpture subtle alterations in brain networks and microcircuits during development. These alterations may explain "microdysgenesis" neuropathology, impulsivity, executive dysfunctions, EEG polyspike waves, and awakening m-t-c convulsions observed in JME patients.

Grey and White Matter Alterations in Juvenile Myoclonic Epilepsy: A Comprehensive Review

Juvenile myoclonic epilepsy (JME) has been classified as a syndrome of idiopathic generalized epilepsy and is characterized by a strong genetic basis, age-specific onset of seizures, specific types of seizures, generalized spike-wave discharges on electroencephalography, and a lack of focal abnormality on magnetic resonance imaging (MRI). Recently, a wide range of advanced neuroimaging techniques have been utilized to elucidate the neuroanatomical substrates and pathophysiological mechanisms underlying JME. Specifically, a number of quantitative MRI studies have reported focal or regional abnormalities of the subcortical and cortical grey matter, particularly the thalamus and frontal cortex, in JME patients. In addition, diffusion tensor imaging studies have pointed to disrupted microstructural integrity of the corpus callosum and multiple frontal white matter tracts as well as thalamofrontal dysconnectivity in JME patients. Converging evidence from neuroimaging studies strongly suggests that JME is a predominantly thalamofrontal network epilepsy, challenging the traditional concept of JME as a generalized epilepsy. There is also limited evidence indicating extrafrontal and extrathalamic involvement in JME. This systematic review outlines the main findings from currently available MRI studies focusing on grey and white matter alterations, and discusses their contributions to the etiology and pathophysiology of JME. The clinical utility, advantages, and drawbacks of each imaging modality are briefly described as well.

Altered thalamocortical functional connectivity in idiopathic generalized epilepsy

OBJECTIVE

Aberrant thalamocortical network has been hypothesized to play a crucial role in the fundamental pathogenesis underlying idiopathic generalized epilepsy (IGE). We aimed to investigate alterations of thalamocortical functional network in patients with IGE using thalamic seed-based functional connectivity (FC) analysis, and their relationships with frontal cognitive functions and clinical characteristics.

METHODS

Forty-nine IGE patients (31 with juvenile myoclonic epilepsy, 17 with IGE with generalized tonic-clonic seizures only, one with juvenile absence epilepsy) and 42 control subjects were prospectively recruited. Voxel-based morphometry (VBM) was first performed to detect thalamic region of gray matter (GM) reduction in patients compared to controls. Between-group comparison of thalamocortical FC was then carried out using resting-state functional magnetic resonance imaging (MRI) analysis seeding at thalamic region of volume difference. In addition, thalamocortical FC was correlated with frontal cognitive performance and clinical variables.

RESULTS

Neuropsychological assessment revealed that patients with IGE had poorer performance than controls on most of the frontal cognitive functions. VBM detected a reduction in GM in the anteromedial thalamus in patients relative to controls. FC analysis seeding at the anteromedial thalamus revealed a reduction of thalamocortical FC in the bilateral medial prefrontal cortex and precuneus/posterior cingulate cortex in patients with IGE compared to controls. Thalamocortical FC strength of bilateral medial prefrontal cortex correlated negatively with disease duration, but did not correlate with seizure frequency or frontal cognitive functions in patients with IGE.

SIGNIFICANCE

Our results indicate that IGE is associated with decreased thalamocortical FC between anteromedial thalamus and medial prefrontal cortex and precuneus/posterior cingulate cortex. Our finding of greater reduction of medial prefrontal FC in relation to increasing disease duration suggests that thalamoprefrontal network abnormality, the proposed pathophysiologic mechanism underlying IGE, may be the consequence of the long-standing burden of the disease.

Evaluation of Oral Glucose Tolerance Test in Children With Epilepsy

Glucose metabolism of children with drug-resistant epilepsy, controlled by antiepileptic drugs epilepsy, and first-time nonfebrile seizures was studied through the performance of an oral glucose tolerance test and through insulin, C-peptide, and glycosylated hemoglobin measurements. In the refractory epilepsy group, there were more abnormal oral glucose tolerance test results (62.07%) in comparison to the controlled epilepsy group (25%) and the group of first-time seizures (21.21%). There was a significant difference between the group of refractory epilepsy and every other group concerning the abnormality of the oral glucose tolerance test (P < .05). The mean values of insulin, HbA_1c, and C-peptide levels were normal for all groups. The results of the present study suggest that there is a distinction of refractory epilepsies from the drug-controlled ones and the first-induced seizures relating to their metabolic profile, regardless of the type of seizures.

Volumetric and shape analysis of thalamus in idiopathic generalized epilepsy

Previous studies using voxel-based morphometry (VBM) provided emerging evidence of structural changes of the thalamus in idiopathic generalized epilepsy (IGE). However, the location of atrophy within the thalamus in IGE has been somewhat inconsistent across the studies. We, therefore, examined the location of thalamic atrophy and its relationship with clinical factors in IGE, using multiple analytic methods. Fifty IGE patients and 50 controls were scanned on a 3T MRI. Structural evaluation consisted of automated thalamic volumetry, VBM, and thalamic shape analysis. Group comparison between patients and controls was made to assess thalamic atrophy. Within-group correlations between thalamic atrophy and clinical variables were further performed in patients. Both thalamic volumes were reduced in IGE patients, and were negatively correlated with disease duration. The VBM showed a significant regional grey matter volume reduction in bilateral anterior-medial thalami in patients compared to controls. Voxel values extracted from the anterior-medial thalamic cluster were negatively correlated with disease duration. Vertex-based shape analysis revealed regional atrophy on the anterior-medial and posterior-dorsal aspects of thalamus bilaterally in patients compared to controls. Correlation analysis showed that anterior-medial and posterior-dorsal aspects of bilateral thalami were negatively correlated with disease duration. Combining multiple analyses, we demonstrated regional atrophy of anterior-medial and posterior-dorsal thalamus in patients with IGE. Given the anatomical connection of these thalamic regions with the frontal lobe, our finding of greater thalamic atrophy in relation to increasing disease duration further supports the pathophysiological concept of thalamo-frontal network abnormality underlying IGE, and may implicate frontal cognitive dysfunctions and disease progression.

Microstructural white matter abnormality and frontal cognitive dysfunctions in juvenile myoclonic epilepsy

PURPOSE

Previous neuroimaging studies provide growing evidence that patients with juvenile myoclonic epilepsy (JME) have both structural and functional abnormalities of the thalamus and frontal lobe gray matter. However, limited data are available regarding the issue of white matter (WM) involvement, making the microstructural WM changes in JME largely unknown. In the present study we investigated changes of WM integrity in patients with JME, and their relationships with cognitive functions and epilepsy-specific clinical factors.

METHODS

We performed diffusion tensor imaging (DTI) and neuropsychological assessment in 25 patients with JME and 30 control subjects matched for age, gender, and education level. Between-group comparisons of fractional anisotropy (FA) and mean diffusivity (MD) were carried out in a whole-brain voxel-wise manner by using tract-based spatial statistics (TBSS). In addition, both FA and MD were correlated with cognitive performance and epilepsy-specific clinical variables to investigate the influence of these clinical and cognitive factors on WM integrity changes.

KEY FINDINGS

Neuropsychological evaluation revealed that patients with JME had poorer performance than control subjects on most of the frontal function tests. TBSS demonstrated that, compared to controls, patients with JME had significantly reduced FA and increased MD in bilateral anterior and superior corona radiata, genu and body of corpus callosum, and multiple frontal WM tracts. Disease severity, as assessed by the number of generalized tonic-clonic seizures in given years, was negatively correlated with FA and positively correlated with MD extracted from regions of significant differences between patients and controls in TBSS.

SIGNIFICANCE

Our findings of widespread disturbance of microstructural WM integrity in the frontal lobe and corpus callosum that interconnects frontal cortices could further support the pathophysiologic hypothesis of thalamofrontal network abnormality in JME. These WM abnormalities may implicate frontal cognitive dysfunctions and disease progression in JME.

Structural abnormalities of the thalamus in juvenile myoclonic epilepsy

Studies have suggested that the thalamus is a key structure in the pathophysiology of juvenile myoclonic epilepsy. The objective of the present investigation was to examine the thalami of patients with juvenile myoclonic epilepsy using a combination of multiple structural neuroimaging modalities. The association between these techniques may reveal the mechanisms underlying juvenile myoclonic epilepsy and help to identify the neuroanatomical structures involved. Twenty-one patients with juvenile myoclonic epilepsy (13 women, mean age=30±9 years) and a control group of 20 healthy individuals (10 women, mean age=31±8 years) underwent MRI in a 2-T scanner. The volumetric three-dimensional sequence was used for structural investigation. Evaluation of the thalamus comprised voxel-based morphometry, automatic volumetry, and shape analysis. Comparisons were performed between patient and control groups. Voxel-based morphometry analysis identified areas of atrophy located in the anterior portion of the thalamus. Post hoc analysis of automatic volumetry did not reveal significant differences between the groups. Shape analysis disclosed differences between patients and controls in the anterior and inferior portions of the right thalamus and in the anterior portion of the left thalamus. The present investigation confirms that thalami of patients with juvenile myoclonic epilepsy are structurally abnormal with impairments located mainly in the anterior and inferior sections.

Gray-matter volume reduction in the thalamus and frontal lobe in epileptic patients with generalized tonic-clonic seizures

BACKGROUND AND PURPOSE

Generalized tonic-clonic seizures (GTCS) comprise a common subsyndrome of idiopathic generalized epilepsy (IGE). Previous studies found that patients with GTCS had structural abnormalities in a few specific brain regions. However, the underlying clinical cause leading to these abnormalities remains unclear. The present study aimed to explore the relationship between changes in gray-matter (GM) volume and duration of epilepsy, based on GM volume differences observed between GTCS patients and healthy controls.

PATIENTS AND METHODS

Voxel-based morphometry (VBM) analysis with DARTEL (diffeomorphic anatomical registration through exponential Lie algebra) was used to investigate GM volume differences in 31 GTCS patients compared with 37 age- and gender-matched healthy controls. Voxel-based correlation analysis was used to explore the relationship between GM volume and duration of epilepsy in GTCS patients.

RESULTS

Compared with healthy controls, GTCS patients showed significant decreases in GM volume in the bilateral thalami, frontal lobe, insula and cerebellum. In addition, GM volume in the bilateral thalami and left medial frontal gyrus had a negative correlation with duration of epilepsy.

CONCLUSION

GM volume changes in the thalamus and frontal lobe were associated with progressive epileptic seizures. The results indicate the presence of an abnormal thalamocortical network, which may reflect an underlying pathophysiological mechanism of GTCS.

Is epilepsy a preventable disorder? New evidence from animal models

Epilepsy accounts for 0.5% of the global burden of disease, and primary prevention of epilepsy represents one of the three 2007 NINDS Epilepsy Research Benchmarks. In the past decade, efforts to understand and intervene in the process of epileptogenesis have yielded fruitful preventative strategies in animal models.This article reviews the current understanding of epileptogenesis, introduces the concept of a "critical period" for epileptogenesis, and examines strategies for epilepsy prevention in animal models of both acquired and genetic epilepsies. We discuss specific animal models, which may yield important insights into epilepsy prevention including kindling, poststatus epilepticus, prolonged febrile seizures, traumatic brain injury, hypoxia, the tuberous sclerosis mouse model, and the WAG/Rij rat model of primary generalized epilepsy. Hopefully, further investigation of antiepileptogenesis in animal models will soon enable human therapeutic trials to be initiated, leading to long-term epilepsy prevention and improved patient quality of life.

Regional grey matter abnormalities in juvenile myoclonic epilepsy: A voxel-based morphometry study

Visual assessment of structural MRI is, by definition, normal in patients with juvenile myoclonic epilepsy (JME), a major subsyndrome of idiopathic generalized epilepsy (IGE). However, recent quantitative MRI studies have shown structural abnormalities in cortical and thalamic grey matter (GM) in JME. Voxel-based morphometry (VBM) is a fully automated, unbiased, operator-independent MRI analysis technique that detects regionally specific differences in brain tissue composition on a voxel-wise comparison between groups of subjects. Using VBM, we examined structural differences in cortical and subcortical GM volume (GMV) between 25 JME patients (15 women, mean age=22.7+/-5.1 years) and age- and sex-matched 44 control subjects (27 women, mean age=23.1+/-4.3 years). We also performed a correlation analysis to delineate a possible relationship between the GMV increases or reductions and the increasing duration of epilepsy. Group comparison showed GMV increases in the superior mesiofrontal region bilaterally and GMV reductions in the thalamus bilaterally in JME patients (P<0.05, corrected for multiple comparisons using false discovery rate). Correlation analysis revealed that bilateral thalamic GMV had negative correlations with the duration of epilepsy (P<0.05, corrected for multiple comparisons after small volume corrections; P<0.05, Pearson correlation test). Our findings of GMV increases in the superior mesiofrontal regions and progressive thalamic atrophy could further support the pathophysiological concept of the functional abnormalities in thalamocortical circuit in JME.

Lack of differences of motorcortical excitability in the morning as compared to the evening in juvenile myoclonic epilepsy—A study using transcranial magnetic stimulation

We used transcranial magnetic stimulation (TMS) in patients with juvenile myoclonic epilepsy (JME) and healthy controls to characterise motorcortical excitability in the morning as compared to the evening. Intra- and interindividual comparisons in JME-patients and controls showed no significant differences of any TMS parameter. The expected rise of the resting motor thresholds (RMT) in JME-patients taking anticonvulsants could not be detected which may indicate a decreased RMT in JME-patients.

CBF changes in drug naive juvenile myoclonic epilepsy patients

PURPOSE

The role of thalamus and brainstem in generalized epilepsy has been suggested in previous studies. The aim of the present study was to assess regional cerebral blood flow (rCBF) abnormality in juvenile myoclonic epilepsy (JME) patients.

METHODS

(99m)Tc-ethylcysteinate dimer brain single photon emission computed tomography (SPECT) was performed in 19 drug naive JME patients and 25 normal controls with the similar age and gender distribution. Differences of rCBF between a JME group and a normal control group were examined by the statistical parametric mapping of brain SPECT images using independent t test. The regression analyses in SPM were also performed between rCBF and the age of seizure onset or the disease duration in JME group.

RESULTS

Compared to normal controls, the JME group showed a significant rCBF reduction in bilateral thalami, red nucleus, midbrain, pons, left hippocampus, and in the cerebelli (FDR corrected p < 0.01) whereas rCBF increase in the left superior frontal gyrus (uncorrected p < 0.001 but FDR corrected p > 0.05). Disease duration was negatively correlated with rCBF in bilateral frontal cortices, caudate nuclei, brainstem and cerebellar tonsils.

CONCLUSIONS

Our results suggest that abnormal neural networks in the thalamus, hippocampus, brainstem and cerebellum are associated with JME.