Brain single photon emission computed tomographic evaluation of patients with childhood absence epilepsy

Preictal neuronal and vascular activity precedes the onset of childhood absence seizure: direct current potential shifts and their correlation with hemodynamic activity

SIGNIFICANCE AIMS

The neurovascular mechanisms underlying the initiation of absence seizures and their dynamics are still not well understood. The objective of this study was to better noninvasively characterize the dynamics of the neuronal and vascular network at the transition from the interictal state to the ictal state of absence seizures and back to the interictal state using a combined electroencephalography (EEG), functional near-infrared spectroscopy (fNIRS), and diffuse correlation spectroscopy (DCS) approach. The second objective was to develop hypotheses about the neuronal and vascular mechanisms that propel the networks to the 3-Hz spikes and wave discharges (SWDs) observed during absence seizures.

APPROACHES

We evaluated the simultaneous changes in electrical (neuronal) and optical dynamics [hemodynamic, with changes in (Hb) and cerebral blood flow] of 8 pediatric patients experiencing 25 typical childhood absence seizures during the transition from the interictal state to the absence seizure by simultaneously performing EEG, fNIRS, and DCS.

RESULTS

Starting from ∼ 20    s before the onset of the SWD, we observed a transient direct current potential shift that correlated with alterations in functional fNIRS and DCS measurements of the cerebral hemodynamics detecting the preictal changes.

DISCUSSION

Our noninvasive multimodal approach highlights the dynamic interactions between the neuronal and vascular compartments that take place in the neuronal network near the time of the onset of absence seizures in a very specific cerebral hemodynamic environment. These noninvasive approaches contribute to a better understanding of the electrical hemodynamic environment prior to seizure onset. Whether this may ultimately be relevant for diagnostic and therapeutic approaches requires further evaluation.

Nuclear Medicine Imaging in Pediatric Neurology

Nuclear medicine imaging can provide important complementary information in the management of pediatric patients with neurological diseases. Pre-surgical localization of the epileptogenic focus in medically refractory epilepsy patients is the most common indication for nuclear medicine imaging in pediatric neurology. In patients with temporal lobe epilepsy, nuclear medicine imaging is particularly useful when magnetic resonance imaging findings are normal or its findings are discordant with electroencephalogram findings. In pediatric patients with brain tumors, nuclear medicine imaging can be clinically helpful in the diagnosis, directing biopsy, planning therapy, differentiating tumor recurrence from post-treatment sequelae, and assessment of response to therapy. Among other neurological diseases in which nuclear medicine has proved to be useful are patients with head trauma, inflammatory-infectious diseases and hypoxic-ischemic encephalopathy.

Patterns of postictal cerebral perfusion in idiopathic generalized epilepsy: a multi-delay multi-parametric arterial spin labelling perfusion MRI study

The cerebral haemodynamic status of idiopathic generalized epilepsy (IGE) is a very complicated process. Little attention has been paid to cerebral blood flow (CBF) alterations in IGE detected by arterial spin labelling (ASL) perfusion magnetic resonance imaging (MRI). However, the selection of an optimal delay time is difficult for single-delay ASL. Multi-delay multi-parametric ASL perfusion MRI overcomes the limitations of single-delay ASL. We applied multi-delay multi-parametric ASL perfusion MRI to investigate the patterns of postictal cerebral perfusion in IGE patients with absence seizures. A total of 21 IGE patients with absence seizures and 24 healthy control subjects were enrolled. IGE patients exhibited prolonged arterial transit time (ATT) in the left superior temporal gyrus. The mean CBF of IGE patients was significantly increased in the left middle temporal gyrus, left parahippocampal gyrus and left fusiform gyrus. Prolonged ATT in the left superior temporal gyrus was negatively correlated with the age at onset in IGE patients. This study demonstrated that cortical dysfunction in the temporal lobe and fusiform gyrus may be related to epileptic activity in IGE patients with absence seizures. This information can play an important role in elucidating the pathophysiological mechanism of IGE from a cerebral haemodynamic perspective.

Tall gastrodis tuber combined with antiepileptic drugs repairs abnormal perfusion foci in focal epilepsy

One hundred patients with focal epilepsy were recruited for the present study and their seizures controlled with antiepileptic drugs. The patients then orally received a capsule of tall gastrodis tuber powder, a traditional Chinese drug, and underwent single photon emission computed tomography, long-term electroencephalogram, and CT/MRI. Blood drug levels were monitored throughout the study. Before treatment with tall gastrodis tuber, 35 of the 100 cases had abnormal CT/MRI scans; 79 cases had abnormal single photon emission computed tomography images; 86 cases had abnormal electroencephalogram; and a total of 146 abnormal perfusion foci were observed across the 100 subjects. After treatment, the number of patients with normal single photon emission computed tomography images increased by 12; normal electroencephalogram was observed in an additional 27 cases and the number of patients with epileptiform discharge decreased by 29 (34% of 86); the total number of abnormal perfusion foci decreased by 52 (36%) and changes in abnormal foci were visible in 65 patients. These changes indicate that the administration of tall gastrodis tuber in combination with antiepileptic drugs repairs abnormal perfusion foci in patients with focal epilepsy. Our results demonstrate that traditional Chinese drugs can repair abnormal perfusion foci and, as such, are a promising new pathway in the treatment of focal epilepsy.

Spectral power of 1-4 Hz frequency in the ictal phase of childhood absence epilepsy

The ictal EEG of childhood absence epilepsy is characterized by short duration bursts of generalized 3-Hz spike-wave discharges, which are widely considered to be symmetric and synchronous. The purpose of this study was to investigate this assertion by studying the topography and spectral power of these discharges. The sample consisted of 7 subjects aged 4 to 9 years who had been diagnosed with childhood absence epilepsy by video-EEG monitoring. Computational EEG analysis was performed focusing on the slow-wave (1-4 Hz) component of the ictal EEG. We compared the spectral power of this slow-wave component in three brain regions (frontocentral, centroparietal, and parieto-occipital) and contrasted the spectral power of left and right fronto-central areas. Although five of seven subjects showed marked frontal dominance of spectral slow-wave power, two subjects had a different pattern characterized by a more diffuse anterior-posterior distribution. Three patterns of spectral power laterality in the frontocentral region were observed: left dominant, equivocal, and right dominant. Each subject demonstrated the same pattern throughout his or her seizures (three to five ictal events) during video-EEG monitoring. These findings suggest that computational EEG may be useful for discerning subtle differences in the distribution of ictal waveforms. These observations also bolster the new ILAE definition of generalized seizures, suggesting that some so-called generalized seizures are not truly generalized but that they instead rapidly engage bilaterally distributed networks with clear asymmetries of scalp electrical discharges.

Space-time network connectivity and cortical activations preceding spike wave discharges in human absence epilepsy: a MEG study

To describe the spatial and temporal profiles of connectivity networks and sources preceding generalized spike-and-wave discharges (SWDs) in human absence epilepsy. Nonlinear associations of MEG signals and cluster indices obtained within the framework of graph theory were determined, while source localization in the frequency domain was performed in the low frequency bands with dynamic imaging of coherent sources. The results were projected on a three-dimensional surface rendering of the brain using a semi-realistic head model and MRI images obtained for each of the five patients studied. An increase in clustering and a decrease in path length preceding SWD onset and a rhythmic pattern of increasing and decreasing connectivity were seen during SWDs. Beamforming showed a consistent appearance of a low frequency frontal cortical source prior to the first generalized spikes. This source was preceded by a low frequency occipital source. The changes in the connectivity networks with the onset of SWDs suggest a pathologically predisposed state towards synchronous seizure networks with increasing connectivity from interictal to preictal and ictal state, while the occipital and frontal low frequency early preictal sources demonstrate that SWDs are not suddenly arising but gradually build up in a dynamic network.

Impaired attention and network connectivity in childhood absence epilepsy

Patients with childhood absence epilepsy (CAE) often demonstrate impaired interictal attention, even with control of their seizures. No previous study has investigated the brain networks involved in this impairment. We used the continuous performance task (CPT) of attentional vigilance and the repetitive tapping task (RTT), a control motor task, to examine interictal attention in 26 children with CAE and 22 matched healthy controls. Each subject underwent simultaneous 3T functional magnetic resonance imaging-electroencephalography (fMRI-EEG) and CPT/RTT testing. Areas of activation on fMRI during the CPT task were correlated with behavioral performance and used as seed regions for resting functional connectivity analysis. All behavioral measures reflecting inattention were significantly higher in patients. Correlation analysis revealed that impairment on all measures of inattention on the CPT task was associated with decreased medial frontal cortex (MFC) activation during CPT. In addition, analysis of resting functional connectivity revealed an overall decrease within an 'attention network' in patients relative to controls. Patients demonstrated significantly impaired connectivity between the right anterior insula/frontal operculum (In/FO) and MFC relative to controls. Our results suggest that there is impaired function in an attention network comprising anterior In/FO and MFC in patients with CAE. These findings provide an anatomical and functional basis for impaired interictal attention in CAE, which may allow the development of improved treatments targeted at these networks.

Association between attention-deficit/hyperactivity disorder and epilepsy in pediatric populations

There is a bidirectional relationship between attention-deficit/hyperactivity disorder (ADHD) and epilepsy. ADHD increases seizure risk, while patients with epilepsy have an increased prevalence of ADHD. The reasons explaining this association are not fully understood. Proposed mechanisms include effects of antiepileptic medications, underlying neurodevelopmental vulnerability, the effects of chronic seizures and subclinical epileptiform activity on cognitive functions and adrenergic dysfunction. There may also be a common genetic defect underlying both disorders in some families. Antiepileptics associated with ADHD-like side effects include phenobarbital, gabapentin, vigabatrin and topiramate. Methylphenidate has been studied in a double-blind setting against placebo for treatment of ADHD comorbid with epilepsy, and has a good risk-benefit ratio. Amphetamine, atomoxetine, clonidine and guanfacine only have case series to support their use and bupropion should be avoided.

Psychiatric disorders and behavioral characteristics of pediatric patients with both epilepsy and attention-deficit hyperactivity disorder

OBJECTIVE

Attention-deficit hyperactivity disorder (ADHD) coexisting with epilepsy is poorly understood; thus, we compared the clinical correlates and psychiatric comorbid conditions of 36 children with epilepsy and ADHD aged 6 to 17 years enrolled in an ADHD treatment trial, with those reported in the literature on children with ADHD without epilepsy.

METHODS

Measures included the Kiddie Schedule for Affective Disorders and Schizophrenia for School-Age Children (KSADS), the Wechsler Abbreviated Scale of Intelligence (WASI), and the Scales for Independent Behavior-Revised (SIB-R).

RESULTS

Mean IQ was 86+/-19, and SIB-R Standard Score was 72+/-26. The ADHD-Combined subtype, composed of both inattentive and hyperactive symptoms, was most frequent (58%). Sixty-one percent exhibited a comorbid disorder, including anxiety disorders (36%) and oppositional defiant disorder (31%).

CONCLUSIONS

Comorbidity in ADHD with epilepsy is similar to that in ADHD without epilepsy reported in the literature. These preliminary data argue that the pathophysiology of ADHD has common components in both populations.

Absence epilepsy associated with moyamoya disease. Case report

The authors present the case of a 6-year-old girl with typical absence epilepsy induced by hyperventilation associated with moyamoya disease (MMD). A diffuse 3-Hz spike-and-wave complex induced by hyperventilation was apparent on an electroencephalogram, and her seizures were intractable to medication. Significant ischemia in the bilateral frontal lobes was present. The epilepsy disappeared after superficial temporal artery-middle cerebral artery anastomosis with encephalomyosynangiosis on both sides. In the treatment of children with intractable absence epilepsy, the possibility of underlying MMD and indications that revascularization surgery may be needed should be taken into consideration.

Hemodynamic and metabolic responses to activation, deactivation and epileptic discharges

To investigate the coupling between the hemodynamic and metabolic changes following functional brain activation as well as interictal epileptiform discharges (IEDs), blood oxygenation level dependent (BOLD), perfusion and oxygen consumption responses to a unilateral distal motor task and interictal epileptiform discharges (IEDs) were examined via continuous EEG-fMRI. Seven epilepsy patients performed a periodic (1 Hz) right-hand pinch grip using approximately 8% of their maximum voluntary contraction, a paradigm previously shown to produce contralateral MI neuronal excitation and ipsilateral MI neuronal inhibition. A multi-slice interleaved pulsed arterial spin labeling and T(2)*-weighted gradient echo sequence was employed to quantify cerebral blood flow (CBF) and BOLD changes. EEG was recorded throughout the imaging session and reviewed to identify the IEDs. During the motor task, BOLD, CBF and cerebral metabolic rate of oxygen consumption (CMR(O(2))) signals increased in the contra- and decreased in the ipsilateral primary motor cortex. The relative changes in CMR(O(2)) and CBF were linearly related, with a slope of 0.46 +/- 0.05. The ratio of contra- to ipsilateral CBF changes was smaller in the present group of epilepsy patients than in the healthy subjects examined previously. IEDs produced both increases and decreases in BOLD and CBF signals. In the two case studies for which the estimation criteria were met, the coupling ratio between IED-induced CMR(O(2)) and CBF changes was estimated at 0.48 +/- 0.17. These findings provide evidence for a preserved coupling between hemodynamic and metabolic changes in response to both functional activation and, for the two case studies available, in response to interictal epileptiform activity.

99mTc-HMPAO single photon emission computed tomography (SPECT) in both asphyxiated and epileptic children with or without status epilepticus

In this study, technetium 99m hexamethylpropyleneamine oxime (99mTc-HMPAO) single photon emission computed tomography (SPECT) was performed on 18 asphyxiated and epileptic children who also had a status epilepticus episode, and the results were compared with those for 21 children without a status epilepticus episode. All patients underwent a detailed neurologic history, interictal electroencephalography, computed tomography, and/or magnetic resonance imaging. Visual evaluation of the SPECT study showed that 16 patients of group 1 had 56 hypoperfused regions in cerebral blood flow. However, in group 2, visual evaluation showed only six detectable hypoperfusion areas in five patients. When an asymmetric index value of 3 was considered as a cutoff point, 82 regions in group 1 and 57 regions in group 2 were above this value after the quantitative SPECT evaluation. The mean number of pathologic brain regions was found to be higher in group 1 (5.1 +/- 4.3) than in group 2 (2.7 +/- 2.4) (P = .014). The localization of hypoperfused regions that were observed in temporal and frontal regions was generally similar in both groups. In conclusion, the functional activities of the brain vary in both asphyctic and epileptic children, with and without status epilepticus. These children might be candidates for refractory convulsive disease, and interictal SPECT can be a reliable method for the detection of brain lesions in these patients.