Effect of lamotrigine on cerebral blood flow in patients with idiopathic generalised epilepsy

Utility of CT perfusion in seizures and rhythmic and periodic patterns

OBJECTIVE

CT hyper-perfusion has been reported in non-convulsive status epilepticus (NCSE), while its occurrence and relevance after single seizures or with rhythmic and periodic patterns (RPPs) that lie along the ictal-interictal continuum (IIC), remain unclear. The goal of the study is to assess the role of CT perfusion (CTP) in diagnosing patients with clinical seizures, subclinical seizures, or RPPs that lie along the IIC, to help in the clinical assessment of these entities.

METHODS

We retrospectively reviewed inpatients who underwent a CTP and an EEG within 6 h of each other. CTP and EEGs were blindly reviewed independent of electronic medical records.

RESULTS

Out of 103 patients, 15 patients (15 %) demonstrated hyper-perfusion, 40 patients (39 %) had hypo-perfusion, while 48 patients (47 %) had normal CTP. Patients with focal CTP hyperperfusion were more likely to have clinical seizures, electrographic seizures, and/or lateralized rhythmic periodic patterns (RPPs) compared to those without CTP hyperperfusion. Focal CTP hyper-perfusion had 34 % sensitivity and 96 % specificity for identifying patients with clinical seizures, and a 40 % sensitivity and 92 % specificity for identifying patients with electrographic seizures or lateralized RPP. Although the numbers were small, none of the patients with generalized periodic discharges or generalized rhythmic delta activity had CTP hyper-perfusion.

CONCLUSIONS

Focal CTP hyper-perfusion has low sensitivity but high specificity for identifying patients with seizures and lateralized RPPs, and may be considered in the clinical assessment of patients where the clinical information are unclear or insufficient.

SIGNIFICANCE

The presence of CTP hyper-perfusion should alert the physician to the possibility of an ictal related etiology accounting for the patient's symptoms.

Identifying and troubleshooting the pitfalls of ictal/interictal brain perfusion SPECT studies

Epilepsy is a prevalent condition, and surgical intervention can benefit patients with refractory seizures. Single photon emission computed tomography (SPECT) using 99mTc-HMPAO or 99mTc-ECD provides assessment of regional cerebral blood flow and is the primary non-invasive approach for imaging brain perfusion in ictal and interictal states. Ictal/interictal SPECT is valuable in localising epileptogenic foci, particularly when MRI and electroencephalography are negative. However, to obtain accurate images reflecting brain perfusion in both states, meticulous preparation of the patient, timely radiotracer injection and close coordination between neurology and nuclear medicine teams are essential. Tracers also have inherent limitations, and patients may present with coexisting brain pathologies for which coregistration of SPECT images with MRI is recommended to improve diagnostic accuracy. Inconclusive SPECT findings may require repeating the exam or considering additional investigations. A comprehensive approach, considering various factors, is crucial for accurate interpretation of SPECT studies in presurgical epilepsy evaluations. This article provides a summary of the organisation and key challenges involved in conducting ictal/interictal SPECT studies, covering the entire process from a patient's hospital arrival to the integration of results within their presurgical pathway and using our experience of 182 patients over 10 years.

Pharmacodynamic effect of gabapentin on central nervous system in patients with chronic low back pain: a [99mTc]Tc-ECD SPECT study

BACKGROUND

Gabapentin is an effective therapeutic alternative for chronic low back pain, indicated in several guidelines for treating neuropathic pain as first-line medication. This study aimed to describe the pharmacodynamics of gabapentin in the central nervous system of patients with chronic low back pain (CLBP) by using single-photon emission CT (SPECT) with [99mTc]Tc-ECD.

METHODS

We selected 13 patients with CLBP due to lumbar disc herniation. They underwent SPECT before and after using gabapentin, compared with a SPECT database of healthy volunteers. A second analysis compared regional cerebral blood flow (rCBF) changes between responders and non-responders to gabapentin and the healthy controls.

RESULTS

The mean age of patients was 41 years, and the mean pain intensity was 5.92 points, measured by the Numeric Rating Scale. After using gabapentin, SPECT showed an increase of rCBF in the bilateral anterior cingulate gyrus and a decrease of rCBF in periaqueductal gray matter. Non-responder patients with gabapentin showed a post-treatment decrease of rCBF in the paracentral lobule of the brain.

CONCLUSIONS

A lack of improvement in some patients with gabapentin may be associated with an activated affective circuit of pain, evidenced by the increase of rCBF of the anterior cingulate cortex. A maladaptive brain state in chronic pain can explain the decrease of rCBF in the default mode network structures. Gabapentin acts directly or indirectly on neurons of periaqueductal gray substance by increasing the pain threshold and decreasing the rCBF of this structure.

Midbrain structure volume, estimated myelin and functional connectivity in idiopathic generalised epilepsy

BACKGROUND

Structural and functional neuroimaging studies often overlook lower basal ganglia structures located in and adjacent to the midbrain due to poor contrast on clinically acquired T1-weighted scans. Here, we acquired T1-weighted, T2-weighted, and resting-state fMRI scans to investigate differences in volume, estimated myelin content and functional connectivity of the substantia nigra (SN), subthalamic nuclei (SubTN) and red nuclei (RN) of the midbrain in IGE.

METHODS

Thirty-three patients with IGE (23 refractory, 10 non-refractory) and 39 age and sex-matched healthy controls underwent MR imaging. Midbrain structures were automatically segmented from T2-weighted images and structural volumes were calculated. The estimated myelin content for each structure was determined using a T1-weighted/T2-weighted ratio method. Resting-state functional connectivity analysis of midbrain structures (seed-based) was performed using the CONN toolbox.

RESULTS

An increased volume of the right RN was found in IGE and structural volumes of the right SubTN differed between patients with non-refractory and refractory IGE. However, no volume findings survived corrections for multiple comparisons. No myelin alterations of midbrain structures were found for any subject groups. We found functional connectivity alterations including significantly decreased connectivity between the left SN and the thalamus and significantly increased connectivity between the right SubTN and the superior frontal gyrus in IGE.

CONCLUSIONS

We report volumetric and functional connectivity alterations of the midbrain in patients with IGE. We postulate that potential increases in structural volumes are due to increased iron deposition that impacts T2-weighted contrast. These findings are consistent with previous studies demonstrating pathophysiological abnormalities of the lower basal ganglia in animal models of generalised epilepsy.

The longitudinal evolution of cerebral blood flow in children with tuberous sclerosis assessed by arterial spin labeling magnetic resonance imaging may be related to cognitive performance

OBJECTIVE

To study longitudinal changes in tuber and whole-brain perfusion in children with tuberous sclerosis complex (TSC) using arterial spin labeling (ASL) perfusion MRI and correlate them with pathological EEG slow wave activity and neurodevelopmental outcomes.

METHODS

Retrospective longitudinal cohort study of 13 children with TSC, 3 to 6 serial ASL-MRI scans between 2 months and 7 years of age (53 scans in total), and an EEG examination performed within 2 months of the last MRI. Tuber cerebral blood flow (CBF) values were calculated in tuber segmentation masks, and tuber:cortical CBF ratios were used to study tuber perfusion. Logistic regression analysis was performed to identify which initial tuber characteristics (CBF value, volume, location) in the first MRI predicted tubers subsequently associated with EEG slow waves. Whole-brain and lobar CBF values were extracted for all patient scans and age-matched controls. CBF ratios were compared in patients and controls to study longitudinal changes in whole-brain CBF.

RESULTS

Perfusion was reduced in tubers associated with EEG slow waves compared with other tubers. Low tuber CBF values around 6 months of age and large tuber volumes were predictive of tubers subsequently associated with EEG slow waves. Patients with severe developmental delay had more severe whole-brain hypoperfusion than those with no/mild delay, which became apparent after 2 years of age and were not associated with a higher tuber load.

CONCLUSIONS

Dynamic changes in tuber and brain perfusion occur over time. Perfusion is significantly reduced in tubers associated with EEG slow waves. Whole-brain perfusion is significantly reduced in patients with severe delay.

KEY POINTS

• Tubers associated with EEG slow wave activity were significantly more hypoperfused than other tubers, especially after 1 year of age. • Larger and more hypoperfused tubers at 6 months of age were more likely to subsequently be associated with pathological EEG slow wave activity. • Patients with severe developmental delay had more extensive and severe global hypoperfusion than those without developmental delay.

Alterations of Cerebral Perfusion and Functional Connectivity in Children With Idiopathic Generalized Epilepsy

Background

Studies have demonstrated that adults with idiopathic generalized epilepsy (IGE) have functional abnormalities; however, the neuropathological pathogenesis differs between adults and children. This study aimed to explore alterations in the cerebral blood flow (CBF) and functional connectivity (FC) to comprehensively elucidate the neuropathological mechanisms of IGE in children.

Methods

We obtained arterial spin labeling (ASL) and resting state functional magnetic resonance imaging data of 28 children with IGE and 35 matched controls. We used ASL to determine differential CBF regions in children with IGE. A seed-based whole-brain FC analysis was performed for regions with significant CBF changes. The mean CBF and FC of brain areas with significant group differences was extracted, then its correlation with clinical variables in IGE group was analyzed by using Pearson correlation analysis.

Results

Compared to controls, children with IGE had CBF abnormalities that were mainly observed in the right middle temporal gyrus, right middle occipital gyrus (MOG), right superior frontal gyrus (SFG), left inferior frontal gyrus (IFG), and triangular part of the left IFG (IFGtriang). We observed that the FC between the left IFGtriang and calcarine fissure (CAL) and that between the right MOG and bilateral CAL were decreased in children with IGE. The CBF in the right SFG was correlated with the age at IGE onset. FC in the left IFGtriang and left CAL was correlated with the IGE duration.

Conclusion

This study found that CBF and FC were altered simultaneously in the left IFGtriang and right MOG of children with IGE. The combination of CBF and FC may provide additional information and insight regarding the pathophysiology of IGE from neuronal and vascular integration perspectives.

Children with epilepsy demonstrate macro- and microstructural changes in the thalamus, putamen, and amygdala

PURPOSE

Despite evidence for macrostructural alteration in epilepsy patients later in life, little is known about the underlying pathological or compensatory mechanisms at younger ages causing these alterations. The aim of this work was to investigate the impact of pediatric epilepsy on the central nervous system, including gray matter volume, cerebral blood flow, and water diffusion, compared with neurologically normal children.

METHODS

Inter-ictal magnetic resonance imaging data was obtained from 30 children with epilepsy ages 1-16 (73% F, 27% M). An atlas-based approach was used to determine values for volume, cerebral blood flow, and apparent diffusion coefficient in the cerebral cortex, hippocampus, thalamus, caudate, putamen, globus pallidus, amygdala, and nucleus accumbens. These values were then compared with previously published values from 100 neurologically normal children using a MANCOVA analysis.

RESULTS

Most brain volumes of children with epilepsy followed a pattern similar to typically developing children, except for significantly larger putamen and amygdala. Cerebral blood flow was also comparable between the groups, except for the putamen, which demonstrated decreased blood flow in children with epilepsy. Diffusion (apparent diffusion coefficient) showed a trend towards higher values in children with epilepsy, with significantly elevated diffusion within the thalamus in children with epilepsy compared with neurologically normal children.

CONCLUSION

Children with epilepsy show statistically significant differences in volume, diffusion, and cerebral blood flow within their thalamus, putamen, and amygdala, suggesting that epilepsy is associated with structural changes of the central nervous system influencing brain development and potentially leading to poorer neurocognitive outcomes.

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.

Effect of levetiracetam monotherapy on background EEG activity and cognition in drug-naïve epilepsy patients

OBJECTIVE

To investigate the cognitive effect of levetiracetam (LEV) monotherapy with quantitative electroencephalogram (EEG) analysis and neuropsychological (NP) tests.

METHODS

Twenty-two drug-naïve epilepsy patients were enrolled. EEG recordings were performed before and after LEV therapy. Relative power of discrete frequency bands was computed, as well as alpha peak frequency (APF) at occipital electrodes. Eighteen patients performed a battery of NP tests twice across LEV treatment.

RESULTS

LEV therapy decreased the power of delta (1-3 Hz, p<0.01) and theta (3-7 Hz, p<0.05) bands and increased that of alpha-2 (10-13 Hz, p<0.05) and beta-2 (19-24 Hz, p<0.05) bands. Region-specific spectral change was observed: delta power change was significant in fronto-polar region, theta in anterior region, alpha-2 in broad region, and beta-2 in left fronto-central region. APF change was not significant. Improvement in diverse NP tests requiring attention, working memory, language and executive function was observed. Change in theta, alpha-2, and beta-2 power was correlated with improvement in several NP tests.

CONCLUSIONS

Our data suggest LEV is associated with acceleration of background EEG frequencies and improved cognitive function. Change in frequency band power could predict improvement in several cognitive domains across LEV therapy.

SIGNIFICANCE

Combined study of quantitative EEG analysis and NP tests can be useful in identifying cognitive effect of antiepileptic drugs.

Brain SPECT Imaging in Complex Psychiatric Cases: An Evidence-Based, Underutilized Tool

Over the past 20 years brain Single Photon Emission Computed Tomography (SPECT) imaging has developed a substantial, evidence-based foundation and is now recommended by professional societies for numerous indications relevant to psychiatric practice. Unfortunately, SPECT in clinical practice is utilized by only a handful of clinicians. This article presents a rationale for a more widespread use of SPECT in clinical practice for complex cases, and includes seven clinical applications where it may help optimize patient care.

Frequency of and rationales for the combined use of electroconvulsive therapy and antiepileptic drugs in Austria and the literature

Our aim was to observe the frequency of combination therapy using antiepileptic drugs (AEDs) and electroconvulsive therapy (ECT) in Austria and the literature, and to provide rationales and recommendations based on clinical and molecular properties. The responsible ECT leaders of eight Austrian departments were contacted for information about combination therapy. A computerized PubMed database search was performed and supplemented by cross-referencing from papers, review articles and psychiatric manuals. The frequency of combination therapy in Austrian departments ranges between 0 and 85.7%. In 17 studies enrolling a total of 189 patients, 87 (46.0%) patients received combination therapy. Of these 87 patients, nine (10.3%) reported adverse effects. ECT and AEDs show overlapping clinical and molecular properties. Combination therapy is an observed reality and, according to the currently available literature, feasible. A comparison of clinical and molecular properties indicates possible augmentative effects, making combination therapy a promising alternative in treatment-resistant cases. But there is still a clear need for prospective case controlled data concerning side effects, safety profiles and effectiveness until it can be recommended.

Drug interactions at the blood-brain barrier: fact or fantasy?

There is considerable interest in the therapeutic and adverse outcomes of drug interactions at the blood-brain barrier (BBB) and the blood-cerebrospinal fluid barrier (BCSFB). These include altered efficacy of drugs used in the treatment of CNS disorders, such as AIDS dementia and malignant tumors, and enhanced neurotoxicity of drugs that normally penetrate poorly into the brain. BBB- and BCSFB-mediated interactions are possible because these interfaces are not only passive anatomical barriers, but are also dynamic in that they express a variety of influx and efflux transporters and drug metabolizing enzymes. Based on studies in rodents, it has been widely postulated that efflux transporters play an important role at the human BBB in terms of drug delivery. Furthermore, it is assumed that chemical inhibition of transporters or their genetic ablation in rodents is predictive of the magnitude of interaction to be expected at the human BBB. However, studies in humans challenge this well-established paradigm and claim that such drug interactions will be lesser in magnitude but yet may be clinically significant. This review focuses on current known mechanisms of drug interactions at the blood-brain and blood-CSF barriers and the potential impact of such interactions in humans. We also explore whether such drug interactions can be predicted from preclinical studies. Defining the mechanisms and the impact of drug-drug interactions at the BBB is important for improving efficacy of drugs used in the treatment of CNS disorders while minimizing their toxicity as well as minimizing neurotoxicity of non-CNS drugs.