Epileptic seizures and syndromes

Circumscribing Laser Cuts Attenuate Seizure Propagation in a Mouse Model of Focal Epilepsy

In partial onset epilepsy, seizures arise focally in the brain and often propagate. Patients frequently become refractory to medical management, leaving neurosurgery, which can cause neurologic deficits, as a primary treatment. In the cortex, focal seizures spread through horizontal connections in layers II/III, suggesting that severing these connections can block seizures while preserving function. Focal neocortical epilepsy is induced in mice, sub-surface cuts are created surrounding the seizure focus using tightly-focused femtosecond laser pulses, and electrophysiological recordings are acquired at multiple locations for 3-12 months. Cuts reduced seizure frequency in most animals by 87%, and only 5% of remaining seizures propagated to the distant electrodes, compared to 80% in control animals. These cuts produced a modest decrease in cortical blood flow that recovered and left a ≈20-µm wide scar with minimal collateral damage. When placed over the motor cortex, cuts do not cause notable deficits in a skilled reaching task, suggesting they hold promise as a novel neurosurgical approach for intractable focal cortical epilepsy.

Overall comorbidities in functional neurological disorder: A narrative review

INTRODUCTION

The importance to assess and include the frequent comorbidities in the personalised care management plan of patients with functional neurological disorders (FND) has arisen through the years. FND patients are not only complaining from motor and/or sensory symptoms. They also report some non-specific symptoms that participate to the burden of FND. In this narrative review, we aim to better describe these comorbidities in terms of prevalence, clinical characteristics and their variability depending on the subtype of FND.

METHODS

The literature was searched for on Medline and PubMed. The search was narrowed to articles between 2000 and 2022.

RESULTS

Fatigue is the most common symptom reported in relation to FND (from 47 to 93%), followed by cognitive symptoms (from 80 to 85%). Psychiatric disorders are reported in 40 to 100% FND patients, depending on the FND subtype (functional motor disorder [FMD], functional dissociative seizures [FDS]…) but also on the type of psychiatric disorder (anxiety disorders being the most frequent, followed by mood disorders and neurodevelopmental disorders). Stress factors such as childhood trauma exposure (emotional neglect and physical abuse predominantly) have also been identified in up to 75% of FND patients, along with maladaptive coping strategies. Organic disorders are commonly reported in FND, such as neurological disorders (including epilepsy in FDS [20%] and FMD in Parkinson's Disease [7%]). Somatic symptom disorders including chronic pain syndromes are frequently associated to FND (about 50%). To be noted, recent data also suggest a high comorbidity between FND and hypermobile Ehlers Danlos Syndrome (about 55%).

CONCLUSION

Put together, this narrative review highlights the high burden of FND patients, not only due to somatosensory alterations but also by considering the frequent comorbidities reported. Thus, such comorbidities must be taken into consideration when defining the FND personalised care management strategy for the patients.

[Functional neurological disorders: A clinical anthology]

Functional neurological disorders have a broad phenotypic spectrum and include different clinical syndromes, which are sometimes associated to each other or appear consecutively over the course of the disease. This clinical anthology provides details on the specific and sensitive positive signs that are to be sought in the context of a suspected functional neurological disorder. Beside these positive elements leading to the diagnosis of functional neurological disorder, we should keep in mind the possibility of an associated organic disorder as the combination of both organic and functional disorders is a relatively frequent situation in clinical practice. Here we describe the clinical characteristics of different functional neurological syndromes: motor deficits, abnormal hyperkinetic and hypokinetic movements, voice or speech disorders, sensory disorders, and functional dissociative seizures. The clinical examination and the identification of positive signs play a critical role in the diagnosis of functional neurological disorder. Knowledge of the specific signs associated with each phenotype render possible to make an early diagnosis. For that matter, it contributes to the improvement of patient care management. It allows to a better engagement in an appropriate care pathway, which influence their prognosis. Highlighting and discussing positive signs with patients can also be an interesting step in the process of explaining the disease and its management.

Psychogenic Non-epileptic Seizures and Pseudo-Refractory Epilepsy, a Management Challenge

Psychogenic nonepileptic seizures (PNES) are neurobehavioral conditions positioned in a gray zone, not infrequently a no-man land, that lies in the intersection between Neurology and Psychiatry. According to the DSM 5, PNES are a subgroup of conversion disorders (CD), while the ICD 10 classifies PNES as dissociative disorders. The incidence of PNES is estimated to be in the range of 1.4-4.9/100,000/year, and the prevalence range is between 2 and 33 per 100,000. The International League Against Epilepsy (ILAE) has identified PNES as one of the 10 most critical neuropsychiatric conditions associated with epilepsy. Comorbidity between epilepsy and PNES, a condition leading to "dual diagnosis," is a serious diagnostic and therapeutic challenge for clinicians. The lack of prompt identification of PNES in epileptic patients can lead to potentially harmful increases in the dosage of anti-seizure drugs (ASD) as well as erroneous diagnoses of refractory epilepsy. Hence, pseudo-refractory epilepsy is the other critical side of the PNES coin as one out of four to five patients admitted to video-EEG monitoring units with a diagnosis of pharmaco-resistant epilepsy is later found to suffer from non-epileptic events. The majority of these events are of psychogenic origin. Thus, the diagnostic differentiation between pseudo and true refractory epilepsy is essential to prevent actions that lead to unnecessary treatments and ASD-related side effects as well as produce a negative impact on the patient's quality of life. In this article, we review and discuss recent evidence related to the neurobiology of PNES. We also provide an overview of the classifications and diagnostic steps that are employed in PNES management and dwell on the concept of pseudo-resistant epilepsy.

In Vivo Femtosecond Laser Subsurface Cortical Microtransections Attenuate Acute Rat Focal Seizures

Recent evidence shows that seizures propagate primarily through supragranular cortical layers. To selectively modify these circuits, we developed a new technique using tightly focused, femtosecond infrared laser pulses to make as small as ~100 µm-wide subsurface cortical incisions surrounding an epileptic focus. We use this "laser scalpel" to produce subsurface cortical incisions selectively to supragranular layers surrounding an epileptic focus in an acute rodent seizure model. Compared with sham animals, these microtransections completely blocked seizure initiation and propagation in 1/3 of all animals. In the remaining animals, seizure frequency was reduced by 2/3 and seizure propagation reduced by 1/3. In those seizures that still propagated, it was delayed and reduced in amplitude. When the recording electrode was inside the partially isolated cube and the seizure focus was on the outside, the results were even more striking. In spite of these microtransections, somatosensory responses to tail stimulation were maintained but with reduced amplitude. Our data show that just a single enclosing wall of laser cuts limited to supragranular layers led to a significant reduction in seizure initiation and propagation with preserved cortical function. Modification of this concept may be a useful treatment for human epilepsy.

Altered GABAA receptor density and unaltered blood-brain barrier [11C]flumazenil transport in drug-resistant epilepsy patients with mesial temporal sclerosis

Studies in rodents suggest that flumazenil is a P-glycoprotein substrate at the blood-brain barrier. This study aimed to assess whether [¹¹C]flumazenil is a P-glycoprotein substrate in humans and to what extent increased P-glycoprotein function in epilepsy may confound interpretation of clinical [¹¹C]flumazenil studies used to assess gamma-aminobutyric acid A receptors. Nine drug-resistant patients with epilepsy and mesial temporal sclerosis were scanned twice using [¹¹C]flumazenil before and after partial P-glycoprotein blockade with tariquidar. Volume of distribution, nondisplaceable binding potential, and the ratio of rate constants of [¹¹C]flumazenil transport across the blood-brain barrier (K₁/k₂) were derived for whole brain and several regions. All parameters were compared between pre- and post-tariquidar scans. Regional results were compared between mesial temporal sclerosis and contralateral sides. Tariquidar significantly increased global K₁/k₂ (+23%) and volume of distribution (+10%), but not nondisplaceable binding potential. At the mesial temporal sclerosis side volume of distribution and nondisplaceable binding potential were lower in hippocampus (both ∼-19%) and amygdala (both ∼-16%), but K₁/k₂ did not differ, suggesting that only regional gamma-aminobutyric acid A receptor density is altered in epilepsy. In conclusion, although [¹¹C]flumazenil appears to be a (weak) P-glycoprotein substrate in humans, this does not seem to affect its role as a tracer for assessing gamma-aminobutyric acid A receptor density.

Prevalence of Side Effects Treatment with Carbamazepine and Other Antiepileptics in Patients with Epilepsy

OBJECTIVE

This paper reveals the studies of carbamazepine monitoring in the manifestation of side effects during clinical use. It is important to realize that these ranges are derived statistically, with most patients who have high levels suffering side effects and some with poor control having low levels. Broadly, the newer agents have advantages of lower risk of side effects and less drug interaction. At the presence they are more expensive than the, than "older" agents. Current recommendations and practice are to use newer agents as second line drugs, although in some countries there are gaining favour as potential first line agents.

METHODS

In the study 91 patients with epilepsy were involved from which 53 or 58.2% were female and 38 or 41.8% were male with no great significant difference between two genders (X(2)=2.47, P=0.116). However, according to the study results female patients had slightly greater prevalence of epilepsy than man. Average age of epileptic patients was 23.2 years (SD ± 16.4 years), in the range 1-66 years. Patient distribution was present within all age-groups, but 59.4% of all patients were up to 20 years old. The highest prevalence of epilepsy was in the group age 6-15 years old: 33.0%. There were also children 1 - 5 years old with 7 or 7.7% of the patients, and the patients older than 60 years with 4 or 4.4% of the patients. Patient distribution according to the age and gender results with no female patient over 60 year old and more female patients in the age group 1-5 years. However statistically this did not produce a highly significant difference (T-test= 0.72, P=0.437) between average age according to the gender. The average age of the female gender was 22.1 year (SD ± 14.2 years), with the range 2-55 years, while the average age of the male patients was 24.6 year (SD ±19.2 years), with the range 1-66 years.

CONCLUSION

Unwanted side effects of antiepileptic drugs analyzed in the study are frequent, but not so severe as to be life threatening. Treatment of epilepsy with these three drugs (carbamazepine, ac.valproic and phenobarbitone) would be the first choice of treatment, with the best safety and efficacy. Application of this therapy is rarely compromised because of the appearance of unwanted side effects. Replacement or termination of therapy may be applied if actual therapy is not adequate for the management of epileptic attacks.

Complex metabolically demanding sensory processing in the olfactory system: implications for epilepsy

Although the olfactory system is not generally associated with seizures, sharp application of odor eliciting activity in a large number of olfactory sensory neurons (OSNs) has been shown to elicit seizures. This is most likely due to increased ictal activity in the anterior piriform cortex-an area of the olfactory system that has limited GABAergic interneuron inhibition of pyramidal output cell activity. Such hyperexcitability in a well-characterized and highly accessible system makes olfaction a potentially powerful model system to examine epileptogenesis.

Modern technology calls for a modern approach to classification of epileptic seizures and the epilepsies

In the last 10-15 years the ILAE Commission on Classification and Terminology has been presenting proposals to modernize the current ILAE Classification of Epileptic Seizures and Epilepsies. These proposals were discussed extensively in a series of articles published recently in Epilepsia and Epilepsy Currents. There is almost universal consensus that the availability of new diagnostic techniques as also of a modern understanding of epilepsy calls for a complete revision of the Classification of Epileptic Seizures and Epilepsies. Unfortunately, however, the Commission is still not prepared to take a bold step ahead and completely revisit our approach to classification of epileptic seizures and epilepsies. In this manuscript we critically analyze the current proposals of the Commission and make suggestions for a classification system that reflects modern diagnostic techniques and our current understanding of epilepsy.

Disrupted functional brain connectivity in partial epilepsy: a resting-state fMRI study

Examining the spontaneous activity to understand the neural mechanism of brain disorder is a focus in recent resting-state fMRI. In the current study, to investigate the alteration of brain functional connectivity in partial epilepsy in a systematical way, two levels of analyses (functional connectivity analysis within resting state networks (RSNs) and functional network connectivity (FNC) analysis) were carried out on resting-state fMRI data acquired from the 30 participants including 14 healthy controls(HC) and 16 partial epilepsy patients. According to the etiology, all patients are subdivided into temporal lobe epilepsy group (TLE, included 7 patients) and mixed partial epilepsy group (MPE, 9 patients). Using group independent component analysis, eight RSNs were identified, and selected to evaluate functional connectivity and FNC between groups. Compared with the controls, decreased functional connectivity within all RSNs was found in both TLE and MPE. However, dissociating patterns were observed within the 8 RSNs between two patient groups, i.e, compared with TLE, we found decreased functional connectivity in 5 RSNs increased functional connectivity in 1 RSN, and no difference in the other 2 RSNs in MPE. Furthermore, the hierarchical disconnections of FNC was found in two patient groups, in which the intra-system connections were preserved for all three subsystems while the lost connections were confined to intersystem connections in patients with partial epilepsy. These findings may suggest that decreased resting state functional connectivity and disconnection of FNC are two remarkable characteristics of partial epilepsy. The selective impairment of FNC implicated that it is unsuitable to understand the partial epilepsy only from global or local perspective. We presumed that studying epilepsy in the multi-perspective based on RSNs may be a valuable means to assess the functional changes corresponding to specific RSN and may contribute to the understanding of the neuro-pathophysiological mechanism of epilepsy.

Pathophysiology and definitions of seizures and status epilepticus

The pathophysiology of seizures is multifactorial and incompletely understood. Experimental work demonstrates that prolonged, abnormal, and excessive neuronal electrical activity in itself is injurious through several mechanisms independent of systemic acidosis and hypoxia. Population survival studies and laboratory investigations support the idea that brain injury and epileptogenesis result from status epilepticus. The basic distinction in seizure types is that of generalized and partial seizures. Correct classification of seizure types will aid in clinical communications and guide correct therapies. Revised definitions of generalized convulsive status epilepticus suggest making this diagnosis with as few as 5 minutes of continuous seizure activity.

CNS disorders--current treatment options and the prospects for advanced therapies

The development of new pharmaceutical products has successfully addressed a multitude of disease states; however, new product development for treating disorders of the central nervous system (CNS) has lagged behind other therapeutic areas. This is due to several factors including the complexity of the diseases and the lack of technologies for delivery through the blood-brain barrier (BBB). This article examines the current state of six major CNS disease states: depression, epilepsy, multiple sclerosis (MS), neurodegenerative diseases (specifically Alzheimer's disease [AD]), neuropathic pain, and schizophrenia. Discussion topics include analysis of the biological mechanisms underlying each disease, currently approved products, and available animal models for development of new therapeutic agents. Analysis of currently approved therapies shows that all products depend on the molecular properties of the drug or prodrug to penetrate the BBB. Novel technologies, capable of enhancing BBB permeation, are also discussed relative to improving CNS therapies for these disease states.

Differential interictal activity of the precuneus/posterior cingulate cortex revealed by resting state functional MRI at 3T in generalized vs. partial seizure

PURPOSE

To characterize, using functional MRI (fMRI), the pattern of active brain regions in the resting state in patients with epilepsy.

MATERIALS AND METHODS

We studied 28 patients with epilepsy, divided into a partial seizure (PS; N = 9) and a generalized seizure group (GS; N = 19), and 34 control subjects. Resting state fMRI was performed using a GE 3T scanner by collecting 200 volumes of echo-planar imaging (EPI) images with subjects relaxed, eyes closed. Data were processed using a modification of the method of Fransson (Hum Brain Mapp 2005;26:15-29), which reveals information on regional low-frequency Blood Oxygenation Level Dependent (BOLD) signal oscillations in the resting state without any a priori hypothesis. The significant active areas in brain were identified with both individual and group analysis.

RESULTS

Controls showed active regions in the precuneus/posterior cingulate cortex (PCC) and medial prefrontal cortex (MPFC)/ventral anterior cingulate cortex (vACC), theregions associated with the brain "default mode." Similar active regions were observed in PS, whereas GS showed no significant activation of precuneus/PCC.

CONCLUSION

In GS, the lack of activation in precuneus/PCC may partly account for their more severe interictal deficits, compared to PS, in cognitive functions such as concentration and memory.

Direct Medical Costs for Partial Refractory Epilepsy in Mexico

BACKGROUND

The aim was to determine the direct medical costs in patients with partial refractory epilepsy at the Mexican Institute of Social Security (IMSS) in Mexico.

METHODS

We carried out a multicenter, retrospective-cohort partial-economic evaluation study of partial refractory epilepsy (PRE) diagnosed patients and analyzed patient files from four secondary- and tertiary-level hospitals. PRE patients >12 years of age with two or more antiepileptic drugs and follow-up for at least 1 year were included. The perspective was institutional (IMSS). Only direct healthcare costs were considered, and the timeline was 1 year. Cost techniques were microcosting, average per-service cost, and per-day cost, all costs expressed in U.S. dollars (USD, 2004).

RESULTS

We reviewed 813 files of PRE patients: 133 had a correct diagnosis, and only 72 met study inclusion criteria. Fifty eight percent were females, 64% were <35 years of age, 47% were students, in 73% maximum academic level achieved was high school, and 53% were single. Fifty one percent of cases experienced simple partial seizures and 94% had more than one monthly seizure. Annual healthcare cost of the 72 patients was 190,486 USD, ambulatory healthcare contributing 76% and hospital healthcare with 24%.

CONCLUSIONS

Annual mean healthcare cost per PRE patient was 2,646 USD; time of disease evolution and severity of the patient's illness did not affect costs significantly.

Therapeutic drug monitoring of old and newer anti-epileptic drugs

The aim of the present paper is to provide information concerning the setting up and interpretation of therapeutic drug monitoring (TDM) for anti-epileptic drugs. The potential value of TDM for these drugs (including carbamazepine, clobazam, clonazepam, ethosuximide, felbamate, gabapentin, lamotrigine, levetiracetam, oxcarbazepine, pheneturide, phenobarbital, phenytoin, primidone, tiagabine, topiramate, valproic acid, vigabatrin and zonisamide) is discussed in relation to their mode of action, drug interactions and their pharmacokinetic properties. The review is based upon available literature data and on observations from our clinical practice. Up until approximately 15 years ago anti-epileptic therapeutics were restricted to a very few drugs that were developed in the first half of the 20th century. Unfortunately, many patients were refractory to these drugs and a new generation of drugs has been developed, mostly as add-on therapy. Although the efficacy of the newer drugs is no better, there is an apparent improvement in drug tolerance, combined with a diminished potential for adverse drug interactions. All new anticonvulsant drugs have undergone extensive clinical studies, but information on the relationship between plasma concentrations and effects is scarce for many of these drugs. Wide ranges in concentrations have been published for seizure control and toxicity. Few studies have been undertaken to establish the concentration-effect relationship. This review shows that TDM may be helpful for a number of these newer drugs.