Lennox-Gastaut syndrome with late-onset and prominent reflex seizures in trisomy 21 patients

Case Report: Late-Onset Lennox-Gastaut Syndrome Treated With Stereotactic Electroencephalography-Guided Radiofrequency Thermocoagulation Before Craniotomy

The onset of Lennox-Gastaut syndrome (LGS), a severe epilepsy syndrome, is typically before 8 years of age. Late-onset LGS (with onset in adolescence and adulthood) is relatively rare clinically and has some differences from classical LGS. Herein, we describe the case of a patient with late-onset LGS and provide a literature review of such cases. The patient had focal epilepsy onset at 8 years of age. After a 9-year evolution, he suffered seizures of different types and had a diagnosis of late-onset LGS. Drug treatment was ineffective. Nothing was found on stereotactic electroencephalography (SEEG) and magnetic resonance imaging (MRI) during the course of the disease. After the second presurgical evaluation, we found a suspicious focus on high-resolution structural MRI which was verified by SEEG at last. After SEEG-guided radiofrequency thermocoagulation (RFTC), his seizures were controlled, and his cognitive function and quality of living clearly improved. However, his seizures recurred 2 years later, and he underwent left occipital resection. Thereafter, his seizures have been controlled until now. This case emphasizes the importance of high-resolution structural MRI in the treatment of LGS. Furthermore, it suggests that late-onset LGS may be caused by focal lesions and evolve from focal epilepsy. Thus, characterizing the clinical symptoms and performing individualized electroencephalographic follow-up are both very important. Additionally, the clinical outcome in this case implies the value and limitations of RFTC in patients with epilepsy and a clear focal lesion. Moreover, this case further supports differences between late-onset and classical LGS in terms of clinical manifestation, cognitive changes, prognosis, and treatment.

Children With Trisomy 21 and Lennox-Gastaut Syndrome With Predominant Myoclonic Seizures

INTRODUCTION

Lennox-Gastaut syndrome is a severe form of pediatric epilepsy that is classically defined by a triad of drug-resistant seizures, including atonic, tonic, and atypical absence seizures; slow spike-and-wave discharges and paroxysmal fast activity on electroencephalography (EEG); and cognitive and behavioral dysfunction. In the vast majority, Lennox-Gastaut syndrome develops in patients with an identified etiology, including genetic or structural brain abnormalities. Long-term prognosis is generally poor with progressive intellectual deterioration and persistent seizures. At present, there are few reported cases of Lennox-Gastaut syndrome and trisomy 21 in the literature. To further delineate the spectrum of epilepsy in trisomy 21, we reviewed children with trisomy 21 and Lennox-Gastaut syndrome at one center over 28 years.

METHODS

This is a retrospective case series. At our institution, all EEG results are entered into a database, which was queried for patients with trisomy 21 from 1992 to 2019. Pertinent electroclinical data was obtained from medical records.

RESULTS

Of 63 patients with trisomy 21 and epilepsy, 6 (10%) had Lennox-Gastaut syndrome and were included in the study. Four of the 6 patients were male and 5 of 6 had neuroimaging, which was normal. Follow-up ranged from 3 to 20 years. Notably, 5 of 6 had predominant myoclonic seizures throughout the course of their epilepsy, associated with generalized spike-wave discharges, <100 milliseconds.

CONCLUSION

We observed myoclonic seizures to be a predominant seizure type in patients with trisomy 21, suggestive that trisomy 21 patients may have a unique pattern of Lennox-Gastaut syndrome.

Epilepsy in Down Syndrome: A Highly Prevalent Comorbidity

Individuals with Down syndrome (DS) have an increased risk for epilepsy during the whole lifespan, but especially after age 40 years. The increase in the number of individuals with DS living into late middle age due to improved health care is resulting in an increase in epilepsy prevalence in this population. However, these epileptic seizures are probably underdiagnosed and inadequately treated. This late onset epilepsy is linked to the development of symptomatic Alzheimer's disease (AD), which is the main comorbidity in adults with DS with a cumulative incidence of more than 90% of adults by the seventh decade. More than 50% of patients with DS and AD dementia will most likely develop epilepsy, which in this context has a specific clinical presentation in the form of generalized myoclonic epilepsy. This epilepsy, named late onset myoclonic epilepsy (LOMEDS) affects the quality of life, might be associated with worse cognitive and functional outcomes in patients with AD dementia and has an impact on mortality. This review aims to summarize the current knowledge about the clinical and electrophysiological characteristics, diagnosis and treatment of epileptic seizures in the DS population, with a special emphasis on LOMEDS. Raised awareness and a better understanding of epilepsy in DS from families, caregivers and clinicians could enable earlier diagnoses and better treatments for individuals with DS.

Infantile Spasms and Trisomy 21: Unfavorable Outcomes with First-line Vigabatrin Therapy

Introduction:

Among children with infantile spasms (ISs), those with trisomy 21 (T21) and those with normal development at onset and no identifiable etiology (previously referred to as “idiopathic”) are expected to have relatively favorable outcomes. The study objective is to determine if differences exist in treatment response, relapse, and subsequent epilepsy between these two groups when vigabatrin is used as first-line treatment.

Methods:

In this retrospective study, patients were classified into the following groups and clinical features were compared: T21 (n = 24) and IS with normal development at onset and no identified etiology (n = 40; control group).

Results:

There was no significant difference in the age of IS onset, sex distribution, or treatment lag between the groups. The T21 compared to the control group required a higher mean number of anti-seizure therapies (3.6 vs. 1.9, p < 0.001), had more relapses [10 (42%) vs. 4 (10%), p < 0.005)], and had higher risk of subsequent epilepsy [11 (46%) vs. 8 (20%), p < 0.003]. Relapses were often delayed in the T21 group, with a mean of 8 months after IS cessation.

Conclusion:

Our results differ from most studies using steroids as first-line treatment where the groups were shown to have similar treatment response and T21 patients had a low risk of relapse and subsequent epilepsy. Therefore, our results suggest that vigabatrin as first-line treatment in T21 with IS may be less favorable than steroids.

Neurologic complications of Down syndrome: a systematic review

Down syndrome (DS) is one of the most well-recognized genetic disorders. Persons with DS are known to have a variety of co-morbid medical problems, affecting nearly all organ systems. Improved healthcare interventions and research have allowed for increased life span of persons with DS, although disorders of the neurologic system remain underexplored. The purpose of this systematic review is to provide clinically pertinent information on the neurological phenotypes of frequently occurring or clinically relevant conditions. A retrospective review of MEDLINE, Scopus, and Pubmed were used to identify sources among seventeen, clinically relevant, search categories. MeSH terms all contained the phrase "Down Syndrome" in conjunction with the topic of interest. 'Frequently-occurring' was defined as prevalent in more than 10% of persons with DS across their lifespan, whereas 'clinically-relevant' was defined as a disease condition where early diagnosis or intervention can augment the disease course. In total, 4896 sources were identified with 159 sources meeting criteria for inclusion. Seventeen clinical conditions were grouped under the following subjects: hypotonia, intellectual and learning disability, cervical instability, autism spectrum disorder, epilepsy, cerebrovascular disease, Alzheimer's disease and neuropsychiatric disease. The results of this review provide a blueprint for the clinical neurologist taking care of persons with DS across the age spectrum and indicate that there are many underrecognized and misdiagnosed co-occurring conditions in DS, highlighting the need for further research.

Late-onset Lennox-Gastaut syndrome: Diagnostic evaluation and outcome

Background

We describe the clinical features and outcome in patients with late-onset Lennox-Gastaut syndrome (LGS).

Methods

Adult patients evaluated between January 1, 2000, and March 1, 2017, who presented with onset of LGS ≥10 years were identified. Data abstracted included age at seizure onset, seizure types, etiology, treatments, EEG and neuroimaging results, cerebrospinal fluid (CSF) findings, and autoimmune evaluation.

Results

Ten patients (8 females) were identified. The mean age at onset of seizures consistent with LGS was 16.5 years (range, 10-32 years). Seizure types included tonic, atonic, and tonic-clonic seizures (all), myoclonic seizures (n = 3), and atypical absence seizures (n = 7). Five patients had normal intellectual function at onset. Prolonged video-EEG monitoring recorded seizures and generalized interictal epileptiform discharges in all. All patients had drug-resistant epilepsy (range of antiseizure drugs tried, 7-16). Two patients had a history of intrathecal methotrexate to treat acute lymphoblastic leukemia. Two patients had malformations of cortical development. CSF analysis (n = 5) showed a mild elevation in the protein level without other abnormalities. Autoantibody determinations in the serum (n = 4) or the CSF (n = 5) and genetic testing (n = 5) were negative. At final follow-up, all but 1 patient was disabled and required a caregiver, and none were driving. One patient died of probable sudden unexpected death in epilepsy (SUDEP).

Conclusions

Late-onset LGS represents a rare, treatment-resistant generalized epilepsy that is disabling and may be associated with progressive cognitive impairment. The elevated CSF protein level in our cohort could have been due to high seizure burden but increases the possibility of an inflammatory component to the pathophysiology of this disorder.

Precipitation and inhibition of seizures in focal epilepsies

INTRODUCTION

There is growing awareness that reflex epileptic seizures offer unique insight into natural seizure generation in humans. In the last years, focus has mostly been on reflex seizures in generalized epilepsies whereas a comprehensive review of their role in focal epilepsies has been missing. Areas covered: This paper reviews reflex seizures strictly in focal epilepsies, not including focal reflex seizures in system epilepsies that also exist. They were categorized according to their triggers which can be sensory or cognitive, simple or complex. Numerous diverse conditions exist some of which are much better investigated than others. They required separate individual literature search in PubMed. Where recent review papers exist, it refers to these, but several conditions have never been reviewed, and here it refer to and discusses original reports. Miscellaneous case reports were only exceptionally included when they contributed aspects otherwise missing. Expert commentary: Research on focal reflex seizures with advanced methods of imaging and neurophysiology to elucidate mechanisms of focal ictogenesis will probably be rapidly increasing and will soon provide much new insight. Sensory and cognitive inhibition, i.e. the counterpart of reflex ictogenesis, is promising but needs more structured and controlled research to establish robust therapeutic approaches.

Reflex epilepsy: triggers and management strategies

Reflex epilepsies (REs) are identified as epileptic seizures that are consistently induced by identifiable and objective-specific triggers, which may be an afferent stimulus or by the patient's own activity. RE may have different subtypes depending on the stimulus characteristic. There are significant clinical and electrophysiologic differences between different RE types. Visual stimuli-sensitive or photosensitive epilepsies constitute a large proportion of the RE and are mainly related to genetic causes. Reflex epilepsies may present with focal or generalized seizures due to specific triggers, and sometimes seizures may occur spontaneously. The stimuli can be external (light flashes, hot water), internal (emotion, thinking), or both and should be distinguished from triggering precipitants, which most epileptic patients could report such as emotional stress, sleep deprivation, alcohol, and menstrual cycle. Different genetic and acquired factors may play a role in etiology of RE. This review will provide a current overview of the triggering factors and management of reflex seizures.

Expert Opinion on the Management of Lennox-Gastaut Syndrome: Treatment Algorithms and Practical Considerations

Lennox–Gastaut syndrome (LGS) is a severe epileptic and developmental encephalopathy that is associated with a high rate of morbidity and mortality. It is characterized by multiple seizure types, abnormal electroencephalographic features, and intellectual disability. Although intellectual disability and associated behavioral problems are characteristic of LGS, they are not necessarily present at its outset and are therefore not part of its diagnostic criteria. LGS is typically treated with a variety of pharmacological and non-pharmacological therapies, often in combination. Management and treatment decisions can be challenging, due to the multiple seizure types and comorbidities associated with the condition. A panel of five epileptologists met to discuss consensus recommendations for LGS management, based on the latest available evidence from literature review and clinical experience. Treatment algorithms were formulated. Current evidence favors the continued use of sodium valproate (VPA) as the first-line treatment for patients with newly diagnosed de novo LGS. If VPA is ineffective alone, evidence supports lamotrigine, or subsequently rufinamide, as adjunctive therapy. If seizure control remains inadequate, the choice of next adjunctive antiepileptic drug (AED) should be discussed with the patient/parent/caregiver/clinical team, as current evidence is limited. Non-pharmacological therapies, including resective surgery, the ketogenic diet, vagus nerve stimulation, and callosotomy, should be considered for use alongside AED therapy from the outset of treatment. For patients with LGS that has evolved from another type of epilepsy who are already being treated with an AED other than VPA, VPA therapy should be considered if not trialed previously. Thereafter, the approach for a de novo patient should be followed. Where possible, no more than two AEDs should be used concomitantly. Patients with established LGS should undergo review by a neurologist specialized in epilepsy on at least an annual basis, including a thorough reassessment of their diagnosis and treatment plan. Clinicians should always be vigilant to the possibility of treatable etiologies and alert to the possibility that a patient’s diagnosis may change, since the seizure types and electroencephalographic features that characterize LGS evolve over time. To date, available treatments are unlikely to lead to seizure remission in the majority of patients and therefore the primary focus of treatment should always be optimization of learning, behavioral management, and overall quality of life.

Reflex Seizures Triggered by Exposure to Characters With Numerical Value: A Case With Right Temporal Cortical Dysplasia

Reflex seizures can be triggered by a variety of stimuli. We present a case with drug-resistant complex partial seizures originating in right temporal lobe triggered extensively by visual, auditory, and mental exposure to multidigit numbers. The patient was investigated in video-EEG monitoring unit and seizures were triggered by numerical stimuli. Scalp EEG findings suggested a right temporal focus but ictal semiological findings suspicious for an extratemporal area necessitated the invasive EEG study. A right anterior temporal seizure focus was established with invasive monitoring and cortical stimulation studies. Magnetic resonance imaging showed a cortical dysplasia in right anterior temporal lobe and ictal single-photon emission computed tomography confirmed the epileptogenic focus, leading to a right temporal lobectomy and amygdalohippocampectomy and a pathological diagnosis of focal cortical dysplasia type Ia. The patient is seizure-free at the end of the second postoperative year despite repeated exposures to numbers. To our knowledge, this is the first report of seizures triggered by numbers. It is also of particular importance as the reflex seizures are associated with a cortical lesion and it may suggest involvement of right anterior temporal lobe in numerical processing.

Reflex Myoclonic Epilepsy of Infancy: Seizures Induced by Tactile Stimulation

Myoclonic epilepsy with reflex seizures in infancy is an extremely rare condition, in which seizures are provoked mainly by auditory or auditory-tactile stimuli. To increase the awareness of pediatricians regarding this underrecognized condition, we describe a child with seizures provoked only by the tactile stimulation of specific areas of the head and face.

Genetics of reflex seizures and epilepsies in humans and animals

INTRODUCTION

Reflex seizures are epileptic events triggered by specific motor, sensory or cognitive stimulation. This comprehensive narrative review focuses on the role of genetic determinants in humans and animal models of reflex seizures and epilepsies.

METHODS

References were mainly identified through MEDLINE searches until August 2015 and backtracking of references in pertinent studies.

RESULTS

Autosomal dominant inheritance with reduced penetrance was proven in several families with photosensitivity. Molecular genetic studies on EEG photoparoxysmal response identified putative loci on chromosomes 6, 7, 13 and 16 that seem to correlate with peculiar seizure phenotype. No specific mutation has been found in Papio papio baboon, although a genetic etiology is likely. Mutation in synaptic vesicle glycoprotein 2A was found in another animal model of photosensitivity (Fayoumi chickens). Autosomal dominant inheritance with incomplete penetrance overlapping with a genetic background for IGE was proposed for some families with primary reading epilepsy. Musicogenic seizures usually occur in patients with focal symptomatic or cryptogenic epilepsies, but they have been reported in rare genetic epilepsies such as Dravet syndrome. A single LGI1 mutation has been described in a girl with seizures evoked by auditory stimuli. Interestingly, heterozygous knockout (Lgi1(+/-)) mice show susceptibility to sound-triggered seizures. Moreover, in Frings and Black Swiss mice, the spontaneous mutations of MASS1 and JAMS1 genes, respectively, have been linked to audiogenic seizures. Eating seizures usually occur in symptomatic epilepsies but evidences for a genetic susceptibility were mainly provided by family report from Sri Lanka. Eating seizures were also reported in rare patients with MECP2 duplication or mutation. Hot water seizures are genetically heterogeneous but two loci at chromosomes 4 and 10 were identified in families with likely autosomal dominant inheritance. Startle-induced seizures usually occur in patients with symptomatic epilepsies but have also been reported in the setting chromosomal disorders or genetically inherited lysosomal storage diseases.

DISCUSSION

The genetic background of reflex seizures and epilepsies is heterogeneous and mostly unknown with no major gene identified in humans. The benefits offered by next-generation sequencing technologies should be merged with increasing information on animal models that represent an useful tool to study the mechanism underlying epileptogenesis. Finally, we expect that genetic studies will lead to a better understanding of the multiple factors involved in the pathophysiology of reflex seizures, and eventually to develop preventive strategies focused on seizure control and therapy optimization.

Cerebal overinhibition could be the basis for the high prevalence of epilepsy in persons with Down syndrome

Down syndrome (DS) is the most common cause of genetic intellectual disability, and the trisomy 21 is associated with more than 80 clinical traits, including higher risk for epilepsy. Several hypotheses have been put forward to explain the mechanisms underlying increased seizure susceptibility in DS: inherent structural brain abnormalities, abnormal cortical lamination, disruption of normal dendritic morphology, and underdeveloped synaptic profiles. A deficiency or loss of GABA inhibition is hypothesized to be one of the main alterations related to the epileptogenic process. Paradoxically, enhanced GABA inhibition has also been reported to promote seizures. One major functional abnormality observed in the brains of individuals and mouse models with DS appears to be an imbalance between excitatory and inhibitory neurotransmission, with excessive inhibitory brain function. This review discusses the GABAergic system in the human DS brain and the possible implication of the GABAergic network circuit in the epileptogenic process in individuals where the pathogenetic basis for epilepsy is unknown.

Autism spectrum disorder and epilepsy: Disorders with a shared biology

There is an increasing recognition of clinical overlap in patients presenting with epilepsy and autism spectrum disorder (ASD), and a great deal of new information regarding the genetic causes of both disorders is available. Several biological pathways appear to be involved in both disease processes, including gene transcription regulation, cellular growth, synaptic channel function, and maintenance of synaptic structure. We review several genetic disorders where ASD and epilepsy frequently co-occur, and we discuss the screening tools available for practicing neurologists and epileptologists to help determine which patients should be referred for formal ASD diagnostic evaluation. Finally, we make recommendations regarding the workflow of genetic diagnostic testing available for children with both ASD and epilepsy. This article is part of a Special Issue entitled "Autism and Epilepsy".

Generalized versus partial reflex seizures: a review

In this review we assess our currently available knowledge about reflex seizures with special emphasis on the difference between "generalized" reflex seizures induced by visual stimuli, thinking, praxis and language tasks, and "focal" seizures induced by startle, eating, music, hot water, somatosensory stimuli and orgasm. We discuss in particular evidence from animal, clinical, neurophysiological and neuroimaging studies supporting the concept that "generalized" reflex seizures, usually occurring in the setting of IGE, should be considered as focal seizures with quick secondary generalization. We also review recent advances in genetic and therapeutic approach of reflex seizures.

Electroclinical features and long-term outcome of cryptogenic epilepsy in children with Down syndrome

OBJECTIVE

To describe the electroclinical features and the long-term outcomes of epilepsy in a large cohort of males and females with Down syndrome who developed epilepsy in childhood.

STUDY DESIGN

Subjects with Down syndrome and cryptogenic epilepsy with onset in childhood were identified retrospectively from the databases of 16 Italian epilepsy centers over a 40-year period. For each subject, age at onset of seizures, seizure semiology and frequency, electroencephalography characteristics, treatment with antiepileptic drugs, and long-term clinical and electroencephalography outcomes were analyzed.

RESULTS

A total of 104 subjects (64 males [61.5%], 40 females [38.5%]) were identified. Seizure onset occurred within 1 year of birth in 54 subjects (51.9%), between 1 and 12 years in 42 subjects (40.4%), and after 12 years in 8 subjects (7.7%). Males had a younger age of seizure onset than females. Of the 104 subjects, 51 (49.0%) had infantile spasms (IS), 35 (33.7%) had partial seizures (PS), and 18 (17.3%) had generalized seizures (GS). Febrile seizures were recorded in 5 (4.8%) subjects. Intractable seizures were observed in 23 (22.1%) subjects, including 5 (9.8%) with IS, 8 (44.4%) with PS, and 10 (31.3%) with GS.

CONCLUSION

Cryptogenic epilepsy in Down syndrome may develop during the first year of life in the form of IS or, successively, as PS or GS. Electroclinical features of IS resemble those of idiopathic West syndrome, with a favorable response to treatment with adrenocorticotropic hormone seen. Patients experiencing PS and GS may be resistant to therapy with antiepileptic drugs.

Neurological features and long-term follow-up in 15q11.2-13.1 duplication

Various rearrangements occurring in the 15q11-q13 region have been reported in association with epilepsy. Deletions are the most frequent and are associated with Angelman or Prader-Willi syndrome. Duplications feature complex phenotypes including developmental delay, autistic-like behaviour and seizures. Among these, trisomy has been described as a milder phenotype compared to tetrasomy, but reports are rare and the phenotype is not yet defined. Here we report two adult cases with a 15q11.2-13.1 duplication showing a complex and similar epileptic phenotype.

Chromosome disorders associated with epilepsy

Epilepsy is a feature of several hundred chromosome abnormalities. However, there are relatively few conditions in which epilepsy is a consistent feature and even fewer in which the electroclinical phenotype is recognizable. Advances in cytogenetics and molecular genetics are leading to the detection of more complex and smaller chromosomal re-arrangements, duplications, and deletions using techniques such as comparative genome hybridization (CGH). This will provide new challenges for the epilepsy specialist who, in partnership with the geneticist, will have to judge the clinical relevance of these abnormalities. Most chromosome anomalies associated with epilepsy are individually rare therefore clinicians must continue to collaborate to describe novel electroclinical phenotypes. Cytogenetic studies should be requested in all individuals with refractory epilepsy and no clear underlying cause even in cases with no dysmorphic features, no learning disability, and an EEG suggestive of genetic generalized epilepsy. In syndromes where epilepsy is a consistent feature the seizure semiology and EEG features can suggest a specific diagnosis and guide the clinician to the appropriate cytogenetic investigation. An early correct diagnosis can save unnecessary investigations and guide prognosis. Children with chromosomal disorders frequently have learning disability, which can be further compromised by an epileptic encephalopathy. Medications should be targeted to specific seizure types.

Neurological phenotypes for Down syndrome across the life span

This chapter reviews the neurological phenotype of Down syndrome (DS) in early development, childhood, and aging. Neuroanatomic abnormalities in DS are manifested as aberrations in gross brain structure as well as characteristic microdysgenetic changes. As the result of these morphological abnormalities, brain circuitry is impaired. While an intellectual disability is ubiquitous in DS, there is a wide range of variation in cognitive performance and a growing understanding between aberrant brain circuitry and the cognitive phenotype. Hypotonia is most marked at birth, affecting gait and ligamentous laxity. Seizures are bimodal in presentation with infantile spasms common in infancy and generalized seizures associated with cognitive decline observed in later years. While all individuals have the characteristic neuropathology of Alzheimer's disease (AD) by age 40 years, the prevalence of dementia is not universal. The tendency to develop AD is related, in part, to several genes on chromosome 21 that are overexpressed in DS. Intraneuronal accumulation of β-amyloid appears to trigger a cascade of neurodegeneration resulting in the neuropathological and clinical manifestations of dementia. Functional brain imaging has elucidated the temporal sequence of amyloid deposition and glucose metabolic rate in the development of dementia in DS. Mitochondrial abnormalities contribute to oxidative stress which is part of AD pathogenesis in DS as well as AD in the general population. A variety of medical comorbidities threaten cognitive performance including sleep apnea, abnormalities in thyroid metabolism, and behavioral disturbances. Mouse models for DS are providing a platform for the formulation of clinical trials with intervention targeted to synaptic plasticity, brain biochemistry, and morphological brain alterations.