Spectrum of epilepsy and electroencephalogram patterns in idic (15) syndrome

Seizures in trisomy 18: Prevalence, description, and treatment

Changes in medical intervention over the last decade have improved outcomes for individuals with trisomy 18, the second most common human aneuploidy syndrome at birth. As children with trisomy 18 live longer, a shared concern of medical experts and parents is the occurrence and treatment of seizures. Previously published surveillance guidelines for this condition have not addressed seizure management. Using parent-reported data collected as part of the Tracking Rare Incidence Syndromes project, we report on the prevalence, course, and management of seizures in individuals with trisomy 18. Twenty-eight percent (52/186) of individuals diagnosed with trisomy 18 in our retrospective cohort experienced generalized, focal, or mixed seizures at some point in their lifetime. For many individuals, seizures were effectively managed by broad-spectrum anti-seizure medications. Correlation analysis showed that focal and generalized seizures were more likely to occur in individuals who had previously experienced infantile spasms or central apnea. Electroencephalogram testing should be considered as part of a standard screening approach in individuals with trisomy 18 to enable early diagnosis and treatment of seizures. An international registry that incorporates parent-reported and clinical data for patients with trisomy 18 may facilitate ongoing research and recruitment into clinical trials for seizure management.

Electro-clinical features in epileptic children with chromosome 15q duplication syndrome

OBJECTIVE

We aimed to describe epilepsy and EEG patterns related to vigilance states and age, in chromosome15-long-arm-duplication-syndrome (dup15q) children with epilepsy, in both duplication types: interstitial (intdup15) and isodicentric (idic15).

METHODS

Clinical data and 70 EEGs of 12 patients (5 intdup15, 7 idic15), followed from 4.5 m.o to 17y4m (median follow-up 8y3m), were retrospectively reviewed. EEGs were analyzed visually and using power spectrum analysis.

RESULTS

Seventy video-EEGs were analyzed (1-16 per patient, median 6), follow-up lasting up to 8y10m (median 4y2m): 25 EEGs in intdup15 (8 m.o to 12y.o, median 4y6m) and 45 EEGs in idic15 (7 m.o to 12 y.o, median 15 m). Epilepsy: 6 West syndrome (WS) (2intdup15, 4idic15); 4 Lennox-Gastaut syndromes (LGS) (1 intdup15, 3 idic15), 2 evolving from WS; focal epilepsy (3 intdup15). In idic15, WS displayed additional myoclonic seizures (3), atypical (4) or no hypsarrhythmia (2) and posterior predominant spike and polyspike bursts (4). Beta-band rapid-rhythms (RR): present in 11 patients, power decreased during non-REM-sleep, localization shifted from diffuse to anterior, peak frequency increased with age.

CONCLUSION

WS with peculiar electro-clinical features and LGS, along with beta-band RR decreasing in non-REM-sleep and shifting from diffuse to anterior localization with age are recognizable features pointing towards dup15q diagnosis in children with autism spectrum disorder and developmental delay.

SIGNIFICANCE

This study describes electroclinical features in both interstitial and isodicentric duplications of chromosome 15q, in epileptic children, including some recent extensions regarding sleep features; and illustrates how the temporo-spatial organization of beta oscillations can be of significant help in directing towards dup15q diagnosis hypothesis.

Treatment of Epilepsy Associated with Common Chromosomal Developmental Diseases

Chromosomal diseases are heterogeneous conditions with complex phenotypes, which include also epileptic seizures. Each chromosomal syndrome has a range of specific characteristics regarding the type of seizures, EEG findings and specific response to antiepileptic drugs, significant in the context of the respective genetic etiology. Therefore, it is very important to know these particularities, in order to avoid an exacerbation of seizures or some side effects. In this paper we will present a review of the epileptic seizures and antiepileptic treatment in some of the most common chromosomal syndromes.

Behavioral characterization of dup15q syndrome: Toward meaningful endpoints for clinical trials

Duplication of 15q11.2-q13.1 (dup15q syndrome) is one of the most common copy number variations associated with autism spectrum disorders (ASD) and intellectual disability (ID). As with many neurogenetic conditions, accurate behavioral assessment is challenging due to the level of impairment and heterogeneity across individuals. Large-scale phenotyping studies are necessary to inform future clinical trials in this and similar ID syndromes. This study assessed developmental and behavioral characteristics in a large cohort of children with dup15q syndrome, and examined differences based on genetic subtype and epilepsy status. Participants included 62 children (2.5-18 years). Across individuals, there was a wide range of abilities. Although adaptive behavior was strongly associated with cognitive ability, adaptive abilities were higher than cognitive scores. Measures of ASD symptoms were associated with cognitive ability, while parent report of challenging behavior was not. Both genetic subtype and epilepsy were related to degree of impairment across cognitive, language, motor, and adaptive domains. Children with isodicentric duplications and epilepsy showed the greatest impairment, while children with interstitial duplications showed the least. On average, participants with epilepsy experienced seizures over 53% of their lives, and half of children with epilepsy had infantile spasms. Parents of children with isodicentric duplications reported more concerns regarding challenging behaviors. Future trials in ID syndromes should employ a flexible set of assessments, allowing each participant to receive assessments that capture their skills. Multiple sources of information should be considered, and the impact of language and cognitive ability should be taken into consideration when interpreting results.

Possible Phenotypic Consequences of Structural Differences in Idic(15) in a Small Cohort of Patients

Among human supernumerary marker chromosomes, the occurrence of isodicentric form of 15 origin is relatively well known due to its high frequency, both in terms of gene content and associated clinical symptoms. The associated epilepsy and autism are typically more severe than in cases with interstitial 15q duplication, despite copy number gain of approximately the same genomic region. Other mechanisms besides segmental aneuploidy and epigenetic changes may also cause this difference. Among the factors influencing the expression of members of the GABA_A gene cluster, the imprinting effect and copy number differences has been debated. Limited numbers of studies investigate factors influencing the interaction of GABA_A cluster homologues. Five isodicentric (15) patients are reported with heterogeneous symptoms, and structural differences of their isodicentric chromosomes based on array comparative genomic hybridization results. Relations between the structure and the heterogeneous clinical picture are discussed, raising the possibility that the structure of the isodicentric (15), which has an asymmetric breakpoint and consequently a lower copy number segment, would be the basis of the imbalance of the GABA_A homologues. Studies of trans interaction and regulation of GABA_A cluster homologues are needed to resolve this issue, considering copy number differences within the isodicentric chromosome 15.

Infantile spasms in a mosaic monocentric and duplicated SMC 15 patient

OBJECTIVE

To report detail of a patient with infantile spasms whose cytogenetic analysis revealed mosaic monocentric and duplicated supernumerary marker chromosome (SMC) 15.

SUBJECT AND METHODS

The subject for this case was a 13-month-old girl with infantile spasms and delayed developmental milestones. Chromosomal analysis with G-band showed the presence of SMC in mosaic. Further investigations using in situ hybridization, methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA), microsatellite marker, and single nucleotide polymorphism (SNP) array analysis were performed.

RESULTS

Her karyotype was noted as mosaic 47,XX,+mar[26]/46,XX[4], ish der(15)(D15Z1+, SNRPN++, PML-) de novo. MS-MLPA analysis showed that the Prader-Willi syndrome/Angelman syndrome critical region is highly methylated, and microsatellite marker analysis proved that the 15q11.2 region of the patient comprises three kinds of alleles: one paternal and two maternal. SNP array analysis suggested an asymmetric structure of SMC(15) composed of 15q11-q13 recombination at breakpoint (BP) 4:BP5.

CONCLUSIONS

This is the first report of SMC(15) with monocentric and duplicated proximal 15q. The clinical presentations are quite similar to those of isodicentric chromosome 15 syndrome. The results of microsatellite and SNP array analysis suggest two possibilities regarding the timing of the mosaic SMC(15) formation. One possibility is that it occurred during maternal meiosis, and the other possibility is formation during a very early stage of embryo development that was initially trisomic of chromosome 15.

Electroclinical findings and long-term outcomes in epileptic patients with inv dup (15)

OBJECTIVE

To define the electroclinical phenotype and long-term outcomes in a cohort of patients with inv dup (15) syndrome.

MATERIAL AND METHODS

The electroclinical data of 45 patients (25 males) affected by inv dup (15) and seizures were retrospectively analysed, and long-term follow-up of epilepsy was evaluated.

RESULTS

Epilepsy onset was marked by generalized seizures in 53% of patients, epileptic spasms in 51%, focal seizures in 26%, atypical absences in 11% and epileptic falls in 9%. The epileptic syndromes defined were: generalized epilepsy (26.7%), focal epilepsy (22.3%), epileptic encephalopathy with epileptic spasms as the only seizure type (17.7%) and Lennox-Gastaut syndrome (33.3%). Drug-resistant epilepsy was detected in 55.5% of patients. There was a significant higher prevalence of seizure-free patients in those with seizure onset after the age of 5 years and with focal epilepsy, with respect to those with earlier epilepsy onset because most of these later developed an epileptic encephalopathy (69.2% vs 34.4%; P = .03), usually Lennox-Gastaut Syndrome in type. In fact, among patients with early-onset epilepsy, those presenting with epileptic spasms as the only seizure type associated with classical hypsarrhythmia achieved seizure freedom (P < .001) compared to patients with spasms and other seizure types associated with modified hypsarrhythmia.

CONCLUSIONS

Epilepsy in inv dup (15) leads to a more severe burden of disease. Frequently, these patients show drug resistance, in particular when epilepsy onset is before the age of five and features epileptic encephalopathy.

Rare partial octosomy and hexasomy of 15q11-q13 associated with intellectual impairment and development delay: report of two cases and review of literature

Background

Small supernumerary marker chromosomes (sSMCs) are common structurally abnormal chromosomes that occur in 0.288% of cases of mental retardation. Isodicentric 15 (idic(15)) is common in sSMCs and usually leads to a rare chromosome disorder with distinctive clinical phenotypes, including early central hypotonia, developmental delay, epilepsy, and autistic behavior. It was previously shown that the partial tetrasomy 15q and partial hexasomy 15q syndromes are usually caused by one and two extra idic(15), respectively. Karyotypes containing a mosaic partial octosomy 15q resulting from three extra idic(15) have rarely been reported.

Case presentation

Two patients with profound intellectual impairment, development delay and hyperpigmentation were recruited for this study. The phenotype was relatively more severe in patient 1 than in patient 2. Conventional cytogenetic analysis of peripheral blood obtained from patients 1 and 2 revealed rare mosaic karyotypes containing sSMCs, i.e., mos 49,XX,+mar × 3[83]/48,XX,+mar × 2[7]/46,XX[10] and mos 48,XX,+mar × 2[72]/47,XX,+mar[28], respectively. The results of analyses of copy number variation (CNV) and fluorescence in situ hybridization (FISH) analyses, showed that the sSMCs were found to be idic(15) involving the Prader-Willi/Angelman Syndrome Critical Region (PWACR) genes and the P gene, with duplication sizes of 6.3 Mb and 9.7 Mb, respectively. DNA fingerprinting analysis of patient 1 showed a maternal origin for the idic(15). Both patients had mosaic idic(15) karyotypes: patient 1 had cells with a 15q partial octosomy (83%), and patient 2 had cells with a 15q partial hexasomy (72%).

Conclusions

We detected two rare mosaic idic(15) karyotypes that were associated with congenital abnormalities, including a rare mosaic octosomy of 15q11-q13. Our cases further validate the notion that the phenotypic severity is correlated with the level of mosaicism and the dosage effect of related genes in the proximal 15q.