Symptomatic generalized epilepsy associated with an inverted duplication of chromosome 15

Electroclinical features of epilepsy in patients with InvDup(15)

PURPOSE

InvDup(15) syndrome is one of the most common chromosomal abnormalities associated with epilepsy. Here we review the seizure types described in InvDup(15) patients and the main electroclinical, therapeutic, and prognostic aspects of the syndrome.

METHODS

A literature search of PubMed, MEDLINE, and EMBASE was performed to identify papers examining InvDup(15) syndrome and epilepsy.

RESULTS

About 65% of the InvDup(15) patients described in the literature had multiple seizure types with a predominance (40.4%) of tonic-clonic seizures. Age at seizure onset was before 10 years in more than half of them. Patients suffered from a variety of EEG abnormalities, generalized spike activity being the most frequent. Brain MRI was unremarkable in the majority of patients. Treatment was with several anticonvulsant drugs used as mono- or polytherapy. Valproic acid was the most common treatment against generalized seizures and was often effective, although drug resistance was a major concern in a large number of cases. Finally, more than 30% of the children suffered from infantile spasms, and status epilepticus was described in nearly 20% of patients, occasionally resulting in death.

CONCLUSION

Seizures are very common in InvDup(15) patients, who suffer from a variety of seizure types. Information about EEG and brain MRI findings, seizure treatment, and prognosis is often poor. The overall prognosis is fair. Prospective studies of larger samples are needed, to gain further insights into the natural history of InvDup(15) syndrome.

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

Previous reports summarized the seizure types occurring in patients with idic(15) syndrome. To better define this issue, we retrospectively analyzed the evolution of electroencephalogram findings and seizures in 35 patients with confirmed idic(15). Epilepsy occurred in 28 patients (80%), with a median age of onset of 3 years 3 months. The initial seizures were infantile spasms associated with a hypsarrhythmic electroencephalogram (nine patients), focal/generalized tonic (seven patients), or atypical absences (eight patients). High doses of oral steroids were given in all nine children with infantile spasms, with remission of seizures and resolution of electroencephalogram abnormalities. Among them, three were seizure free at the time of evaluation, but six later developed Lennox-Gastaut syndrome or Lennox-Gastaut-like syndrome. The eight patients with atypical absences developed Lennox-Gastaut syndrome or Lennox-Gastaut-like syndrome. Epilepsy was well controlled in 32% of the patients; satisfactorily controlled (seizures reduced >75%) in 21.4%; partially controlled (seizures reduced <50%) in 10.7%; and uncontrolled in 32%. One patient was not taking any anti-epileptic drugs by his parents' choice. Fourteen percent were on monotherapy; whereas the other 82% were on polytherapy. Seizures stopped at a median age of 5 years 5 months. The interictal electroencephalogram showed slow/sharp waves, and/or biphasic spikes-polyspikes, spike/wave complexes, and an excess of fast activity mainly over the fronto-temporal areas. Epilepsy is a major clinical challenge in patients with idic(15), associated with a poor prognosis in 55%. Frontal lobe seizures are a novel finding. © 2016 Wiley Periodicals, Inc.

A survey of seizures and current treatments in 15q duplication syndrome

OBJECTIVE

Seizures are common in individuals with duplications of chromosome 15q11.2-q13 (Dup15q). The goal of this study was to examine the phenotypes and treatments of seizures in Dup15q in a large population.

METHODS

A detailed electronic survey was conducted through the Dup15q Alliance containing comprehensive questions regarding seizures and their treatments in Dup15q.

RESULTS

There were 95 responses from Dup15q families. For the 83 with idic(15), 63% were reported to have seizures, of which 81% had multiple seizure types and 42% had infantile spasms. Other common seizure types were tonic-clonic, atonic, myoclonic, and focal. Only 3 of 12 individuals with int dup(15) had seizures. Broad spectrum antiepileptic drugs (AEDs) were the most effective medications, but carbamazepine and oxcarbazepine were also effective, although typical benzodiazepines were relatively ineffective. There was a 24% response rate (>90% seizure reduction) to the first AED tried. For those with infantile spasms, adrenocorticotropic hormone (ACTH) was more effective than vigabatrin.

SIGNIFICANCE

This is the largest study assessing seizures in Duplication 15q syndrome, but because this was a questionnaire-based study with a low return rate, it is susceptible to bias. Seizures are common in idic(15) and typically difficult to control, often presenting with infantile spasms and progressing to a Lennox-Gastaut-type syndrome. Seizures in those with int dup(15) are less common, with a frequency similar to the general autism population. In addition to broad spectrum AED, medications such as carbamazepine and oxcarbazepine are also relatively effective in controlling seizures in this population, suggesting a possible multifocal etiology, which may also explain the high rate of infantile spasms. Our small sample suggests a relative lack of efficacy of vigabatrin and other γ-aminobutyric acid (GABA)ergic medications, such as typical benzodiazepines, which may be attributable to abnormal GABAergic transmission resulting from the duplication of a cluster of GABAβ3 receptor genes in the 15q11.2-13 region.

A case of isodicentric chromosome 15 presented with epilepsy and developmental delay

We report a case of isodicentric chromosome 15 (idic(15) chromosome), the presence of which resulted in uncontrolled seizures, including epileptic spasms, tonic seizures, and global developmental delay. A 10-month-old female infant was referred to our pediatric neurology clinic because of uncontrolled seizures and global developmental delay. She had generalized tonic-clonic seizures since 7 months of age. At referral, she could not control her head and presented with generalized hypotonia. Her brain magnetic resonance imaging scans and metabolic evaluation results were normal. Routine karyotyping indicated the presence of a supernumerary marker chromosome of unknown origin (47, XX +mar). An array-comparative genomic hybridization (CGH) analysis revealed amplification from 15q11.1 to 15q13.1. Subsequent fluorescence in situ hybridization analysis confirmed a idic(15) chromosome. Array-CGH analysis has the advantage in determining the unknown origin of a supernumerary marker chromosome, and could be a useful method for the genetic diagnosis of epilepsy syndromes associated with various chromosomal aberrations.

Familial partial trisomy 15q11-13 presenting as intractable epilepsy in the child and schizophrenia in the mother

Various rearrangements involve the proximal long arm of chromosome 15, including deletions, duplications, translocations, inversions and supernumerary marker chromosome of an inverted duplication. The large marker 15, that contains the Prader-Willi syndrome (PWS)/Angelman syndrome (AS) chromosome region, is usually associated with an abnormal phenotype of moderate to severe mental retardation, seizures, poor motor coordination, early-onset central hypotonia, autism and autistic-like behavior, schizophrenia and mild dysmorphic features. We report a ten year-old girl with normal intelligence prior to the onset of seizures, who developed severe intractable epilepsy at the age of seven years. Family history was significant for a mother with recurrent episodes of acute psychosis. The patient's and mother's karyotype revealed 47,XX+m. Array comparative genomic hybridization (A-CGH) identified a gain of 13 BAC clones from 15q11.2 through 15q13.1, which was then confirmed by FISH to be part of the marker chromosome. This duplicated region contains the SNRPN/UBE3A locus. This case demonstrates that a duplication of 15q11-13 can present differently in the same family either as intractable epilepsy or as a psychiatric illness and that intelligence can be preserved. We suggest that CGH microarray should be performed in cases with intractable epilepsy or schizophrenia, with or without mental retardation.

Inv dup (15): Is the electroclinical phenotype helpful for this challenging clinical diagnosis?

OBJECTIVE

To study the electroclinical phenotype in 5 patients with large supernumerary marker chromosome referred as inv dup (15), in an attempt to analyze the electroclinical spectrum in order to determine if the binomial epilepsy-EEG is stereotyped enough to corroborate this challenging diagnosis.

METHODS

Five patients with large inv dup (15) were submitted to EEG and/or V-EEG, with a minimum duration of 2h. Two certified neurophysiologists analyzed all EEG tracings simultaneously, blinded to clinical and molecular data. Epilepsy was characterized by detailed history and a standard questionnaire according to International League Against Epilepsy guidelines and corroborated by V-EEG findings.

RESULTS

Epilepsy started during infancy in 4 patients, in 3 with spasms. Spasms were easily controlled in one but not in others. Epilepsy evolved with generalized seizures in two patients and, generalized and focal in one. Currently, 3 patients present refractory epilepsy and two are seizure-free. In one patient, only one isolated episode suggestive of a secondary generalized tonic-clonic event occurred at the age of 12 years without recurrence. Regarding the EEG, patients had distinct features, except for two patients with very high amplitude fast activity, resembling recruiting rhythm. Despite good seizure outcome in 3 patients, EEGs remained remarkably abnormal with frequent epileptiform discharges over poorly organized background.

CONCLUSIONS

Our data showed a heterogeneous electroclinical phenotype with generalized and partial epilepsy, presenting distinct degrees of severity and refractoriness.

SIGNIFICANCE

Our findings suggest that it is not possible to delineate an electroclinical phenotype in this neurogenetic syndrome. Therefore, inv dup (15) remains as a diagnostic challenge and epilepsy and EEG features are valuable only when inserted in the proper clinical context.

L'épilepsie dans les aberrations chromosomiques

Epilepsy is among the most frequent finding in many chromosome aberrations. While most chromosome aberrations can be associated with different seizure types, there are few aberrations which feature specific seizures and EEG patterns. Among the 400 different chromosomal imbalances described with seizures and EEG abnormalities, eight have a high association with epilepsy. These comprise: the monosomy 1p36, Wolf-Hirschhorn syndrome (4p-), Angelman syndrome, Miller-Dieker del 17p13.3, the inversion duplication 15 syndrome, ring 20 and ring 14 syndromes, Down's syndrome. These chromosomal regions where aberrations have an evident association with epilepsy may be useful targets for gene hunters. On the other hand, a better characterisation of epileptic syndrome in these disorders may lead to a better and specific treatment.

A patient with Prader-Willi syndrome and a supernumerary marker chromosome r(15)(q11.1-13p11.1)pat and maternal heterodisomy

We report on a Prader-Willi patient with a de novo supernumerary marker chromosome (SMC) in 16% of the cells. The SMC was a ring chromosome and it included the PWS/AS critical region as was demonstrated by FISH. Segregation analysis indicated that the SMC originated from a paternal chromosome 15 and the two normal chromosomes 15 of the patients were of the maternal homologues. Namely, the patient had maternal heterodisomy in 85% of the cells and triplication of the PWS/AS region in 15% of the cells. The Prader-Willi features were the result of the low mosaicism of the SMC. The evolution of the maternal heterodisomy and the SMC were two unrelated events, the occurrence of both events in the same embryo rescued it from lethality.

Inherited epilepsies

Epilepsy may be acquired or inherited. At least one half of epilepsy is genetic in origin; this figure is likely higher in children regardless of whether seizures are generalized or partial. Inherited epilepsies are classified as benign, cryptogenic, or symptomatic depending on associated clinical, electrographic, and neuroimaging features. To date, genetic mutations in the idiopathic inherited epilepsies affect channel function within the central nervous system; genes underlying symptomatic epilepsies are more heterogeneous. Accurate diagnosis of an inherited epilepsy syndrome provides useful prognostic information; it also may help guide diagnostic evaluation, including request for specific gene testing. In the near future, the relationship between genetic defect and response to specific anticonvulsants may also be better defined.