Seizure characteristics in pallisterkillian syndrome

Seizure Characteristics in Pallister–Killian SyndromeMeghan S. Candee,1* John C. Carey,2 Ian D. Krantz,3 and Francis M. Filloux11Division of Pediatric Neurology, Department of Pediatrics, University of Utah School of Medicine, Salt Lake City, Utah2Division of Medical Genetics, Department of Pediatrics, University of Utah School of Medicine, Salt Lake City, Utah; Intermountain Healthcare,Salt Lake City, Utah3Division of Human Genetics, The Children’s Hospital of Philadelphia and the Perelman School of Medicine at the University of Pennsylvania,Philadelphia, Pennsylvania Manuscript Received: 11 February 2012; Manuscript Accepted: 18 June 2012 Pallister–Killian syndrome (PKS) is a congenital disorder attrib-uted to supernumerary isochromosome 12p mosaicism. Cranio- facial dysmorphism, learning impairment and seizures are Candee MS, Carey JC, Krantz ID, Filloux. FM.
considered cardinal features. However, little is known regarding the seizure and epilepsy patterns in PKS. To better define the prevalence and spectrum of seizures in PKS, we studied 51 patients (39 male, 12 female; median age 4 years and 9 months;age range 7 months to 31 years) with confirmed 12p tetrasomy.
Using a parent-based structured questionnaire, we collected dataregarding seizure onset, frequency, timing, semiology, and med- frequently identified in cells cultured from skin fibroblasts or buccal ication therapy. Patients were recruited through our practice, at mucosa [Bielanska et al., 1996]. Given the mosaic nature of the PKS Kids family events, and via the PKS Kids website. Epilepsy condition, genetic diagnosis is often elusive as karyotypes per- occurred in 27 (53%) with 23 (85%) of those with seizures having formed only on blood cells may fail to identify the condition seizure onset prior to 3.5 years of age. Mean age at seizure onset [Horneff et al., 1993; Bielanska et al., 1996]. The PKS phenotype was 2 years and 4 months. The most common seizure types were is typically described by the presence of three general findings: myoclonic (15/27, 56%), generalized convulsions (13/27, 48%), craniofacial dysmorphism, cognitive impairment [Stalker et al., and clustered tonic spasms (similar to infantile spasms; 8/27, 2006] (ranging from moderate to severe intellectual disability), and 30%). Thirteen of 27 patients with seizures (48%) had more than one seizure type with 26 out of 27 (96%) ever having taken The majority of existing literature on PKS has focused on antiepileptic medications. Nineteen of 27 (70%) continued to reaffirming the craniofacial dysmorphisms (e.g., forehead promi- have seizures and 17/27 (63%) remained on antiepileptic medi- nence, temporal balding, and hypertelorism as shown in Fig. 1), cation. The most commonly used medications were: levetirace- associated congenital defects (e.g., diaphragmatic hernia, cleft tam (10/27, 37%), valproic acid (10/27, 37%), and topiramate palate, heart anomalies, etc.), physical exam findings (e.g., hypoto- (9/27, 33%) with levetiracetam felt to be ‘‘most helpful’’ by nia and anomalous skin pigmentation) and genotypic variations parents (6/27, 22%). Further exploration of seizure timing, observed [Smigiel et al., 2008]. Thus far, there does not appear to be in-depth analysis of EEG recordings, and collection of MRI a correlation between the proportion of tetrasomic cells and the data to rule out confounding factors is warranted.
severity of a patient’s clinical presentation (i.e., severity of congeni- tal abnormalities, survival, and degree of cognitive impairment)[Schinzel, 1991; Speleman et al., 1991]. Exploration of the critical Key words: Pallister; Killian; seizures; epilepsy; 12p; tetrasomy gene region of i12p responsible for PKS is ongoing.
In contrast to what is known about the epilepsy characteristics of other chromosomal disorders (e.g., Angelman [Minassian et al.,1998], Wolf–Hirschhorn (4pÀ) [Battaglia et al., 2009], inverted duplication 15 [Battaglia et al., 1997], terminal deletion 1p36 Pallister–Killian syndrome (PKS), also known as Pallister mosaic aneuploidy syndrome [Reynolds et al., 1987], is a rare sporadic Meghan S. Candee, Division of Pediatric Neurology, Department of disorder first described in adults in 1977 by Pallister [Pallister et al., Pediatrics, Primary Children’s Medical Center, 100 N. Mario Capecchi 1977] and in children in 1981 by Killian and Teschler-Nicola Drive, Salt Lake City, UT 84113. E-mail: meghan.candee@hsc.utah.edu [1981]. PKS is caused by the presence of a supernumerary isochro- Article first published online in Wiley Online Library mosome (i12p) which confers tetrasomy. The chromosomal anom- aly is often absent in peripheral blood lymphocytes but is more AMERICAN JOURNAL OF MEDICAL GENETICS PART A children had onset of clustered epileptic spasms after infancy(‘‘late-onset spasms’’) and one of these children had an EEGconsistent with ‘‘modified hypsarrhythmia.’’ Of these four chil-dren, one had onset of ‘‘massive myoclonic jerks’’ at age 13 monthsthat appeared photosensitive in nature, and clustered tonic spasmsonly emerged later at age 4 [Cerminara et al., 2010]. The last of thesefive children had onset of partial clonic seizures at age 5.5 yearsfollowed by the appearance of clustered tonic spasms in flexion1 year later [Cerminara et al., 2010]. This prior data, though basedon a very small sample size, would suggest that children with PKScould be prone to later onset clustered spasms as a particularepileptic phenotype. Other case reports (Table I) suggest alternativeseizure semiology. For example, Smigiel et al. [2008] reporteduncategorized seizures in a neonate with PKS, while Spelemanet al. [1991] described two patients with generalized seizures whowere treated with valproic acid. Clearly, the existing informationavailable with respect to the seizure and epilepsy characteristics in FIG. 1. PKS patient facial characteristics. Note hypertelorism, PKS (Table I) is limited and presented in a fairly inconsistent and temporal balding, forehead prominence, and macrostomia.
fragmentary manner. This is because seizures were never before thefocus of investigation as such. Further delineation of an epilepsyphenotype (or phenotypes) in PKS may aid in seizure diagnosis, Bahi-Buisson et al., 2008a,b] and ring chromosome 20 syndromes improve anti-epileptic management, and provide a better under- [Inoue et al., 1997]), very little is known regarding the frequency of standing of prognosis for families and physicians [Battaglia et al., seizures, age of onset, typical seizure types, response to treatment or In the present paper, we describe the seizure characteristics of 51 Prior case series and meta-analyses (Table I) suggest seizure patients with PKS, the largest cohort of such patients to be evaluated prevalence in PKS to be in the vicinity of 42–59% [Bielanska et al., for seizures and epilepsy to date. This was made possible via web- 1996; Stalker et al., 2006]. However, these numbers are rough based contact and alliance with the family support group for people estimates, not to be mistaken for careful analysis of a particular affected by Pallister–Killian syndrome [http://pkskids.net/].
To date, only three groups (Table I) have described the detailed semiology and clinical characteristics of epileptic seizures in atotal of five children with PKS [Sanchez-Carpintero et al., 2005; Fifty-one patients with a diagnosis of Pallister–Killian syndrome Yamamoto et al., 2007; Cerminara et al., 2010]. Four of these (39 males and 12 females), as confirmed by parent-reported chro- TABLE I. Pallister–Killian Syndrome Seizure Literature Review—Comparison between Previously Reported Pallister–Killian Syndrome Neonatal–4 y Staring spells Æ quick head jerks, Myoclonic, partial, flex/extensor spasms Mean 2 y 4 m Myoclonic, generalized, infantile spasm, y, years; m, months; NR, not reported; CBZ, carbamazepine; CLB, clobazam; CNZ, clonazepam; DPH, diphenylhydantoin; ESM, thosuximide; LEV, levetiracetam; LTG, lamotrigine; OCBZ, oxcarbazepine;PHB, phenobarbitol; TPM, topiramate; VGB, vigabatrin; VPA, valproic acid; Vit B6, vitamin B6.
mosomal analysis, were included. Patients were identified initially Informed consent was obtained as the study involved voluntary via clinical contact, attendance at PKS support group meetings provision of personal medical information and requested the or by contact via notifications on the PKS Kids family web site option (which patients could refuse) of future contact by the investigators. The study was reviewed and approved by theInstitutional Review Board of the University of Utah in Salt LakeCity, UT.
Inclusion Criteria1. Any patient presenting (or having presented within the past 20 years) to the pediatric neurology or pediatric genetics divi- sions at University of Utah Medical Center/Primary Children’sMedical Center with a diagnosis of Pallister–Killian syndrome The parents of 51 children with a confirmed diagnosis of PKS was offered participation. In addition, patients/parents involved completed our survey. The median age of all patients at the time of in the international PKS Kids organization, families of patients study was 4 years and 9 months with a range of 7 months to 31 years visiting the PKS Kids web site, and families attending the (Table II). Seizures/epilepsy affected 27 of the 51 patients (53%).
2009 or 2010 annual PKS Kids Family meetings were offered Amongst patients diagnosed with seizures, the mean age was 8 years and 4 months, with a range of 19 months to 31 years 2. Parent-reported genetic diagnosis of PKS (i.e., mosaic tetrasomy (Table III). An additional 10% of parents suspected that their 12p as confirmed by fluorescence in situ hybridization, in child had seizures (Fig. 2). Taken together, 63% of patients fibroblast culture, or other tissue).
in our cohort were identified as having confirmed or suspectedseizures.
More than half of the patients diagnosed with seizures (56%) had seizure onset by 2 years of age, and nearly all of the patients withseizures (96%) had onset by 6 years (Fig. 3). The majority of Patients (and their families) were excluded if the diagnosis of PKS the patients (63%) had seizures during both the day and night.
had not yet been confirmed by chromosomal analysis (i.e., if their Twenty-two percent of parents reported that their child had ever diagnosis was suspected purely based on clinical presentation).
experienced status epilepticus. The most common seizure types Clinical details were obtained through a parent-based structured noted in our cohort of children with PKS were (in decreasing order questionnaire which was handed, mailed, or emailed to parents of frequency, as shown in Fig. 4) myoclonic (15/27, 56%), general- of children with PKS. The questionnaire included (but was not ized convulsive (13/27, 48%), clustered tonic spasms (i.e., ‘‘infantile’’ spasms though usually occurring beyond infancy; 8/27, 30%), brief staring episodes (5/27, 19%), and complex partial seizures (3/27, 11%). Only one of the eight patients with clustered tonic spasms (‘‘infantile spasms’’) had spasm onset prior to 2 years * Seizure type, frequency, timing (day/night/both), dura- of age. Nearly half of patients with seizures (13/27, 48%) had more Ninety-six percent of patients with seizures had ever taken antiepileptic medication with 56% having tried two or more (Table III). Sixty-three percent of patients with seizures remained on antiepileptic medication at the time of study. The most frequently used medications were valproic acid (10/27, 37%), levetiracetam (10/27, 37%), topiramate (9/27, 33%), phenobarbital(6/27, 22%), and lamotrigine (6/27, 22%; Fig. 5). The medications Of note, precise delineation of seizure timing (e.g., while waking/ considered to be most helpful by parents were: levetiracetam (6/27, awake/falling asleep/asleep, conditions which are not mutually 22%), and phenobarbital, valproic acid, topiramate, and lamotri- exclusive in that patients can have seizures at multiple levels of alertness) was not distinctly elucidated, largely because the questionpertaining to this information was only added into a later version ofthe survey. Direct parent interviews and/or phone/email contactwith parents was employed in order to ascertain specific details notfully clarified in the initially completed survey (e.g., when a question TABLE II. Selected Patient Characteristics was left blank or incomplete). Copies of pertinent medical records(e.g., EEG and MRI reports) were also requested and are still being collected at this time. As such, the EEG and MRI findings will not be discussed here. No incentives for participation were offered or Data from the collected surveys were summarized using descrip- tive statistics such as percentages, means, and standard deviations.
AMERICAN JOURNAL OF MEDICAL GENETICS PART A TABLE III. Seizure Patient Characteristics (n ¼ 27) AEDs, antiepileptic drugs.
aLikely confounded by longer spasm clusters.
FIG. 3. Timing of seizure onset. Fifty-six, eighty-five, and ninety-sixpercent of patients with seizures had seizure onset by 2, 3.5, and 6years, respectively.
Including 51 patients with PKS, this is the largest cohort to date ofpatients with PKS to be evaluated for seizures and epilepsy. Our data Although it has been previously suggested that most of the confirm that seizures are a common occurrence in children with patients with PKS who are going to develop seizures do so shortly PKS, affecting more than 50% of children by age 2 years.
after birth [Schinzel, 1991], our data suggest otherwise as only Our total of 63% of patients with confirmed or suspected seizures eleven (35% or about one third) of the patients with seizures had is noticeably higher than some previously reported prevalence seizures prior to 1 year of age and neonatal seizures were only estimates (e.g., 42% noted by Bielanska et al. [1996) but quite reported in one child (2%). Likewise, our findings do support the similar to that noted by Reynolds et al. [1987] in their case series of notion suggested in the five previously described patients [Sanchez- 10 patients and one stillborn fetus with PKS (i.e., 70%; also see Carpintero et al., 2005; Yamamoto et al., 2007; Cerminara et al., Table I). The inclusion of many very young children in our cohort 2010 also see Table I] that late onset spasms (occurring after 1 year along with the broad spectrum of seizure types diagnosed and the of age, and hence after the typical age of onset for ‘‘infantile suspicion (on behalf of parents) that their children have seizures spasms’’) may represent a relatively common epileptic pattern which are not always formally diagnosed, suggest that seizures may for children with PKS. Although 22% of parents reported that be even more common than we report here. This emphasizes the their child had ever experienced status epilepticus, based on subse- importance of following this cohort into the future as well as the quent careful review of our survey data, we believe this number to be need to expand the awareness of practitioners in looking for seizures falsely elevated secondary to parental reporting of longer clusters of tonic spasms as continuous seizure activity. Our finding that 70% FIG. 4. Common seizure types. More than half of the patients withseizures had demonstrated myoclonic seizures while nearly halfhad experienced generalized convulsions. Nearly half (48%) had FIG. 2. Seizure prevalence. Note that 63% of the patients in our PKS more than one seizure type. *Seven out of eight patients with cohort had been diagnosed or were suspected of having seizures.
‘‘infantile spasms’’ (87.5%) had onset at later than 2 years.
mal, often exhibiting a so-called ‘‘split-brain’’ pattern [Ohtsukaet al., 1993; Aicardi, 2005].
Based on the above observations, we hypothesized that children with PKS may also exhibit some predictable epilepsy or seizurepatterns. Our data so far, modestly support this hypothesis. Asreported by parents, the seizure pattern/epilepsy syndrome associ-ated with PKS is characterized by the following key elements: (1)absence of neonatal seizures; (2) onset by 2–5 years of age; (3) mixedseizure types with a predominance of myoclonic seizures and late-onset clustered tonic spasms (‘‘late-onset infantile spasms’’ withonset at greater than 1 year of age); (4) rarity of convulsive status FIG. 5. Anti-epileptic medications most frequently used and noted to epilepticus; and (5) periods of relative refractoriness.
be ‘‘most helpful.’’ While valproic acid and levetiracetam were most Although there does not appear to be a correlation between the commonly used, levetiracetam was identified as the most proportion of tetrasomic cells and the severity of a patient’s clinical presentation, further examination of the scope of seizure severitywithin this population, when combined with genetic analysis, mayshed light on the neurophysiologic mechanism of seizures in PKS. Alonger term goal of our research is to identify optimal management (19/27) of our patients with seizures continued to have seizures strategies for the treatment of seizures in PKS. While we have despite 63% (17/27) remaining on anti-epileptic medication dem- limited information in this respect thus far, it appears that the onstrates a presumed medication-refractory nature of seizures in majority of children diagnosed with seizures have required a trial of PKS. In the absence of long term follow-up data, it is not possible to more than one AED. Though levetiracetam has been identified by propose a single medication or specific regimen likely to be most parents as the most commonly effective single agent in this cohort, it effective for all or a majority of PKS children.
is by no means consistently effective. No other AED stands out as the Unfortunately, the relatively young age of many of our patients obvious second choice (see also Gerstner et al., 2008 for description limits our ability to accurately assess long-term prognosis in of valproate-associated encephalopathy in a child with PKS). Only children with PKS. However, it is interesting to note that the two patients in our cohort have required or been treated with the two oldest patients studied (now aged 29 and 31 years) are currently ketogenic diet. None had undergone vagal nerve stimulator im- seizure free. One of these two adults with PKS also appears to be one plantation. The latter two observations may speak to the relative of the ‘‘higher-functioning’’ individuals in our cohort.
lesser severity of the seizure phenotype in these children. Although Epilepsy is a common symptom of many congenital and/or our data do not yet allow us to firmly describe the long-term genetic syndromes that affect the nervous system. Some of these epilepsy prognosis of these patients, they do suggest that the overall are associated with specific epilepsy or electroencephalographic severity of epilepsy in this population is relatively less than for patterns [Battaglia et al., 1997, 2009; Inoue et al., 1997; Minassian children with Aicardi syndrome, or with other epileptic encepha- et al., 1998; Bahi-Buisson et al., 2008a,b]. For example, epilepsy is lopathies of childhood (such as Lennox–Gastaut syndrome, Myo- very common in children with Angelman syndrome and Wolf– clonic Astatic Epilepsy, or Dravet syndrome). The potential for Hirschhorn syndromes but differs substantially between the two. In remission may be less than that observed in Wolf–Hirschhorn the former, children often have mixed seizure types with frequent syndrome, but better than for girls with Rett syndrome and drop attacks and atypical absence seizures, accompanied by a certainly those with Aicardi syndrome.
characteristic EEG pattern described as periodic, large amplitude, Our survey-based study results are inherently limited by expec- slow spike-wave discharges often occurring in prolonged clusters or tation, recall and selection bias. Parents are not clinically trained trains [Minassian et al., 1998; Korff et al., 2005; Valente et al., 2006; to diagnose seizure activity and may over/under-report episodes.
Conant et al., 2009; Thibert et al., 2009]. A fair percentage of these In addition, parents with a child with epilepsy were likely more children will eventually go into remission [Uemura et al., 2005; motivated to fill out this questionnaire. Considerable variability Valente et al., 2006; Thibert et al., 2009]. In contrast, more than 90% with respect to parental interpretation of questions and terms was of children with Wolf–Hirschhorn syndrome have epilepsy, but noted as well. For example, some parents could describe a seizure most have generalized tonic–clonic seizures and about half suffer but not identify the category of seizure type. The differentiation episodes of status epilepticus. However, the majority eventually between the duration of a single seizure versus a cluster of seizures experience full seizure control or remission in childhood was not always entirely clear. We have tried and intend to continue [Worthington et al., 2008; Battaglia et al., 2009]. Girls with Rett to address such potential obstacles by conducting a thorough syndrome have a mixture of seizure types, but, perhaps similar to medical record review down the road. That being said, a children with PKS, also have a variety of non-epileptic paroxysmal questionnaire-driven approach is particularly helpful in the case events which can confound management [Laan et al., 1998; Moser of rare diseases for which ascertainment of cohorts of substantial et al., 2007; Bahi-Buisson et al., 2008a,b; Buoni et al., 2008]. Finally, size is challenging [Bahi-Buisson et al., 2008a,b; Battaglia et al., girls with Aicardi syndrome, experience early onset infantile spasms 2009; Thibert et al., 2009; Cardoza et al., 2011].
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