PRRT2 mutation in Japanese children with benign infantile epilepsy

Mutations in PRRT2 genes have been identified as a major cause of benign infantile epilepsy and/or paroxysmal kinesigenic dyskinesia. We explored mutations in PRRT2 in Japanese patients with BIE as well as its related conditions including convulsion with mild gastroenteritis and benign early infantile epilepsy. We explored PRRT2 mutations in Japanese children who had had unprovoked infantile seizures or convulsion with mild gastroenteritis. The probands included 16 children with benign infantile epilepsy, 6 children with convulsions with mild gastroenteritis, and 2 siblings with benign early infantile epilepsy. In addition, we recruited samples from family members when PRRT2 mutation was identified in the proband. Statistical analyses were performed to identify differences in probands with benign infantile epilepsy according to the presence or absence of PRRT2 mutation. Among a total of 24 probands, PRRT2 mutations was identified only in 6 probands with benign infantile epilepsy. A common insertion mutation, c.649_650insC, was found in 5 families and a novel missense mutation, c.981C>G (I327M), in one. The family history of paroxysmal kinesigenic dyskinesia was more common in probands with PRRT2 mutations than in those without mutations. Our study revealed that PRRT2 mutations are common in Japanese patients with benign infantile epilepsy, especially in patients with a family history of paroxysmal kinesigenic dyskinesia.     

Genetic analysis of PRRT2 for benign infantile epilepsy,infantile convulsions with choreoathetosis syndrome,and benign convulsions with mild gastroenteritis

Purpose: PRRT2 mutations were recently identified in benign familial infantile epilepsy (BFIE) and infantile convulsions with paroxysmal choreoathetosis (ICCA) but no abnormalities have so far been identified in their phenotypically similar seizure disorder of benign convulsions with mild gastroenteritis (CwG), while mutations in KCNQ2 and KCNQ3 have been recognized in benign familial neonatal epilepsy (BFNE). The aim of this study was to identify PRRT2 mutations in infantile convulsions in Asian families with BFIE and ICCA, CwG and BFNE. Methods: We recruited 26 unrelated Japanese affected with either BFIE or non-familial benign infantile seizures and their families, including three families with ICCA. A total of 17 Japanese and Taiwanese with CwG, 50 Japanese with BFNE and 96 healthy volunteers were also recruited. Mutations of PRRT2 were sought using direct sequencing. Results: Heterozygous truncation mutation (c.649dupC) was identified in 15 of 26 individuals with benign infantile epilepsy (52.1%). All three families of ICCA harbored the same mutation (100%). Another novel mutation (c.1012+2dupT) was found in the proband of a family with BFIE. However, no PRRT2 mutation was found in either CwG or BFNE. Conclusions: The results confirm that c.649dupC, a truncating mutation of PRRT2, is a hotspot mutation resulting in BFIE or ICCA regardless of the ethnic background. In contrast, PRRT2 mutations do not seem to be associated with CwG or BFNE. Screening for PRRT2 mutation might be useful in early-stage differentiation of BFIE from CwG.     

Re-evaluation of PRRT2 mutations in paroxysmal disorders

Mutations in PRRT2 have recently been identified as the major cause of autosomal dominant benign familial infantile epilepsy (BFIE), infantile convulsions with choreoathetosis syndrome (ICCA), and paroxysmal kinesigenic dyskinesia (PKD). Other paroxysmal disorders like febrile seizures, migraine, paroxysmal exercise-induced dyskinesia, and paroxysmal non-kinesigenic dyskinesia have also been shown to be associated with this gene. We re-evaluated PRRT2 mutations and genetic–clinical correlations in additional cases with PKD/ICCA and other paroxysmal disorders. Two novel mutations in PRRT2 were revealed in PKD/ICCA cases, while no mutations were detected in other diseases, which suggests BFIE and PKD are still core phenotypes of PRRT2-related spectrum disorders.     

Familial PRRT2 mutation with heterogeneous paroxysmal disorders including paroxysmal torticollis and hemiplegic migraine

PRRT2 is the gene recently associated with paroxysmal kinesigenic dyskinesia (PKD), benign familial infantile epilepsy, and choreoathetosis infantile convulsions. We report four family members with PRRT2 mutations who had heterogeneous paroxysmal disorders. The index patient had transient infantile paroxysmal torticollis, then benign infantile epilepsy that responded to carbamazepine. The index patient's father had PKD and migraine with aphasia, and his two brothers had hemiplegic migraine with onset in childhood. All four family members had the same PRRT2 c.649dupC mutation. We conclude that heterogeneous paroxysmal disorders are associated with PRRT2 mutations and include paroxysmal torticollis and hemiplegic migraine. We propose that PRRT2 is a new gene for hemiplegic migraine.     

Mutations in PRRT2 are not a common cause of infantile epileptic encephalopathies

Heterozygous mutations in PRRT2 have recently been identified as the major cause of autosomal dominant benign familial infantile epilepsy (BFIE), infantile convulsions with choreoathetosis syndrome (ICCA), and paroxysmal kinesigenic dyskinesia (PKD). Homozygous mutations in PRRT2 have also been reported in two families with intellectual disability (ID) and seizures. Heterozygous mutations in the genes KCNQ2 and SCN2A cause the two other autosomal dominant seizure disorders of infancy: benign familial neonatal epilepsy and benign familial neonatal‐infantile epilepsy. Mutations in KCNQ2 and SCN2A also contribute to severe infantile epileptic encephalopathies (IEEs) in which seizures and intellectual disability co‐occur. We therefore hypothesized that PRRT2 mutations may also underlie cases of IEE. We examined PRRT2 for heterozygous, compound heterozygous or homozygous mutations to determine their frequency in causing epileptic encephalopathies (EEs). Two hundred twenty patients with EEs with onset by 2 years were phenotyped. An assay for the common PRRT2 c.649‐650insC mutation and high resolution‐melt analysis for mutations in the remaining exons of PRRT2 were performed. Neither the common mutation nor any other pathogenic variants in PRRT2 were detected in the 220 patients. Our findings suggest that mutations in PRRT2 are not a common cause of IEEs.     

The PRRT2 mutation c.649dupC is the so far most frequent cause of benign familial infantile convulsions

PurposeMutations in the PRRT2 gene have been recently described as a cause of paroxysmal kinesigenic dyskinesia, infantile convulsions with choreoathetosis syndrome and, less often, infantile convulsions. We have analysed the frequency of PRRT2 mutations in families with benign familial infantile convulsions without paroxysmal kinesigenic dyskinesia.Methods and resultsDirect sequencing of the coding region identified the PRRT2 mutation c.649dupC in 5/5 families with infantile convulsions. The mutation was present in 23 family members, of which 18 were clinically affected and 2 were obligate carriers. The affected carriers of this mutation presented with different types of epileptic seizures during early childhood but did not develop additional neurological symptoms later in life.ConclusionOur data demonstrate that the PRRT2 mutation c.649dupC is a frequent cause of benign familial infantile convulsions.     

Peri-ictal EEG in infants with PRRT2-related self-limited infantile epilepsy

Objective

Pathogenic PRRT2 variants cause self-limited (familial) infantile epilepsy (SeLIE), which is responsive to sodium channel blocking antiseizure medications. The interictal EEG is typically normal. We describe a cohort of infants with PRRT2-related SeLIE with striking peri-ictal EEG abnormalities.

Methods

We included all infants diagnosed with PRRT2-related SeLIE during July 2020 to November 2021 at the Royal Children's Hospital, Melbourne. Clinical features and results of aetiologic investigations were collected from electronic medical records. All EEGs were reviewed independently by two epileptologists.

Results

Ten infants presented with focal seizures at a median age of 5 months (range: 3–6 months). Eight had a family history of epilepsy, paroxysmal kinesigenic dyskinesia (PKD) or hemiplegic migraine. Seven of the eight infants with an EEG performed within 24 h of the most recent seizure had epileptiform discharges. Their EEGs showed focal sharp waves, spikes, polyspikes or fast activity independently over the left and right temporo-occipital regions. Conversely, the two infants with last known seizure greater than 24 h prior to their EEG had no epileptiform discharges. Oxcarbazepine was commenced in two infants and was effective. Eight infants were initially treated with levetiracetam, and all were subsequently switched to oxcarbazepine due to ongoing seizures or side effects.

Significance

Posterior polymorphic focal epileptiform discharges on a peri-ictal EEG recording are a feature of PRRT2-related SeLIE. This finding, particularly in the presence of a family history of infantile epilepsy, PKD or hemiplegic migraine, suggests a diagnosis of PRRT2-related SeLIE and has important treatment implications.     

Epilepsy and EEG paroxysmal abnormalities in autism spectrum disorders

The occurrence of epilepsy in autism is variable; nevertheless, EEG paroxysmal abnormalities (PA) are frequently recorded in patients with autism, although the influence of epilepsy and/or EEG PA on the autistic regression has not been clarified yet. We examine a large sample of 345 inpatients with autism, divided into three groups: (1) patients without epilepsy and EEG PA; (2) patients with EEG PA but no seizures; (3) patients with epilepsy including febrile convulsions. The prevalence of epilepsy (24.9%) and EEG PA (45.5%) was higher than that reported in the general population. The significant differences among the three groups concerned autistic regression (comparison between groups 1 and 2, p < 0.05; comparison between groups 1 and 3, p < 0.01), cerebral lesions (comparison between groups 1 and 2, p < 0.05; between groups 1 and 3, p < 0.001), and symptomatic autism (comparison between groups 1 and 2 as much as comparison between groups 1 and 3, p < 0.001), which were prevalent in groups 2 and 3; while severe/profound mental retardation was more frequent in group 3 compared to group 1 (p < 0.01). Focal epilepsy (43.0%) and febrile convulsions (33.7%) were frequent in the third group with epilepsy. EEG PA were mainly localized in temporal and central areas (31.4%). Only 2.6% of patients had subcontinuous/continuous EEG PA during sleep. Seizures and EEG PA were not related to autistic regression. EEG PA occurred mainly in childhood, while epilepsy tended to occur (p < 0.001) as age increased. The age at onset of seizures had two peaks: between 0 and 5 and between 10 and 15 years with no difference between idiopathic and symptomatic cases. In 58.5% of subjects aged ?20 years, epilepsy including febrile seizures occurred at some point of their lives, while cases with only EEG PA were less frequent (9.7%). The relationship among autism, EEG PA and epilepsy should be clarified and investigated. In autism, seizures and EEG PA could represent an epiphenomenon of a cerebral dysfunction independent of apparent lesions.     

Mutation screening of the PRRT2 gene for benign epilepsy with centrotemporal spikes in Chinese mainland population

Proline-rich transmembrane protein 2 gene (PRRT2) mutations are reported to cause common paroxysmal neurological disorders and show a remarkable pleiotropy. Benign epilepsy with centrotemporal spikes (BECTS) is considered to be the most common epilepsy syndrome in childhood. It is placed among the idiopathic localization related epilepsies. Recently, it was reported that a girl with a PRRT2 mutation c.649_650insC developed infantile focal epilepsy with bilateral spikes which resembled the rolandic spikes. Hereby we performed a comprehensive genetic mutation screening of PRRT2 gene in a cohort of 53 sporadic BECTS patients. None of the 53 sporadic BECTS patients and other 250 controls carried mutations including c.649_650insC in PRRT2. Our data indicated that the PRRT2 mutations might most likely not be associated with BECTS in Chinese mainland population.     

Panayiotopoulos-type benign childhood occipital epilepsy: a prospective study

OBJECTIVE: To characterize the clinical and EEG features of the syndrome of benign childhood partial seizures with ictal vomiting and EEG occipital spikes (Panayiotopoulos syndrome [PS]). METHODS: Prospective study of children with normal general and neurologic examinations who had seizures with ictal vomiting and EEG with occipital spikes. RESULTS: From February 1990 to 1997, the authors found 66 patients with PS and 145 children with benign childhood epilepsy with centrotemporal spikes. Peak age at onset of PS was 5 years. Ictal deviation of the eyes and progression to generalized seizures were common. One-third had partial status epilepticus. During sleep, all had seizures. While awake, one-third also had seizures. Five children with PS had concurrent symptoms of rolandic epilepsy and another five developed rolandic seizures after remission of PS. Prognosis was excellent: one-third had a single seizure, one-half had two to five seizures, and only 4.5% had frequent seizures. CONCLUSIONS: Panayiotopoulos-type benign childhood occipital epilepsy is less common than benign childhood epilepsy with centrotemporal spikes but is well defined and recognizable by clinical and EEG features.     

Paroxysmal EEG abnormalities and epilepsy in pervasive developmental disorders: Follow-up study until adolescence and beyond

This study examined paroxysmal abnormalities and epilepsy in EEG for individuals with pervasive developmental disorders (PDD) in two parts: first with a large number of subjects (n = 1624); and second with extracted subjects followed from ?5 years into adolescence and beyond (n = 92). Many paroxysms in PDD patients in their childhood tended to appear at various sites and the same held for paroxysms at the time of epilepsy onset. However, in adolescence and beyond, paroxysms in the frontal region prevailed as those appearing at sites other than the frontal region tended to disappear. The same held for paroxysms at the time of epilepsy onset. These paroxysms in the frontal area characteristic of PDD were named “Paroxysms at F.” It was suggested that functional abnormality in the frontal region exists in PDD through paroxysmal EEG abnormalities and epilepsy.     

Benign familial and non-familial infantile seizures (Fukuyama-Watanabe–Vigevano syndrome): A study of 14 cases from Saudi Arabia

Purpose: Benign infantile seizures [BIS], familial and non-familial, represent a benign, age-related idiopathic syndrome of infancy. The aim of the current paper is to document the presence of the syndrome in Saudi Arabia and in Arab populations and to discuss the characteristic electroclinical features and the benign nature of this syndrome. Patients and methods: A case series of 275 patients with epileptic seizures (age range: 2 months–13 years) were followed over a period of 3 years and 7 months. The inclusion criteria for BIS were as follows (1) age of seizure onset between 2 and 24 months, (2) normal development before, during and after the onset of seizures, (3) normal interictal EEG, (4) normal brain imaging, and (5) good response to treatment. We analyzed these infants with respect to age at seizure onset, sex, physical and neurological examination, consanguinity, frequency and type of convulsions, associated conditions and laboratory and radiological investigations. A waking and sleeping interictal EEG was performed on all patients, and for one patient (No. 1), ictal EEG and video clips were recorded. Results: Fourteen infants (12.0%) showed electroclinical features consistent with BIS. Eleven patients fulfilled the criteria of benign non-familial infantile seizures (BNFIS), and for three patients, their family pedigrees showed the possibility of benign familial infantile seizures (BFIS). All of the patients responded to anti-epileptic treatment, and 50% of them responded within 3 months. Conclusions: To our knowledge, this is the first study to document the presence of BIS (Fukuyama-Watanabe–Vigevano syndrome) in Saudi Arabian and Arab populations. We highlighted the characteristic features of BIS and demonstrated the benign nature of the syndrome.     

Magnetoencephalography localizing spike sources of atypical benign partial epilepsy

Rationale: Atypical benign partial epilepsy (ABPE) is characterized by centro-temporal electroencephalography (EEG) spikes, continuous spike and waves during sleep (CSWS), and multiple seizure types including epileptic negative myoclonus (ENM), but not tonic seizures. This study evaluated the localization of magnetoencephalography (MEG) spike sources (MEGSSs) to investigate the clinical features and mechanism underlying ABPE. Methods: We retrospectively analyzed seizure profiles, scalp video EEG (VEEG) and MEG in ABPE patients. Results: Eighteen ABPE patients were identified (nine girls and nine boys). Seizure onset ranged from 1.3 to 8.8 years (median, 2.9 years). Initial seizures consisted of focal motor seizures (15 patients) and absences/atypical absences (3). Seventeen patients had multiple seizure types including drop attacks (16), focal motor seizures (16), ENM (14), absences/atypical absences (11) and focal myoclonic seizures (10). VEEG showed centro-temporal spikes and CSWS in all patients. Magnetic resonance imaging (MRI) was reported as normal in all patients. MEGSSs were localized over the following regions: both Rolandic and sylvian (8), peri-sylvian (5), peri-Rolandic (4), parieto-occipital (1), bilateral (10) and unilateral (8). All patients were on more than two antiepileptic medications. ENM and absences/atypical absences were controlled in 14 patients treated with adjunctive ethosuximide. Conclusion: MEG localized the source of centro-temporal spikes and CSWS in the Rolandic-sylvian regions. Centro-temporal spikes, Rolandic-sylvian spike sources and focal motor seizures are evidence that ABPE presents with Rolandic-sylvian onset seizures. ABPE is therefore a unique, age-related and localization-related epilepsy with a Rolandic-sylvian epileptic focus plus possible thalamo-cortical epileptic networks in the developing brain of children.     

Ictal EEG patterns in epilepsy with centro-temporal spikes

Purpose: To describe the EEG pattern of seizures in patients with benign childhood epilepsy with centro-temporal spikes (BCECTS). Methods: The clinical and EEG data of 701 BCECTS patients with at least a 3 years follow-up were reviewed from 10 epilepsy centers. Results: Thirty-four seizures were recorded in 30 patients. Four different ictal EEG patterns (A-D) were identified. The most frequent (pattern A) was characterized by low voltage activity of fast rhythmic spikes, increasing in amplitude and decreasing in frequency, and occurred in 14 children. Pattern B (six patients) was constituted by a discharge of spikes intermixed with sharp waves increasing in frequency and amplitude. Pattern C (seven children) consisted of monomorphic theta which progressively formed a discharge increasing in amplitude and decreasing in frequency. Pattern D (5 children) was characterized by a initial focal depression of the electrical activity, followed by one of the three above described patterns. In 21 out of 28 children, the initial ictal pattern, altered from one pattern to another one. No clinical or EEG feature was predictive of a specific ictal pattern. Discussion: We failed to identify a unique ictal EEG pattern in our patients with BCECTS. The occurrence of per-ictal features, e.g., initial EEG depression or post-ictal slowing, is common and should not be interpreted with prejudice. Alteration of ictal EEG pattern from one to another is not in conflict with the diagnosis of BCECTS.     

Alexander disease with mild dorsal brainstem atrophy and infantile spasms

We present the case of a Japanese male infant with Alexander disease who developed infantile spasms at 8 months of age. The patient had a cluster of partial seizures at 4 months of age. He presented with mild general hypotonia and developmental delay. Macrocephaly was not observed. Brain magnetic resonance imaging (MRI) findings fulfilled all MRI-based criteria for the diagnosis of Alexander disease and revealed mild atrophy of the dorsal pons and medulla oblongata with abnormal intensities. DNA analysis disclosed a novel heterozygous missense mutation (c.1154 C>T, p.S385F) in the glial fibrillary acidic protein gene. At 8 months of age, tonic spasms occurred, and electroencephalography (EEG) revealed hypsarrhythmia. Lamotrigine effectively controlled the infantile spasms and improved the abnormal EEG findings. Although most patients with infantile Alexander disease have epilepsy, infantile spasms are rare. This comorbid condition may be associated with the distribution of the brain lesions and the age at onset of Alexander disease.     

Abstracts of the 38th Congress of the Japan Epilepsy Society, Shizuoka, Japan, September 30-October 1, 2004

Diagnosis and Treatment of Idiopathic Focal Epilepsies (Benign Partial Epilepsies) in Infancy and Childhood. ¹ Tamiko Negoro ( ¹ Department of Laboratory Medicine, Nagoya University Hospital, Nagoya, Japan ). Introduction: According to the revised classification of epilepsies and epileptic syndromes proposed by the Commission on Classification and Terminology of the International League Against Epilepsy (1989), benign childhood epilepsy with centrotemporal spikes (BCECT), childhood epilepsy with occipital paroxysms (Gastaut‐type late‐onset CEOP), and primary reading epilepsy were included in the idiopathic localization‐related epilepsies (ILRE). Since then, new epileptic syndromes such as Panayiotopoulos‐type early‐onset benign childhood occipital epilepsy (also known as benign childhood epilepsy with occipital paroxysms or BCEOP) and benign partial epilepsies in infancy (BPEI) have been additionally included as ILRE. The diagnostic criteria for benign partial epilepsies include (1) normal neurological examination; (2) normal intelligence; (3) normal neuroimaging; (4) a family history of benign‐type seizures; (5) brief stereotyped seizures; (6) frequent nocturnal occurrence; (7) easy control with antiepileptic drugs (AEDs), except ethosuximide; and (8) remission before adolescence. The EEG features include (1) normal background activity; (2) spikes with a characteristic morphology and location; (3) sleep activation; and (4) occasional generalized paroxysms. In our 114 cases of childhood onset localization‐related epilepsies (LRE) diagnosed between 1997 and 2000, 48 cases (42%) were diagnosed as ILRE and 66 were cryptogenic or symptomatic LRE. Among the 48 ILRE cases, 28 (58%) were classified as BCECT, six (13%) as BPEI, five (10%) as BCEOP, two (4%) as atypical benign partial epilepsy, and seven (15%) as unclassified. Carbamazepine (CBZ), valproate (VPA) and clonazepam (CZP) were equally effective in controlling the seizures in our ILRE patients. This review describes briefly the diagnosis and treatment of BCECT, BCEOP, and BPEI. Benign Childhood Epilepsy with Centrotemporal Spikes: BCECT is the most common ILRE (also known as idiopathic focal epilepsies) in infancy and childhood. Sylvian seizures (simple partial seizures or focal motor or sensory seizures beginning unilaterally at the lower part of the face) and EEG findings (central‐midtemporal high‐amplitude, repetitive sharp waves) are quite stereotyped, and diagnosis of typical cases is relatively easy. Frontal lobe seizures with bilateral perioral twitches or unilateral eyelid twitches may sometimes be misdiagnosed as Sylvian seizures. Since status epilepticus is very rare and many patients only have occasional seizures, many physicians choose not to treat the disorder. If treatment is necessary, the seizures are usually easily controlled with carbamazepine, valproic acid, or clonazepam. Continuation of AEDs is not necessary after the EEG has normalized around puberty. The prognosis is excellent. However, a small percentage of patients may show atypical evolutions such as atypical benign partial epilepsy, epilepsy with continuous spike‐and‐waves in slow wave sleep, or epilepsy with centrotemporal spikes and oromotor deficit. Seizure and EEG exacerbations by AEDs, especially carbamazepine, have to be considered. Early recognition and proper treatment are necessary for these conditions. Benign Childhood Epilepsy with Occipital Paroxysms: BCEOP is also known as Panayiotopoulos‐type early‐onset benign childhood occipital epilepsy. The mean age at first seizure is around 5 years. Seizures comprise an unusual constellation of autonomic, mainly emetic, syndromes with unilateral deviation of the eyes and impairment of consciousness. Visual symptoms, which are the main symptoms in Gastaut‐type, late‐onset CEOP, are exceptions in BCEOP. According to our 41 cases examined between 1984 and 1993, two‐thirds of the patients show hemi‐ or generalized convulsions and one‐fourth experience prolonged seizures for longer than 30 minutes. EEG findings (bilateral occipital paroxysms) consist of some extraoccipital abnormalities especially in the frontal area (48% of our cases) or generalized paroxysmal discharges (32% of ours cases), together with various migrations of spike foci. EEG findings seem to normalize around the age of 10 years. Many patients only have occasional seizures and these seizures are usually easy to control with carbamazepine or valproic acid. The prognosis is excellent. Prevention of status epilepticus is the major problem in this disorder. Recently, new concepts including early‐onset benign occipital seizure susceptibility syndrome (EBOSS) and Panayiotopoulos syndrome (idiopathic susceptibility to early‐onset benign childhood seizures with mainly autonomic symptoms), have been introduced for BCEOP. Benign Partial Epilepsies in Infancy: BPEI comprise two forms. One is partial epilepsy with complex partial seizures (CPS) and the other is partial epilepsy with secondarily generalized seizures (SGS). Onset is mostly during the first year of life. Seizures often occur in clusters and are characterized by motion arrest, decreased responsiveness, staring or blank eyes often with automatisms, and mild convulsive movements in the CPS form; and motion arrest or opening of eyes with staring or blank eyes followed by generalized tonic–clonic seizures in the SGS form. Interictal EEGs mostly show no abnormal findings. According to the ictal EEGs, the most frequent site of seizure origin is in the frontal or temporal area in the CPS form; and central, parietal, or occipital area in the SGS form. Treatment with carbamazepine, phenobarbital, zonisamide or valproic acid immediately stops the cluster of seizures. The prognosis is excellent. Recently, sleep‐related and low‐voltage Rolandic and vertex spikes have been reported as an EEG marker of benignity in this disorder. Most of benign infantile convulsions may belong to partial epilepsy with SGS, although confirmation with ictal EEG recording is necessary for accurate diagnosis.     

Benign familial infantile seizures: further delineation of the syndrome

Benign familial infantile seizures are an autosomal dominant epilepsy disorder that is characterized by convulsions, with onset at age 3 to 12 months and a favorable outcome. Benign familial infantile seizures have been linked to chromosome 19q whereas infantile convulsions and choreoathetosis syndrome, in which benign familial infantile seizure is associated with paroxysmal choreoathetosis, has been linked to chromosome 16p 12-q12. Many additional families from diverse ethnic backgrounds have similar syndromes that have been linked to the chromosome 16 infantile convulsions and choreoathetosis syndrome region. Moreover, in one large pedigree with paroxysmal kinesiogenic dyskinesias only, the syndrome has also been linked to the same genomic area. Families with pure benign familial infantile seizures may be linked to chromosome 16 as well. In this study, we present a series of 19 families and 24 otherwise healthy infants with benign familial infantile seizures. Two of these families include members affected with benign familial infantile seizures and paroxysmal choreoathetosis. We included patients with normal neurologic examinations, who started having simple partial seizures, complex partial seizures, or apparently generalized seizures without recognized etiology between 2 months and 2 years of age. Neurologic studies were normal, but in all patients, there was a history of similar seizures and age at onset in either the father or the mother. Twenty-four patients (14 girls and 10 boys) were evaluated at our hospital between February 1990 and February 2001. Age at onset, sex, family history of epilepsy and/or paroxysmal dyskinesias, neurologic examination, semiology, distribution, and frequency and duration of seizures were evaluated. Electroencephalographic (EEG) and neuroradiologic studies were also performed. Seizures began between 3 and 22 months of life, with a median age of 5 1/2 months. Nine patients (37.5%) had only apparently generalized seizures, 5 patients (20.8%) had only partial seizures, and 10 patients had both partial and apparently generalized seizures (41.6%). Seizures were invariably brief, occurred during the waking state (100%), and presented mainly in clusters in 12 patients (50%). Interictal EEG was normal in 23 patients (95.8%). Sixteen patients (66.6%) had a confirmed history of convulsions in family members other than parents. Twenty-two patients became seizure free after 30 months of life. Two brothers in the same family had brief paroxysmal episodes of choreoathetosis in the hemibody triggered by stress while awake at 15 and 17 years old, respectively. One of them had paroxysmal choreoathetosis only, and the other was associated with benign familial infantile seizures. One father had brief spontaneous episodes of paroxysmal choreoathetosis when awake at age 18 years. All of them had a good response to antiepilepsy drugs, and neurologic examination and EEG and neuroradiologic studies were normal. Benign familial infantile seizure is a genetic epilepsy syndrome with autosomal dominant inheritance. It may be associated with paroxysmal choreoathetosis (infantile convulsions and choreoathetosis syndrome), which has been linked to the chromosome 16 infantile convulsions and choreoathetosis syndrome region. Patients in families with infantile convulsions and choreoathetosis syndrome could display either benign familial infantile seizures or paroxysmal choreoathetosis or both. It is likely that the disease in families with pure benign familial infantile seizures may be linked to the infantile convulsions and choreoathetosis region as well. We cannot exclude the possibility that the youngest patients may develop choreoathetosis or other dyskinesias later in life.     

A new case of concurrent existence of PRRT2-associated paroxysmal movement disorders with c.649dup variant and 16p11.2 microdeletion syndrome

BackgroundThe PRRT2 gene located at 16p11.2 encodes proline-rich transmembrane protein 2. In recent reviews, clinical spectrum caused by pathogenic PRRT2 variants is designated as PRRT2-associated paroxysmal movement disorders, which include paroxysmal kinesigenic dyskinesia, benign familial infantile epilepsy, and infantile convulsions with choreoathetosis, and hemiplegic migraine. The recurrent 16p11.2 microdeletion encompassing PRRT2 has also been reported to cause neurodevelopmental syndrome, associated with autism spectrum disorder. Although PRRT2 variants and 16p11.2 microdeletion cause each disease with the autosomal dominant manner, rare cases with bi-allelic PRRT2 variants or concurrent existence of PRRT2 variants and 16p11.2 microdeletion have been reported to show more severe phenotypes.Case reportA 22-year-old man presents with episodic ataxia, paroxysmal kinesigenic dyskinesia, seizure, intellectual disability and autism spectrum disorder. He also has obesity, hypertension, hyperuricemia, and mild liver dysfunction. Exome sequencing revealed a c.649dup variant in PRRT2 in one allele and a de novo 16p11.2 microdeletion in another allele.ConclusionsOur case showed combined clinical features of PRRT2-associated paroxysmal movement disorders and 16p11.2 microdeletion syndrome. We reviewed previous literatures and discussed phenotypic features of patients who completely lack the PRRT2 protein.     

Long-term changes in electroencephalogram findings in a girl with a nonsense SMC1A variant: A case report

IntroductionPathogenic truncating variants in SMC1A, which is located on chromosome Xp11.2, are known to cause infantile-onset epilepsy and severe intellectual disability in girls. Several studies have reported a correlation between SMC1A truncations and seizure clustering; however, the associated electroencephalogram (EEG) patterns remain largely unknown.Case presentationWe investigated an 12-year-old girl who had developed epilepsy at the age of 4 months. The patient experienced unknown onset, tonic-clonic seizures that occurred in clusters several times a week. Her interictal EEG at the age of 2 years showed paroxysmal, generalized, high-amplitude slow waves, whereas epileptiform discharges were scarce. The patient’s interictal EEG gradually deteriorated; at the age of 11 years, diffuse continuous spike-and-wave discharges were predominantly observed in the left temporal region and were particularly obvious in the awake state. Although the unknown onset, tonic seizures occurring weekly persisted under multiple antiepileptic medications, the patient did not experience seizure clustering since the age of 9 years. Whole-genome sequencing revealed a de novo known nonsense variant in SMC1A (c.2923C > T, p.R975*).ConclusionOur patient presented with a mild abnormality in the interictal EEG during infancy and early childhood despite frequent seizure clustering. Notably, the patient’s EEG findings gradually deteriorated over time, which was inconsistent with the amelioration of seizure clustering.     

Early onset and focal spike discharges as indicators of poor prognosis for myoclonic-astatic epilepsy

Background: Myoclonic-astatic epilepsy (MAE) is an epileptic syndrome characterized by unique myoclonus, myoclonic-astatic, or astatic seizures in childhood. MAE prognosis vary from spontaneous remission to intractable seizures with profound mental retardation. Aim: Identifying early risk factors may optimize the treatment of children with MAE. Our hypothesis is early onset age and focal spike discharges on EEG indicate a poor MAE prognosis. Methods: Using the medical records of 9 children with MAE, we analyzed their clinical histories, EEG findings, and seizure symptoms. All patients were given follow-up observations/treatments by our department for at least 2 years after MAE onset. Results: Five of the patients were given favorable prognoses because their seizures disappeared within 2 years of onset; the other 4 received poor prognoses because their seizures continued more than 2 years. MAE onset in patient with refractory seizures was earlier than that in those with a favorable prognosis (7–24 months vs. 23–38 months). All the patients with refractory seizures showed moderate or severe mental retardation. Among the 5 patients with good prognosis, EEGs showed two with focal spike discharges and three with only generalized spike discharges. In contrast, all cases with a poor prognosis had focal spike discharges. Conclusions: MAE onset in patients with refractory seizures occurs earlier than in those with favorable prognosis. Prognosis was excellent when EEG findings show no focal spike discharges. Both early seizure onset and the focal spike discharges associated with MAE are indicators of poor prognosis.