Alternating Hemiplegia of Childhood: neurological comorbidities and intrafamilial variability

Twin girls were born to unrelated Italian parents. The clinical features and course of disorder was rather similar in both girls but one (Case 2) exhibited milder manifestations as regards the frequency and the intensity of the AHC episodes. In both twins, ID was mild. A wider clinical manifestation of the twins has been previously reported [12]. The clinical onset started in their first few months of life with bath-induced paroxysmal events lasted 2 years. At 2 years, both twins had an episode of acute encephalopathy rapidly solved. Around 3 years, they presented with typical recurrent episodes of hemiplegia prevailing in the right side. Signs of distonic movements were further noted. In the following years, a marked reduction of hemiplegic attacks to the disappearance was observed with mild persistence of the other disturbances. During the adolescence, in both girls ID remained mild, instead brief dystonic movements and severe episodes of headache were registered.

Written informed consent for publication of their clinical details was obtained from the patient’s parents. A copy of the consent form is available for review by the Editor of this journal.

The siblings’ mother had atresia of the proximal part of the bile ducts and was admitted for liver transplantation in the first months of her life. The parents are neurologically normal and denied to have suffered from paralysis or seizures.

This is a six and half years old male patient. He was born at the 37th week of gestation by cesarean section. The mother complained that the child was suffering from frequent episodes of upper airways infections and nocturnal cyanotic crises with breathing cessation due to obstructive sleep apnea syndrome (OSAS). The child grew up normally without specific clinical manifestations (except for episodes of OSAS) until 4 years old, when he experienced, for the first time, loss of bladder control followed by recurrent attacks of generalized tonic-clonic seizures in clusters. The video-EEG showed multifocal spike/wave pattern mainly evident in the Fronto-Centro-Parietal regions (Fig. 1 a-b). The child started treatment with valproate (20 mg/Kg/die), which managed to control the seizures. Few months later, he presented the first episode of AHC prevailing in right side, which was followed by inability to walk for 2 months. During this period, the child was fed by nasogastric tube because he was unable to swallow. During the following 2 years, he was admitted to Pediatric Clinic Institution (University of Catania, Italy) for several times in coincidence with the admission of his brother (Case 4, see next paragraph). He manifested frequent episodes of hemiplegia affecting prevalently the right side. The crises were less frequent and less severe compared to those of his brother. He attended the school with sufficient performance. At the most recent follow-up visit (seven and half years old), neurological examination displayed mild ID (IQ 64 WISC III), normal speech and language skills and notably reduced sensitivity to pain. The paroxysmal episodes of hemiparesis were infrequent (1–2 every 3 months) and no seizure was reported. Brain MRI, EMG, and NCS were normal. EEG in the awake state and during sleep showed same previous EEG anomalies with multifocal spikes and waves. Treatment consisted of valproate (20 mg/Kg/die) and levetiracetam (10 mg/Kg/die).

This is older brother who came to Pediatric Clinic Institution in Catania (Italy) at the age of 3 months because of seizures. He was born at the 39th week of gestation by cesarean section due to the threatened abortion and internal podalic version. At admission, trans-fontanellar ultrasound and EEG recordings were normal as well routine laboratory analysis. The child was discharged with valproate treatment at the dosage of 20 mg/Kg/die. In the subsequent months, two other seizures were recorded. At 18 months, he showed difficulty in standing up without support. The delay also involved the language development. Furthermore, the boy manifested an episode of generalized hypertonia of short duration followed by right hemiparesis resolved after 48 h initially referred to as Todd’s paralysis, but the clinical suspect of alternating hemiplegia of childhood (AHC) came out. At 2 years, the hemiplegic attacks were frequent as well as tonic and dystonic attacks. The child showed to be apathetic with poor social skills. At 2 years and 9 months, the boy continued to present unfrequent epileptic seizures (1–2 for months) no coincidentally occuring with episodes of hemiparesis mainly right sided. Treatment with flunarizine (10mg/Kg/die) was started, but irregularly conducted. At examination, after the hemiparetic episode, the affected side of the body was hypotonic, there was difficulty to stimulate patellar reflexes, and reduction of tactile, thermal, and pain sensibility were also noted. Some months later, the clinical manifestations of AHC involved alternatively both sides, and sometimes both sides at the same time. Video-EEG at awake and during the sleep showed multifocal spike and waves mainly expressed in the frontal region. Treatment with valproate was maintained 20 mg/Kg/die plus levetiracetam (10 mg/Kg/die) in add-on. During the following years, the epileptic seizures and paretic episodes were frequent and barely responsive to any type of treatment including flunarizine (10mg/Kg/die), irregularly conducted, and anticonvulsants. The hemiplegic manifestations showed a wide variability with some episodes lasting for one hour, and others being prolonged to several days up to 2–3 months. Serial EEG in the awake state and during the sleep showed the presence of multiple spike and wave mainly expressed in frontal region (a seizure recorded during the EEG registration) (Fig. 2 a-b). At 10 years old, the child showed a fairly good condition at physical examination. He attended the regular school with sufficient scholastic performance. At neurological examination, pain sensitivity was found to be reduced. Brain MRI was normal. At the most recent follow-up visit (11 years old), the parents referred that he attends the school regularly with support. He had a mild ID (IQ = 58) WISC III and mild speech impairment consisting of poor expressive vocabulary with scant sentences. He had very few clinical manifestations, and the attacks of hemiparesis and seizures became less frequent and less severe compared to the past. He is still taking valproate and levetiracetam at the same dosage as previously.

Total genomic DNA was extracted from peripheral blood samples for the mutational analysis, following informed consent by parents of Family 1 and 2 included in the present research.

For twins of Family 1, the molecular diagnosis was carried on ATP1A2 and ATP1A3 genes by sequencing of PCR-amplified DNA. PCR products amplified by LightCycler 480® (Roche Life Science) were determined by direct sequencing on ABI Prism® 3100 Genetic Analyzer (Thermo fisher Scientific) according to the manufacturer’s protocol. Sequence analysis was done by Applied Biosystems DNA Sequencing Analysis v.5.1 and ABI PRISM 310 Data Collection Software Version 3.1 software (ThermoFisher Scientific). Analysis of the pathogenic variant was performed using public repositories of genome variation, such as dbSNP and ClinVar database.

For siblings of Family 2 and their parents whole exome sequencing (WES) was carried. WES analysis was performed using the Illumina TruSight One panel. The samples were sequenced by using the Illumina NextSeq 500 platform (Illumina Inc.) with 2 × 150 bp paired-end reads. Alignments and variant calls were generated using NextGene software (v2.4.1, 2015). Variant calls (with coverage <15X) were limited to the genes of interest. For the clinical interpretation of genomic variants was used Alamut-Batch (Version 1.4.0, 2015), the high-throughput annotation software for NGS analysis. Alamut Visual (Version 2.7) was used for integrating genetic and predictive information on missense, nonsense, frameshift, and splice-site variants, providing computational algorithms for SIFT, PolyPhen-2 (Version 2.2.2, 2012) and Mutation taster. Variants were annotated for minor allele frequencies in the Exome Aggregation Consortium (ExAC) database (Version 0.3), and heterozygous variants with minor allele frequencies > 0.01 (1%) were filtered out. Variants were classified as pathogenic/likely pathogenic/VUS/likely benign/benign according to the 2015 American College of Medical Genetics and Genomics (ACMG) guidelines [13]. The validation of variants was performed using Sanger sequencing in the probands.

Variability in clinical expression of paroxysmal and non-paroxysmal episodes in AHC individuals is well known. In the present cases, the intrafamilial variable clinical expression was observed as regard to the intensity and frequency of clinical features more pronounced in Case 1 between twins and in Case 3 between siblings. The cognitive impairment was mild in both twins and no seizures were recorded. In siblings, the seizures were more severe in Case 4 who showed more marked hemiplegic attacks. Cognitive impairment was mild in both siblings and speech delay was reported only in the oldest sibling. It is presumable that epigenetic events have conditioned the intrafamilial clinical variability.

The diagnosis of AHC is mainly clinical but may be supported by molecular analysis. Typical gene mutations involved in the pathogenesis of AHC are located in ATP1A2 and in ATP1A3 genes as found in twins, but in some cases of AHC, however, these mutations are not found (as in children of Family 2). At WES analysis, we found in the Case 4 the identical haplotype inherited from the asymptomatic father, constituted of three heterozygous variants in GRIN2A (c.3175 T > A), SCN1B (c.632G > A) and KCNQ2 (c.1870G > A) gene, while in the younger child (Case 3), who had a milder phenotype, only the variant in GRIN2A gene as in the healthy father was found. The GRIN2A gene encoding the NMDA receptor (NMDAR) subunit GluN2A has been suggested to constitute a locus for mutations in a subset of individuals with early-onset seizures [23]. Additionally two likely pathogenetic variants SCN1B (rs 150,721,582) and the KCNQ2 (rs771211103) genes have been implicated in childhood epilepsies [24‐26]. The role of three variants in the clinical expression observed in the children of family 2 is difficult to explain since the variants were also found in the healthy father and no previous cases of AHC with these variants have been reported.

To date, no drugs are available to cure AHC. The treatment usually comprises multiple drug therapy regimen. The aim of these therapeutic agents is prophylactic against the paroxysmal attacks. Flunarizine is a calcium channel blocker that has been widely indicated as the most effective drug for AHC treatment [4, 6, 11, 27, 28]. The results achieved suggested that flunarizine therapy reduced the duration and severity of hemiplegic attacks, but did not interfere with the natural course of the disease. No severe side-effects have been seen in any patients during the time of treatment [17]. Recently, new treatment modalities have been proposed with triheptanoin [17], aripiprazole, [29] and verapamil [30] with notable reduction in frequency, severity, and duration of the hemiplegic attacks. In association to flunarizine, anticonvulsants have been applied in the treatment of the seizures using benzodiazepine, carbamazepine, barbiturates and valproate [31, 32]. In the siblings, valproate and leveticaretam managed to control the seizures.