Diagnosis and Treatment of Alternating Hemiplegia of Childhood

BK Channelopathies and KCNMA1-Linked Disease Models

Novel KCNMA1 variants, encoding the BK K+ channel, are associated with a debilitating dyskinesia and epilepsy syndrome. Neurodevelopmental delay, cognitive disability, and brain and structural malformations are also diagnosed at lower incidence. More than half of affected individuals present with a rare negative episodic motor disorder, paroxysmal nonkinesigenic dyskinesia (PNKD3). The mechanistic relationship of PNKD3 to epilepsy and the broader spectrum of KCNMA1-associated symptomology is unknown. This review summarizes patient-associated KCNMA1 variants within the BK channel structure, functional classifications, genotype-phenotype associations, disease models, and treatment. Patient and transgenic animal data suggest delineation of gain-of-function (GOF) and loss-of-function KCNMA1 neurogenetic disease, validating two heterozygous alleles encoding GOF BK channels (D434G and N999S) as causing seizure and PNKD3. This discovery led to a variant-defined therapeutic approach for PNKD3, providing initial insight into the neurological basis. A comprehensive clinical definition of monogenic KCNMA1-linked disease and the neuronal mechanisms currently remain priorities for continued investigation.

Characteristics of non-sleep related apneas in children with alternating hemiplegia of childhood

BACKGROUND

Non-sleep related apnea (NSA) has been observed in alternating hemiplegia of childhood (AHC) but has yet to be characterized.

GOALS

Investigate the following hypotheses: 1) AHC patients manifest NSA that is often severe. 2) NSA is usually triggered by precipitating events. 3) NSA is more likely in patients with ATP1A3 mutations.

METHODS

Retrospective review of 51 consecutive AHC patients (ages 2-45 years) enrolled in our AHC registry. NSAs were classified as mild (not needing intervention), moderate (needing intervention but not perceived as life threatening), or severe (needing intervention and perceived as life threatening).

RESULTS

19/51 patients (37 %) had 52 NSA events (6 mild, 11 moderate, 35 severe). Mean age of onset of NSA (± Standard Error of the Mean (SEM)): 3.8 ± 1.5 (range 0-24) years, frequency during follow up was higher at younger ages as compared to adulthood (year 1: 2.2/year, adulthood: 0.060/year). NSAs were associated with triggering factors, bradycardia and with younger age (p < 0.008 in all) but not with mutation status (p = 0.360). Triggers, observed in 17 patients, most commonly included epileptic seizures in 9 (47 %), anesthesia, AHC spells and intercurrent, stressful, conditions. Management included use of pulse oximeter at home in nine patients, home oxygen in seven, intubation/ventilatory support in seven, and basic CPR in six. An additional patient required tracheostomy. There were no deaths or permanent sequalae.

CONCLUSIONS

AHC patients experience NSAs that are often severe. These events are usually triggered by seizures or other stressful events and can be successfully managed with interventions tailored to the severity of the NSA.

Methodology of a Natural History Study of a Rare Neurodevelopmental Disorder: Alternating Hemiplegia of Childhood as a Prototype Disease

Here, we describe the process of development of the methodology for an international multicenter natural history study of alternating hemiplegia of childhood as a prototype disease for rare neurodevelopmental disorders. We describe a systematic multistep approach in which we first identified the relevant questions about alternating hemiplegia of childhood natural history and expected challenges. Then, based on our experience with alternating hemiplegia of childhood and on pragmatic literature searches, we identified solutions to determine appropriate methods to address these questions. Specifically, these solutions included development and standardization of alternating hemiplegia of childhood-specific spell video-library, spell calendars, adoption of tailored methodologies for prospective measurement of nonparoxysmal and paroxysmal manifestations, unified data collection protocols, centralized data platform, adoption of specialized analysis methods including, among others, Cohen kappa, interclass correlation coefficient, linear mixed effects models, principal component, propensity score, and ambidirectional analyses. Similar approaches can, potentially, benefit in the study of other rare pediatric neurodevelopmental disorders.

Development and testing of methods to record and follow up spells in patients with alternating hemiplegia of childhood

BACKGROUND

Developing methods to record Alternating Hemiplegia of Childhood (AHC) spells is essential for clinical trials and patient care.

OBJECTIVES

Test the following hypotheses: 1) Video-library training improves participants' ability to correctly identify AHC spells. 2) A custom-designed event-calendar with weekly reviews results in consistent documentation of such events over time. 3) Use of an electronic diary (e-Diary) to register events is a useful tool.

METHODS

1) A video-library of AHC type spells was developed along with specific training; the effect of the training was tested in 36 caregivers. 2) An event-calendar was similarly developed and provided to 5 caregivers with weekly videoconference meetings for 8 weeks. 3) An e-Diary was developed and offered to 33 patients; time of usage and caregivers' feedback (telephone interview) were analyzed.

RESULTS

1) Video-library training: Wilcoxon test showed improvement in caregiver identification of spells (p = 0.047), Cohen's Kappa demonstrated high degree of agreement between caregivers'-experts' classifications (>0.9). 2) Event-calendar: 96.42% of entries had complete information; this did not change during follow up (p = 0.804). 3) e-Diary: whereas 52% of respondents used the e-Diary when offered (duration: 10.5 ± 8.1 months), 96.3% indicated they would use it in future studies. Those who used it for 13 months, were very likely to use it during the rest of that year.

CONCLUSIONS

Video-library training improved spell identification. Calendar with weekly reviews resulted in a sustained and consistent record keeping. Caregivers' e-Diary feedback was encouraging with long-term usage in many. These approaches could be helpful for AHC and, potentially, in similar disorders.

ATP1A3-related phenotypes in Chinese children: AHC, CAPOS, and RECA

The aim of this research is to study the phenotype, genotype, treatment strategies, and short-term prognosis of Chinese children with ATP1A3 (Na⁺/K⁺-ATPase alpha 3 gene)-related disorders in Southwest China. Patients with pathogenic ATP1A3 variants identified using next-generation sequencing were registered at the Children's Hospital of Chongqing Medical University from December 2015 to May 2019. We followed them as a cohort and analyzed their clinical data. Eleven patients were identified with de novo pathogenic ATP1A3 heterozygous variants. One (c.2542 + 1G > T, splicing) has not been reported. Eight patients with alternating hemiplegia of childhood (AHC), one with cerebellar ataxia, areflexia, pes cavus, optic atrophy, and sensorineural hearing loss (CAPOS), and two with relapsing encephalopathy with cerebellar ataxia (RECA) were included. The initial manifestations of AHC included hemiplegia, oculomotor abnormalities, and seizures, and the most common trigger was an upper respiratory tract infection without fever. All patients had paroxysmal hemiplegic attacks during their disease course. The brain MRI showed no abnormalities. Six out of eight AHC cases reached a stable disease state after treatment. The initial symptom of the patient with CAPOS was ataxia followed by developmental regression, seizures, deafness, visual impairment, and dysarthria, and the brain MRI indicated mild cerebellar atrophy. No fluctuation was noted after using Acetazolamide. The initial manifestations of the two RECA cases were dystonia and encephalopathy, respectively. One manifested a rapid-onset course of dystonia triggered by a fever followed by dysarthria and action tremors, and independent walking was impossible. The brain MRI image was normal. The other one presented with disturbance of consciousness, seizures, sleep disturbance, tremor, and dyskinesias. The EEG revealed a slow background (δ activity), and the brain MRI result was normal. No response to Flunarizine was noted for them, and it took 61 and 60 months for them to reach a stable disease state, respectively.

CONCLUSION

Pathogenic ATP1A3 variants play an essential role in the pathogenesis of Sodium-Potassium pump disorders, and AHC is the most common phenotype. The treatment strategies and prognosis depend on the phenotype categories caused by different variation sites and types. The correlation between the genotype and phenotype requires further exploration.

WHAT IS KNOWN

• Pathogenic heterozygous ATP1A3 variants cause a spectrum of neurological phenotypes, and ATP1A3-disorders are viewed as a phenotypic continuum presenting with atypical and overlapping features. • The genotype-phenotype correlation of ATP1A3-disorders remains unclear.

WHAT IS NEW

• In this study, the genotypes and phenotypes of ATP1A3-related disorders from Southwest of China were described. The splice-site variation c.2542+1G>T was detected for the first time in ATP1A3-related disorders. • The prognosis of twins with AHC p. Gly947Arg was more serious than AHC cases with other variants, which was inconsistent with previous reports. The phenomenon indicated the diversity of the correlation between the genotype and phenotype.

Alternating hemiplegia of childhood

Alternating hemiplegia of childhood (AHC) is characterized by recurrent episodes of hemiplegia which may alternate sides between attacks. The condition is associated with severe neurodevelopmental disorder presenting in early infancy, and may encompass a wide range of other paroxysmal manifestations (e.g., dystonia, nystagmus, dysautonomia) and pervasive neurological disabilities (e.g., developmental delay, learning disabilities, choreoathetosis, and ataxia). Epileptic seizures are particularly common among patients with AHC. Diagnosis is usually based on history and clinical grounds using the Aicardi criteria. Mutations in the ATP1A3 gene are implicated in the disease pathology of the condition, as well as several other neurodevelopmental disorders, suggesting AHC forms part of a spectrum of overlapping clinical syndromes rather than a distinct clinical entity per se. Management of patients with AHC includes the rapid induction of sleep during paroxysmal attacks and the avoidance of identified triggers. Pharmacotherapeutic treatments have a role in managing epileptic seizures, as well as in the prevention of paroxysmal attacks wherein flunarizine remains the treatment of choice.

The Genetic Landscape of Complex Childhood-Onset Hyperkinetic Movement Disorders

BACKGROUND AND OBJECTIVE

The objective of this study was to better delineate the genetic landscape and key clinical characteristics of complex, early-onset, monogenic hyperkinetic movement disorders.

METHODS

Patients were recruited from 14 international centers. Participating clinicians completed standardized proformas capturing demographic, clinical, and genetic data. Two pediatric movement disorder experts reviewed available video footage, classifying hyperkinetic movements according to published criteria.

RESULTS

One hundred forty patients with pathogenic variants in 17 different genes (ADCY5, ATP1A3, DDC, DHPR, FOXG1, GCH1, GNAO1, KMT2B, MICU1, NKX2.1, PDE10A, PTPS, SGCE, SLC2A1, SLC6A3, SPR, and TH) were identified. In the majority, hyperkinetic movements were generalized (77%), with most patients (69%) manifesting combined motor semiologies. Parkinsonism-dystonia was characteristic of primary neurotransmitter disorders (DDC, DHPR, PTPS, SLC6A3, SPR, TH); chorea predominated in ADCY5-, ATP1A3-, FOXG1-, NKX2.1-, SLC2A1-, GNAO1-, and PDE10A-related disorders; and stereotypies were a prominent feature in FOXG1- and GNAO1-related disease. Those with generalized hyperkinetic movements had an earlier disease onset than those with focal/segmental distribution (2.5 ± 0.3 vs. 4.7 ± 0.7 years; P = 0.007). Patients with developmental delay also presented with hyperkinetic movements earlier than those with normal neurodevelopment (1.5 ± 2.9 vs. 4.7 ± 3.8 years; P &lt; 0.001). Effective disease-specific therapies included dopaminergic agents for neurotransmitters disorders, ketogenic diet for glucose transporter deficiency, and deep brain stimulation for SGCE-, KMT2B-, and GNAO1-related hyperkinesia.

CONCLUSIONS

This study highlights the complex phenotypes observed in children with genetic hyperkinetic movement disorders that can lead to diagnostic difficulty. We provide a comprehensive analysis of motor semiology to guide physicians in the genetic investigation of these patients, to facilitate early diagnosis, precision medicine treatments, and genetic counseling. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Characterization of sedation and anesthesia complications in patients with alternating hemiplegia of childhood

BACKGROUND

Alternating hemiplegia of childhood (AHC) pathophysiology suggests predisposition to sedation and anesthesia complications.

GOALS

Hypotheses: 1) AHC patients experience high rates of sedation-anesthesia complications. 2) ATP1A3 mutation genotype positivity, age, and AHC severity correlate with more severe complications. 3) Prior short QTc correlates with cardiac rhythm complications.

METHODS

Analysis of 34 consecutive AHC patients who underwent sedation or anesthesia. Classification of complications: mild (not requiring intervention), moderate (intervention), severe (intervention, risk for permanent injury or potential life-threatening emergency).

STATISTICS

Fisher Exact test, Spearman correlations.

RESULTS

These patients underwent 129 procedures (3.79 ± 2.75 procedures/patient). Twelve (35%) experienced complications during at least one procedure. Fourteen/129 procedures (11%) manifested one or more complications (2.3% mild, 7% moderate, 1.6% severe). Of the total 20 observed complications, six (33.3%) were severe: apneas (2), seizures (2), bradycardia (1), ventricular fibrillation that responded to resuscitation (1). Moderate complications: non-life-threatening bradycardias, apneas, AHC spells or seizures. Complications occurred during sedation or anesthesia and during procedures or recovery periods. Patients with disease-associated ATP1A3 variants were more likely to have moderate or severe complications. There was no correlation between complications and age or AHC severity. Presence of prior short QTc correlated with cardiac rhythm complications. After this series was analyzed, another patient had severe recurrent laryngeal dystonia requiring tracheostomy following anesthesia with intubation.

CONCLUSIONS

During sedation or anesthesia, AHC patients, particularly those with ATP1A3 variants and prior short QTc, are at risk for complications consistent with AHC pathophysiology. Increased awareness is warranted during planning, performance, and recovery from such procedures.

ATP1A3-Encoded Sodium-Potassium ATPase Subunit Alpha 3 D801N Variant Is Associated With Shortened QT Interval and Predisposition to Ventricular Fibrillation Preceded by Bradycardia

Background

Pathogenic variation in the ATP1A3‐encoded sodium‐potassium ATPase, ATP1A3, is responsible for alternating hemiplegia of childhood (AHC). Although these patients experience a high rate of sudden unexpected death in epilepsy, the pathophysiologic basis for this risk remains unknown. The objective was to determine the role of ATP1A3 genetic variants on cardiac outcomes as determined by QT and corrected QT (QTc) measurements.

Methods and Results

We analyzed 12‐lead ECG recordings from 62 patients (male subjects=31, female subjects=31) referred for AHC evaluation. Patients were grouped according to AHC presentation (typical versus atypical), ATP1A3 variant status (positive versus negative), and ATP1A3 variant (D801N versus other variants). Manual remeasurements of QT intervals and QTc calculations were performed by 2 pediatric electrophysiologists. QTc measurements were significantly shorter in patients with positive ATP1A3 variant status (P<0.001) than in patients with genotype‐negative status, and significantly shorter in patients with the ATP1A3‐D801N variant than patients with other variants (P<0.001). The mean QTc for ATP1A3‐D801N was 344.9 milliseconds, which varied little with age, and remained <370 milliseconds throughout adulthood. ATP1A3 genotype status was significantly associated with shortened QTc by multivariant regression analysis. Two patients with the ATP1A3‐D801N variant experienced ventricular fibrillation, resulting in death in 1 patient. Rare variants in ATP1A3 were identified in a large cohort of genotype‐negative patients referred for arrhythmia and sudden unexplained death.

Conclusions

Patients with AHC who carry the ATP1A3‐D801N variant have significantly shorter QTc intervals and an increased likelihood of experiencing bradycardia associated with life‐threatening arrhythmias. ATP1A3 variants may represent an independent cause of sudden unexplained death. Patients with AHC should be evaluated to identify risk of sudden death.

ATP1A3-related disorders in the differential diagnosis of acute brainstem and cerebellar dysfunction

Alternating Hemiplegia of Childhood (AHC), Rapid-onset Dystonia-Parkinsonism (RDP), and CAPOS syndrome (Cerebellar ataxia, Areflexia, Pes cavus, Optic atrophy, and Sensorineural hearing loss) are all caused by mutations in the same gene: ATP1A3. Although initially they were considered separate disorders, recent evidence suggests a continuous clinical spectrum of ATP1A3-related disorders. At onset all these disorders can present with acute brainstem dysfunction triggered by a febrile illness. An infectious or autoimmune disorder is usually suspected. A genetic disorder is rarely considered in the first acute episode. We present three patients with ATP1A3 mutations: one patient with AHC, one patient with RDP, and one patient with CAPOS syndrome. We describe the acute onset and overlapping clinical features of these three patients with classical phenotypes. These cases highlight ATP1A3-related disorders as a possible cause of acute brainstem dysfunction with normal ancillary testing.

Alternating hemiplegia of childhood: evolution over time and mouse model corroboration

Alternating hemiplegia of childhood is a rare neurodevelopmental disorder caused by ATP1A3 mutations. Some evidence for disease progression exists, but there are few systematic analyses. Here, we evaluate alternating hemiplegia of childhood progression in humans and in the D801N knock-in alternating hemiplegia of childhood mouse, Mashlool, model. This study performed an ambidirectional (prospective and retrospective data) analysis of an alternating hemiplegia of childhood patient cohort (n = 42, age 10.24 ± 1.48 years) seen at one US centre. To investigate potential disease progression, we used linear mixed effects models incorporating early and subsequent visits, and Wilcoxon Signed Rank test comparing first and last visits. Potential early-life clinical predictors were determined via multivariable regression. We also compared EEG background at first encounter and at last follow-up. We then performed a retrospective confirmation study on a multicentre cohort of alternating hemiplegia of childhood patients from France (n = 52). To investigate disease progression in the Mashlool mouse, we performed behavioural testing on a cohort of Mashlool^- mice at prepubescent and adult ages (n = 11). Results: US patients, over time, demonstrated mild worsening of non-paroxysmal disability index scores, but not of paroxysmal disability index scores. Increasing age was a predictor of worse scores: P < 0.0001 for the non-paroxysmal disability index, intellectual disability scale and gross motor scores. Earliest non-paroxysmal disability index score was a predictor of last visit non-paroxysmal disability index score (P = 0.022), and earliest intellectual disability score was a predictor of last intellectual disability score (P = 0.035). More patients with EEG background slowing were noted at last follow-up as compared to initial (P = 0.015). Similar worsening of disease with age was also noted in the French cohort: age was a significant predictor of non-paroxysmal disability index score (P = 0.001) and first and last non-paroxysmal disability index score scores significantly differed (P = 0.002). In animal studies, adult Mashlool mice had, as compared to younger Mashlool mice, (i) worse balance beam performance; (ii) wider base of support; (iii) higher severity of seizures and resultant mortality; and (iv) no increased predisposition to hemiplegic or dystonic spells. In conclusion, (i) non-paroxysmal alternating hemiplegia of childhood manifestations show, on average over time, progression associated with severity of early-life non-paroxysmal disability and age. (ii) Progression also occurs in Mashlool mice, confirming that ATP1A3 disease can lead to age-related worsening. (iii) Clinical findings provide a basis for counselling patients and for designing therapeutic trials. Animal findings confirm a mouse model for investigation of underlying mechanisms of disease progression, and are also consistent with known mechanisms of ATP1A3-related neurodegeneration.

Hypothalamic-pituitary dysfunction in alternating hemiplegia of childhood

BACKGROUND

Many central nervous system disorders result in hypothalamic-pituitary (HP) axis dysfunction. Alternating Hemiplegia of Childhood (AHC) is usually caused by mutations in the ATP1A3 subunit of the Na⁺/K⁺ ATPase, predominantly affecting GABAergic interneurons. GABAergic interneurons and the ATP1A3 subunit are both important for function of the hypothalamus. However, whether HP dysfunction occurs in AHC and, if so, how such dysfunction manifests remains to be investigated.

METHODS

We conducted a retrospective review of a cohort of 50 consecutive AHC patients for occurrence of HP related manifestations and analyzed the findings of the 6 patients, from that cohort, with such manifestations.

RESULTS

Six out of 50 AHC patients manifested HP dysfunction. Three of these patients were mutation positive and 3 were mutation negative. Of the 6 patients with HP dysfunction, 3 had central precocious puberty. A fourth had short stature due to growth hormone deficiency. Two other patients had recurrent episodes of fever of unknown origin (FUO) diagnosed, after workups, as being secondary to central fever. All patients were evaluated and co-managed by pediatric neurology and endocrinology or rheumatology.

CONCLUSION

AHC was associated with HP dysfunction in about 12% of patients. Awareness of such dysfunction is important for anticipatory guidance and management particularly in the case of FUO which often presents a diagnostic dilemma. Our findings are also consistent with current understandings of the underlying pathophysiology of AHC and of the HP axis.

De novo ATP1A2 variants in two Chinese children with alternating hemiplegia of childhood upgraded the gene-disease relationship and variant classification: a case report

Background

ATP1A2 gene mutation has been indicated to cause alternating hemiplegia of childhood (AHC); however, limited evidence supports this relationship so far.

Case presentation

We reported two Chinese patients with de novo ATP1A2 variants (c.970G>A and c.889G>A). Both patients presented with episodes of alternating hemiplegia, seizures and mild developmental delay. Brain magnetic resonance imaging revealed abnormal signals in both patients.

Conclusions

The new genetic evidence we reported here strengthened the gene–disease relationship, and the gene curation level between ATP1A2 and AHC became “Moderate” following the ClinGen Standard Operation Procedure. Consequently, the two variants can be reclassified as likely pathogenic.

Paroxysmal Genetic Movement Disorders and Epilepsy

Paroxysmal movement disorders include paroxysmal kinesigenic dyskinesia, paroxysmal non-kinesigenic dyskinesia, paroxysmal exercise-induced dyskinesia, and episodic ataxias. In recent years, there has been renewed interest and recognition of these disorders and their intersection with epilepsy, at the molecular and pathophysiological levels. In this review, we discuss how these distinct phenotypes were constructed from a historical perspective and discuss how they are currently coalescing into established genetic etiologies with extensive pleiotropy, emphasizing clinical phenotyping important for diagnosis and for interpreting results from genetic testing. We discuss insights on the pathophysiology of select disorders and describe shared mechanisms that overlap treatment principles in some of these disorders. In the near future, it is likely that a growing number of genes will be described associating movement disorders and epilepsy, in parallel with improved understanding of disease mechanisms leading to more effective treatments.

A novel ATP1A2 variant associated with severe stepwise regression, hemiplegia, epilepsy and movement disorders in two unrelated patients

Pathogenic variants in ATP1A2, a gene encoding the α subunit of the Na,K-ATPase, cause familial hemiplegic migraine type 2 (FHM2). In contrast, pathogenic variants in ATP1A3, an ATP1A2 paralog, cause alternating hemiplegia of childhood (AHC), a severe neurodevelopmental disorder with infantile onset hemiplegic attacks, seizures, dystonia, chorea and developmental delay. Despite high sequence homology with ATP1A3, ATP1A2 variants rarely associate with severe phenotypes resembling those linked to ATP1A3. Here we describe two unrelated patients with infantile onset hemiplegic attacks, refractory epilepsy, movement disorders, abnormal eye movements and truncal ataxia with a shared de novo variant in ATP1A2, c.2438T > A (p.Met813Lys). The variant is not found in population databases, is predicted to be damaging by in silico analysis, and affects a highly conserved residue. Both patients experienced severe attacks with unilateral cerebral edema followed by sustained, stepwise regression. This report highlights the need to sequence ATP1A2 in the workup of patients with features of AHC that do not fulfill AHC diagnostic criteria.

Novel presentations associated with a PDHA1 variant - Alternating hemiplegia in Hemizygote proband and Guillain Barre Syndrome in Heterozygote mother

We report a 5-year-old male with a PDHA1 variant who presented with alternating hemiplegia of childhood and later developed developmental regression, basal ganglia injury and episodic lactic acidosis. Enzyme assay in lymphocytes confirmed a diagnosis of Pyruvate Dehydrogenase Complex (PDC) deficiency. His mother who was heterozygous for the same variant suffered from ophthalmoplegia, chronic migraine and developed flaccid paralysis at 36 years of age. PDHA1 is the most common genetic cause of PDC deficiency and presents with a myriad of neurological phenotypes including neonatal form with lactic acidosis, non-progressive infantile encephalopathy, Leigh syndrome subtype and intermittent ataxia. The presentations in our 2 patients contribute to the clinical heterogeneity of this neurogenetic condition.

Adeno-Associated Virus-Mediated Gene Therapy in the Mashlool, Atp1a3Mashl/+, Mouse Model of Alternating Hemiplegia of Childhood

Alternating Hemiplegia of Childhood (AHC) is a devastating autosomal dominant disorder caused by ATP1A3 mutations, resulting in severe hemiplegia and dystonia spells, ataxia, debilitating disabilities, and premature death. Here, we determine the effects of delivering an extra copy of the normal gene in a mouse model carrying the most common mutation causing AHC in humans, the D801N mutation. We used an adeno-associated virus serotype 9 (AAV9) vector expressing the human ATP1A3 gene under the control of a human Synapsin promoter. We first demonstrated that intracerebroventricular (ICV) injection of this vector in wild-type mice on postnatal day 10 (P10) results in increases in ouabain-sensitive ATPase activity and in expression of reporter genes in targeted brain regions. We then tested this vector in mutant mice. Simultaneous intracisterna magna and bilateral ICV injections of this vector at P10 resulted, at P40, in reduction of inducible hemiplegia spells, improvement in balance beam test performance, and prolonged survival of treated mutant mice up to P70. Our study demonstrates, as a proof of concept, that gene therapy can induce favorable effects in a disease caused by a mutation of the gene of a protein that is, at the same time, an ATPase enzyme, a pump, and a signal transduction factor.

Status Dystonicus, Oculogyric Crisis and Paroxysmal Dyskinesia in a 25 Year-Old Woman with a Novel KCNMA1 Variant, K457E

The diagnosis of a paroxysmal dyskinesia is difficult and status dystonicus is a rare life threatening movement disorder characterised by severe, frequent or continuous episodes of dystonic spasms. A 25 year old woman with chronic ataxia and paroxysmal dyskinesia presented with facial twitching, writhing of arms, oculogyric crisis and visual and auditory hallucinations. She developed respiratory failure and was ventilated. No cause was found so whole exome sequencing was performed and this revealed a novel, non-synonymous heterozygous variant in exon 11 of the KCNMA1 gene, K457E (c 1369A>G) in the patient but not her parents. This variant has not been previously reported in gnomAD or ClinVar. The finding of a de novo variant in a potassium channel gene guided a trial of the potassium channel antagonist 3,4 diaminopyridine resulting in significant improvement, discharge from the intensive care unit and ultimately home.

Characterization of Severe and Extreme Behavioral Problems in Patients With Alternating Hemiplegia of Childhood

BACKGROUND

Alternating hemiplegia of childhood often manifests severe or extreme behavioral problems, the nature of which remains to be fully characterized.

METHODS

We analyzed 39 consecutive patients with alternating hemiplegia of childhood for occurrence of behavioral problems and categorized those by severity: mild (not requiring intervention), moderate (requiring intervention but no risk), severe (minor risk to self, others, or both), and extreme (major risk). We then analyzed behavioral manifestations, concurrent morbidity, and medication responses in patients with severe or extreme symptoms.

RESULTS

Two patients had mild behavioral problems, five moderate, 10 severe, six extreme, and 16 none. Extreme cases exhibited disruptive behaviors escalating to assaults. Triggers, when present, included peer-provocation, low frustration tolerance, limits set by others, and sleep disruption. Reversible psychotic symptoms occurred in two patients: in one triggered by infection and trihexyphenidyl, and in another triggered by sertraline. Of the 16 patients with severe or extreme symptoms, 13 had concurrent neuropsychiatric diagnoses. Occurrence of severe or extreme symptoms did not correlate with age, puberty, severity of intellectual disability, or mutation status (P > 0.05). A multidisciplinary team including mental health professionals comanaged all patients with severe or extreme symptoms with either behavioral therapy, medications, or both. When considering medications prescribed to more than four patients, medicines that demonstrated efficacy or partial efficacy in more than 50% of patients were alpha-adrenergic agonists and selective-serotonin-reuptake-inhibitors.

CONCLUSIONS

Patients with alternating hemiplegia of childhood (41%) often experience severe or extreme behavioral problems and, rarely, medication-triggered psychotic symptoms. These observations are consistent with current understanding of underlying alternating hemiplegia of childhood brain pathophysiology. Increasing awareness of these behavioral problems facilitates alternating hemiplegia of childhood management and anticipatory guidance.

Effect of Flunarizine on Alternating Hemiplegia of Childhood in a Patient with the p.E815K Mutation in ATP1A3: A Case Report

Alternating hemiplegia of childhood (AHC) (MIM 104290) is characterized by transient repeated attacks of paresis on either or both sides of the body, oculomotor and autonomic abnormalities, movement disorders, and cognitive impairment. Preventing paroxysmal attacks, such as paresis and spasm, in patients with AHC is often difficult. An 8-month-old girl presented to our institution with intractable epilepsy. She developed AHC, with left-right alternating or bilateral recurrent plegia upon waking, involuntary movements, eye movement abnormalities, and psychomotor retardation. She had a heterozygous de novo p.E815K mutation in the <i>ATP1A3</i>gene. Patients with this mutation develop severe hemiplegic spells and convulsions, have a poor neuromotor developmental outcome, and are particularly difficult to treat. Flunarizine treatment has limited therapeutic effect in such patients; however, it was definitely effective for bulbar palsy in the present case. The present case further highlights the need for the development of other new treatments, such as a ketogenic diet.

Cardiac phenotype in ATP1A3-related syndromes: A multicenter cohort study

OBJECTIVE

To define the risks and consequences of cardiac abnormalities in ATP1A3-related syndromes.

METHODS

Patients meeting clinical diagnostic criteria for rapid-onset dystonia-parkinsonism (RDP), alternating hemiplegia of childhood (AHC), and cerebellar ataxia, areflexia, pes cavus, optic atrophy, and sensorineural hearing loss (CAPOS) with ATP1A3 genetic analysis and at least 1 cardiac assessment were included. We evaluated the cardiac phenotype in an Atp1a3 knock-in mouse (Mashl^+/-) to determine the sequence of events in seizure-related cardiac death.

RESULTS

Ninety-eight patients with AHC, 9 with RDP, and 3 with CAPOS (63 female, mean age 17 years) were included. Resting ECG abnormalities were found in 52 of 87 (60%) with AHC, 2 of 3 (67%) with CAPOS, and 6 of 9 (67%) with RDP. Serial ECGs showed dynamic changes in 10 of 18 patients with AHC. The first Holter ECG was abnormal in 24 of 65 (37%) cases with AHC and RDP with either repolarization or conduction abnormalities. Echocardiography was normal. Cardiac intervention was required in 3 of 98 (≈3%) patients with AHC. In the mouse model, resting ECGs showed intracardiac conduction delay; during induced seizures, heart block or complete sinus arrest led to death.

CONCLUSIONS

We found increased prevalence of ECG dynamic abnormalities in all ATP1A3-related syndromes, with a risk of life-threatening cardiac rhythm abnormalities equivalent to that in established cardiac channelopathies (≈3%). Sudden cardiac death due to conduction abnormality emerged as a seizure-related outcome in murine Atp1a3-related disease. ATP1A3-related syndromes are cardiac diseases and neurologic diseases. We provide guidance to identify patients potentially at higher risk of sudden cardiac death who may benefit from insertion of a pacemaker or implantable cardioverter-defibrillator.

Alternating Hemiplegia of Childhood: gastrointestinal manifestations and correlation with neurological impairments

Background

Alternating Hemiplegia of Childhood (AHC) is caused by mutations of the ATP1A3 gene which is expressed in brain areas that include structures controling autonomic, gastrointestinal, gut motility and GABAergic functions. We aimed to investigate, in a cohort of 44 consecutive AHC patients, two hypotheses: 1) AHC patients frequently manifest gastrointestinal, particularly motility, problems. 2) These problems are often severe and their severity correlates with neurological impairments.

Results

41/44 (93%) exhibited gastrointestinal symptoms requiring medical attention. For these 41 patients, symptoms included constipation (66%), swallowing problems (63%), vomiting (63%), anorexia (46%), diarrhea (44%), nausea (37%), and abdominal pain (22%). Symptoms indicative of dysmotility occurred in 33 (80%). The most common diagnoses were oropharyngeal dysphagia (63%) and gastroesophageal reflux (63%). 16 (39%) required gastrostomy and two fundoplication. Severity of gastrointestinal symptoms correlated with non-paroxysmal neurological disability index, Gross Motor Function Classification System scores, and with the presence/absence of non-gastrointestinal autonomic dysfunction (p = 0.031, 0.043, Spearman correlations and 0.0166 Cramer’s V, respectively) but not with the paroxysmal disability index (p = 0.408).

Conclusions

Most AHC patients have gastrointestinal problems. These are usually severe, most commonly are indicative of dysmotility, often require surgical therapies, and their severity correlates with that of non-paroxysmal CNS manifestations. Our findings should help in management-anticipatory guidance of AHC patients. Furthermore, they are consistent with current understandings of the pathophysiology of AHC and of gastrointestinal dysmotility, both of which involve autonomic and GABAergic dysfunction.

Alternating Hemiplegia of Childhood: A Series of Genetically Confirmed Four Cases from Southern India with Review of Published Literature

Alternating hemiplegia of childhood (AHC) is a rare autosomal dominant neurodevelopmental disorder with mutation on ATP1A3 gene. Delay in diagnosis and inappropriate diagnosis are common. In this article, we described four genetically confirmed AHC patients to provide an improved understanding of the disorder. First symptom in two patients was seizures and in other two patients was abnormal eye deviation. All had onset of plegic attacks within the first 18 months of their life. Tone abnormalities and movement disorders were present in all patients. Electroencephalogram was abnormal in two patients and all had normal magnetic resonance imaging of the brain. Response to treatment of plegic attacks was poor and also epilepsy was drug resistant. All cases had significant development delay and disability as of last follow-up. Although there is no effective treatment so far, early diagnosis is required to avoid unnecessary treatment.

D-DEMØ, a distinct phenotype caused by ATP1A3 mutations

Objective

To describe a phenotype caused by ATP1A3 mutations, which manifests as dystonia, dysmorphism of the face, encephalopathy with developmental delay, brain MRI abnormalities always including cerebellar hypoplasia, no hemiplegia (Ø) (D-DEMØ), and neonatal onset.

Methods

Review and analysis of clinical and genetic data.

Results

Patients shared the above traits and had whole-exome sequencing that showed de novo variants of the ATP1A3 gene, predicted to be disease causing and occurring in regions of the protein critical for pump function. Patient 1 (c.1079C>G, p.Thr360Arg), an 8-year-old girl, presented on day 1 of life with episodic dystonia, complex partial seizures, and facial dysmorphism. MRI of the brain revealed cerebellar hypoplasia. Patient 2 (c.420G>T, p.Gln140His), an 18-year-old man, presented on day 1 of life with hypotonia, tremor, and facial dysmorphism. He later developed dystonia. MRI of the brain revealed cerebellar hypoplasia and, later, further cerebellar volume loss (atrophy). Patient 3 (c.974G>A, Gly325Asp), a 13-year-old girl, presented on day 1 of life with tremor, episodic dystonia, and facial dysmorphism. MRI of the brain showed severe cerebellar hypoplasia. Patient 4 (c.971A>G, p.Glu324Gly), a 14-year-old boy, presented on day 1 of life with tremor, hypotonia, dystonia, nystagmus, facial dysmorphism, and later seizures. MRI of the brain revealed moderate cerebellar hypoplasia.

Conclusions

D-DEMØ represents an ATP1A3-related phenotype, the observation of which should trigger investigation for ATP1A3 mutations. Our findings, and the presence of multiple distinct ATP1A3-related phenotypes, support the possibility that there are differences in the underlying mechanisms.

Social impairments in alternating hemiplegia of childhood

AIM

To evaluate presence and severity of social impairments in alternating hemiplegia of childhood (AHC) and determine factors that are associated with social impairments.

METHOD

This was a retrospective analysis of 34 consecutive patients with AHC (19 females, 15 males; mean age: 9y 7mo, SD 8y 2mo, range 2y 7mo-40y), evaluated with the Social Responsiveness Scale, Second Edition (SRS-2).

RESULTS

SRS-2 scores, indicating level of social impairment, were higher than population means (75, SD 14 vs 50, SD 10, p<0.001). Of these, 27 out of 34 had high scores: 23 severe (>76), four moderate (66-76). All subscale domains, including social cognition, social communication, social awareness, social motivation, restricted interests, and repetitive behavior, had abnormal scores compared to population means (p<0.001). High SRS-2 scores were associated with the presence of autism spectrum disorder (ASD) and epilepsy (p=0.01, p=0.04), but not with other scales of AHC disease symptomatology. All nine patients who received formal evaluations for ASD, because they had high SRS-2 scores, were diagnosed with ASD.

INTERPRETATION

Most patients with AHC have impaired social skills involving multiple domains. ASD is not uncommon. High SRS-2 scores in patients with AHC support referral to ASD evaluation. Our findings are consistent with current understandings of the pathophysiology of AHC and ASD, both thought to involve GABAergic dysfunction.

WHAT THIS PAPER ADDS

Most patients with alternating hemiplegia of childhood (AHC) have impaired social skills involving multiple domains. These impairments are significant compared to population means. Most patients with AHC have high Social Responsiveness Scale, Second Edition (SRS-2) scores. Patients with AHC with high SRS-2 scores are likely to have autism spectrum disorder.

Magnetic resonance imaging volumetric analysis in patients with Alternating hemiplegia of childhood: A pilot study

Quantitative MRI is increasingly being used as a biomarker in neurological disorders. Cerebellar atrophy occurs in some Alternating Hemiplegia of Childhood (AHC) patients. However, it is not known if cerebellar atrophy can be a potential biomarker in AHC or if quantitative MRI is a reliable method to address this question. Here we determine the reproducibility of an MRI-volumetrics method to investigate brain volumes in AHC and apply it to a population of 14 consecutive AHC patients (ages 4-11 years). We studied method reproducibility in the first 11 patients and then performed correlation of cerebellar volumes, relative to published normal population means, with age in all 14. We used FreeSurfer 6.0.0 to automatically segment MRI images, then performed manual resegmentation correction by two different observers. No significant differences were observed in any of ten brain regions between the two reviewers: p > .591 and interclass Correlation Coefficient (ICC) ≥0.975 in all comparisons. Additionally, there were no significant differences between the means of the two reviewers and the automatic segmentation values: p ≥ .106 and ICC ≥0.994 in all comparisons. We found a negative correlation between cerebellar volume and age (R = -0.631, p = .037), even though only one patient showed any cerebellar atrophy upon formal readings of the MRIs by neuroradiology. Sample size did not allow us to rule out potential confounding variables. Thus, findings from this cross-sectional study should be considered as exploratory. Our study supports the prospective investigation of quantitative MRI-volumetrics of the cerebellum as a potential biomarker in AHC.

[Alternating hemiplegia]

Alternating hemiplegia, a rare neurological disease that manifests in children under the age of 18 months, is characterized by transient episodes of hemiparesis of an alternating nature in the waking period. In addition to transient hemiparesis, neurological symptoms in the form of choreoathetosis, ataxia, dystonia, autonomic dysfunction, ocular apraxia, nystagmus, seizures, dysarthria and intellectual disorders may develop. Mutation in the ATP1A3 gene is the cause of the disease in more than 75% of patients. In some cases, the use of flunarizine, adenosine triphosphate and a ketogenic diet can reduce the frequency and duration of hemiplegic attacks. The authors report a case of a patient with alternating hemiplegia caused by a heterozygous mutation in exon 8 of the ATP1A3 gene (chr19: 42489098A>T, rs606231428), resulting in an amino acid substitution at position 335 (p.Val335Asp, NM_001256214.1). The use of flunarizin in a dose of 5 mg/day significantly reduces the number and duration of seizures, while oral adenosine-5-triphosphoric acid in a dose of 20 mg/kg/day is not effective.

Management of Alternating Hemiplegia of Childhood: A Review

Alternating hemiplegia of childhood is a severe neurological disorder with infantile-onset recurrent episodes of hemiplegia on either side of the body and other paroxysmal events such as seizures, dystonia, tonic episodes, abnormal eye movements or autonomic dysfunction, primarily due to de novo pathogenic mutations in the ATP1A3 gene. The burden of neuromorbidities is significant and includes epilepsy; attention-deficit/hyperactivity disorder; behavioral difficulties; motor, cognitive, adaptive, and learning impairment; ataxia; movement disorders; and migraine. Comprehensive multispecialty clinic with the availability of various specialists with considerable experience in alternating hemiplegia of childhood is beneficial. A comprehensive treatment plan including strict maintenance of a diary about different paroxysmal events is helpful. Disease-modifying therapy of alternating hemiplegia of childhood does not exist, and several agents such as benzodiazepines, flunarizine, topiramate, ketogenic diet, triheptanoin, steroid, amantadine, memantine, aripiprazole, oral ATP, coenzyme Q, acetazolamide, dextromethorphan, and vagus nerve stimulator have been tried with various rates of success by aborting attacks or reducing the frequency or severity of paroxysmal spells. The apparent efficacy of flunarizine is based on its use in hundreds of patients, albeit in open-label experience, but most of the other agents' reports of efficacy were from single case reports or case series of only a handful of patients. Besides reviewing existing data about individual agent active against paroxysmal events, we also review the management principles for coexisting neurological issues. However, with rapid advancement in the understanding of molecular pathogenesis and network abnormality of this disease, the treatment paradigm of alternating hemiplegia of childhood may significantly alter over the next decade.

Clinical and Genetic Spectrum of ATP1A3-Related Disorders in a Korean Pediatric Population

Background and Purpose

The aim of this study was to expand the understanding of the genotype-phenotype spectrum of ATP1A3-related disorders and to evaluate the therapeutic effect of a ketogenic diet in patients with alternating hemiplegia of childhood (AHC).

Methods

The clinical information of 13 patients with ATP1A3 mutations was analyzed by performing retrospective chart reviews. Patients with the AHC phenotype who consented to ketogenic diet were included in the trial.

Results

Ten patients presented with the clinical phenotype of AHC, two patients presented with rapid-onset dystonia parkinsonism, and one patient presented with cerebellar ataxia, areflexia, pes cavus, optic atrophy, and sensorineural hearing loss. Two novel mutations of the AHC phenotype were identified: p.Ile363Thr and p.Asn743Ser. The clinical phenotypes of three mutations differed from those in previous reports: p.Arg597Pro, p.Thr769Pro, and p.Arg756Cys. One of the two patients who started a ketogenic diet experienced seizure provocation and so immediate stopped consuming the diet, while the other patient continued the ketogenic diet for 1 year, but this produced no clear benefit such as reduction of paroxysmal symptoms.

Conclusions

Our study is the first case series of ATP1A3-related disorders to be described in Korea and which further expands the understanding of its genotype-phenotype spectrum. A ketogenic diet showed no clear benefit for the patients with AHC.

The epileptology of alternating hemiplegia of childhood

OBJECTIVE

To report our experience and investigate 5 original hypotheses: (1) multiple types of epileptic seizures occur in alternating hemiplegia of childhood (AHC), and these can be the initial presentation; (2) epileptiform abnormalities often appear well after clinical seizures; (3) nonepileptic reduced awareness spells (RAS) occur frequently; (4) epilepsy is commonly drug resistant but may respond to vagal nerve stimulation (VNS); and (5) status epilepticus (SE) is common and is usually refractory and recurrent.

METHODS

We analyzed a cohort of 51 consecutive patients with AHC.

RESULTS

Thirty-two of 51 patients had epilepsy: 18 focal seizures, frontal more frequently than temporal, and then posterior. Eleven had primary generalized seizures (tonic-clonic, myoclonic, and/or absence). Epileptic seizures preceded other AHC paroxysmal events in 8 (lag 5.63 ± 6.55 months; p = 0.0365). In 7 of 32, initial EEGs were normal, with the first epileptiform EEG lagging behind by 3.53 ± 4.65 years (p = 0.0484). RAS occurred equally in patients with epilepsy (16 of 32) and patients without epilepsy (10 of 19, p = 1.0). Twenty-eight patients had video-EEG; captured RAS showed no concomitant EEG changes. Nineteen patients (59%) were drug resistant. VNS resulted in >50% reduction in seizures in 5 of 6 (p < 0.04). Twelve patients (38%) had SE (9 of 12 multiple episodes), refractory/superrefractory in all (p < 0.001), and 4 of 12 had regression after SE.

CONCLUSIONS

Epilepsy in AHC can be focal or generalized. Epileptic seizures may be the first paroxysmal symptom. EEG may become epileptiform only on follow-up. Epilepsy, although frequently drug resistant, can respond to VNS. RAS are frequent and nonepileptic. SE often recurs and is usually refractory/superrefractory. Our observations are consistent with current data on AHC-ATP1A3 pathophysiology.

Physical Therapy for a Patient With Alternating Hemiplegia of Childhood: A Case Report

PURPOSE

Alternating hemiplegia of childhood (AHC) is a rare neurological disorder that can influence posture and movement during critical periods of motor development. There are no descriptions of physical therapy for children with AHC. The purpose of this case report is to present an example of physical therapy evaluation, intervention, and outcomes for a child with AHC.

SUMMARY OF KEY POINTS

Physical therapy services were provided over 9 sequential plans of care between 14 and 52 months of age. The child demonstrated improvements in motor control, walked independently at 16.5 months of age, and her Gross Motor Function Measure-88 score increased from 78% to 95% between 27 and 52 months of age.

CONCLUSIONS AND RECOMMENDATIONS FOR CLINICAL PRACTICE

The importance in this case lies in the use of a multisystem approach to treatment, careful consideration of frequency of intervention, and discussion of the unique features of AHC.

Heart rate variability in a patient with alternating hemiplegia

Alternating hemiplegia of childhood (AHC) is a rare disorder characterized by repetitive episodes of transient hemiplegia. Although autonomic nervous system dysfunction is believed to be associated with AHC, there are no reports of heart rate variability (HRV) in patients with AHC. In the current study, we analyzed HRV in a 20-year-old female with this disorder. The frequency of paralytic attacks have decreased since the patient was a teenager, compared to when she was < ten years old; however, as a 20-year-old, she still experiences paralytic attacks several times per month to more than ten times per month. Thus far, she has only suffered paralytic attacks and no epileptic seizures. Using Sanger sequencing, Gly947Arg (2839G>A) in the sodium-potassium (Na⁺/K⁺)-ATPaseα3 subunit gene (ATP1A3) was confirmed from her blood sample. An elevated heart rate lasting one to two minutes and sometimes longer, was primarily observed at night while the patient was sleeping. Large fluctuations in HRV, including low- and high- frequency components, were primarily observed while the patient was sleeping but suppressed during paralytic attacks. These results confirm the presence of an autonomic nervous system disorder in AHC. Because large variation of the autonomic nervous function was observed at night, the pathophysiological function should be investigated for 24 hours.

Cognitive, adaptive, and behavioral profiles and management of alternating hemiplegia of childhood

AIM

To determine the neuropsychological abnormalities that occur in alternating hemiplegia of childhood (AHC) and report on our experience in managing them.

METHOD

Patients underwent evaluations according to our standardized AHC pathway. Data were entered into our prospective AHC database and then analyzed.

RESULTS

Of the cohort of 25 consecutive patients (ages 15mo-42y), eight had initial chief complaints about cognition, 14 language, five attention, and 11 behavior. As compared to population norms means, neuropsychological and behavioral assessment tools (including Child Behavior Checklist, Vineland Adaptive Behavior Scales, Peabody Picture Vocabulary, and Wechsler Intelligence Quotient tests) showed significant impairments in multiple domains: cognition, expressive and receptive language, executive function/attention, and behavior (p<0.05 in all comparisons). Evaluations generated management recommendations in all patients. Twenty had neuropsychiatric diagnoses: 10 attention-deficit/hyperactivity disorder (ADHD), seven disruptive behavior, and three anxiety disorder. Eight out of nine patients with ADHD who were prescribed medications responded to pharmacotherapy.

INTERPRETATION

Patients with AHC have developmental difficulties related to impairments in multiple neuropsychological domains. This supports the hypothesis that the underlying AHC pathophysiology involves diffuse neuronal dysfunction. Testing generated recommendations to help manage these difficulties. Patients with AHC also have a range of neuropsychiatric diagnoses, the most common being ADHD which responds to pharmacotherapy.

WHAT THIS PAPER ADDS

Patients with alternating hemiplegia of childhood (AHC) have developmental difficulties with underlying neuropsychological impairments. The findings in this study are consistent with an underlying AHC pathophysiology which involves diffuse neuronal, probably largely GABAergic, dysfunction. Patients with AHC have a range of neuropsychiatric diagnoses, the most common being attention-deficit/hyperactivity disorder.

Polysomnography Findings and Sleep Disorders in Children With Alternating Hemiplegia of Childhood

STUDY OBJECTIVES

Patients with alternating hemiplegia of childhood (AHC) experience bouts of hemiplegia and other paroxysmal spells that resolve during sleep. Patients often have multiple comorbidities that could negatively affect sleep, yet sleep quality and sleep pathology in AHC are not well characterized. This study aimed to report sleep data from both polysomnography (PSG) and clinical evaluations in children with AHC.

METHODS

We analyzed nocturnal PSG and clinical sleep evaluation results of a cohort of 22 consecutive pediatric patients with AHC who were seen in our AHC multidisciplinary clinic and who underwent evaluations according to our comprehensive AHC clinical pathway. This pathway includes, regardless of presenting symptoms, baseline PSG and evaluation by a board-certified pediatric sleep specialist.

RESULTS

Out of 22 patients, 20 had at least one type of sleep problem. Six had obstructive sleep apnea as documented on polysomnogram, of whom two had no prior report of sleep-disordered breathing symptoms. Patients had abnormal mean overall apnea-hypopnea index of 5.8 (range 0-38.7) events/h and an abnormal mean arousal index of 15.0 (range 4.8-46.6) events/h. Based on sleep history, 16 patients had difficulty falling asleep, staying asleep, or both; 9 had behavioral insomnia of childhood; and 2 had delayed sleep-wake phase syndrome.

CONCLUSIONS

Sleep dysfunction is common among children with AHC. Physicians should routinely screen for sleep pathology, with a low threshold to obtain a nocturnal PSG.

Alternating Hemiplegia of Childhood in Two Adult Patients with a Mild Syndrome

We describe the cognitive-behavioral functioning of two adult patients with a mild form of alternating hemiplegia of childhood (AHC). AHC is a rare, chronic neurodevelopmental syndrome manifesting in infancy or early childhood, with recurrent hemiplegic or hemidystonic attacks, various nonepileptic paroxysmal events, and cognitive-behavioral impairments, including mental delay of varying degrees. We conducted neurologic and neuroimaging examinations, as well as a neuropsychological assessment, of two men (22 and 30 years old) with mutations in the ATP1A3 gene (p.Leu757Pro and p.Val332Glu) who were experiencing typical AHC transient episodes of alternating weakness or paralysis in order to investigate causes of their poor social functioning. During neurologic examinations of both patients, which were performed between attacks, we observed involuntary movements such as chorea and upper-limb tremor. One patient also had dysarthria. Magnetic resonance imaging revealed no parenchymal brain lesions or atrophy in either patient. Neuropsychological examinations demonstrated near-normal (patient 1) or normal (patient 2) global cognitive functioning, with some isolated executive functioning deficits. Both patients had emotional and social dysfunction as well as difficulties adapting to normal adult life. Although the clinical presentation of AHC is usually dramatic, some patients have mild forms of the syndrome (eg, no significant intellectual disability). However, motor and movement disorders, as well as coexisting emotional-affective abnormalities, may affect these patients' ability to adapt to independent life.

Mechanisms of increased hippocampal excitability in the Mashl+/- mouse model of Na+ /K+ -ATPase dysfunction

OBJECTIVE

Na⁺ /K⁺ -ATPase dysfunction, primary (mutation) or secondary (energy crisis, neurodegenerative disease) increases neuronal excitability in the brain. To evaluate the mechanisms underlying such increased excitability we studied mice carrying the D801N mutation, the most common mutation causing human disease, specifically alternating hemiplegia of childhood (AHC) including epilepsy. Because the gene is expressed in all neurons, particularly γ-aminobutyric acid (GABA)ergic interneurons, we hypothesized that the pathophysiology would involve both pyramidal cells and interneurons and that fast-spiking interneurons, which have increased firing rates, would be most vulnerable.

METHODS

We performed extracellular recordings, as well as whole-cell patch clamp recordings from pyramidal cells and interneurons, in the CA1 region on hippocampal slices. We also performed immunohistochemistry from hippocampal sections to count CA1 pyramidal cells as well as parvalbumin-positive interneurons. In addition, we performed video-electroencephalography (EEG) recordings from the dorsal hippocampal CA1 region.

RESULTS

We observed that juvenile knock-in mice carrying the above mutation reproduce the human phenotype of AHC. We then demonstrated in the CA1 region of these mice the following findings as compared to wild type: (1) Increased number of spikes evoked by electrical stimulation of Schaffer collaterals; (2) equalization by bicuculline of the number of spikes induced by Schaffer collateral stimulation; (3) reduced miniature, spontaneous, and evoked inhibitory postsynaptic currents, but no change in excitatory postsynaptic currents; (4) robust action potential frequency adaptation in response to depolarizing current injection in CA1 fast-spiking interneurons; and (5) no change in the number of pyramidal cells, but reduced number of parvalbumin positive interneurons.

SIGNIFICANCE

Our data indicate that, in our genetic model of Atp1α3 mutation, there is increased excitability and marked dysfunction in GABAergic inhibition. This supports the performance of further investigations to determine if selective expression of the mutation in GABAergic and or glutamatergic neurons is necessary and sufficient to result in the behavioral phenotype.

Assessment of acute motor deficit in the pediatric emergency room

OBJECTIVES

This review article aimed to present a clinical approach, emphasizing the diagnostic investigation, to children and adolescents who present in the emergency room with acute-onset muscle weakness.

SOURCES

A systematic search was performed in PubMed database during April and May 2017, using the following search terms in various combinations: "acute," "weakness," "motor deficit," "flaccid paralysis," "child," "pediatric," and "emergency". The articles chosen for this review were published over the past ten years, from 1997 through 2017. This study assessed the pediatric age range, from 0 to 18 years.

SUMMARY OF THE DATA

Acute motor deficit is a fairly common presentation in the pediatric emergency room. Patients may be categorized as having localized or diffuse motor impairment, and a precise description of clinical features is essential in order to allow a complete differential diagnosis. The two most common causes of acute flaccid paralysis in the pediatric emergency room are Guillain-Barré syndrome and transverse myelitis; notwithstanding, other etiologies should be considered, such as acute disseminated encephalomyelitis, infectious myelitis, myasthenia gravis, stroke, alternating hemiplegia of childhood, periodic paralyses, brainstem encephalitis, and functional muscle weakness. Algorithms for acute localized or diffuse weakness investigation in the emergency setting are also presented.

CONCLUSIONS

The clinical skills to obtain a complete history and to perform a detailed physical examination are emphasized. An organized, logical, and stepwise diagnostic and therapeutic management is essential to eventually restore patient's well-being and full health.