ATP1A2-related epileptic encephalopathy and movement disorder: Clinical features of three novel patients

OBJECTIVE

Variants in the ATP1A2 gene exhibit a wide clinical spectrum, ranging from familial hemiplegic migraine to childhood epilepsies and early infantile developmental epileptic encephalopathy (EIDEE) with movement disorders. This study aims to describe the epileptology of three unpublished cases and summarize epilepsy features of the other 17 published cases with ATP1A2 variants and EIDEE.

METHODS

Medical records of three novel patients with pathogenic ATP1A2 variants were retrospectively reviewed. Additionally, the PUBMED, EMBASE, and Cochrane databases were searched until December 2023 for articles on EIDEE with ATP1A2 variants, without language or publication year restrictions.

RESULTS

Three female patients, aged 6 months-10 years, were investigated. Epilepsy onset occurred between 5 days and 2 years, accompanied by severe developmental delay, intellectual disability, drug-resistant epilepsy, severe movement disorder, and recurrent status epilepticus. All individuals had pathogenic variants of the ATP1A2 gene (ATP1A2 c.720_721del (p.Ile240MetfsTer9), ATP1A2c.3022C > T (p.Arg1008Trp), ATP1A2 c.1096G > T (p.Gly366Cys), according to ACMG criteria. Memantine was p) rescribed to three patients, one with a reduction in ictal frequency, one with improvement in gait pattern, coordination, and attention span, and another one in alertness without significant side effects.

SIGNIFICANCE

This study reinforces the association between ATP1A2 variants and a severe phenotype. All patients had de novo variants, focal motor seizures with impaired awareness as the primary type of seizure; of the 11 EEGs recorded, 10 presented a slow background rhythm, 7 multifocal interictal epileptiform discharges (IED), predominantly temporal IEDs, followed by frontal IED, as well as ten ictal recordings, which showed ictal onset from the same regions mentioned above. Treatment with antiseizure medication was generally ineffective, but memantine showed moderate improvement. Prospective studies are needed to enlarge the phenotype and assess the efficacy of NMDA receptor antagonist therapies in reducing seizure frequency and improving quality of life.

Binding and Dynamics Demonstrate the Destabilization of Ligand Binding for the S688Y Mutation in the NMDA Receptor GluN1 Subunit

Encephalopathies are brain dysfunctions that lead to cognitive, sensory, and motor development impairments. Recently, the identification of several mutations within the N-methyl-D-aspartate receptor (NMDAR) have been identified as significant in the etiology of this group of conditions. However, a complete understanding of the underlying molecular mechanism and changes to the receptor due to these mutations has been elusive. We studied the molecular mechanisms by which one of the first mutations within the NMDAR GluN1 ligand binding domain, Ser688Tyr, causes encephalopathies. We performed molecular docking, randomly seeded molecular dynamics simulations, and binding free energy calculations to determine the behavior of the two major co-agonists: glycine and D-serine, in both the wild-type and S688Y receptors. We observed that the Ser688Tyr mutation leads to the instability of both ligands within the ligand binding site due to structural changes associated with the mutation. The binding free energy for both ligands was significantly more unfavorable in the mutated receptor. These results explain previously observed in vitro electrophysiological data and provide detailed aspects of ligand association and its effects on receptor activity. Our study provides valuable insight into the consequences of mutations within the NMDAR GluN1 ligand binding domain.

Consensus-based statements for the management of mitochondrial stroke-like episodes

Background: Focal-onset seizures and encephalopathy are prominent features of a stroke-like episode, which is a severe neurological manifestation associated with subtypes of mitochondrial disease. Despite more than 30 years of research, the acute treatment of stroke-like episodes remains controversial. Methods: We used the modified Delphi process to harness the clinical expertise of a group of mitochondrial disease specialists from five European countries to produce consensus guidance for the acute management of stroke-like episodes and commonly associated complications. Results: Consensus on a new definition of mitochondrial stroke-like episodes was achieved and enabled the group to develop diagnostic criteria based on clinical features, neuroimaging and/or electroencephalogram findings. Guidelines for the management of strokelike episodes were agreed with aggressive seizure management strongly recommended at the outset of stroke-like episodes. Conclusions: Our consensus statement defines stroke-like episodes in terms of an epileptic encephalopathy and we have used this to revise both diagnostic criteria and guidelines for management. A prospective, multi-centre, randomised controlled trial is required for evaluating the efficacy of any compound on modifying the trajectory of stroke-like episodes.

Neonatal Encephalopathies: A Clinical Perspective

Seizures are the most acute evident manifestation of central nervous system dysfunction in neonates. The incidence is higher in very low weight neonates, about 58/100 live births, as opposed to full-term infants, estimated about 3.5/100 live births. Neonatal seizures represent the clinical manifestation of a non-specific disorder of cortical cerebral dysfunction, which could lead to permanent brain injury. The etiology is multifactorial and requires a judicious assessment of each clinical scenario. The diagnosis and its management are further complicated as most neonatal seizures may have very subtle or no clinical changes and the diagnosis may be just based on EEG findings, so-called subclinical. The treatment is dependent on the etiology, but early and opportune intervention can prevent further brain damage and improve prognosis. Although early identification and treatment are essential, the diagnosis of neonatal seizures can be further complicated by the clinical presentations, possible etiologies, and treatments. Nevertheless, research studies and clinical evidence have shown that early treatment with anti-seizure medications can change the outcome.

Myoclonic Disorders

Few movement disorders seem to make a straightforward approach to diagnosis and treatment more difficult and frustrating than myoclonus, due to its plethora of causes and its variable classifications. Nevertheless, in recent years, exciting advances have been made in the elucidation of the pathophysiology and genetic basis of many disorders presenting with myoclonus. Here, we provide a review of all of the important types of myoclonus encountered in pediatric and adult neurology, with an emphasis on the recent developments that have led to a deeper understanding of this intriguing phenomenon. An up-to-date list of the genetic basis of all major myoclonic disorders is presented. Randomized studies are scarce in myoclonus therapy, but helpful pragmatic approaches at diagnosis as well as treatment have been recently suggested.

Neurologic complications of bone marrow transplantation

Although bone marrow transplantation has been recognized as an effective therapy for malignant and nonmalignant blood disorders, the modality has also been associated with side-effects and complications. Among these adverse events, neurologic complications emerged as an important and frequent source of treatment-related morbidity and mortality. The survival of patients who died from complications related to central nervous system abnormalities appears to be shorter compared to those who died from non-neurological complications. The incidence of neurologic complications appears to correlate with the degree of human leukocyte antigen (HLA) disparity and the risk status of the underlying disease. Nonrelapse mortality associated with reduced intensity regimens is lower compared to myeloablative conditioning regimens. However, reduced intensity regimens are still associated with significant incidence of complications, including graft-versus-host disease, opportunistic infections, organ toxicity, and neurologic complications. Complications of sepsis-related encephalopathy in mechanically ventilated patients are frequently either overlooked or misdiagnosed. Obtaining a microbiological diagnosis through body fluid cultures or tissue identification is important in order to identify the source of infection and guide an effective antimicrobial therapy. However, pursuing a microbiological diagnosis must not delay the administration of antibiotics and resuscitation of a patient with septic shock.

Nonconvulsive status epilepticus: a diagnostic and therapeutic challenge in the intensive care setting

Nonconvulsive status epilepticus (NCSE) comprises a group of syndromes that display a great diversity regarding response to anticonvulsants ranging from virtually self-limiting variants to entirely refractory forms. Therefore, treatment on intensive care units (ICUs) is required only for a selection of cases. The aetiology and clinical form of NCSE are strong predictors for the overall prognosis. Absence status epilepticus is commonly seen in patients with idiopathic generalized epilepsy and is rapidly terminated by low-dose of benzodiazepines. The management of complex partial status epilepticus is straightforward in patients with pre-existing epilepsy, but poses major problems if occurring in the context of acute brain lesions. Subtle status epilepticus represents the late stage of undertreated previous overt generalized convulsive status epilepticus and always requires aggressive ICU treatment. Within the intensive care setting, the diagnostic challenge may be seen in the difficulty in delineating nonepileptic conditions such as posthypoxic, metabolic or septic encephalopathies from NCSE. Although all important forms are considered, the focus of this review lies on clinical presentations and electroencephalogram features of comatose patients treated on ICUs and possible diagnostic pitfalls.