Deep Brain Stimulation of Bilateral Centromedian Thalamic Nuclei in Pediatric Patients with Lennox-Gastaut Syndrome: An Institutional Experience

BACKGROUND

Surgical management of pediatric patients with nonlesional, drug-resistant epilepsy, including patients with Lennox-Gastaut syndrome (LGS), remains a challenge given the lack of resective targets in most patients and shows seizure freedom rates <50% at 5 years. The efficacy of deep brain stimulation (DBS) is less certain in children than in adults. This study examined clinical and seizure outcomes for pediatric patients with LGS undergoing DBS targeting of the centromedian thalamic nuclei (CMTN).

METHODS

An institutional review board-approved retrospective analysis was performed of patients aged ≤19 years with clinical diagnosis of LGS undergoing bilateral DBS placement to the CMTN from 2020 to 2021 by a single surgeon.

RESULTS

Four females and 2 males aged 6-19 years were identified. Before surgery, each child experienced at least 6 years of refractory seizures; 4 children had experienced seizures since infancy. All took antiseizure medications at the time of surgery. Five children had previous placement of a vagus nerve stimulator and 2 had a previous corpus callosotomy. The mean length of stay after DBS was 2 days. No children experienced adverse neurologic effects from implantation; the mean follow-up time was 16.3 months. Four patients had >60% reduction in seizure frequency after surgery, 1 patient experienced 10% reduction, and 1 patient showed no change. No children reported worsening seizure symptoms after surgery.

CONCLUSIONS

Our study contributes to the sparse literature describing CMTN DBS for children with drug-resistant epilepsy from LGS. Our results suggest that CMTN DBS is a safe and effective therapeutic modality that should be considered as an alternative or adjuvant therapy for this challenging patient population. Further studies with larger patient populations are warranted.

A de novo GRIN1 Variant Associated With Myoclonus and Developmental Delay: From Molecular Mechanism to Rescue Pharmacology

N-Methyl-D-aspartate receptors (NMDARs) are highly expressed in brain and play important roles in neurodevelopment and various neuropathologic conditions. Here, we describe a new phenotype in an individual associated with a novel de novo deleterious variant in GRIN1 (c.1595C>A, p.Pro532His). The clinical phenotype is characterized with developmental encephalopathy, striking stimulus-sensitive myoclonus, and frontal lobe and frontal white matter hypoplasia, with no apparent seizures detected. NMDARs that contained the P532H within the glycine-binding domain of GluN1 with either the GluN2A or GluN2B subunits were evaluated for changes in their pharmacological and biophysical properties, which surprisingly revealed only modest changes in glycine potency but a significant decrease in glutamate potency, an increase in sensitivity to endogenous zinc inhibition, a decrease in response to maximally effective concentrations of agonists, a shortened synaptic-like response time course, a decreased channel open probability, and a reduced receptor cell surface expression. Molecule dynamics simulations suggested that the variant can lead to additional interactions across the dimer interface in the agonist-binding domains, resulting in a more open GluN2 agonist-binding domain cleft, which was also confirmed by single-molecule fluorescence resonance energy transfer measurements. Based on the functional deficits identified, several positive modulators were evaluated to explore potential rescue pharmacology.

EEG Correlates of Delirium in Children and Young Adults With CD19-Directed CAR T Cell Treatment-Related Neurotoxicity

INTRODUCTION

EEG patterns in chimeric antigen receptor T cell treatment-associated neurotoxicity (immune effector cell-associated neurotoxicity syndrome) have not yet been systematically studied. We tested the hypothesis that EEG background abnormalities in immune effector cell-associated neurotoxicity syndrome correlate with clinical signs of neurotoxicity. In addition, we describe ictal and interictal EEG patterns to better understand the natural history of immune effector cell-associated neurotoxicity syndrome-associated seizures.

METHODS

EEGs were obtained in 19 of 100 subjects in a prospective cohort study of children and young adults undergoing CD19-directed chimeric antigen receptor T cell therapy. We classified the EEG background on a severity scale of 0 to 5 during 30-minute epochs. EEG grades were compared with neurotoxicity scored by Common Terminology Criteria for Adverse Events and Cornell Assessment of Pediatric Delirium scores. Descriptive analysis was conducted for ictal and interictal EEG abnormalities.

RESULTS

EEG background abnormality scores correlated well with Common Terminology Criteria for Adverse Events neurotoxicity scores (P = 0.0022) and Cornell Assessment of Pediatric Delirium scores (P = 0.0085). EEG was better able to differentiate the severity of coma patterns compared with the clinical scores. The EEG captured electroclinical seizures in 4 of 19 subjects, 3 of whom had additional electrographic-only seizures. Seizures most often arose from posterior head regions. Interictal epileptiform discharges were focal, multifocal, or lateralized periodic discharges. No seizures or interictal epileptiform abnormalities were seen in subjects without previous clinical seizures.

CONCLUSIONS

Continuous EEG monitoring is high yield for seizure detection in high-risk chimeric antigen receptor T cell patients, and electrographic-only seizures are common. Increasing severity of EEG background abnormalities correlates with increasing neurotoxicity grade.

Co-occurrence of Metachromatic Leukodystrophy in Phelan-McDermid Syndrome

Phelan-McDermid syndrome or 22q13.3 deletion syndrome is a rare neurodevelopmental disorder characterized by neonatal hypotonia, severe speech delay, moderate to profound intellectual disability, and minor dysmorphic features. Regression of developmental milestones is often recognized as characteristic of this syndrome. We report a 6-year-old patient with Phelan-McDermid syndrome who presented with rapid neurologic deterioration secondary to metachromatic leukodystrophy due to a mutation of the arylsulfatase A gene (ARSA) on the other allele of 22q13.3. Metachromatic leukodystrophy was diagnosed later after clinical deterioration. Currently, there are no guidelines for screening Phelan-McDermid syndrome patients for metachromatic leukodystrophy. We propose screening for urine sulfatides at the time of Phelan-McDermid syndrome diagnosis to identify patients with pre-symptomatic or early symptomatic metachromatic leukodystrophy as it is important to facilitate discussion of treatment options and prognosis and provide medical surveillance for associated complications.

Diagnosing Coexisting Conditions of Angelman and Klinefelter Syndromes Using Chromosomal Microarray

We report here a 4-year-old male patient who presented with clinical features of Angelman syndrome (AS, OMIM 105830) including dysmorphic features, hypotonia, lack of language development, ataxia, severe developmental delay, and seizures. Due to insurance denial for DNA methylation test, a chromosomal microarray (CMA) was performed, which showed an approximately 5.0 Mb deletion of Prader–Willi/AS critical region (15q11.2 to q13.1). Subsequent Prader–Willi/AS methylation analysis was consistent with the diagnosis of AS. Gain of an X chromosome (Klinefelter syndrome, KS) was also detected by CMA. KS is not usually diagnosed before puberty due to lack of specific clinical features in early childhood. It is unclear if there is any direct association between these two genetic disorders. There has only been one other published case, to our knowledge, of a patient with coexistence of AS due to 15q11.2-q13 deletion and KS. CMA is a fast and effective diagnostic test to determine multiple genetic disorders. Early genetic diagnostic testing using CMA as an alternative first-step diagnostic genetic testing for children with clinical suspicion of AS would be beneficial.

Expanding clinical phenotype in CACNA1C related disorders: From neonatal onset severe epileptic encephalopathy to late-onset epilepsy

CACNA1C (NM_000719.6) encodes an L-type calcium voltage-gated calcium channel (Ca_v 1.2), and pathogenic variants have been associated with two distinct clinical entities: Timothy syndrome and Brugada syndrome. Thus far, CACNA1C has not been reported as a gene associated with epileptic encephalopathy and is less commonly associated with epilepsy. We report three individuals from two families with variants in CACNA1C. Patient 1 presented with neonatal onset epileptic encephalopathy (NOEE) and was found to have a de novo missense variant in CACNA1C (c.4087G>A (p.V1363M)) on exome sequencing. In Family 2, Patient 2 presented with congenital cardiac anomalies and cardiomyopathy and was found to have a paternally inherited splice site variant, c.3717+1_3717+2insA, on a cardiomyopathy panel. Her father, Patient 3, presented with learning difficulties, late-onset epilepsy, and congenital cardiac anomalies. Family 2 highlights variable expressivity seen within a family. This case series expands the clinical and molecular phenotype of CACNA1C-related disorders and highlights the need to include CACNA1C on epilepsy gene panels.

Haemodynamic response associated with both ictal and interictal epileptiform activity using simultaneous video electroencephalography/near infrared spectroscopy in a within-subject study

This paper reports the findings from a pilot study of four patients with medically refractory epilepsy undergoing pre-surgical evaluation with ages ranging from 5 to 17 years. Video electroencephalography recordings and data from a near infrared spectroscopy cerebral/somatic oximeter were gathered and related to electrographic seizure onset and offset as determined by a paediatric epileptologist. All four patients showed haemodynamic changes associated with epileptiform activities. The increased blood flow clearly coincided with epileptiform activity and continued to increase as the epileptiform activity built up. Regional cerebral oxygen saturation increased in the epileptogenic focus, perhaps due to loss of cerebrovascular autoregulation. These findings reinforce that near infrared spectroscopy can potentially be used in a wide spectrum of patients with epilepsy regardless of the underlying brain pathology.

Evaluation of the child with acute ataxia: a systematic review

Evaluation of acute ataxia in a child poses a dilemma for the clinician in determining the extent and timing of initial screening tests. This article reviews the evidence concerning the diagnostic yield of commonly ordered tests in evaluating the child with acute ataxia. The literature revealed the following frequencies of laboratory screening abnormalities in children with acute ataxia: CT (∼2.5%), MRI (∼5%), lumbar puncture (43%), EEG (42%), and toxicology (49%). In most studies, abnormalities detected by these screening tests were nondiagnostic. There are insufficient data to assess yields of testing for autoimmune disorders or inborn errors of metabolism. A toxicology screen should be considered in all children presenting with acute ataxia. Neuroimaging should be considered in all children with new onset ataxia. Cerebrospinal fluid analysis has limited diagnostic specificity unless clinically indicated. Studies to examine neurophysiology testing did have sufficient evidence to support their use. There is insufficient evidence to establish a role for autoantibody testing or for routine screening for inborn error of metabolism in children presenting with acute ataxia. Finally, in a child presenting with ataxia and opsoclonus myoclonus, urine catecholamine testing for occult neuroblastoma is recommended. Nuclear scan may be considered, however, there is insufficient evidence for additional body imaging.