Clinical features, investigations, and outcomes of pediatric limbic encephalitis: A multicenter study.

OBJECTIVES: To describe the clinical presentation, investigations, management, and disease course in pediatric autoimmune limbic encephalitis (LE). METHODS: In this retrospective observational study, from the UK Childhood Neuroinflammatory Disease network, we identified children from six tertiary centers with LE <18 years old between 2008 and 2021. Clinical and paraclinical data were retrieved from medical records. RESULTS: Twenty-five children fulfilling LE criteria were identified, with median age of 11 years (IQR 8, 14) and median follow-up of 24 months (IQR 18, 48). All children presented with seizures; 15/25 (60%) were admitted to intensive care. Neuroimaging demonstrated asymmetric mesial temporal changes in 8/25 (32%), and extra-limbic changes with claustrum involvement in 9/25 (38%). None were positive for LGI1/CASPR2 antibodies (Abs), 2/25 were positive for serum anti-NMDAR Abs, and 2/15 positive for anti-Hu Abs; one died from relapsing neuroblastoma. Two children had serum and CSF anti-GAD antibodies. Initial immune therapy included steroids in 23/25 (92%), intravenous immunoglobulin (IVIg) in 14/25 (56%), and plasma exchange in 7/25 (28%). The commonest second-line treatment was rituximab in 15/25 (60%). Median duration of hospital admission was 21 days (IQR 11, 30). At last follow-up, 13/25 (52%) had refractory seizures and 16/25 (64%) had memory impairment. Six children (24%) had modified Rankin Scale (mRS) scores ≥3. There was no significant difference in mRS, or long-term cognitive and epilepsy outcomes in those who received rituximab versus those who did not. INTERPRETATION: A diagnosis of autoimmune LE was associated with significant morbidity and adverse outcomes in this pediatric cohort.

Incidence of paediatric multiple sclerosis and other acquired demyelinating syndromes: 10-year follow-up surveillance study.

AIM: To describe a 10-year follow-up of children (<16y) with acquired demyelinating syndromes (ADS) from a UK-wide prospective surveillance study. METHOD: Diagnoses were retrieved from the patients' records via the patients' paediatric or adult neurologist using a questionnaire. Demyelinating phenotypes at follow-up were classified by an expert review panel. RESULTS: Twenty-four out of 125 (19.2%) children (64 males, 61 females; median age 10y, range 1y 4mo-15y 11mo), identified in the original study, were diagnosed with multiple sclerosis (incidence of 2.04/million children/year); 23 of 24 fulfilled 2017 McDonald criteria at onset. Aquaporin-4-antibody neuromyelitis optica spectrum disorders were diagnosed in three (2.4%, 0.26/million children/year), and relapsing myelin oligodendrocyte glycoprotein antibody-associated disease in five (4%, 0.43/million children/year). Three out of 125 seronegative patients relapsed and 85 of 125 (68%) remained monophasic over 10 years. Five of 125 patients (4%) originally diagnosed with ADS were reclassified during follow-up: three children diagnosed initially with acute disseminated encephalomyelitis were subsequently diagnosed with acute necrotising encephalopathy (RAN-binding protein 2 mutation), primary haemophagocytic lymphohistiocytosis (Munc 13-4 gene inversion), and anti-N-methyl-d-aspartate receptor encephalitis. One child initially diagnosed with optic neuritis was later diagnosed with vitamin B12 deficiency, and one presenting with transverse myelitis was subsequently diagnosed with Sjögren syndrome. INTERPRETATION: The majority of ADS presentations in children are monophasic, even at 10-year follow-up. Given the implications for treatment strategies, multiple sclerosis and central nervous system autoantibody mimics warrant extensive investigation.

Isolated central nervous system familial hemophagocytic lymphohistiocytosis (fHLH) presenting as a mimic of demyelination in children.

Isolated central nervous system (CNS) presentations of haemophagocytic lymphohistiocytosis (HLH), traditionally a systemic inflammatory condition, have been reported in adults and children. We identified nine patients with a diagnosis of isolated CNS familial hemophagocytic lymphohistiocytosis (fHLH) with symptom onset <18 years of age, and one asymptomatic sibling. Children with atypical chronic/recurrent CNS inflammation should be considered for immunological and genetic panel testing for fHLH even in the absence of any systemic inflammatory features. Despite haematopoietic stem cell transplantation (HSCT) being a mainstay of treatment, treatment failure and high morbidity and mortality post-HSCT suggest that alternative immune therapies may be worth considering.

Opsoclonus-myoclonus in Aicardi-Goutières syndrome.

Aicardi-Goutières syndrome (AGS) is a rare genetic neuroinflammatory disorder caused by abnormal upregulation of type 1 interferon signalling. Opsoclonus-myoclonus syndrome is a rare autoimmune phenotype demonstrating a disturbance in the humoral immune response mostly seen in the context of paraneoplastic or postinfectious states, although its pathophysiology is incompletely understood. We report the first three children described with AGS demonstrating transient opsoclonus and myoclonus after irritability and/or developmental regression, suggesting a pathological association. We describe the presentation, clinical features, progress, cerebrospinal fluid (CSF) inflammatory markers, electroencephalogram (EEG), and magnetic resonance imaging (MRI) findings in these children. Two patients had developmental regression but demonstrated a positive response to JAK1/2 inhibition clinically and on serial examination of CSF inflammatory markers. These findings suggest that AGS should be considered in children presenting with opsoclonus-myoclonus, and that the association between AGS and opsoclonus-myoclonus further supports the role of immune dysregulation as causal in the rare neurological phenomenon opsoclonus and myoclonus. What this paper adds There is a phenotypic association between opsoclonus-myoclonus syndrome and Aicardi-Goutières syndrome. There is clinical evidence of immune dysregulation in the pathogenesis of opsoclonus and myoclonus.

Neuroinflammatory Disease as an Isolated Manifestation of Hemophagocytic Lymphohistiocytosis.

Isolated neuroinflammatory disease has been described in case reports of familial hemophagocytic lymphohistiocytosis (FHL), but the clinical spectrum of disease manifestations, response to therapy and prognosis remain poorly defined. We combined an international survey with a literature search to identify FHL patients with (i) initial presentation with isolated neurological symptoms; (ii) absence of cytopenia and splenomegaly at presentation; and (iii) systemic HLH features no earlier than 3 months after neurological presentation. Thirty-eight (20 unreported) patients were identified with initial diagnoses including acute demyelinating encephalopathy, leukoencephalopathy, CNS vasculitis, multiple sclerosis, and encephalitis. Median age at presentation was 6.5 years, most commonly with ataxia/gait disturbance (75%) and seizures (53%). Diffuse multifocal white matter changes (79%) and cerebellar involvement (61%) were common MRI findings. CSF cell count and protein were increased in 22/29 and 15/29 patients, respectively. Fourteen patients progressed to systemic inflammatory disease fulfilling HLH-2004 criteria at a mean of 36.9 months after initial neurological presentation. Mutations were detected in PRF1 in 23 patients (61%), RAB27A in 10 (26%), UNC13D in 3 (8%), LYST in 1 (3%), and STXBP2 in 1 (3%) with a mean interval to diagnosis of 28.3 months. Among 19 patients who underwent HSCT, 11 neurologically improved, 4 were stable, one relapsed, and 3 died. Among 14 non-transplanted patients, only 3 improved or had stable disease, one relapsed, and 10 died. Isolated CNS-HLH is a rare and often overlooked cause of inflammatory brain disease. HLH-directed therapy followed by HSCT seems to improve survival and outcome.

Development and Validation of a Targeted Next-Generation Sequencing Gene Panel for Children With Neuroinflammation.

Importance: Neuroinflammatory disorders are a range of severe neurological disorders causing brain and spinal inflammation and are now increasingly recognized in the pediatric population. They are often characterized by marked genotypic and phenotypic heterogeneity, complicating diagnostic work in clinical practice and molecular diagnosis. Objective: To develop and evaluate a next-generation sequencing panel targeting genes causing neuroinflammation or mimicking neuroinflammation. Design, Setting, and Participants: Cohort study in which a total of 257 genes associated with monogenic neuroinflammation and/or cerebral vasculopathy, including monogenic noninflammatory diseases mimicking these entities, were selected. A customized enrichment capture array, the neuroinflammation gene panel (NIP), was created. Targeted high-coverage sequencing was applied to DNA samples taken from eligible patients referred to Great Ormond Street Hospital in London, United Kingdom, between January 1, 2017, and January 30, 2019, because of onset of disease early in life, family history, and/or complex neuroinflammatory phenotypes. Main Outcomes and Measures: The main outcome was the percentage of individuals with definitive molecular diagnoses, variant classification, and clinical phenotyping of patients with pathogenic variants identified using the NIP panel. The NIP panel was initially validated in 16 patients with known genetic diagnoses. Results: The NIP was both sensitive (95%) and specific (100%) for detection of known mutations, including gene deletions, copy number variants, small insertions and deletions, and somatic mosaicism with allele fraction as low as 3%. Prospective testing of 60 patients (30 [50%] male; median [range] age, 9.8 [0.8-20] years) presenting with heterogeneous neuroinflammatory phenotypes revealed at least 1 class 5 (clearly pathogenic) variant in 9 of 60 patients (15%); 18 of 60 patients (30%) had at least 1 class 4 (likely pathogenic) variant. Overall, a definitive molecular diagnosis was established in 12 of 60 patients (20%). Conclusions and Relevance: The NIP was associated with molecular diagnosis in this cohort and complemented routine laboratory and radiological workup of patients with neuroinflammation. Unexpected genotype-phenotype associations in patients with pathogenic variants deviating from the classic phenotype were identified. Obtaining an accurate molecular diagnosis in a timely fashion informed patient management, including successful targeted treatment in some instances and early institution of hematopoietic stem cell transplantation in others.

A framework for measurement and harmonization of pediatric multiple sclerosis etiologic research studies: The Pediatric MS Tool-Kit.

BACKGROUND: While studying the etiology of multiple sclerosis (MS) in children has several methodological advantages over studying etiology in adults, studies are limited by small sample sizes. OBJECTIVE: Using a rigorous methodological process, we developed the Pediatric MS Tool-Kit, a measurement framework that includes a minimal set of core variables to assess etiological risk factors. METHODS: We solicited input from the International Pediatric MS Study Group to select three risk factors: environmental tobacco smoke (ETS) exposure, sun exposure, and vitamin D intake. To develop the Tool-Kit, we used a Delphi study involving a working group of epidemiologists, neurologists, and content experts from North America and Europe. RESULTS: The Tool-Kit includes six core variables to measure ETS, six to measure sun exposure, and six to measure vitamin D intake. The Tool-Kit can be accessed online ( www.maelstrom-research.org/mica/network/tool-kit ). CONCLUSION: The goals of the Tool-Kit are to enhance exposure measurement in newly designed pediatric MS studies and comparability of results across studies, and in the longer term to facilitate harmonization of studies, a methodological approach that can be used to circumvent issues of small sample sizes. We believe the Tool-Kit will prove to be a valuable resource to guide pediatric MS researchers in developing study-specific questionnaire.

Surveillance for variant CJD: should more children with neurodegenerative diseases have autopsies?

OBJECTIVES: To report investigations performed in children with progressive neurodegenerative diseases reported to this UK study. DESIGN: Since 1997 paediatric surveillance for variant Creutzfeldt-Jakob disease (vCJD) has been performed by identifying children aged less than 16 years with progressive intellectual and neurological deterioration (PIND) and searching for vCJD among them. SETTING: The PIND Study obtains case details from paediatricians who notify via the British Paediatric Surveillance Unit. PARTICIPANTS: Between May 1997 and October 2017, a total of 2050 cases meeting PIND criteria had been notified and investigated. RESULTS: Six children had vCJD. 1819 children had other diagnoses, made in 12 cases by antemortem brain biopsy and in 15 by postmortem investigations. 225 children were undiagnosed: only 3 had antemortem brain biopsies and only 14 of the 108 who died were known to have had autopsies; postmortem neuropathological studies were carried out in just 10% (11/108) and only two had prion protein staining of brain tissue. Of the undiagnosed cases 43% were known to come from Asian British families. CONCLUSIONS: Most of the notified children had a diagnosis other than vCJD to explain their neurological deterioration. None of the undiagnosed cases had the clinical phenotype of vCJD but brain tissue was rarely studied to exclude vCJD. Clinical surveillance via the PIND Study remains the only practical means of searching for vCJD in UK children.

Diagnostic algorithm for relapsing acquired demyelinating syndromes in children.

OBJECTIVE: To establish whether children with relapsing acquired demyelinating syndromes (RDS) and myelin oligodendrocyte glycoprotein antibodies (MOG-Ab) show distinctive clinical and radiologic features and to generate a diagnostic algorithm for the main RDS for clinical use. METHODS: A panel reviewed the clinical characteristics, MOG-Ab and aquaporin-4 (AQP4) Ab, intrathecal oligoclonal bands, and Epstein-Barr virus serology results of 110 children with RDS. A neuroradiologist blinded to the diagnosis scored the MRI scans. Clinical, radiologic, and serologic tests results were compared. RESULTS: The findings showed that 56.4% of children were diagnosed with multiple sclerosis (MS), 25.4% with neuromyelitis optica spectrum disorder (NMOSD), 12.7% with multiphasic disseminated encephalomyelitis (MDEM), and 5.5% with relapsing optic neuritis (RON). Blinded analysis defined baseline MRI as typical of MS in 93.5% of children with MS. Acute disseminated encephalomyelitis presentation was seen only in the non-MS group. Of NMOSD cases, 30.7% were AQP4-Ab positive. MOG-Ab were found in 83.3% of AQP4-Ab-negative NMOSD, 100% of MDEM, and 33.3% of RON. Children with MOG-Ab were younger, were less likely to present with area postrema syndrome, and had lower disability, longer time to relapse, and more cerebellar peduncle lesions than children with AQP4-Ab NMOSD. A diagnostic algorithm applicable to any episode of CNS demyelination leads to 4 main phenotypes: MS, AQP4-Ab NMOSD, MOG-Ab-associated disease, and antibody-negative RDS. CONCLUSIONS: Children with MS and AQP4-Ab NMOSD showed features typical of adult cases. Because MOG-Ab-positive children showed notable and distinctive clinical and MRI features, they were grouped into a unified phenotype (MOG-Ab-associated disease), included in a new diagnostic algorithm.

N-methyl-d-aspartate (NMDA) receptor antibodies encephalitis mimicking an autistic regression.

Expressive dysphasia and mutism are common clinical features in children and adults with N-methyl-d-aspartate receptor antibodies (NMDAR-Ab) encephalitis, and are likely to result from NMDAR hypofunction. A prodromal loss of social and communication skills can typify that of an autistic regression, particularly when presenting under the age of 3 years. Here we describe two toddlers who presented with developmental regression, particularly of their social communication skills, mimicking an autistic regression, who were found to have NMDAR-Ab in the serum and cerebrospinal fluid. Although both patients had some other neurological features, they were subtle, which resulted in delayed diagnosis of NMDAR-Ab encephalitis. Importantly, immunotherapy was beneficial in both patients, with significant improvement of their language skills and behaviour.

Acute idiopathic transverse myelitis in children: early predictors of relapse and disability.

OBJECTIVE: To identify early prognostic factors of relapse and disability in children presenting with an acute idiopathic transverse myelitis (TM). METHODS: Ninety-five children with acute idiopathic TM from 2 national European cohorts (France and United Kingdom) of CNS demyelinating diseases in children were identified and studied for early factors that predict relapse and disability using logistic regression models. RESULTS: Sixteen (17%) relapsed, with a diagnosis of multiple sclerosis in 13 (14%) and neuromyelitis optica in 3 (3%). Logistic regression revealed 2 main criteria as risk factors for relapse: female sex (odds ratio [OR] 3.21, 95% confidence interval [CI] 0.88-11.78) and presence of associated brain lesions (OR 14.0, 95% CI 2.8-69.3). Twenty-eight (30%) children had a poor outcome defined by a Kurtzke Expanded Disability Status Scale score ≥4 or an American Spinal Injury Association impairment (ASIA) scale

Mutations in CECR1 associated with a neutrophil signature in peripheral blood.

BACKGROUND: A reduction of ADA2 activity due to autosomal recessive loss of function mutations in CECR1 results in a newly described vasculopathic phenotype reminiscent of polyarteritis nodosa, with manifestations ranging from fatal systemic vasculitis with multiple strokes in children to limited cutaneous disease in middle-aged individuals. Evidence indicates that ADA2 is essential for the endothelial integrity of small vessels. However, CECR1 is not expressed, nor is the ADA2 protein detectable, in cultured human endothelial cells, thus implicating additional cell types or circulating factors in disease pathogenesis. METHODS: Considering the phenotypic overlap of ADA2 deficiency with the type I interferonopathy Aicardi-Goutières syndrome due to mutations in SAMHD1, we looked for the presence of an interferon signature in the peripheral blood of two newly ascertained ADA2-deficient patients. RESULTS: We identified biallelic CECR1 mutations in two patients consistent with ADA2 deficiency. Both patients demonstrated an upregulation of interferon stimulated gene transcripts in peripheral blood. More strikingly however, genome-wide analysis revealed a marked overexpression of neutrophil-derived genes, suggesting that the vasculitis seen in ADA2 deficiency may be an indirect effect resulting from chronic and marked activity of neutrophils. CONCLUSIONS: We hypothesise that ADA2 may act as a regulator of neutrophil activation, and that a reduction of ADA2 activity results in significant endothelial damage via a neutrophil-driven process.

Paediatric autoimmune encephalopathies: clinical features, laboratory investigations and outcomes in patients with or without antibodies to known central nervous system autoantigens.

OBJECTIVE: To report the clinical and investigative features of children with a clinical diagnosis of probable autoimmune encephalopathy, both with and without antibodies to central nervous system antigens. METHOD: Patients with encephalopathy plus one or more of neuropsychiatric symptoms, seizures, movement disorder or cognitive dysfunction, were identified from 111 paediatric serum samples referred from five tertiary paediatric neurology centres to Oxford for antibody testing in 2007-2010. A blinded clinical review panel identified 48 patients with a diagnosis of probable autoimmune encephalitis whose features are described. All samples were tested/retested for antibodies to N-methyl-D-aspartate receptor (NMDAR), VGKC-complex, LGI1, CASPR2 and contactin-2, GlyR, D1R, D2R, AMPAR, GABA(B)R and glutamic acid decarboxylase. RESULTS: Seizures (83%), behavioural change (63%), confusion (50%), movement disorder (38%) and hallucinations (25%) were common. 52% required intensive care support for seizure control or profound encephalopathy. An acute infective organism (15%) or abnormal cerebrospinal fluid (32%), EEG (70%) or MRI (37%) abnormalities were found. One 14-year-old girl had an ovarian teratoma. Serum antibodies were detected in 21/48 (44%) patients: NMDAR 13/48 (27%), VGKC-complex 7/48(15%) and GlyR 1/48(2%). Antibody negative patients shared similar clinical features to those who had specific antibodies detected. 18/34 patients (52%) who received immunotherapy made a complete recovery compared to 4/14 (28%) who were not treated; reductions in modified Rankin Scale for children scores were more common following immunotherapies. Antibody status did not appear to influence the treatment effect. CONCLUSIONS: Our study outlines the common clinical and paraclinical features of children and adolescents with probable autoimmune encephalopathies. These patients, irrespective of positivity for the known antibody targets, appeared to benefit from immunotherapies and further antibody targets may be defined in the future.

Recessive germline SDHA and SDHB mutations causing leukodystrophy and isolated mitochondrial complex II deficiency.

BACKGROUND: Isolated complex II deficiency is a rare form of mitochondrial disease, accounting for approximately 2% of all respiratory chain deficiency diagnoses. The succinate dehydrogenase (SDH) genes (SDHA, SDHB, SDHC and SDHD) are autosomally-encoded and transcribe the conjugated heterotetramers of complex II via the action of two known assembly factors (SDHAF1 and SDHAF2). Only a handful of reports describe inherited SDH gene defects as a cause of paediatric mitochondrial disease, involving either SDHA (Leigh syndrome, cardiomyopathy) or SDHAF1 (infantile leukoencephalopathy). However, all four SDH genes, together with SDHAF2, have known tumour suppressor functions, with numerous germline and somatic mutations reported in association with hereditary cancer syndromes, including paraganglioma and pheochromocytoma. METHODS AND RESULTS: Here, we report the clinical and molecular investigations of two patients with histochemical and biochemical evidence of a severe, isolated complex II deficiency due to novel SDH gene mutations; the first patient presented with cardiomyopathy and leukodystrophy due to compound heterozygous p.Thr508Ile and p.Ser509Leu SDHA mutations, while the second patient presented with hypotonia and leukodystrophy with elevated brain succinate demonstrated by MR spectroscopy due to a novel, homozygous p.Asp48Val SDHB mutation. Western blotting and BN-PAGE studies confirmed decreased steady-state levels of the relevant SDH subunits and impairment of complex II assembly. Evidence from yeast complementation studies provided additional support for pathogenicity of the SDHB mutation. CONCLUSIONS: Our report represents the first example of SDHB mutation as a cause of inherited mitochondrial respiratory chain disease and extends the SDHA mutation spectrum in patients with isolated complex II deficiency.

Mutations in ADAR1 cause Aicardi-Goutières syndrome associated with a type I interferon signature.

Adenosine deaminases acting on RNA (ADARs) catalyze the hydrolytic deamination of adenosine to inosine in double-stranded RNA (dsRNA) and thereby potentially alter the information content and structure of cellular RNAs. Notably, although the overwhelming majority of such editing events occur in transcripts derived from Alu repeat elements, the biological function of non-coding RNA editing remains uncertain. Here, we show that mutations in ADAR1 (also known as ADAR) cause the autoimmune disorder Aicardi-Goutières syndrome (AGS). As in Adar1-null mice, the human disease state is associated with upregulation of interferon-stimulated genes, indicating a possible role for ADAR1 as a suppressor of type I interferon signaling. Considering recent insights derived from the study of other AGS-related proteins, we speculate that ADAR1 may limit the cytoplasmic accumulation of the dsRNA generated from genomic repetitive elements.

Degos disease: a new simulator of non-accidental injury.

Recent high-profile cases have made paediatricians very aware of the serious implications of either missing or wrongly diagnosing non-accidental injury. Subdural fluid collections in non-mobile infants usually represent haemorrhage caused by non-accidental injury. We report a 6-month-old male who presented to the Accident and Emergency Department of Birmingham Heartlands Hospital with bilateral subdural fluid collections and skin ulcers resembling cigarette burns. Non-accidental injury was considered to be the most likely diagnosis. However, while under observation in hospital, the child's neurological condition deteriorated with progressive cerebral infarctions, and serial photographs of the skin lesions showed failure to heal. The revised diagnosis, confirmed histologically, was Degos disease, an extremely rare and often fatal occlusive vasculopathy. The child was treated palliatively and died 8 weeks after presentation. This report informs doctors of a new simulator of non-accidental injury to be considered in infants with otherwise unexplained subdural fluid collections.

Diagnostic yield of brain biopsies in children presenting to neurology.

The role of brain biopsy is well established in patients with neoplastic lesions, with a diagnostic yield approaching 95%. The diagnostic yield of brain biopsy in adults with neurological decline varies from 20% to 43%. Only a few studies have examined the diagnostic yield of brain biopsy in children with idiopathic neurological decline. A retrospective analysis was conducted on all open and closed pediatric brain biopsies performed between January 1988 and May 2003. Biopsies were performed for diagnostic purposes in patients showing a progressively deteriorating neurologic course in whom less-invasive modalities such as neuroimaging, electroencephalography (EEG), and molecular genetic studies were either negative or inconclusive. Immunocompromised patients were included. Patients were excluded if the preoperative diagnosis was a neoplasm or if the patient was undergoing a resection as part of a work-up for intractable epilepsy. Each patient underwent numerous investigations before brain biopsy. The utility of each biopsy was analyzed. Sixty-six children had brain biopsies performed for diagnostic purposes during the study period. Patient ages ranged from 2 months to 16 years and 9 months at the time of biopsy. The diagnostic yield was 48.5% overall, with a yield of 68.8% between 1996 and 2003. Of the total, 26 (39.4%) biopsies were both diagnostic and useful. Patients most frequently presented with seizures (56.1%) and encephalopathy (33%). The most frequently diagnosed disease was vasculitis (18.2%). A total of 71.9% of patients with diagnostic biopsies improved with appropriate treatment. Brain biopsy in children had a diagnostic yield of 48.5% in our series. A specific diagnosis may help in management and outcome, especially with a diagnosis of vasculitis.