Lyme neuroborreliosis presenting with urinary retention and spastic paraparesis.

Progressive myelopathy, urinary retention and gait problems are rare presenting features of Lyme neuroborreliosis. A 30-year-old man had 11 months of urinary retention and 3 months of spastic paraparesis. MR scans of the brain and the spinal cord showed leptomeningeal thickening with contrast enhancement. Cerebrospinal fluid showed mononuclear pleocytosis, decreased glucose, increased protein and chemokine ligand 13, with intrathecal Borrelia-specific IgM and IgG antibodies. He received 14 days of intravenous ceftriaxone followed by 14 days of oral doxycycline. Despite improvement at 6 months, he still had severe gait problems. Urinary retention in otherwise healthy people needs investigation, and Lyme neuroborreliosis is a rare cause.

Repeated falls as onset of Creutzfeldt-Jakob disease.

Creutzfeldt-Jakob disease is the most common prion disease in humans. Neuropsychiatric symptoms are common, and objective findings are myoclonus, pyramidal and extrapyramidal including cerebellar dysfunction. This is a case report of a 77-year-old woman with gradual onset of repeated falls due to cerebellar dysfunction. She had severe visuospatial difficulties, and she was unaware of her problems. Her MRI showed increased diffusion restriction in the caudate and lentiform nuclei. Her cerebrospinal fluid real-time quaking-induced conversion test was positive, fulfilling criteria for probable sporadic Creutzfeldt-Jakob disease.

School performance and psychiatric comorbidity in childhood absence epilepsy: A Danish cohort study.

The aim was to determine school performance and psychiatric comorbidity in children with childhood absence epilepsy (CAE). We reviewed the medical records in children with ICD-10 codes for idiopathic generalized epilepsy before 18 years of age, and pediatric neurologists confirmed the International League Against Epilepsy criteria for CAE were met. Control groups were the general pediatric population or children with non-neurological chronic disease. Outcomes were from nationwide and population-based registers on school performance and psychiatric comorbidity. We compared the mean grade point average using linear regression and estimated hazard ratios (HR) using Cox regression for the other outcomes. Analyses were adjusted for the child's sex, and year of birth, and parental highest education, receipt of cash benefits or early disability pension. We included 114 children with CAE with a median age at onset of 5.9 years (interquartile range = 4.5-7.3 years). Compared with both population controls and non-neurological chronically ill children, children with CAE had increased hazard of special needs education (HR = 2.7, 95% confidence interval (CI) = 1.8-4.1, p < 0.0001), lower grade point average at 9th grade by 1.7 grade points (95% CI = -2.5 to -1.0, p < 0.001), increased ADHD medicine use (HR = 4.4, 95% CI = 2.7-7.2, p < 0.001), increased sleep medicine use (HR = 2.7, 95% CI = 1.7-4.3, p < 0.001), and increased psychiatry visits (HR = 2.1, 95% CI = 1.1-4.0, p = 0.03). In conclusion, children with CAE have increased psychiatric comorbidity and a considerable proportion of these children receive special needs education in primary/secondary school, albeit insufficient to normalize their considerably lower grade point average in the 9th grade.

[Neuroleptic malignant syndrome caused by olanzapine, risperidone and haloperidol].

Neuroleptic malignant syndrome is a rare neuropsychiatric complication caused by antipsychotic drugs. Symptoms include decreased consciousness, fever, muscle rigidity and autonomic dysfunction. Creatine kinase concentration is often elevated. This is a case report of a 27-year-old man who developed neuroleptic malignant syndrome after administration of olanzapine, risperidone and haloperidol. He was treated with benzodiazepine, dantrolene, amantadine and electroconvulsive therapy with good recovery.

Oligoclonal bands, age 11-17 years, occipital lesion, and female sex differentiate pediatric multiple sclerosis from acute disseminated encephalomyelitis: A nationwide cohort study.

BACKGROUND: Our aim was to propose criteria to distinguish multiple sclerosis (MS) from acute disseminated encephalomyelitis (ADEM) at onset based on age at onset, sex, cerebrospinl fluid (CSF)-specific oligoclonal bands, and MRI. METHODS: A neuroradiologist undertook retrospective evaluation of the baseline magnetic resonance imaging (MRI) in a nationwide cohort of children with medical record-validated MS (n = 67) and monophasic ADEM (n = 46). Children with ADEM had at least 5 years of follow-up for relapse. We used forward stepwise conditional logistic regression to develop our criteria based on age at onset, sex, CSF-specific oligoclonal bands, and MRI. We undertook sensitivity analyses using children with ADEM including encephalopathy and polyfocal neurological deficits and in those with onset between 11 and 17 years of age. We estimated accuracy statistics from our criteria and all previously proposed MRI criteria to distinguish MS and ADEM. RESULTS: The best performing criteria to differentiate MS from ADEM were scoring at least three points in the following categories: presence of CSF-specific oligoclonal bands (2 points), occipital lesion (1 point), age 11-17 years (1 point), female sex (1 point). These criteria gave highly reliable discrimination with sensitivity of 95% (95% CI=89%-100%), specificity of 100% (95% CI=100%-100%), and area under the curve of 98% (95% CI=95%-100%). The best performing MRI criteria had area under the curve of 84% (95% CI=78%-91%). Previously proposed MRI criteria had the following areas under the curve: Callen (75%), KIDMUS (82%), and McDonald 2017 criteria (68%). CONCLUSION: Combining sex, age at onset, CSF-specific oligoclonal bands, and MRI gives highly reliable differentiation between pediatric MS and monophasic ADEM at onset.

School performance and psychiatric comorbidity in juvenile absence epilepsy and juvenile myoclonic epilepsy: a Danish population-based cohort study.

BACKGROUND: We aimed to determine school performance and psychiatric comorbidity in juvenile absence epilepsy (JAE), juvenile myoclonic epilepsy (JME), and generalized tonic-clonic seizures (GTCS) alone. METHODS: All children (< 18 years) fulfilled International League Against Epilepsy criteria after review of their medical records. Control groups were the pediatric background population or children with non-neurological chronic disease. Outcomes were on school performance and psychiatric comorbidity. We compared mean grade point averages using linear regression and estimated hazard ratios using Cox regression in the remaining analyses. We adjusted for the child's sex, age, and year of birth; and parental highest education, receipt of cash benefits or early retirement. RESULTS: We included 92 JAE, 190 JME, 27 GTCS alone, 15,084 non-neurological chronic disease controls, and population controls. JAE had two times increased hazard for special needs education compared with age-matched population controls (hazard ratio 2.2, 95% CI = 1.1‒4.6, p = 0.03); this was not seen in JME. Compared with population controls, both JAE and JME had lower grade point average in secondary and high school (JME: 9th grade: - 0.5 points, 95% CI = -0.9 to -0.06, p = 0.03; high school: - 0.6 points, 95% CI = -1.3 to -0.1, p = 0.04), and 8% fewer JME and 15% fewer JAE attended high school. Both JME and JAE had higher hazard for redeeming sleep medication compared with non-neurological chronic disease; additionally, JAE had increased hazard for ADHD medicine redemptions. CONCLUSIONS: Both JAE and JME had marginally poorer school performance; performance seemed worse in JAE than in JME. Both JAE and JME had increased use of sleep medication.

Validation of Pediatric Idiopathic Generalized Epilepsy Diagnoses from the Danish National Patient Register During 1994‒2019.

Objective: To identify pediatric idiopathic generalized epilepsy (IGE) during 1994-2019 using ICD-10 codes in the Danish National Patient Register and anti-seizure prescriptions in the Danish Prescription Database. Study Design and Setting: We reviewed the medical records in children with ICD-10 codes for IGE before 18 years of age, and pediatric neurologists confirmed that the International League Against Epilepsy criteria were met. We estimated positive predictive values (PPV) and sensitivity for ICD-10 alone, including combinations of codes, anti-seizure prescription, and age at first code registration using medical record-validated diagnoses as gold standard. Results: We validated the medical record in 969 children with an ICD-10 code of IGE, and 431 children had IGE (115 childhood absence epilepsy, 97 juvenile absence epilepsy, 192 juvenile myoclonic epilepsy, 27 generalized tonic-clonic seizures alone). By combining ICD-10 codes with antiseizure prescription and age at epilepsy code registration, we found a PPV for childhood absence epilepsy at 44% (95% confidence interval [CI]=34%‒54%) and for juvenile absence epilepsy at 44% (95% CI=36%-52%). However, ethosuximide prescription, age at ethosuximide code registration before age 8 years and a combination of ICD-10 codes yielded a PPV of 59% (95% CI=42%‒75%) for childhood absence epilepsy but the sensitivity was only 17% (20/115 children identified). For juvenile myoclonic epilepsy the highest PPV was 68% (95% CI=62%‒74%) using the code G40.3F plus antiseizure prescription and age at epilepsy code registration after age 8 years, with sensitivity of 85% (164/192 children identified). For generalized tonic-clonic seizures alone the highest PPV was 31% (95% CI=15%‒51%) using G40.3G during 2006-2019 plus antiseizure prescription and age at code registration after age 5 years. Conclusion: The Danish National Patient Register and the Danish Prescription Database are not suitable for identifying children with IGE subtypes, except for juvenile myoclonic epilepsy which can be identified with caution.

Magnetic resonance imaging criteria at onset to differentiate pediatric multiple sclerosis from acute disseminated encephalomyelitis: A nationwide cohort study.

BACKGROUND: MRI of the nervous system is the critical in distinguishing pediatric MS from acute disseminated encephalomyelitis (ADEM). Our aim was to propose MRI criteria to distinguish MS from monophasic ADEM based on the first MRI and to validate previously proposed MRI criteria. METHODS: A neuroradiologist undertook retrospective evaluation of the MRI at the first demyelinating event in children (<18 years) with medical record-validated MS and ADEM in Denmark during 2008-15. We used forward stepwise logistic regression to identify MRI categories that differed significantly between MS and ADEM. We estimated accuracy statistics for all MRI criteria to distinguish MS from ADEM. RESULTS: The monophasic ADEM cohort (n=46) was nationwide and population-based during 2008-15; the median age at onset of 5.3 years (range 0.8‒17.2) and children had at least five years of follow-up to ensure a monophasic disease course. Children with MS (n=67) had a median age at onset of 16.3 years (range 3.3‒17.9). Having at least two categories best distinguished MS from monophasic ADEM by an area under the curve of 83% to 89%: (a) corpus callosum long axis perpendicular lesion; (b) only well-defined lesions; (c) absence of basal ganglia or thalamus lesion OR, (a) corpus callosum long axis perpendicular lesion; (b) only well-defined lesions; (c) absence of diffuse large lesions; (d) black holes. The Callen, KIDMUS, and IPMSSG criteria performed well. The McDonald 2017, Barkhof, MAGNIMS, and Verhey criteria had poorer performance. CONCLUSION: This study provides Class II evidence that MRI has good performance in differentiating MS from monophasic ADEM at onset.

Employment, health visits, mental health, and mortality in parents with a chronically ill child: a Danish nationwide population-based cohort study.

Chronic diseases in children can impact their parents; this may be overlooked in a clinical setting. Our aim was to investigate associations of chronic diseases in children with their parents' employment, health care utilization, mental health, and mortality. In a matched cohort study using nationwide and population-based data in Denmark, we included parents to children (< 18 years) with acute disseminated encephalomyelitis, multiple sclerosis, type 1 diabetes, inflammatory bowel disease, and rheumatoid arthritis/juvenile idiopathic arthritis during 2008-2015. The reference group was parents to unaffected children. Outcomes were parental employment (early retirement, cash benefits, income), health care utilization (e.g., general practitioner, or hospital visits), mental health (visits to psychiatry/psychology clinics, antidepressant drug redemptions), and mortality. We included 13,769 parents with a chronically ill child and 138,606 control parents. Annual income was unaffected for two-parent families after the child's disease onset, but two-parent families had increased hazard of early retirement of 25% (95% CI = 1.01-1.54; p = 0.04). Parents with a chronically ill child had (a) increased rate of antidepressant drug redemptions or psychology/psychiatry visits (hazard ratio 1.37; 95% CI = 1.28-1.46 at 1-year follow-up); (b) increased health care utilization, with an increased marginal mean in primary care of 1% (95% CI = 1.00-1.02; p = 0.005), hospital-affiliated visits of 19% (95% CI = 1.14-1.24; p < 0.0001), and hospital admissions of 14% (95% CI = 1.09-1.20; p < 0.0001); and (c) 69% increased mortality hazard (95% CI = 1.30-2.18; p < 0.0001) in parents younger than 50 years with no comorbidities, albeit small in absolute numbers. CONCLUSION: Pediatric chronic diseases were negatively associated with parental employment, mental health, and mortality, and increased health care utilization. WHAT IS KNOWN: • Studies on the impact of pediatric chronic diseases on parental health are qualitative. • Knowledge is unavailable regarding the impact on parental work, health care utilization, and mortality. WHAT IS NEW: • Among 13,769 parents with a chronically ill child and 138,606 control parents, parents with a chronically ill child had 37% increased antidepressant drug redemptions, and these parents <50 years without comorbidities had 69% increased mortality hazard. • Medical doctors should consider the parental health condition and societal challenges related to having child with a chronic disease.

Validation of MRI radiological reports in pediatric MS according to the McDonald 2017 criteria: A Danish nationwide multicenter cohort study.

BACKGROUND: MRI allows demonstration of dissemination in space and time at the first demyelinating event. However, no pediatric MS study has investigated the validity of MS-specific outcomes described in MRI radiological reports that clinicians rely on to make the MS diagnosis and to assess the MS treatment effect. Our aim was to validate MS-specific outcomes in hospital MRI reports in pediatric MS by comparing MS-specific outcomes in MRI reports with secondary MRI review. METHODS: A senior consultant and a resident neurologist extracted data on MS-specific outcomes from MRI reports at baseline and follow-up in children with MS onset during 2008-15 in Denmark. Gold standard was an expert neuroradiologist's secondary MRI review. We estimated percent agreement and Kappa values by comparing data extracted from hospital MRI reports (what we wanted to test) with results from the secondary MRI reviews (our gold standard). RESULTS: Among 55 children with MS, we included 44 baseline and 48 follow-up MRIs. The median age at MS onset was 16.3 years (range 9.2‒17.9). Agreement between the MRI reports and the secondary MRI review ranged 68%-100% for MS-specific outcomes; agreement was higher when MRI outcomes were present. Kappa values ranged from 0.42 ("moderate") to 1.00 ("excellent"). Kappa for fulfillment of the McDonald 2017 criteria was 0.60 on baseline MRI, and 0.53 on follow-up MRI. Kappa for a new lesion on follow-up MRI was 0.41. CONCLUSION: Agreement was moderate to good for most MS-specific outcomes between MS neurologists' data extraction from hospital MRI radiological reports compared with a neuroradiologist's secondary MRI review. The agreement was moderate for both fulfilling the McDonald 2017 criteria and acquiring a new lesion on follow-up MRI. We recommend structured MRI reporting in children suspected of acquired demyelinating syndromes to increase validity of hospital MRI reports and clinical use.

[Guillian Barré syndromeafter mRNA-1273 vaccination against COVID-19].

Vaccination may on rare occasions trigger Guillian Barré syndrome, and the syndrome has previously been associated with vaccines against H1N1 swine flu. We present a case report of a 73-year-old man who received SARS-CoV-2 mRNA-1273-vaccine (Spikevax, Moderna Inc., MA, USA) and subsequently experienced diarrhoea, sensory ataxia, gait disorder, back pain, bilateral facial palsy, and dysarthria. A nerve conduction study was compatible with demyelinating polyneuropathy, and he was diagnosed with Guillian Barré syndrome. We discuss vaccines as triggers of Guillian Barré syndrome and recommendations for revaccination in these individuals.

School performance, psychiatric comorbidity, and healthcare utilization in pediatric multiple sclerosis: A nationwide population-based observational study.

BACKGROUND: Pediatric multiple sclerosis (MS) may hamper educational achievements due to psychiatric comorbidity and cognitive impairment. Our aims were to investigate school performance, psychiatric comorbidity, and healthcare utilization following pediatric MS and to differentiate between disability in MS and that arising from a non-brain-related chronic disease. METHODS: We included all children (<18 years) with MS onset during 2008-2015 in Denmark with a medical record-validated MS diagnosis. The control groups were children from the general population or children with non-brain-related chronic diseases. Outcomes were register-based on 9-12 grade point average, psychiatric comorbidity, and healthcare visits. RESULTS: Cohorts were children with MS (n = 92), control children matched to children with MS (n = 920), children with non-brain-related chronic diseases (n = 9108), and "healthy" children with neither MS nor brain-related chronic disease (n = 811,464). School performance in grades 9-12 was similar, but children with MS compared to those with non-brain-related chronic disease had an almost doubled hazard for psychiatric comorbidity (hazard ratio = 1.87; 95% confidence interval = 1.38-2.53; p < 0.0001) and a higher rate of all hospital visits (p < 0.0001) but a lower rate of hospital admissions (p = 0.001). CONCLUSION: Children with MS have a seemingly standard school performance but increased psychiatric comorbidity and a high rate of healthcare utilization.

Magnetic resonance imaging at baseline and follow-up to differentiate between pediatric monophasic acquired CNS demyelination and MS.

BACKGROUND: It is essential to distinguish acute disseminated encephalomyelitis (ADEM) from MS early. Our aim was to determine MRI features at baseline and follow-up to distinguish pediatric ADEM from MS stratified according to age at onset. METHODS: Using hospital ICD-10 codes for acquired demyelinating syndromes from a nationwide register and subsequent chart review, we identified 52 children (<18 years) with ADEM and 66 children with MS. We undertook a retrospective analysis of MRI scans at onset and at follow-up. The MRI rater was a senior neuroradiologist blinded to clinical characteristics. RESULTS: At baseline, children with ADEM had more diffuse poorly demarcated lesions, particularly in the basal ganglia/thalamus (p = 0.001) and cerebellar peduncles (p < 0.0001). Further, longitudinal extensive transverse myelitis was strongly associated with ADEM (p<0.0001). Children with ADEM had fewer contrast-enhancing lesions (p = 0.0004), occipital lesions (p = 0.01), optic nerve lesions (p = 0.01), periventricular lesions, well-defined lesions only (p<0.0001), and fewer fulfilled dissemination in time according to the McDonald 2017 criteria (p = 0.005). On baseline MRI, dissemination in space and time was fulfilled in 17% of children with ADEM and in 34% of children with MS (p = 0.06), and 60% of children with ADEM fulfilled the criterion for dissemination in space. The mean time from baseline MRI to follow-up MRI was 1.0 year for children with ADEM and 2.1 years for children with MS. On follow-up MRI, 85% of children with ADEM had partial or complete T2 lesion resolution, but in the 58% without complete resolution lesions were predominantly frontal. Only 47% of children with MS had partial or complete T2 lesion resolution, and therefore more MRI features differed between children with ADEM and MS on follow-up. MRI had the greatest distinguishing value after age 11 years because MS is exceptional in the first decade of life. CONCLUSION: Age at onset and the timing of MRI in relation to disease onset are critical in the interpretation of MRI to distinguish between ADEM and MS.

Nusinersen treatment of spinal muscular atrophy - a systematic review.

INTRODUCTION: 5q spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder caused by insufficient survival motor neuron protein. Untreated SMA involves death or permanent respiratory support (type 1), inability to walk (type 2) or ability to walk (type 3). The incidence of SMA is 1 in 7,500 live births, equivalant to eight children being born with SMA in Denmark annually. METHODS: We undertook a systematic review of the efficacy of nusinersen as SMA treatment. We included randomised controlled trials and cohort studies. Our primary endpoints were survival without permanent respiratory support and change in motor function. RESULTS: We identified 658 articles and included 13 of these (two randomised controlled trials and 11 cohort studies). Nusinersen increased survival without permanent respiratory support in SMA type 1 and increased motor function development in types 1-3. Nusinersen treatment before symptom onset in children with presymptomatic SMA produced near-normal motor development. So far, nusinersen has only minor safety concerns mostly related to the lumbar puncture. CONCLUSIONS: Nusinersen increased survival without permanent ventilatory support in children with SMA type 1. Improvements in SMA type 2 and 3 were less evident. Better outcomes were seen in young children with a short disease duration, particularly in children receiving nusinersen before symptom onset. Newborn SMA screening may facilitate presymptomatic treatment with splice modification (nusinersen, risdiplam) or gene implantation therapy (AVXS-101, zolgensma).

[Atypical aura caused by a stroke in a 42-year-old man with migraine with aura].

Ischaemic stroke in persons with migraine may present with aura-like symptoms. In this case report a 42-year-old man with migraine with aura presented with a change in usual aura including visual loss and disorientation. A brain MRI revealed ischaemic stroke in precuneus compatible with these symptoms. We discuss the pathophysiology, the causes and the secondary prophylaxis in persons with migraine with aura and stroke.

[Reversible cerebral vasoconstriction syndrome causing acute-onset headache].

Reversible cerebral vasoconstriction syndrome is caused by narrowing of cerebral arteries. The cardinal symptom is relapsing acute-onset headache also known as thunderclap headache, which may be accompanied by neurologic deficits. This is a case report of a 61-year-old woman with CT angiography-verified reversible cerebral vasoconstriction syndrome. We discuss the diagnostic work-up, i.e. lumbar puncture including test for xanthochromia and important brain imaging, differential diagnoses and treatment of the most important causes of thunderclap headache.

[Carbon monoxide poisoning and development of delayed neuropsychiatric syndrome in a 77-year-old woman].

This case report describes carbon monoxide (CO) poisoning in a woman. CO is a toxic, odourless and colourless gas. Delayed cognitive sequelae have been described in up to 40% of patients with significant CO poisoning. A 77-year-old woman suffered from severe smoke- and CO poisoning and received hyperbaric O2 therapy, but she continued to have memory impairment and unsteady gait at day 26. Brain MRI showed diffuse white matter lesions in both hemispheres with increased signal on diffusion-weighted imaging. Diagnosis, pathogenesis and treatment of CO poisoning are discussed.

[Serotonin syndrome shortly after the administration of low-dose mirtazapine].

Serotonin syndrome is a rare neuropsychiatric complication caused by serotonergic drugs. Symptoms include confusion, psychosis, tremor, palpitations, hyperthermia, and the neurological examination shows signs of central nervous system deficits. This is a case report of a 67-year-old woman, who developed serotonin syndrome in the form of delusions, tremor, cerebellar ataxia and upper neuron signs one day after administration of low-dose mirtazapine therapy. Complete symptom remission occurred one week after the discontinuation of mirtazapine.

School performance and psychiatric morbidity 6 years after pediatric acute disseminated encephalomyelitis: A nationwide population-based cohort study.

BACKGROUND: Acute disseminated encephalomyelitis (ADEM) can cause cognitive impairment in children. However, long-term consequences for school performance and psychiatric morbidity have never been characterized. Our aim was to investigate long-term school performance and psychiatric morbidity after pediatric ADEM (<18 years). METHODS: We identified all children with ADEM 2008-2015 in Denmark using hospital diagnostic codes for acquired demyelinating syndromes. We reviewed all medical records to validate ADEM including blinded MRI review. Reference children were the entire pediatric (<18 years) population or randomly sampled sex and age-matched reference children. Outcomes were from nationwide population-based registers on special needs assistance, grade point average, highest completed education, in-hospital psychiatric hospital diagnoses, out-of-hospital psychiatric consultations or psychopharmacological drug prescriptions. RESULTS: 52 children had ADEM (median onset age: 5.5 years; median age at follow-up end: 13.4 years). Secondary school grade point average was similar among children with ADEM and reference children; however, children with ADEM had increased psychiatric morbidity (hazard ratio = 2.4; 95% confidence interval = 1.2-5.1; p = 0.02), primarily due to increased drug prescriptions for sleep problems and depression. CONCLUSION: Children with prior ADEM have increased sleep problems and possibly also depression; however, school performance is seemingly unaffected. Clinicians should consider problems with sleep and mood at follow-up.

Pediatric autoimmune encephalitis in Denmark during 2011-17: A nationwide multicenter population-based cohort study.

BACKGROUND: The incidence of pediatric autoimmune encephalitis (AIE) is unknown. Our aim was to assess the incidence of pediatric AIE in Denmark 2011-17. METHODS: In a nationwide population-based setting, we retrieved data on all children tested for AIE before age 18 years. We reviewed medical records in a) children with AIE antibodies (n = 18) to assess whether children fulfilled the AIE consensus criteria, b) children tested negative for AIE antibodies who were registered with an AIE diagnostic code to estimate the incidence of "antibody negative but probable AIE", and c) a reference cohort (n = 596) to determine the positive predictive value of International Classification of Diseases (ICD) codes used for anti-NMDAR encephalitis. RESULTS: 375 children were tested for AIE 2011-17 (median age 11.1 years; 54% girls); 18 children (5%) had AIE antibodies (percentage tested positive): CSF GAD65-IgG (3.1%), plasma NMDAR-IgG (2.8%), CSF NMDAR-IgG (1.8%), plasma GAD65-IgG (1.0%), and plasma CASPR2-IgG (0.4%). Five children fulfilled the criteria for probably/definite anti-NMDAR encephalitis (incidence: 0.07/100,000 person-years; 95% CI = 0.03-0.17), and 4 children with anti-GAD65 associated AIE (incidence = 0.055/100,000 person-years, 95% CI = 0.021-0.15). The incidence of "antibody negative but probable AIE" was 0.055/100,000 person-years (95% CI = 0.021-0.15). The positive predictive value of ICD diagnostic codes used for anti-NMDAR encephalitis was 8%. CONCLUSIONS: We diagnosed only children with anti-NMDAR, anti-GAD65, and "antibody negative but probable AIE". Before examining AIE antibodies, clinical presentation, paraclinical studies (CSF, EEG, and MRI), and incidence of pediatric AIEs should be considered. Updating the ICD to include AIE codes is warranted.