Incidence of narcolepsy in Norwegian children and adolescents after vaccination against H1N1 influenza A.

BACKGROUND: From October 2009 to January 2010, approximately 470,000 children and adolescents in Norway ages 4-19 years were vaccinated with Pandemrix® against influenza A (H1N1 subtype). The vaccination coverage in this age cohort was approximately 50%. OBJECTIVES: Our study was performed to evaluate the possible association between Pandemrix® vaccination and narcolepsy in Norway. METHODS: Children and adolescents with sudden onset of excessive daytime sleepiness (EDS) and cataplexy occurring after the 2009-2010 vaccination period were registered by the National Institute of Public Health in cooperation with the Norwegian Resource Center for AD/HD, Tourette Syndrome, and Narcolepsy. RESULTS: Fifty-eight vaccinated children and adolescents (35 girls, 23 boys) ages 4-19 years (mean age, 10.5 years) were diagnosed as new cases of confirmed narcolepsy and were included in our study during 2010 and 2011. Forty-two children had onset of symptoms within 6 months after vaccination, with 12 of them having symptoms within the first 6 weeks. All had EDS, 46 had documented cataplexy, 47 had mean sleep latency less than 8 min, and 43 had two or more sleep-onset rapid eye movement sleep (SOREM) periods in multiple sleep latency tests (MSLT). Cerebrospinal fluid (CSF) hypocretin levels were measured in 41 patients, with low levels in all. Thirty seven patients that were analyzed had tissue type HLADQB1*0602. During the same period, 10 unvaccinated cases were reported (mean age, 12.5 years). CONCLUSION: The data collected during 3 years following vaccination showed a significantly increased risk for narcolepsy with cataplexy (P<.0001) and reduced CSF hypocretin levels in vaccinated children ages 4-19 years the first year after Pandemrix® vaccination, with a minimum incidence of 10 of 100,000 individuals per year. The second year after vaccination, the incidence was 1.1 of 100,000 individuals per year, which was not significantly different from the incidence of 0.5-1 of 100,000 per year in unvaccinated children during the same period.

Does a sedative dose of chloral hydrate modify the EEG of children with epilepsy?

Chloral hydrate (CH) is used to sedate children unable to cooperate during investigations such as EEG requiring the patient to be still. It is not known if CH or its metabolites modify the EEG and our aim was to answer this question. Recordings of the EEG before, during and after rectal administration of CH (50-77 mg/kg) in 13 children aged 1.5-13.5 years with severe epilepsy and additional neurological impairments were made. All children had frequent spike-wave activity before CH. In 9 children CH had no effect on the EEG. In 3 children there was a significant reduction in epileptic activity after 20-50 min and in one a significant increase. Cardiovascular parameters were stable throughout. At sedative doses, CH can generally be used before an EEG recording without loss of information but in 4 out of 13 children there were changes which could alter interpretation.

Medium chain acyl-CoA dehydrogenase deficiency and fatal valproate toxicity.

A boy with delayed psychomotor development, attention deficit disorder, and therapy-resistant epilepsy was treated with valproate. The patient died of liver failure after 4 months of valproate treatment. Postmortem investigation of cultured fibroblasts suggested medium chain acyl-CoA dehydrogenase deficiency, an unexpected finding since the boy had not presented typical manifestations of this disease. Because medium chain acyl-CoA dehydrogenase is an important enzyme in the beta-oxidation of fatty acids, our patient probably had a genetically reduced tolerance to valproate. This drug should be omitted in the treatment of seizures in patients with possible medium chain acyl-CoA dehydrogenase deficiency.