F57. EEG findings in pediatric parainfectious acute bilateral striatal necrosis

Introduction Acute bilateral striatal necrosis (ABSN) is a clinicoradiological syndrome with different causes: genetic (mostly, inborn errors of metabolism) and acquired. Among these, parainfectious forms are especially relevant, since they may be confused with genetic forms, but carry a better prognosis and may benefit from immunomodulation. ABSN presents with any combination of movement disorders, altered state of awareness and seizures. The latter warrant an EEG, likely to be performed before imaging can confirm the syndromic diagnosis. Aim To describe the electroclinical findings of pediatric patients with confirmed parainfectious ABSN attending our hospital between 01/2015 and 12/2015. Methods Retrospective review of clinical records of patients fulfilling the following: Inclusion criteria – Age at onset ⩽ 16 years. – Onset of movement disorders, altered level of awareness or seizures within 3 weeks of a febrile episode. – Acute bilateral neostriatal lesions (enlargement and T2/Flair hyperintensity on MR or hypodensity on CT of caudate and/or putamen bilaterally). – Evidence of recent/ongoing infection in biological samples (Direct: Positive culture/PCR; Indirect: Seroconversion/Raising antibody titres). Exclusion criteria – Progressive course after 6 weeks – Evidence of a metabolic disorder (Positive genetic testing for pathogenic mutations or confirmed altered enzyme activity/altered biochemical markers in biological samples). – Alternative cause. Results We found 2 cases: 1. 11 year old boy presenting with focal seizures and parkinsonism, 48 h after a febrile episode. MR showed symmetric striatal inflammation and patchy cortical edema, predominantly frontal. CSF analysis showed mononuclear pleocytosis and increased protein. A tracheal aspirate disclosed M. pneumoniae infection. Metabolic screening was negative. Control of seizures was difficult, requiring combined treatment with LEV, LCM, VPA, Antibiotics, IVIG and glucocorticoids. Serial EEGs showed diffuse background slowing and focal asymmetric fronto-temporal slowing (right worse). He was discharged asymptomatic after 13 days, on LEV and LCM, which were stopped over the following 5 months. MR and EEG were normal 3 months after onset. 2: 2 year old girl presenting with parkinsonism, dystonia and bulbar symptoms 7 days after a febrile episode. MR showed symmetric striatal inflammation. CSF analysis was normal, but HHV6 replication was shown in plasma and CSF. EEG was normal. Metabolic screening showed raised urinary 3-OH-glutaric acid, not confirmed on repeated tests. She was treated with foscarnet, IVIG and glucocorticoids and was discharged after 43 days, with mild symptoms. She was asymptomatic at 8 months follow-up. Control MR showed atrophy and cavitation of posterior putamina. Conclusion EEG allows objective assessment and monitoring of brain function in parainfectious ABSN, when it presents with seizures and/or altered level of awareness. Focal abnormalities may correlate with damage beyond the striatum and into the cortex.