Clinical and Neuroimaging Features of Basal Ganglia Encephalitis in Children

Postinfectious neurological syndromes in children encompass a spectrum of immune-mediated disorders. To delineate the clinical features, neuroimaging characteristics, and long-term outcomes of a distinct pediatric postinfectious syndrome involving acute, symmetric basal ganglia lesions, termed "basal ganglia encephalitis."

We performed a retrospective study on a cohort of pediatric patients admitted to Beijing Children's Hospital. Eligibility criteria required normal baseline development, acute neurological onset within 6 weeks of infection, and symmetric basal ganglia lesions on cranial magnetic resonance imaging (MRI). Metabolic, demyelinating, toxic, or other etiologies were excluded. Clinical, laboratory, and longitudinal follow-up data were systematically reviewed.

Twenty-one patients (14 males) with a median onset age of 7.5 years were identified. The initial symptoms comprised altered consciousness or behavioral changes (10/21, 47.6%), followed by movement disorders (8/21, 38%) and seizures (6/21, 28.5%). Evidence of Mycoplasma pneumoniae infection was confirmed in 14 patients (66.7%). Cerebrospinal fluid analysis revealed mild pleocytosis in 66.7% and positive oligoclonal bands in 42.1%. Acute brain MRI consistently demonstrated symmetric basal ganglia T2/Fluid-Attenuated Inversion Recovery hyperintensities with characteristic apparent diffusion coefficient hyperintensity, indicative of vasogenic edema. All children received immunotherapy, and 15 patients also received antimycoplasma treatment. Eighteen children (85.7%) had achieved complete neurological recovery at a median follow-up of 3.5 years; only three patients exhibited minor residual neurological deficits. Follow-up MRI (n = 17) showed significant lesion resolution.

Basal ganglia encephalitis is a distinct immune-mediated pediatric syndrome frequently associated with M. pneumoniae, radiologically characterized by symmetric basal ganglia lesions. The majority of patients achieve favorable outcomes with anti-infective and immunotherapy.