Neuroimaging Abnormalities and Genotype-Phenotype Correlations in Noonan Syndrome: A Multicenter Cohort Study.
CONTEXT Neuroradiological findings in Noonan syndrome (NS) remain insufficiently characterized. OBJECTIVE To characterize neuroimaging abnormalities in children with genetically confirmed NS and evaluate their associations with clinical phenotype. DESIGN, SETTING, AND PARTICIPANTS In this multicenter retrospective study, brain MRI scans and longitudinal clinical and genetic data were reviewed from children with genetically confirmed NS evaluated between 2008 and 2023 at seven pediatric endocrinology centers. MAIN OUTCOME MEASURES Prevalence and spectrum of neuroimaging abnormalities and their associations with genotype and clinical features. RESULTS The cohort included 130 individuals with NS (71 males; mean age at MRI, 9.7 years), most carrying PTPN11 variants (69.2%). Structural brain abnormalities were identified in 84.7% and included midbrain-hindbrain malformations (69.2%), callosal anomalies (52.3%), cortical malformations (50%), white matter abnormalities (48.4%), and cranio-cervical junction anomalies (40%). Brain tumors and Chiari I malformation were present in 12.3% and 10.7%, respectively. Seizures were associated with cortical tumors (p = 0.02) and callosal anomalies (p = 0.03), whereas developmental delay was associated with callosal anomalies (p = 0.02) and microcephaly (p < 0.01). Follow-up MRI, available in 41 patients over a mean duration of 6.3 years, showed interval changes in 48.7%, including tumor progression, progressive tonsillar descent, odontoid retroversion, and newly detected lesions. CONCLUSIONS In this selected cohort of children with NS who underwent brain MRI as part of routine clinical care, structural brain abnormalities were frequent and were associated with neurological manifestations. These findings support a role for RAS/MAPK pathway dysregulation in brain development and highlight the clinical value of MRI in selected patients with NS.