OBJECTIVE: Our objective was to investigate prenatal imaging findings, clinical course and outcomes associated with isolated congenital aqueductal stenosis (ICAS). METHOD: A retrospective study was conducted in the period of 2010-2023, including patients with ICAS confirmed postnatally who were imaged prenatally with ≥ 1 year of follow-up. Patients with additional anomalies (structural or genetic) were excluded. Neurodevelopmental outcomes were verified by pediatricians, and imaging underwent standardized measurement by a neuroradiologist. RESULTS: Twenty-one patients were prenatally diagnosed with ICAS, at a median gestational age (GA) of 19.7 weeks. Overall, 13/14 patients exhibited a fronto-occipital horn ratio (FOHR) >
0.5, indicating clinically significant ventriculomegaly in initial MRI at 18-32 weeks GA. There was an increase in the median size of the third ventricular coronal width from 7 mm in prenatal imaging to 12 mm in postnatal imaging (p = 0.01). Twenty patients (95.2%) required shunting or endoscopic third ventriculostomy and bilateral choroid plexus cauterization (ETV/CPC), with 10 undergoing multiple CSF diversion procedures during follow-up. Among the study group, nine patients experienced epilepsy, 6/8 aged <
5 years exhibited global developmental delay, and 6/12 aged ≥ 5 years required special education services. CONCLUSION: Our findings indicate a progressive increase in prenatal ventricular sizes, with most children requiring hydrocephalus treatment and experiencing neurodevelopmental impairment.