OBJECTIVE The aim of this cohort study was to describe and analyze the surgical treatment and outcome of posterior fossa arachnoid cysts (PFACs) in infants. METHODS Patients presenting with a PFAC at infancy or prenatally, between the years 2000 and 2019, and who were surgically treated before the age of 2 years, were included in this study. Patient data were retrospectively collected including baseline characteristics and surgical variables. Factors related to revision surgery were analyzed through uni- and multivariate analysis. RESULTS Thirty-five patients, of whom 54.3% were male, were included. The cyst was diagnosed prenatally in 23 patients (65.7%). Surgery was typically recommended after a mean cyst follow-up of 3.4 ± 3.9 months, with a mean age at surgery of 6.1 ± 5.1 months. In 54.3% of patients (n = 19), surgery was performed before the age of 6 months. The PFAC was treated purely neuroendoscopically in 57.1% of patients (n = 20), while 28.6% of patients underwent open cyst procedures (n = 10), 5.7% (n = 2) were treated with a shunt, and 8.6% (n = 3) underwent a combined procedure. Additional surgery was required in 31.4% of patients (n = 11; mean 2.36 ± 2.11 surgeries per patient). At the last follow-up (61.40 ± 55.33 months), no mortality or permanent morbidity was seen; radiological improvement was apparent in 83.9% of the patients. Those patients treated before the age of 6 months (p = 0.09) and who presented before surgery with a stable cyst size that was maintained throughout preoperative monitoring (p = 0.08) showed a trend toward higher revision rates after surgical treatment. CONCLUSIONS PFACs in infancy may require surgical treatment before the age of 6 months. Navigated endoscopy was a valid surgical option. Overall mortality or permanent morbidity was rare. Additional surgery was required in up to 30% of the patients; younger age and a preoperatively stable cyst might be risk factors for revision surgery.
