Surgical fenestration might not be the best option for very young patients with middle fossa arachnoid cysts.

PURPOSE Surgical fenestration is widely accepted as a primary treatment for middle fossa arachnoid cysts (MFACs) in pediatric patients. However, postoperative subdural effusion and/or hydrocephalus always affect treatment outcomes. In this study, we presented our experience of treating MFACs with surgical fenestration in pediatric patients and analyzed the cases complicated by postoperative subdural effusion and/or hydrocephalus, to give insight into the clinical characteristics predisposing the complications. METHODS We retrospectively analyzed 21 pediatric cases with MFACs treated by surgical fenestration suffering postoperative subdural effusion and/or hydrocephalus in our department from November 2011 to April 2019. We reviewed the clinical characteristics and treatment outcomes. RESULTS A total of 21 patients, among a total of 53 pediatric patients with MFACs treated by surgical fenestration, developed subdural effusion and/or hydrocephalus postoperatively. The mean age at the time of the initial surgery was 49 months. A total of 75% (6/8) of the patients under 2 years old and 13.3% (6/45) of the older patient group sustaining postoperative subdural effusion and/or hydrocephalus required further surgeries, respectively (Fisher's exact test, p = 0.001). Notably, among the 21 cases with postoperative subdural effusion and/or hydrocephalus, all the 6 patients under 2 years old needed additional surgeries, while of the other 15 older patients, only 40% (6/15) needed further surgical interventions (Fisher's exact test, p = 0.019). CONCLUSION The immature CSF absorption in MFAC patients younger than 2 years old might predispose them to the relatively serious postoperative subdural effusion and/or hydrocephalus. For very young patients with giant MFACs, surgical fenestration might not be the best option.