Posterior fossa surgery represents on of the most demanding procedure in neurosurgery. Retrosygmoid (RS), key-hole retrosygmoid (KR) and cerebellar hemispheric (CH) are the most common approaches used to access in this area. Despite they are not technically difficult to perform, these approaches can be burdened by postoperative cerebrospinal fluid (CSF) leakage, both at short and long-term follow-up, with an high risk of meningitis. Many techniques were employed to avoid this risk, but it can still be estimated between 2% and 11% according to literature1-4. Spena et al. reported a CSF leakage rate of 6.8% in a previous experience5. As a consequence, newer efforts are necessaries to avoid this potentially lethal complication. By this explorative study, we want to retrospectively analyzed our experience with a newer technique of bone closure, called O'Ring, in patients subdued to posterior fossa surgery by RS, KR and CH approaches, focusing on postoperative CSF leakage (primary objective), wound complications and subcutaneous CSF collections (secondary objectives).

Inclusion Criteria:

• age ≥18 years,
• availability of pre- and postoperative radiological and clinical data,
• a follow-up period of at least 3 months.

Exclusion Criteria:

• Lacking of clinical, radiological and surgical data

Patients operated for a disease located in posterior fossa for which a RS, KR or CH approach has to be performed. Patients between January 2018 and October 2023 will be considered for the study.Lacking of clinical, radiological and surgical data represented exclusion criteria.