This aim is fulfilled even in 51 % and depends on multiple factors. It is achievable through a suboccipital retrosigmoid approach, when the preoperative hearing was determined as usable. Hearing preservation is one of the goals during the surgery of vestibular schwannoma (VS). However, CT with a bone window is a necessary tool for the purposes of this procedure. The size of the drilling tip may be used as an intraoperative measuring scale during this procedure. Preoperative radiological planning using the safe drilling coefficients is of value for the hearing preservation surgery in vestibular schwannoma. In all cases, no endolymphatic duct injury was observed.

Mean results of safe drilling coefficients were: lateral drilling distance: 10 ± 2 mm, total length of internal acoustic meatus: 9 ± 2 mm, drilled length of internal acoustic meatus: 7 ± 2 mm.

Revision of the internal acoustic meatus was performed with the use of a microscope. The dura was excised and endolymphatic duct was injected with a latex. After this, a surgical exposure was performed, using size of a drill tip as measuring scale. Safe drilling line was evaluated and after that drilling distances were analysed: the lateral drilling distance, total length of internal acoustic meatus, drilled length of internal acoustic meatus. CT scans with the bone window were obtained in the standard position.

The study was performed on 14 human temporal bones. The goal of the study was to evaluate the empirical utility of presurgical planning using CT with the bone window for the hearing preservation surgery. During vestibular schwannoma surgery there is a risk of endolymphatic duct and sac injury, which may cause a loss or a deterioration of hearing.

Efilm lite acoustic neuroma