magnum is not opened. The dura is then opened in a cruciate fashion. A self-retaining retractor is introduced to retract the cerebellum posteriorly. Early drainage of CSF facilitates the exposure, minimizing neuraxis retraction. This is performed by identifying the lower cranial nerves and opening the inferior cerebellopon-tine cistern. These cranial nerves are then protected with a cottonoid pattie. The tumor is then examined and the arachnoidal plane around the superior and posterior poles opened. If the tumor is small, the proximal VII and VIII nerve complex will be seen at this early stage. Care must be taken to ensure that the facial nerve passes anterior to the tumor rather than taking an aberrant course over the posterior or superior aspects of the tumor. With larger tumors internal debulking, preferentially performed with the cavitating ultrasonic surgical aspirator, will be required prior to identification of the neural structures. Careful dissection of the tumor is then performed, with the objective of preserving the facial and auditory nerves. The vestibular nerves are divided.
Rather than follow the tumor mass along the internal auditory canal, the safest approach is to drill off the posterior wall of the internal auditory canal. The petrous dura is incised and retracted, enabling the posterior lip of the porus and the opening for the endolymphatic sac to be identified. Radical removal of the porus acousti-cus can inadvertently fenestrate the inner ear, destroying auditory function. After opening the internal auditory canal, the dura is incised, exposing the intracanalicular tumor and the distal nerves. The facial and cochlear nerves are preserved, whilst the vestibular nerves are divided. The tumor is then dissected towards the porus acousticus. With meticulous attention, this most adherent part of the tumor can be removed. Hemostasis is secured, and the drilled petrous bone is sealed with bone wax and covered with a piece of fascia lata (2 x 2 cm) secured with fibrin glue. The dura is closed in a watertight fashion with fascia lata to bridge any defects. Fat patches are placed over the dura. The pericranium, muscles, fascia, subcutaneous fat and skin are closed in separate layers.
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