**3.5 Complication avoidance**

Cerebrospinal fluid leak is one of the most common complications of surgery to the middle fossa and petrous apex. CSF leak typically manifests two ways, as rhinorrhea or leakage from the surgical wound. Otorrhea is not commonly encountered through the middle fossa or trans-pterygoid approaches. We routinely obliterate communication between pneumatized air cells in the temporal bone with fat, to prevent leakage of CSF through the skin incision or the eustachian tube. Before doing so, the exposed air cells or dehiscence in the middle fossa floor are covered with wax or fascia. Incisional leaks are managed with wound oversewing and lumbar drainage. Rhinorrhea is managed with lumbar drainage. If either method fails to control the leak, wound exploration is performed.

Stroke can be a result of arterial or venous injury. We perform pre-operative CT or MR angiography on all patients with tumors adjacent to the arteries or veins of the skull base. If there is evidence of invasion or stenosis of the blood vessels of the skull base, formal cerebral angiography is performed. This helps evaluate the degree of collateral inflow and outflow from the resection site. A balloon occlusion test may help establish the feasibility of vessel sacrifice at the time of surgery. Whenever possible, sacrifice is avoided for benign lesions should be avoided.
