Complications of Neurotologic Surgery

The treatment of vestibular schwannomas (VSs) and other skull base lesions has evolved quite remarkably since the first surgery for VS was described by Ballance in 1895. Whereas the reduction in mortality was the focus of surgical advancement in the first half of the 20th century, the reduction in morbidity associated with cranial neuropathies has been the goal since that time. This has largely been accomplished with the introduction of the microscope to neurotology, intraoperative cranial nerve monitoring, and advances in neuroanesthesia.

Despite the current low incidence of complications of neurotologic surgery, an understanding of the pathogenesis, predisposing contributing factors, and management of these complications is critical.

Preoperative Workup

Prevention of complications begins with a careful preoperative evaluation of the patient. A careful neurotologic examination will reveal preexisting neurologic deficits such as facial weakness or numbness, signs of cerebellar compression, and hydrocephalus. Preoperative imaging aids in confirming not only the tumor type and size, but also the relationship of the tumor to surrounding neurovascular structures. Tumor size and proximity to critical structures is directly related to anticipated complications and cranial nerve deficits.

An appropriate medical evaluation of the patient is also mandatory. Medical comorbidities should be identified and controlled as well as possible prior to subjecting the patient to a neurotologic procedure. At our institution, we include in the health care team an internist experienced with the care of the neurotologic patient. This expertise has greatly augmented the perioperative care of our patients.

Complications

Cerebrospinal Fluid Leak

Cerebrospinal fluid (CSF) leak is one of the most common complication of acoustic neuroma surgery, with a reported incidence of 2 to 30%. This problem persists despite advancement in acoustic tumor surgical techniques, and contributes to prolonged hospital stays and postoperative meningitis. Our current rate of CSF leak at the House Clinic is 4.3%, which compares favorably with the 9.4% incidence published in the past. Only one third of patients who experience a postoperative CSF leak require an additional procedure for control of the leak. The remaining patients are managed conservatively. We attribute this low incidence to our current intraoperative closure practice, as outlined below.

In any surgical approach to acoustic neuroma, the pneumatized air cell system of the temporal bone is entered, and a potential communication between the temporal bone and the subarachnoid space can persist, resulting in leakage of CSF through the skin incision or the eustachian tube (presenting as rhinorrhea). Despite differences in technique, no significant difference in the rate of CSF leaks among the translabyrinthine, retrosigmoid, and middle fossa approaches to acoustic tumor surgery has been shown.

Closure of a translabyrinthine craniotomy involves obliteration of the partial dural defect with fat harvested from the lower abdomen. The fat is cut into strips and soaked in bacitracin. The dura is closed along the posterior fossa incision, and fat strips are tightly packed into the dural opening and the internal auditory canal (IAC), extending 2 cm into the cerebellopontine angle. Additional fat is packed in the mastoid defect. The incus is removed and the eustachian tube is filled with Surgicel mixed with bone wax, followed by muscle. The middle ear space is also obliterated with muscle. Alternatively, the incus may be left in place and the antrum packed with muscle. A titanium cranioplasty mesh is inserted over the mastoid cavity to better secure the fat grafts. Any air cells exposed during the procedure are sealed with bone wax. The wound is closed in layers and a pressure dressing is applied.

Following tumor removal in a retrosigmoid approach, we prefer to use bone wax to seal all exposed air cells. The petrosal defect created after opening of the IAC is packed with abdominal fat and secured with dural suture or fibrin glue. The wound is then closed in layers, and a compressive dressing is applied.

In a middle cranial fossa approach, all exposed air cells are waxed and obliterated with abdominal fat, and the IAC is filled with abdominal fat. Air cells or dehiscences in the floor of the middle cranial fossa are waxed or covered with fascia. Following release of retraction of the temporal lobe, any dural defects are repaired with suture or fat graft. The craniotomy bone flap is replaced, the wound closed, and a pressure dressing is applied.