Faculty Bibliography

The authors report a novel technique for the treatment of cholesterol granulomas. An extradural middle fossa approach was used to access the granuloma, with drainage through silastic tubes into the sphenoid sinus via the anteromedial triangle between V1 and V2. Cholesterol granulomas occur when the normal aeration and drainage of temporal bone air cells is occluded, resulting in vacuum formation and transudation of blood into the air cells. This process results in anaerobic breakdown of the blood with resulting cholesterol crystal formation and an inflammatory reaction. Traditional treatment of this lesion involves extensive drilling of the temporal bone to drain the granuloma cyst and establish a drainage tract into the middle ear. Such drainage procedures can be time consuming and difficult, and potentially involve structural damage to the inner ear and facial nerve. An extradural middle fossa approach provides easy access to the granuloma and anterior petrous bone entry into the granuloma for resection. Granuloma drainage is then achieved using shunt tubing in the sphenoid sinus via a small hole in the anteromedial triangle between V1 and V2. Five patients with symptomatic cholesterol granuloma were treated without complication using this novel extradural middle fossa approach. One patient required reoperation 1-year postoperatively for cyst regrowth and occlusion of the drainage tube. At the 5-year follow-up examination, no patient reported recurrent symptoms. Extradural middle fossa craniotomy and silastic tube drainage into the sphenoid sinus is a viable alternative method for treatment of cholesterol granuloma.

Neurotologic and skull base surgery involves working around important neurovascular and neurotologic structures and can incur unwarranted complications. Knowledge of surgical anatomy, good preoperative planning, intraoperative monitoring, and excellent microsurgical technique contribute to minimizing and avoiding complications. In the event of a complication, however, the neurotologic surgeon should be prepared to manage it. In this article, the authors focus on the management of complications encountered in neurotologic skull base surgery, including hemorrhage, stroke, cerebrospinal fluid leak, extraocular motility deficits, facial paralysis, hearing loss, dizziness, lower cranial nerve palsies, and postoperative headache.

OBJECTIVE: We describe our surgical posterior transpetrosal technique, particularly the transcrusal variant for lesions involving the upper and middle clivus, petroclival regions, and lesions that involve both the posterior and middle fossae. METHODS: An outline of the posterior transpetrosal technique involved, particularly the transcrusal variant, is described. Important superficial landmarks are identified, and a radical mastoidectomy is performed. The antrum is identified and entered, and, upon completion of the mastoidectomy and when Trautman's triangle is defined, the temporal and suboccipital craniotomies are completed. After bone flap elevation, dura opening, and incision along the middle fossa dura, the superior petrosal sinus is ligated and cut. Tentorium cut completion is at the incisura posterior to the trochlear nerve. Watertight dural closure and standard flap replacement and skin closure complete the technique. RESULTS: Clival exposure and the degree of temporal bone resection increase. Operative freedom also increases with increased temporal bone resection, especially when going from the retrolabyrinthine to transcrusal variants. Little is gained in terms of operative freedom and exposure of the clivus with resection of additional temporal bone beyond that of the transcrusal variant, and resection carries the cost of increasing morbidity, especially with respect to VIIth and VIIIth nerve function. CONCLUSION: The posterior transpetrosal approach and the transcrusal variant provide a lateral operative corridor to lesions of the upper and middle clivus. The transcrusal variant provides increased exposure and operative freedom similar to that provided by the transcochlear approach while minimizing cranial nerve morbidity.

OBJECT: The authors conducted a cadaveric anatomical study to quantify and compare the area of surgical exposure and the freedom available for instrument manipulation provided by the following four surgical approaches to the extracranial periclival region: simple transoral (STO), transoral with a palate split (TOPS), Le Fort I osteotomy (LFO), and median labioglossomandibulotomy (MLM). METHODS: Twelve unembalmed cadaveric heads with normal mouth opening capacity were serially dissected. For each approach, quantitation of extracranial periclival exposure and freedom for instrument manipulation (known here as surgical freedom) was accomplished by stereotactic localization. To quantify the extent of extracranial clival exposure obtained, anatomical measurements of the extracranial clivus were performed on 17 dry skull bases. The values (means +/- standard deviations in mm2) for periclival exposure and surgical freedom, respectively, for the surgical approaches studied were as follows: STO = 492 +/- 229 and 3164 +/- 1900; TOPS = 743 +/- 319 and 3478 +/- 2363; LFO = 689 +/- 248 and 2760 +/- 1922; and MLM 1312 +/- 384 and 8074 +/- 6451. The extent of linear midline clival exposure and the percentage of linear midline clival exposure relative to the total linear midline exposure were as follows, respectively: STO = 0.6 +/- 4.9 mm and 7.8 +/- 11%; TOPS = 8.9 +/- 5.5 mm and 24.2 +/- 16.7%; LFO = 32.9 +/- 10.2 mm and 85.0 +/- 18.7%; and MLM = 2.1 +/- 4.4 mm and 6.7 +/- 11.1%. CONCLUSIONS: The choice of approach and the resulting degree of complexity and associated morbidity depends on the location of the pathological entity. The authors found that the MLM approach, like the STO approach, provided good exposure of the craniocervical junction but limited exposure of the clivus. The TOPS approach, an approach attended by a lesser risk of morbidity, provided adequate exposure of the extracranial inferior clivus. Maximal exposure of the extracranial clivus proper was provided by the LFO approach.

OBJECTIVES: To evaluate the effect of the 1.5 Tesla magnetic resonance imager (MRI) on the Cochlear Nucleus 24 Device without removing the internal magnet. To determine whether device fixation using a compression dressing could prevent internal magnet displacement in the MRI scanner and potentially obviate the need for surgical removal of the internal magnet. STUDY DESIGN: Prospective cadaveric study. METHODS: Four cadaver heads were implanted bilaterally with the Nucleus device with the internal magnet in place and placed into the 1.5 Tesla MRI scanner. The devices were then explanted after interaction with the MRI and evaluated for displacement of the internal magnet. Conditions tested include device fixation with a commercially available compression dressing and no fixation (worst-case scenario). Magnet strength was measured before and after each of the test conditions. RESULTS: Moderate to severe displacement of the magnet from the internal device occurred in 14 of 16 (87%) implants when no compression dressing was placed. Displacement occurred in 0 of 16 (0%) implants when the compression dressing was applied. No decrease in the strength of the implant magnet was found with the initial or subsequent MRI/implant interactions. CONCLUSIONS: Use of the 1.5 Tesla MRI on subjects with Cochlear Nucleus 24 implants did not result in any significant demagnetization of the internal magnet and did not cause displacement of the magnet when an external compression dressing was applied. Surgical removal of the internal magnet before scanning with the 1.5 Tesla MRI may not be necessary if a compression dressing is applied.

An understanding of normal CSF physiology is a prerequisite to treating problems such as CSF fistulae and pseudomeningoceles. CSF diversion techniques fall into two categories, external and internal. External lumbar drainage is useful when temporary CSF diversion is necessary (eg, in cases necessitating manipulation and retraction of the brain to gain access to deep lesions) and in treating otorrhea or rhinorrhea following traumatic or iatrogenic insults to the cranial base. Drawbacks include insertion discomfort and limited duration of therapy.LP and VP shunts came into widespread use in the 1970s, and both systems share risks of bowel perforation, obstruction, over drainage and wound-related complications. In addition, VP shunts add the risks of intracerebral hematoma and ventriculitis. New valve technology has made it possible to alter the volume drained, thus alleviating problems of over-and under drainage.

The authors report on a surgical technique involving a one-piece osteoplastic bone flap, which incorporates the frontal, temporal, and lateral portions of the orbital rim as a technically simpler alternative to the standard orbitozygomatic (OZ) craniotomy. The orbital rim component extends just laterally from the supraorbital foramen/notch to the frontozygomatic suture. This craniotomy obviates the need for removing the zygoma and has evolved from the authors' experience in more than 200 patients with a variety of pathological lesions, both vascular and tumorous. The osteoplastic aspect of this technique was initially evaluated in 14 cadaveric sites in seven heads dissected prior to implementing this procedure clinically. The osteoplastic bone flap minimally obstructs the surgical view and provides all the advantages of a standard OZ craniotomy. Temporalis muscle atrophy leading to temporal hollowing is avoided, a bone union to the calvaria is improved, and the possibility of bone infection is decreased. The osteoplastic component of the technique adds to the improved long-term cosmesis and warrants active consideration in the art of neurosurgery.

The anterior clinoid process (ACP), located on the skull base, is a relatively small structure, although its removal provides enormous gain in facilitating the management of lesions--either tumors or aneurysms--in the paraclinoid region and upper basilar artery. The extensive surgical field gained contributes to safer exposure of the neurovascular elements in the vicinity while avoiding excessive and hazardous retraction of the brain. In this report the authors present a technically simpler avenue for performing an extradural anterior clinoidectomy after reviewing the anatomy of the ACP and its anatomical variations. Additionally, the original Dolenc procedure and its subseqtient derivatives are compared and contrasted to the authors' simpler and less laborious technique. Different clinical situations in which to use the procedure are described based on the authors' experience from 60 cases (40 aneurysm cases and 20 tumor cases) during a 4-year period.

The authors present a modification to a previously reported supraorbital craniotomy procedure that is smaller, simpler, safe, and cosmetically pleasing. Minimal brain retraction is used without compromising the surgical exposure of the orbital roof, floor of the anterior fossa, and the parasellar region to treat tumoral lesions that are located medial to the ipsilateral optic nerve as well as aneurysms of the anterior communicating artery.

HYPOTHESIS: Fixation of cochlear implants using prosthetic mesh is an improvement of the traditional fixation methods. STUDY DESIGN: A retrospective chart review was performed examining all adult and pediatric patients between 1998 and 2003 who underwent cochlear implantation using polypropylene mesh and titanium screws to fix the cochlear implant internal receiver. Patient age at implantation, postoperative infections, device failures, device migrations or extrusions, cerebrospinal fluid (CSF) leaks, flap complications, epidural hematoma data, and follow-up data were evaluated. RESULTS: Two hundred and eighty-five patients were identified who received cochlear implantation using the polypropylene mesh securing technique. There were five postoperative infections, two device failures, zero flap complications, zero device migrations or extrusions, zero cerebral spinal fluid leaks, and zero epidural hematomas. The two delayed device failures in this series were not related to fixation technique. CONCLUSIONS: We conclude that this technique is widely applicable, technically superior, and not associated with increased complications.