Faculty Bibliography

OBJECTIVE: We studied the hearing results and outcomes after transcrusal craniotomy. STUDY DESIGN: We conducted a retrospective review. SETTING: This study was conducted at a tertiary care hospital. PATIENTS: We studied 10 consecutive patients, including two men and eight women, who underwent transcrusal craniotomy for petroclival masses or tumors. INTERVENTION: The intervention consisted of therapeutic removal of petroclival meningioma. MAIN OUTCOME MEASURE: The main outcome measure of this study was hearing preservation as measured by standard audiogram. RESULTS: There were six meningiomas, one eighth nerve schwannoma, one fifth nerve schwannoma, one chordoma, and one midbasilar artery aneurysm. Postoperative hearing was measured according to the AAOHNS criteria. Complications and further therapies were recorded. Postoperative hearing was measured in eight. The cochlear nerve was severed in one patient. One was unavailable for follow up. Eight patients retained hearing at or near preoperative levels, seven with SRT within 10 dB and speech discrimination within 10% of preoperative levels. Four patients presented with trigeminal symptoms, one with third nerve palsy and two with facial weakness. Postoperative deficits included fourth, sixth, seventh, and eighth nerve palsies in three patients. Complications included one wound infection, two cerebrospinal fluid leak, and two cases of meningitis, both of which were sterile. There were secondary procedures in five patients-three radiosurgery, two shunts, one tracheotomy, and one g-tube. CONCLUSIONS: Transcrusal craniotomy is a safe and effective approach to the petroclival region. Excellent hearing results can be expected with this technique.

OBJECT: Conventional wisdom regarding skull base surgery says that more extensive bone removal equals greater exposure. Few researchers have quantitatively examined this assertion, however. In this study the authors used a frameless stereotactic system to measure quantitatively the area of petroclival exposure and surgical freedom for manipulation of instruments with successive steps of temporal bone removal. METHODS: With the aid of high-power magnification and a high-speed drill, 12 cadaveric specimens were dissected in four predetermined, successive bone removal steps: 1) removal of the Kawase triangle; 2) removal of the Glasscock triangle; 3) removal of the cochlea together with skeletonization of the anterior internal auditory canal; and 4) inferior displacement of the zygoma. Step 1 offered 62 +/- 43 mm2 of exposed petroclival area, with 84 +/- 69 mm2 of surgical freedom; Step 2, 61 +/- 22 and 76 +/- 58 mm2; Step 3, 128 +/- 47 and 109 +/- 87 mm2; and Step 4, 135 +/- 38 and 102 +/- 69 mm2, respectively. CONCLUSIONS: The middle fossa approach provided a means surgically to expose the petroclival area. When examined quantitatively by using a frameless stereotactic device, the authors determined that the removal of the cochlea and skeletonization of the anterior internal auditory canal (Step 3) provided the most significant increase in both exposure and surgical freedom. Removal of the zygoma improved neither exposure nor surgical freedom.

The clinical and aspiration cytologic details of a case of temporomandibular joint pigmented villonodular synovitis are presented and correlated with imaging, surgical, histopathologic, and clinical follow-up findings; the origin of such lesions is discussed. The lesion originally presented in a 36-year-old, otherwise healthy, white man as a unilateral mass involving the temporal fossa and temporomandibular joint region. The tumor's extent was defined by magnetic resonance imaging and computed tomographic scan; there was destruction of the temporomandibular joint and erosion of the temporal cranial bones by a lesion whose maximum dimensions were estimated by imaging to be 2.75 x 3.25 cm. The lesion was initially sampled and classified by computed tomography-guided fine-needle aspiration biopsy. Following complete resection, the original diagnosis was confirmed with both hematoxylin-eosin-stained paraffin sections and immunohistochemical staining. The patient remains free of disease 7 years postoperatively.

OBJECTIVE: The outcomes of surgery for acoustic neuromas have improved dramatically since the development of modern surgical techniques, the operating microscope, magnetic resonance imaging (MRI), and cranial nerve monitoring. The goals of acoustic neuroma surgery are now preservation of facial nerve function and, when feasible, hearing preservation. Many large series do not report standardized hearing and facial function grading, and they include patients who did not benefit from the most modern techniques. The purpose of this study was to present the results of acoustic neuroma surgery using the most modern techniques and equipment, using standardized grading systems. STUDY DESIGN: Retrospective review. SETTING: Tertiary referral center. PATIENTS: 97 patients who underwent surgical removal of acoustic neuromas from 1992 to 1998. INTERVENTION: All patients underwent acoustic neuroma surgery and had preoperative audiograms and MRI with contrast. In addition, all patients had preoperative and postoperative facial function graded by the House-Brackmann scale and intraoperative facial nerve monitoring. Hearing preservation was attempted in patients with tumors of any size who had preoperative function of grade A or B according to the Committee on Hearing and Equilibrium guidelines for reporting results of acoustic neuroma surgery. MAIN OUTCOME MEASURES: Hearing preservation was considered successful if the patient retained serviceable hearing grade A or B. House-Brackmann grade 1 or 2 was considered excellent facial function. Complications were recorded. RESULTS: Facial nerve integrity was preserved in 96 of 97 patients (99%). Eight of 8 (100%) patients with intracanalicular tumors had excellent facial nerve function (HB 1-2). Fifty-two of 55 (95%) of patients with small tumors had excellent facial nerve function, and 15 of 24 (63%) with medium tumors had HB grade 1-2. Hearing was preserved in 29% of patients with tumors under 2 cm. The overall complication rate was 20%; cerebrospinal fluid leak was the most common. CONCLUSION: These results show that with modern imaging and surgical techniques, acoustic neuroma surgery is extremely safe and outcomes are very good. Surgery remains the treatment of choice for most tumors until alternative therapies, such as gamma knife, use uniform grading scales and show long-term facial and hearing results.

As a term, the "petrosal approach" to the petroclival region has a variety of meanings. The authors define a common nomenclature based on historical contributions and add new terminology to describe a technique of hearing preservation that allows for greater exposure of the petroclival region. The degree of temporal bone dissection defines five stages of operation. The authors used the second or "transcrusal" stage, in which the posterior and superior semicircular canals are sacrificed while preserving hearing, in six consecutive cases. Use of a common terminology ensures better understanding among surgeons. In the authors' hands, hearing has been successfully preserved in six patients after partial labyrinthectomy.

OBJECTIVES/HYPOTHESIS: Surgery has been the most common treatment for acoustic neuromas, but gamma knife radiosurgery has emerged as a safe and efficacious alternative to microsurgery. This meta-analysis compares the outcomes of the two modalities. STUDY DESIGN: A retrospective MEDLINE search was used to find all surgical and gamma knife studies published from 1990 to 1998 and strict inclusion criteria were applied. RESULTS: For tumors less than 4 cm in diameter, there is no difference in hearing preservation (P = .82) or facial nerve outcome (P = .2). Surgery on all sized tumors has a significantly lower complication rate than radiosurgery performed on tumors smaller than 4 cm (P = 3.2 x 10(-14)). Surgery also has a lower major morbidity rate than gamma knife radiosurgery (P = 2.4 x 10(-14)). Tumor control was defined as no tumor recurrence or no tumor regrowth. Surgery has superior tumor control when tumors are totally resected (P = 9.02 x 10(-11)). Assuming that all partially resected tumors will recur, surgery still retains a significant advantage over radiosurgery for tumor control (P = .028). CONCLUSION: Data from these studies date back to the late 1960s and do not completely reflect outcomes using current imaging and procedures. A major difficulty encountered in this study is inconsistent data reporting. Future surgical and radiation reports should use standardized outcomes scales to allow valid statistical comparisons. In addition, long-term results from gamma knife radiosurgery using lower dosimetry have not been reported. Surgery should remain the therapy of choice for acoustic neuromas until tumor control rates can be established.

OBJECT: The petrosal approach to the petroclival region has been used by a variety of authors in various ways and the terminology has become quite confusing. A systematic assessment of the benefits and limitations of each approach is also lacking. The authors classify their approach to the middle and upper clivus, review the applications for each, and test their hypotheses on a cadaver model by using frameless stereotactic guidance. METHODS: The petrosal approach to the upper and middle clivus is divided into four increasingly morbidity-producing steps: retrolabyrinthine, transcrusal (partial labyrinthectomy), transotic, and transcochlear approaches. Four latex-injected cadaveric heads (eight sides) underwent dissection in which frameless stereotactic guidance was used. An area of exposure 10 cm superficial to a central target (working area) was calculated. The area and length of clival exposure with each subsequent dissection was also calculated. The retrolabyrinthine approach spares hearing and facial function but provides for only a small window of upper clival exposure. The view afforded by what we have called the transcrusal approach provides for up to four times this exposure. The transotic and transcochlear procedures, although producing more morbidity, add little in terms of a larger clival window. However, with each step, the surgical freedom for manipulation of instruments increases. CONCLUSIONS: The petrosal approach to the upper and middle clivus is useful but should be used judiciously, because levels of morbidity can be high. The retrolabyrinthine approach has limited utility. For tumors without bone invasion, the transcrusal approach provides a much more versatile exposure with an excellent chance of hearing and facial nerve preservation. The transotic approach provides for greater versatility in treating lesions but clival exposure is not greatly enhanced. Transcochlear exposure adds little in terms of intradural exposure and should be reserved for cases in which access to the petrous carotid artery is necessary.

OBJECT: The purpose of this study was to evaluate the far-lateral transcondylar transtubercular approach (complete FLA) based on quantitative measurements of the exposure of the foramen magnum and petroclival area obtained after each successive step of this approach. METHODS: The complete FLA was reproduced in eight specially prepared cadaveric heads (a total of 15 sides). The approach was divided into six steps: 1) C-1 hemilaminectomy and suboccipital craniectomy with unroofing of the sigmoid sinus (basic FLA); 2) partial resection of the occipital condyle (up to the hypoglossal canal); 3) removal of the jugular tuberculum; 4) mastoidectomy (limited to the labyrinth and the fallopian canal) and retraction of the sigmoid sinus; 5) resection of the lateral mass of C-1 with mobilization of the vertebral artery; and 6) resection of the remaining portion of the occipital condyle. After each successive step, a standard set of measurements was obtained using a frameless stereotactic device. The measurements were used to estimate two parameters: the size of the exposed petroclival area and the size of a spatial cone directed toward the anterior rim of the foramen magnum, which depicts the amount of surgical freedom available for manipulation of instruments. The initial basic FLA provided exposure of only 21 +/- 6% of the petroclival area that was exposed with the full, six-step maximally aggressive (complete) FLA. Likewise, only 18 +/- 9% of the final surgical freedom was obtained after the basic FLA was performed. Each subsequent step of the approach increased both petroclival exposure and surgical freedom. The most dramatic increase in petroclival exposure was noted after removal of the jugular tuberculum (71 +/- 12% of final exposure), whereas the least improvement in exposure occurred after the final step, which consisted of total condyle resection. CONCLUSIONS: The complete FLA provides wide and sufficient exposure of the foramen magnum and lower to middle clivus. The complete FLA consists of several steps, each of which contributes to increasing petroclival exposure and surgical freedom. However, the FLA may be limited to the less aggressive steps, while still achieving significant exposure and surgical freedom. The choice of complete or basic FLA thus depends on the underlying pathological condition and the degree of exposure required for effective surgical treatment.