NASBS News and Upcoming Events

Vol 10 No 1 Archive

Presentation Abstracts: Presenting Authors K-L

IMAGE FUSION IN 100 SKULL BASE, VASCULAR, AND MICROVASCULAR PROCEDURES: PRELIMINARY RESULTS

Amin B. Kassam, MD, FRCS(C) (presenter), Michael Horowitz, MD, Ricardo Carrau, MD, Carl Snyderman, MD, Barry Hirsch, MD, William Welch, MD, Greta Seever, RN (Pittsburgh, USA)

Image fusion (IF) is a new technology that allows the surgeon to simultaneously use both endoscopic and microscopic images to perform intricate surgical procedures. This technology, developed by Olympus Corporation and refined for clinical application by the University of Pittsburgh differs from other systems in that the surgeon has endoscopic images projected onto both of his/her microscope oculars (simultaneous binocular visualization). Other systems available on the market divide these images so that the microscopic image remains on one ocular while the endoscopic image appears on the other. While useful to some degree, the latter systems take away the advantage of the microscope, namely binocular rendered depth perception. By projecting the endoscopic image onto both oculars and retaining the normal binocular microscopic images surgeon is better able to dissect out fine structures while simultaneously using the endoscopic image to better visualize the structures of interest. Ultimately the surgeon finds he/she is using both endoscopic and microscopic images simultaneously and fluidly to perform the surgical dissection without actually clearly focusing on one image modality or the other (thus the term image fusion).

THE CAROTID-VERTEBRAL SPACE: AN EXTENDED LATERAL WINDOW TO THE VENTRO-MEDIAL CRANIAL BASE AND LOWER CRANIOCERVICAL JUNCTION

Amin B. Kassam, MD, FRCS(C) (presenter), Michael Horowitz, MD, Atul Patel MD, Ricardo Carrau, MD, Carl Snyderman, MD, Barry Hirsch, MD, William Welch, MD, Greta Seever, RN (Pittsburgh, USA)

Access to the ventromedial skull base and craniocervical junction can be difficult. Those structures that impede access are the jugular vein, jugular bulb, vertebral artery, jugular foramen, carotid artery, occipital condyle , C1 superior articular facet, and cranial nerves 7, 9, 10, 11 and 12. Preservation of these structures through mobilization and transposition permits surgeons to remove skull base abnormalities with reduction in surgical morbidity. We have used the carotid-vertebral space extended lateral approach in six patients. The procedure and results will be presented.

GLOSSOPHARYNGEAL NEURALGIA: A TEN YEAR EXPERIENCE IN 200 PATIENTS

Amin B. Kassam, MD, FRCS(C) (presenter), Michael Horowitz, MD, Atul Patel MD, Yue Fang Chang, PhD, Greta Seever, RN (Pittsburgh, USA)

Significance: Glossopharyngeal Neuralgia (GPN) is a rare condition with significant morbidity that often results in ability to maintain nutrition. Medical management for this condition has not been very effective, resulting in a variety of surgical procedures ranging from nerve section to microvascular decompression (MVD). Over the past twenty years over 200 patients with GPN have undergone MVD at the University of Pittsburgh Medical Center.

Methods: A retrospective review of our database was undertaken to identify patients with typical GPN. Patients were divided into four quartiles of approximately fifty cases in each quartile to assess changes in outcomes over time. A functional outcomes scale was developed and patients were subjected to a telephone interview reporting on patient satisfaction, relief of symptoms and complications. Univariate and multivariate analysis were performed to identify predictors of good outcome.

Results: Overall immediate success rate exceeded 80% with 10% experiencing partial relief. The incidence of lower cranial dysfunction was 18% though this was substantially lower when only patients over the last two years were considered. Overall patient outcomes and satisfaction was best within the typical GPN group, ie., when the pain syndrome was restricted to the throat and palate. There was significant improvement in outcomes over time (p=0.04) with a concomitant reduction in morbidity. The factors that we feel responsible for these findings will be discussed in detail.

Conclusion: Glossopharyngeal neuralgia is a rare condition, which is likely underdiagnosed. Microvascular decompression is a safe and effective form of therapy for typical GPN.

MAJOR VENOUS SINUS RESECTION IN THE SURGICAL TREATMENT OF RECURRENT AGGRESSIVE DURAL BASED TUMORS.

Keith A. Kattner, DO (presenter), Raul A. Rodas, DO, Robert A. Fenstermaker, MD (Bloomington, USA)

Despite gross total resection, dural-based tumors have high recurrence rates with poor long-term survivability. Options for aggressive surgical management of dural sinus invasion may be limited by the high risk of mortality and morbidity.

Between July 1996 and May 2000, four cases of recurrent dural-based tumors presented to the neuro-oncology service. Gross total resection was performed at primary surgery. Tumor pathology included one malignant meningioma, two atypical meningiomas, and one hemangiopericytoma. All tumors recurred within 3 to 40 months and occluded a major venous sinus (three superior sagittal, one dominant right transverse sinus). Radical resection of the tumor and sinuses was performed in each case. One patient died of tumor progression at ten months. Three patients showed no sign of clinical or radiographic recurrence (8 to 36 months, mean 18 months).

Although dural-based tumors commonly reoccur in the major venous sinuses, radical resection can be safely performed with long-term survival.

CASE ILLUSTRATIONS OF PITUITARY HYPERPLASIA IN THE YOUNG ADULT FEMALE POPULATION

Keith A. Kattner, DO (presenter) (Bloomington, USA)

Pituitary hyperplasia can result from either physiological or endocrine etiologies. Hyperplasia can mimic macroadenoma and should be considered in the differential diagnosis of sellar masses.

Three patients presented with clinical and neuroradiographic features suggestive of pituitary adenoma. All patients were young females (ages 17 to 29). After endocrine and neuroradiographic evaluation, all patients were diagnosed with pituitary hyperplasia.

Patient 1 presented with enlargement of the pituitary gland and intermittent galactorrhea. This patient was found to have hyperplasia from hypothyroidism. ¹ With a regiment of replacement therapy, MRI showed complete resolution.

Patient 2 was found to have hyperplasia resulting from pregnancy. The patient presented with bitemporal visual impairment at 28 weeks gestation. Optic nerve compression was noted on MRI. Symptoms spontaneously resolved after the delivery.

Patient 3 presented with a two-month history of hypermenorrhea. An MRI confirmed enlargement of the pituitary gland. Hyperplasia from delayed puberty was suspected and close observation recommended.

APPROACH TO SKULL BASE LESIONS BY OPERATIVE EXPOSURE AND MANAGEMENT OF PETROUS PORTION OF INTERNAL CAROTID ARTERY

Mumtaz J. Khan, MD (presenter), Garth Olson, MD, Thomas C. Naslund, MD, James L. Netterville, MD (Nashville, USA)

Introduction: Exposure of the petrous portion of the internal carotid artery (ICA) facilitates surgical resection of infratemporal fossa lesions involving the internal carotid artery. This is most commonly accomplished via a transtemporal or middle fossa craniotomy approach. For lesions or aneurysms involving the skull base, these approaches are excessive resulting in unnecessary surgical morbidity.

Method: This report outlines a preauricular trans-glenoid approach to expose the petrous carotid artery in eight patients with aneurysms or tumors requiring resection and grafting of the infratemporal ICA.

Results: Exposure of the petrous ICA through infratemporal fossa and lateral skull base route prevents profound conductive hearing loss and avoids the need of craniotomy. Drilling both the vertical and horizontal portions of the petrous ICA allows removal of bone around 270^o of the artery, resulting in excellent mobility for exposure and/or bypass. This surgical approach results in permanent loss of Eustachian tube and in sacrifice of chorda tympani nerve. Post-operative complications included transient paresis of facial nerve, vagus nerve and spinal accessory nerve in one patient and mild stroke with unilateral upper extremity weakness in another patient. No permanent neurological damage was noted.

Conclusion: Direct operative approach to the petrous ICA results in minimal morbidity and reduced risk of neurological sequelae and provides an excellent approach for the treatment of skull base lesions.

SURGICAL TACTICS AND APPLICATIONS OF THE PRESERVATIVE PETROSECTOMY

Han-Kyu Kim, MD (presenter), In-Seog Park, MD, Do-Heon Kim, MD, Yong-Woon Cho, MD, Byung-Chan Jeon, MD (Pusan, KOREA)

The selection of surgical approaches in patients harboring skull base pathologies at the ventral brain stem dg upper and mid clivus with intact hearing is sometimes difficult. Anterior petrosal or retrolabyrinthine posterior petrosal approach could be selected in these cases but the exposure is not always enough. The authors modified the petrosal approach to overcome the limitations of exposure of the conventional petrosal approaches. This, the so called preservative petrosectomy, is an approach to remove all the air cells and bones of the petrose pyramid preserving the cochlea, otic capsule fallopian canal and GSPN. The key tactics of this approach is to preserve the cochlea, otic capsule and vestibule by removal of the non-functioning petrose bone maximizing the exposure of the ventral brain stem which has not been considered importantly in the conservative petrosectomies. The authors practiced the microsurgical anatomical details in 10 sides of the cadaver head and applied to 7 clinical cases with good results. The exposure was excellent in all 7 cases of AICA aneurysms, petroclival meningiomas and, NF II extending to the cavernous sinus. The microsurgical tactics and the clinical results will be presented and discussed.

CEREBELLOPONTINE ANGLE EPIDERMOIDS PRESENTING WITH CRANIAL NERVE HYPERACTIVE DYSFUNCTION: PATHOGENESIS AND LONG-TERM SURGICAL RESULTS OF 30 CASES

Hitoshi Kobata, MD (presenter), Akiniri Kondo, MD, Koichi Iwasaki, MD (Osaka, JAPAN)

Objective: To provide the characteristics and surgical results of the patients harboring cerebellopontine angle (CPA) epidermoids presenting with trigeminal neuralgia (TN) or hemifacial spasm (HFS).

Methods: A total of 30 patients with CPA epidermoids showing TN (28 patients) and HFS (two patients) were reviewed.

Results: The average age of the patients was 37.8 years at the onset and 49.3 years at the operation. The tumor-nerve relationship was classified into four types, i.e., complete encasement of the nerve by the tumor, compression and distortion of the nerve by the tumor, compression of the nerve by an artery located contralateral to the tumor, and that by an artery ipsilateral to the nerve. Epidermoids were totally removed in 17 cases (56.7%). Microvascular decompression (MVD) of the respective cranial nerve was also achieved in nine cases. The symptom was relieved completely in all cases.

Conclusions: Hyperactive dysfunction of the cranial nerves, especially TN, may be the initial and the only symptom of the patients harboring CPA epidermoids. MVD to straighten of the neuraxis should be done in some cases to obtain complete cure of symptoms in addition to careful resection of the tumor.

FRONTO-ORBITAL APPROACH IN MANAGEMENT OF NEOPLASMS OF ANTERIOR CRANIAL FOSSA AND PARASELLAR REGION.

Romuald Krajewski, MD (presenter), Andrzej Kukwa, MD, Wieslaw Bonicki, MD, Wojciech Maksymowicz, MD, Andrzej Sobieraj, MD, Radoslaw Michalik, MD (Warsaw, POLAND)

Fronto-orbital craniotomy involving frontal sinus, nasal bone and superomedial parts of orbits provides direct exposure of anterior cranial fossa, ethmoid sinuses and orbits. The same craniotomy can be used to expose optic chiasm, parasellar region, sphenoid sinus and clivus. The approach has been used in 42 patients with anterior cranial fossa (ACF) neoplasms (16 malignant and 26 benign), in 52 cases of giant pituitary adenoma and in 19 with other parasellar tumors. Macroscopically total tumor removal was achieved in 78% of procedures (35 ACF tumors, 42 adenomas, 11 other parasellar tumors). Reconstruction of dural defects with fascia lata, pediculated periosteal flap attached to the edges of bone defect and free fat graft obliteration of dead space provided efficient separation of intracranial and nasal cavities. Serious complications occurred in 8 patients (infection in 2, CSF leak in 3, pneumocephalus in 1, intracranial hematoma in 3). Three patients died in postoperative period. Fronto-orbital approach can be successfully used for a variety of tumors in anterior cranial fossa, parasellar and ethmoid-sphenoid sinuses areas.

MIDLINE ANTERIOR SKULL BASE RECONSTRUCTION: TECHNIQUES AND EXPERIENCE

James T. Kryzanski, MD (presenter), Carl B. Heilman, MD (Boston, USA)

We report our experience with reconstruction procedures following surgical treatment of 35 midline anterior skull base lesions. In all, we performed 19 biorbitofrontal craniotomies, 7 bifrontal craniotomies, 4 unilateral frontal craniotomies, 2 unilateral orbitofrontal craniotomies and 3 pterional craniotomies. Reconstruction of small defects was performed with anteriorly based vascularized pericranium alone in 11 cases or with vascularized pericranium and free dural graft in 12 cases. For larger defects, vascularized outer table bone graft was used in 7 cases and titanium mesh wrapped in pericranial graft in three cases. Complications occurred in 6 of 35 patients. There was one case of meningitis and no postoperative cerebrospinal fluid leaks in our series. The talk will focus on technical aspects of anterior skull base reconstruction. After a case of meningitis early in the series we began completing the cranial portion of the case and sealing the dura prior to entering the nasal cavity or sinuses. Secondly, we use vascularized outer table bone grafts whenever possible to repair large bony defects. Finally, when closing an orbitofrontnasal craniotomy, the location of the vascularized pericranial graft in relation to the bone flaps is dependent on the shape of the orbitonasal bar. If a significant portion of the nasal bone is elevated with the biorbital bar, the pericranium is placed on top of this bar and beneath the bifrontal craniotomy. Otherwise we generally try to place the pericranial flap beneath both the biorbital bar and the frontal bone flap to isolate both from the nasal cavity.

TRANSFACIAL AND TRANSTEMPORAL APPROACHES TO THE ANTERO-LATERAL SKULL BASE-A CADAVERIC STUDY

M. Abraham Kuriakose, MD (presenter), Andrew Fishman MD, Renato Giacchi MD, Arun Gadre MD, Ho-Sheng Lin MD, Ramesh Babu MD, Mark D. DeLacure MD (New York, USA)

Introduction: Facial translocation and transtemporal approaches, with distinct morbidity profile are described to gain access to the antero-lateral skull base. The objective of this study was to directly compare the extent of exposure of key anatomic structures, which may be obtained by these techniques.

Materials and methods: Surgical procedures were carried out on five fresh frozen adult cadavers (ten sides). This consisted of Fisch Type-C procedure and variations of facial translocation approaches. Measurements were carried out to determine distance from the surgical plane and the angle of exposure of two groups of anatomic points (pre-styloid structures- pterygoid plates, pharyngeal opening and isthmus of eustachian tube, foramens ovale, spinosum, and rotundum and post-styloid structures spine of sphenoid, carotid canal and the internal carotid artery). The ratio of the area of skull base exposed and tissue displaced was also determined (E/D ratio).

Results: Distances from the surgical plane to the anatomic reference points were comparable with all techniques (3 to 6 cm), except for extended midfacial translocation and bilateral facial traslocation approaches. With these the pre-styloid and contralateral structures had a shorter distance of 1 to 3 cm. The primary difference was the angle of exposure of key anatomic points. While the transtemporal approach provided excellent post-styloid exposure angle (74 to 84 degrees), transfacial approaches were superior in exposing the pre-styloid region. Contralateral structures were better exposed by either extended midfacial or bilateral translocation approaches. With respect to the E/D ratio, all techniques had a similar ratio (2 to 7) except the trans-zygomatic, which had a ratio of 21.

Conclusions: Based on this result a schema is proposed to assist in choosing surgical approaches to the antero-lateral skull base.

ENDOSCOPIC REPAIR OF CSF LEAKS

Jose Alberto Landeiro, MD (presenter), José Alberto Landeiro, MD, Marlo S. Flores, MD, Igor de Castro, MD (Rio de Janeiro, BRAZIL)

CSF rhinorrhea implies a communication between the subarachnoid space with the upper respiratory tract. Trauma (blunt or penetrating) and postoperative defects are the most common etiology of CSF rhinorrhea. The usual methods of treatment are conservative measures (such as bed rest, elevation of the head and using of spinal tap or drains). More effective treatment is required in some patients. CSF leak in a patient operated with a skull base lesion can be a devastating complication and increase the mortality.

The repair using endoscopic techniques allows the surgeon to treat these skull base defects transnasally. We performed in the last 2 years, 6 procedures (4 traumatic cases and 2 postoperative cases) with an excellent result.

In our series, the use of fluorescein prove to be very effective in the visualization of the leak. The repair was performed with autologous materials (such as fascialata, fat and fibrin glue). In only one patient the lumbar drains was used for 3 days after the endoscopic procedure.

ENDOSCOPIC TRANSSPHENOIDAL APPROACH FOR PITUITARY TUMORS

Jose Alberto Landeiro, MD (presenter), Marlo Steiner Flores, MD, Igor de Castro, MD, Carlos André Ramos Lopes, MD, Mario Alberto Lapenta, MD, Carlos Henrique Ribeiro, MD (Rio de Janeiro, BRAZIL)

Objective: Although transsphenoidal surgery has became the preferred approach to remove pituitary tumors even in giant tumors, the operation under endoscopic guidance allows a fast and safe approach to the sphenoid sinus and subsequently removal of the sellar lesions.

Methods: Twenty one patients were operated using a 4 mm rigid endoscope with 0⁰ angle to open the anterior wall of the sphenoid sinus after the incision in the posterior part of the septum, removing the vomer. Subsequently the sinus was opened with microrongeurs, the nasal speculum was placed and the tumors were removed under endoscopic visualization.

Results: The procedure was done in 21 patients with pituitary tumors. Twelve patients had macroadenomas and 9 microadenomas. Among them there are 12 non-functioning tumors, 4 GH hormone-secreting tumors and 5 adrenocorticotropic hormone secreting microadenomas. The four acromegalic patients had resolution of their symptons. The result in the Cushing disease patients was impressive. The cases of macroadenomas the total resection was possible in only 8 patients and 4 patients required another procedure.

Conclusion: In our series endoscopic removal of pituitary tumors proved to be safe and provide good results without increase the mortality and morbidity rates.

OCCIPTAL TRANSTENTORIAL APPROACH

Jose Alberto Landeiro, MD (presenter), Marlo S. Flores, MD, Igor de Castro, MD (Rio de Janeiro, BRAZIL)

The Occiptal Transtentorial approach is well described to treat lesions localized at pineal region and dorsum mesencephalon region, but few reports have been founded about this approach to deal with lesions at the superior surface of cerebellum and tentorium.

Eight patients were submitted a surgical procedure using this approach in the last 2 years.( 6 Meningiomas, 2 metastases: one from a breast cancer and the other from a prostatic carcinoma).

The craniotomy was placed at parietoocciptal region always above and below the transverse sinus. In every case the transverse sinus and the sinus confluence (Torcula Herophili) were carefully studied with MRV studies.

The total removal was achieved in all cases without complications, no visual problems were observed in the postoperative course.

At last, the lesions localized at the superior surface of cerebellum and tentorium can be easily and safely removed using this approach. The sinus ligature is possible but great attention should be paid regarding the sinus anatomy and type of sinus confluence.

TRANSORAL APPROACH TO THE CRANIOCERVICAL JUNCTION

Jose Alberto Landeiro, MD (presenter), Marlo Steiner Flores, MD, Igor de Castro, MD, Carlos André Ramos Lopes, MD, Mario Alberto Lapenta, MD, Carlos Henrique Ribeiro, MD (Rio de Janeiro, BRAZIL)

The transoral approach is the most direct access to the pathologies located on the ventral side of the craniocervical junction. The craniocervical junction comprises a bone channel formed by the foramen magnum, the atlas and the axis that gives access to the medulla oblongata, the cervicomedullary junction and the upper cervical cord. Therefore, bone junction abnormalities are likely to compress and to affect the neural and vascular structures, and the LCR circulation. The bone junction lesions of the craniocervical junction can be classified into four major types: congenital, acquired, traumatic and neoplastic.

This presentation reviews the indications of the transoral approach, its limitations and the surgical technique used after treating 51 patients with craniocervical junction lesions. The majority of the patients presented with myelopathy. The surgery was performed under microscopic vision and fluoroscopic control. Additional exposure was achieved with soft palate incision, hard palate resection, maxillotomy and extended maxillotomy. There was one post-operative mortality, and less postoperative morbidity and this approach is an excellent option in the treatment of extradural lesions of this region.

Recently two patients were underwent a new procedure. Those patients presented evidence of clinical deterioration (tetraparesis and impairment of lower cranial nerves). A severe ventral compression due to scar tissue was appreciated at the MRI studies. An another transoral procedure was performed in both cases without major complications.

SKULL BASE SURGERY AN EVIDENCE BASED APPROACH

Dorothy Lang, MD (presenter), Glenn Neil-Dwyer, Barrie Evans, Ann Davis (Southhampton, UNITED KINGDOM)

Background: In the setting of modern skull base surgery using craniofacial access is it possible to apply an evidence based approach? Such a strategy would involve analysis of skull base procedures combined with an analysis of outcome and relevant evidence based appraisal of the literature.

Method: Two groups of patients were studied. The first group had petroclival meningiomas and their operations were done using a transpetrous approach. The second group had deep seated lesions in the central skull base and these were resected using an extended transbasal approach. The clinical questions were defined, comparative studies identified in the literature and an audit of the results carried out. Outcome was assessed by surgeons using the Glasgow Outcome Score (GOS) and by the patients who completed an SF36 questionnaire.

Results: The GOS results were acceptable while the SF36 analysis showed that in the majority of patients the pathology and skull base interventions affected their quality of life adversely. A further finding in the patients with petroclival meningiomas was the significant impact on carers' lifestyle and employment. The available literature tended to be technique driven and focused on surgical morbidity and mortality analysis.

Summary: This work demonstrates that comparative audit was difficult because of problems with case-mix and other baseline data. Outcome assessment needs to be patient orientated and focussed on quality of life issues as well as function.

ORBITOZYGOMATIC APPROACH FOR TREATMENT OF ANEURYSMS: REVIEW OF 100 CASES

G. Michael Lemole, Jr, MD (presenter), Jeffrey S. Henn, MD, Howard Riina, MD, and Robert F. Spetzler, MD (Phoenix, USA)

The orbitozygomatic craniotomy is an extremely useful skull-base approach for treating intracranial aneurysms. We review our experience with 100 consecutive cases in which the orbitozygomatic craniotomy was used to treat 120 aneurysms (single aneurysm in 81 patients, multiple aneurysms in 19 patients) over a 3-year period. The most common aneurysm locations were the anterior communicating (40), middle cerebral (22), basilar tip (14), and internal carotid arteries (12). In decreasing frequency other locations included the posterior communicating, posterior cerebral, ophthalmic, superior cerebellar, anterior cerebral, and anterior choroidal arteries.

In each case, the orbitozygomatic craniotomy was chosen to maximize exposure while minimizing the need for retraction. The approach also offers a shorter working distance and improves the angle for clip application. This versatile approach can be tailored to treat aneurysms successfully at a variety of locations typically addressed with other surgical approaches.

OUTCOME ANALYSIS OF PATIENTS WITH BELL'S PALSY

Thomas E. Linder, MD (presenter), Sandra Vanek, MS (Zurich, SWITZERLAND)

Appropriate evaluation and treatment of patients with acute facial nerve palsy continues to be a topic of debate. The benefit of facial nerve grading systems, the value of electroneurono-graphy (ENoG), the significance of MR imaging and the outcome of patients undergoing conservative and surgical treatment were evaluated prospectively.

Between 1997 and 1999 over one hundred patients with acute peripheral facial nerve palsy were enrolled consecutively into our study group. Facial function was recorded using the Fisch and House-Brackmann grading systems. Repeated ENoG measurements were performed once the facial function became paralytic. Medical treatment was initiated and facial nerve decompression was offered to a subset of patients.

Patients with incomplete palsy recovered to normal function within 90 days. Only 58% of patients with facial paralysis completely recovered within 12 months. Deterioration of ENoG above 90% denervation had a poor prognosis. MRI consistently located the site of injury at the meatal foramen, however had no predictive value regarding severity of the disease. A diagnostic algorithm and the therapeutic concept including middle fossa decompression surgery will be presented based on our findings and current knowledge of the disease.

INDICATIONS AND OUTCOME OF SUBTOTAL PETROSECTOMY

Thomas E. Linder, MD (presenter), Stephan Schmid, MD (Zurich, SWITZERLAND)

Subtotal Petrosectomy (SP) has been defined and performed by U. Fisch for many decades. SP is not only the key component of the Infratemporal Fossa Approaches A-C, but can be used as a distinct procedure for a variety of ear and skull base pathologies. In a retrospective analysis we evaluated our personal experience with SP over the last 4 years. The indications involved mainly revision surgeries for chronic draining ears with precedent severe sensorineural hearing loss, cochlear implant surgeries in patients with cochlear malformation or ossification, and patients suffering from malignant tumors involving the temporal bone. The important surgical steps will be reviewed and the indications and morbidity discussed.

A CEREBELLOPONTINE ANGLE CRANIOPHARYNGIOMA IN A PATIENT WITH GARDNER'S SYNDROME: CASE REPORT AND REVIEW OF THE LITERATURE

Michael J. Link, MD (presenter), Colin LW Driscoll, MD, Caterina Giannini, MD (Rochester, USA)

A 29 year-old man with a history of Gardner's syndrome presented with a 1-year history of diplopia, right-sided hearing loss, right hypalgesia and dysphagia. A MRI scan revealed a large inhomogeneously enhancing, partially cystic lesion in the right cerebellopontine (CP) angle. There was faint calcification on CT and it was angiographically avascular. A right suboccipital craniotomy was performed with gross total resection of the tumor. The tumor appeared to originate from the right foramen of Lushka. The pathology was consistent with craniopharyngioma.

This is only the third reported case of a craniopharyngioma of the CP angle. The pathogenesis and management for this rare occurrence is discussed. The genetics relating tumors in Gardner's syndrome and craniopharyngioma is also reviewed.

MALIGNANT SQUAMOUS DEGENERATION OF A CEREBELLOPONTINE ANGLE EPIDERMOID TUMOR. CASE REPORT AND REVIEW OF THE LITERATURE.

Michael J. Link, MD (presenter), John M. Tew, Jr, MD (Rochester, USA)

A 57 year-old woman initially presented in July 1996 with left V3 trigeminal neuralgia, progressive hearing loss and facial weakness. A MRI scan revealed a non-enhancing mass in the left cerebellopontine (CP) angle. An epidermoid was near-totally resected via a suboccipital craniotomy. One year later, she developed vertigo, near syncope, increased swallowing difficulty. Follow-up MRI scans in April and July 1997 revealed an enlarging, inhomogeneously enhancing mass in the left CP angle, pons and middle cerebellar peduncle. The previous suboccipital craniotomy was reopened and a posterior petrosectomy was performed. A subtotal resection was again performed and the pathology was consistent with squamous cell carcinoma arising in an epidermoid. She subsequently received external beam radiotherapy with radiosurgery boost with good short-term response.

The pathogenesis, differential diagnosis, management and review of the literature for this rare occurrence will be discussed.