NASBS News and Upcoming Events

Vol 10 No 1 Archive

Presentation Abstracts: Presenting Authors A-B

THE ONE-PIECE ORBITOZYGOMATIC APPROACH: THE MACCARTY BURR HOLE AND THE INFERIOR ORBITAL FISSURE AS KEYS TO TECHNIQUE AND APPLICATION

Khaled M. Abdel Aziz, MD, PhD (presenter), Sebastien C. Froelich, MD, Paul L. Cohen, MD, Abhay Sanan, MD, Harry R. van Loveren, MD, Jeffrey T. Keller, PhD, John M. Tew, Jr, MD (Cincinnati, USA)

Objective: Using the MacCarty keyhole burr hole and the inferior orbital fissure provides simplicity and safety to performing a one-piece frontotemporal orbitozygomatic (FTOZ1) approach.

Methods: We performed the FTOZ1 approach with its 3 subtypes (i.e., total, temporal, and frontal) in cadaveric head specimens and subsequently in surgical cases.

Results: The MacCarty burr hole is used to facilitate orbital cuts, and the anterolateral portion of the inferior orbital fissure connects the orbital cuts to the zygomatic cuts, allowing the FTOZ1 craniotomy flap to be easily "out-fractured." The 3 types of FTOZ1 approach are described step by step.

Conclusions: The frontotemporal orbitozygomatic (FTOZ) approach provides an expanded exposure to the anterior and middle cranial fossae, and enables the surgeon to create a window to the posterior cranial fossa. The 3 types of the FTOZ1 approach enable the surgeon to tailor the approach according to the surgical exposure needed for each lesion.

REVERSAL OF CRANIAL NERVE DEFICITS AFTER RADIOSURGERY FOR CAVERNOUS SINUS MENINGIOMAS

Khaled M. Abdel Aziz, MD, PhD (presenter), Sebastien C. Froelich, MD, Abhay Sanan, MD, Harry R. van Loveren, MD, John C. Breneman, MD, John M. Tew, Jr, MD (Cincinnati, USA)

Objective: To prove the efficacy of radiosurgery for the management of primary holocavernous meningiomas.

Methods: Retrospective analysis of 21 patients who presented from December 1990 through December 1999 with primary holocavernous meningiomas with cranial nerve (CN) deficit or evidence of tumor growth in their follow-up MRI and received focused radiation therapy. Patients were followed clinically to assess ocular CN outcome, and radiologically to assess tumor growth within a mean follow-up of 54 months.

Results: Patients were treated with 3-dimensional conformal radiation therapy (50 G), X-Knife (12-18 G), or stereotactic radiosurgery (12-18 G). Clinically, patients had dysfunction in 31 CNs before radiotherapy. Fifteen (48%) CNs improved in function after treatment. Radiologically, 16 of 21 patients (76%) exhibited the same size tumor, and the remaining 5 (24%) tumors decreased in size after treatment.

Conclusion: Although a longer follow-up period is required, our data and the literature indicate that radiosurgery is a non-invasive alternative management tool for primary cavernous sinus meningiomas.

PROBLEMS ON DURAL RESECTION AND PLASTY DURING EN BLOC RESECTION OF MAXILLARY MALIGNANT TUMORS WITH ANTERIOR AND MIDDLE SKULL BASE

Yasuhiko Ajimi, MD (presenter), Hideo Nameki, MD., Satoshi Fukuzumi, MD, Yasuo Toda, MD, Jun Shinoda, MD, Masachika Sago, MD, Fumito Yamada, MD (Shizuoka City, JAPAN)

We propose 4 problems with dural resection and plasty on en bloc removal of maxillary malignant tumors with the anterior and middle skull base. The first problem is cerebral ischemia not only due to the internal carotid artery (IC) stenosis but also due to the systemic hypotension as an autonomic reflex caused by careless packing with hemostatic substances against much bleeding due to increased blood flow of the cavernous sinus (CS). It is better to cut the dura mater on the posterior side of the foramen ovale to control bleeding from CS, while it is possible to preserve the mandibular nerve. The second is the direct exposure of infected tissues and tumor to the surgical field in case of cutting the dural ring. This procedure is inevitable to mobilize IC from the skull base. The third is narrow working space for repairing the broad dural defect with a fascia lata autograft following dural resection. Additionally, the narrow working space is close to the infected cavities such as the nasal or paranasal sinuses. These disadvantages are involved in repairing the dural defect immediately after dural resection. This procedure has advantages such as avoiding both of cerebral infection and dryness and controlling hemorrhage from the resected sites of the soft tissue of the face and skull base. The last problem is a slim margin of dura mater to sew up and the possibility of subdural bleeding from the edge of CS which is placed inside the subdural space. These disadvantages are involved in suturing the medial wall (pericranium) instead of the lateral wall (dura proper) with a fascia lata autograft as a dural substitute in order to envelop mobilized IC in the subdural space.

RECONSTRUCTIVE CONCEPTS FOLLOWING SURGERY FOR INFECTIONS OF THE LATERAL SKULL BASE

Ford D. Albritton IV, MD (presenter), Danko Cerenko, MD, PhD, Grant Carlson, MD (Atlanta, USA)

Surgical approach to the lateral skull base is indicated in a variety of lesions. Reconstruction of the resulting defect with non-collapsible walls and suboptimal blood supply is challenging. The problem is amplified in the face of life threatening chronic infections of lateral skull base. The first group are chronic infections of skull base lesions, like infected petrous apex cholesteatomas or cholesterol granulomas. The second group are chronic infections of the lateral skull base structures which occur in poorly vascularized tissues as in irradiated patients (bacterial or fungal osteomyelitis of lateral skull base). The successful reconstruction includes filling of the defect, prevention of CSF leak, and prevention of meningitis. Many lateral cranial base defects may be repaired with free abdominal fat and/or local muscle flaps. However, in cases with chronic infection or poorly viable surrounding tissue, we recommend reconstruction with exclusive use of free muscle flaps. These flaps not only fill the surgical defect, but provide crucially needed blood supply capable of delivering therapeutic antibiotic/antifungal medical therapy to the disease site.

CRANIOFACIAL APPROACH MODIFICATIONS WHEN USING A STEREOTACTIC HEADSET

Joseph P. Allegretti, MD (presenter), Manish Wani, MD, Gail L. Rosseau, MD, William R. Panje, MD (Chicago, USA)

The purpose of this study is to review our modifications to the transfacial, transnasal, and midfacial degloving approaches, when utilizing an image-aided stereotactic headset for craniofacial surgery. We evaluated our experience using the VTI electromagnetic localizing system in combined otolaryngology and neurosurgery, cases for advanced skull base tumors. The headset from this popular system is set in at the medial canthus, and the verification tape is positioned over the nasal bones. Thus, we describe the modified lateral rhinotomy, endoscopic, and sublabial approaches done prior to a craniotomy to allow dissection safely around the extracranial vital structures. Minor alterations in the standard incisions are required in some cases to avoid interfering with the tracking system. Thereafter, a frontal craniotomy, if needed, and intracranial and extracranial resection of the tumor can be done in harmony with less risk. We have used this technique in six paranasal sinus, nasopharyngeal or sella turcica neoplasms. Although skull-imbedded posts for cranial base surgery have been designed, their registration is more tedious and their accuracy still has not been perfected. Thus, we describe our technique for utilizing the well-proven headsets, which are becoming increasingly available at many institutions.

PARACLINOID ANEURYSM PRESENTING WITH CEREBRAL ISCHEMIA

Jeffrey D. Atkinson, MD (presenter), Denis J. Sirhan, MD, David S. Sinclair, MD (Montreal, CANADA)

Often regarded as a formidable technical challenge for the neurosurgeon, the paraclinoid aneurysm most often presents either incidentally, with subarachnoid hemorrhage or by visual disturbances. The authors report an unusual case of a 30-year old female who developed an acute left-sided hemiparesis for which an exhaustive stroke work-up revealed a right paraclinoid wide-necked aneurysm.

Following a 3-week clinical recuperation, the patient underwent a subsequent aneurysm clipping via a right cranio-orbital approach with intradural clinoidectomy, unroofing of the optic canal, and delicate mobilization of the optic nerve. Proximal control was achieved via a cervical carotid exposure. The patient remains neurologically intact following the surgical exclusion of the aneurysm.

The very rare association of an ischemic insult potentially caused by a paraclinoid aneurysm is reviewed. A possible etiopathogenesis is suggested.

THE ASTERION: IS IT A USEFUL SURFACE LANDMARK?

Emel Avci, MD (presenter) (Washington DC, USA)

The asterion was examined in twelve adult cadaver specimens and ten dried skulls. Distances were measured utilizing the Marathon 8 inch/200 mm Electronic Digital Caliper. To localize the position of the asterion relative to the underlying dura and venous structures, the B1 bit of the Midas Rex was used to create a hole the diameter of the bit through the asterion. A needle was passed into the underlying dura and a craniotomy was performed.

Of 24 cadaver sides, there was no clear asterion and occipitomastoid suture found on 14 sides (~60%). It was always seen in dry skulls. The asterion was never found over the occipitoparietal dura. It was found to overlie the transverse sinus when the asterion could be identified, was found to lie at least 1.0 cm medial to the transverse-sigmoid junction and always found to lie above the superior nuchal line. It was found to be variable in its anatomic relations to other identifiable structures (table 1). This variability in relation to other posterior fossa bony landmarks limits its usefulness as a consistent marker for intracranial structures.

TABLE 1

DISTANCE (mm)	RANGE (mm)	AVERAGE (mm)
A - MT	45.03 - 55 45.0 - 59.1	50.3 49.9
A - ZR	45.9 - 69.0 50.4 - 64.6	55.6 56.6
A - ML	50.3 - 71.0 56.9 - 68.02	65.4 61.4
A - HS	30.0 - 46.5 34.6 - 51.4	39.0 43.0
A - T/S	10.0 - 22.1 -------------	15.16 ------

Normal = Cadaver Specimens Bold = Dry Skulls

A = asterion ZR = zygomatic root MT = mastoid tip ML = midline HS = Henle's spine T/S = transverse/sigmoid junction

CASE REPORT: TREATMENT OF BASILAR INVAGINATION IN A PATIENT WITH A KLIPPEL-FEIL SYNDROME

Emel Avci, MD (presenter), Damirez Fossett, MD, Timothy Burke, MD (Washington DC, USA)

A 57 y/o Hispanic male presented with an eight year history of progressive quadraparesis. His cranial nerve function was normal. Imaging revealed basilar invagination, a Chiari malformation, a C3 intramedullary lipoma, and a severe Klippel-Feil syndrome. Additionally, he had an abnormal airway, cardiomegaly, one kidney, low set ears, a webbed neck, and a left Sprengle's deformity.

A trach and PEG, suboccipital craniotomy, C1-C4 laminectomy, subtotal resection of his lipoma, and duraplasty were performed. Additionally, an occipital - cervical fusion was performed. His left scapula, which protruded between the C2 and C3 spinous processes, was subtotally resected.

Post-operatively, he was nearly full strength with resolution of his myelopathy. His tracheostomy was quickly removed and he was transferred to rehabilitation. Because of a rapid decompensation to near quadriplegia, he returned. Utilizing frameless stereotaxy, a transoral resection of the lower clivus, arch of C1 and the dens were achieved. Post-operatively he regained much of his strength and no lower cranial nerve deficits were identified.

Cervicomedullary compression from cranial base pathology often requires anterior and posterior decompression for restoration and preservation of neurologic function.

ELEVATION OF THE INTERNAL AUDITORY CANAL PRESSURE BY VESTIBULAR SCHWANNOMAS

Behnam Badie, MD (presenter), Samir Lapsiwala, MD, Peter Nguyen, MD, Mark Pyle, MD (Madison, USA)

The exact mechanism of hearing loss in patients with vestibular schwannomas remains unclear. To test whether pressure on the cochlear nerve from tumor growth in the internal auditory canal (IAC) is responsible for this clinical finding, we measured the intracanalicular pressure (ICaP) in 36 consecutive patients undergoing a retrosigmoid approach for tumor excision.

Before any tumor manipulation, a Codman pressure microsensor was zeroed relative to the cerebellopontine angle cistern and inserted into the IAC. The pressure readings were then recorded and correlated to the tumor size.

The ICaP was elevated in most patients (median: 16 mm Hg, range: 0 to 45 mm Hg) and directly correlated to tumor extension into the IAC (r2=3D0.64, p=3D0.0001). There was no correlation, however, between the ICaP and total tumor size (r2=3D -0.20, p=3D0.24).

Intracanalicular tumor growth results in the elevation of IAC pressure and may play a role in hearing loss caused by vestibular schwannomas. The relevance of these findings to surgical techniques will be discussed.

INTRAOPERATIVE MICROVASCULAR DOPPLER SONOGRAPHY FOR ARTERIAL LOCALIZATION DURING SKULL BASE SURGERY

Jeffrey R. Balzer, PhD (presenter), Amin B. Kassam, MD, Michael Horowitz, MD, Ricardo Carrau, MD, Carl Snyderman, MD, Barry Hirsch, MD (Pittsburgh, USA)

Complications during skull base approaches may result from inadvertent injury vasculature not visible during exposure and/or tumor dissection. Intraoperative microvascular doppler sonography (IMDS) can provide for immediate identification of underlying vasculature and guide the surgeon during exposure of arterial anatomy. Here we report the use of Doppler sonography during tumor resection via a variety of skull base approaches. A 20 mHz 1 mm probe was employed to insonate vasculature encased in either bone and/or tumor. Depth of insonation could be advanced in 1 mm steps up to 10 mm. In all cases, successful insonation and identification of vascular structures was accomplished. We found IMDS most useful in safely identifying the petrous carotid and the vertebral artery during infratemporal and transcondylar exposures respectively. No instances of inadvertent injury of any vasculature occurred. IMDS is an effective means by which to locate and identify critical vasculature thereby allowing for resection of skull base masses when visual identification of that vasculature is obstructed by the lesion. This technique has been found to be safe, accurate, and invaluable for identification of underlying vascular anatomy.

MULTIMODALITY NEUROPHYSIOLOGICAL MONITORING DURING SKULL BASE SURGERY

Jeffrey R. Balzer, PhD (presenter), Amin B. Kassam, MD, Donald Krieger, PhD, Donald Crammond, PhD, Robert J. Sclabassi, MD, PhD, Michael B. Horowitz, MD, Ricardo Carrau, MD, Carl Snyderman, MD, Barry Hirsch, MD (Pittsburgh, USA)

Cranial base surgery poses significant risk to the functioning of cranial nerves, cerebral hemispheres and brainstem. Risk is due to problems associated with maintaining adequate blood supply to the cerebral hemispheres and brainstem and to the effect of various operative exposures aimed at, for example, adequate tumor removal. These risks may be reduced if appropriate information concerning the relationships between surgical manipulations and their impact on the functioning of the CNS is available. To provide this information, aimed at reducing the probability and severity of injury to neural tissue, we have adopted and successfully implemented a multimodality monitoring approach during cranial base procedures. We routinely and successfully monitor as many as five different neurophysiologic variables simultaneously. These modalities include EEG, EMG recorded from multiple cranial nerves, brainstem evoked potentials, somatosensory evoked potentials and motor potentials. Because the integrity of the CNS cannot be examined during skull base procedures due to anesthesia, the measures described here provide the only immediate assessment of the effects of surgery on the CNS, with implications for modifying surgical techniques and consequently improving surgical outcome.

ACOUSTIC NEUROMAS IN THE PEDIATRIC POPULATION: SPORADIC AND NF2 POPULATIONS

Fred G. Barker, MD (presenter), Michael McKenna, MD, Dennis Poe, MD, Joseph Nadol, MD, Robert Martuza, MD, Robert G. Ojemann, MD (Boston, USA)

Introduction: Acoustic neuromas are uncommon in children. We reviewed the Massachusetts General Hospital experience with resection of acoustic neuromas in young patients between 1985 and 2000. Methods. Retrospective case series. Results. 21 patients age 7 to 19 underwent acoustic neuroma resections. 8 patients had unilateral, apparently sporadic tumors and 13 were diagnosed with NF2. All NF2 patients had bilateral tumors visible on MRI images before initial resection; 70% also had intracranial meningiomas or other cranial nerve schwannomas, and 61% had family histories of NF2. No unilateral tumor was associated with other cranial or spinal manifestations of NF2 or with a family history of meningioma or acoustic neuroma, and no unilateral patient developed a contralateral tumor during follow-up. NF2 and unilateral patients were similar with regard to sex, age at first resection, tumor size and side. Hearing loss at presentation was more common in sporadic unilateral tumors, as some NF2 tumors were discovered by screening asymptomatic children. Technical aspects of resection were similar to older patients, although in 2 of 8 sporadic tumors the facial nerve passed through the tumor rather than on its surface. Some patients with postoperative facial paresis required psychiatric counseling.

Conclusions: Acoustic neuromas in children resemble those seen in older individuals except that passage of the facial nerve through the tumor may be more common. Children with unilateral acoustic neuromas, no family history of NF2, and no other intracranial lesions are likely to have sporadic tumors rather than a mild presentation of NF2.

TRANSTYMPANIC ELECTRODE PLACEMENT AS A RISK FACTOR FOR BACTERIAL MENINGITIS AFTER SUBOCCIPITAL APPROACH FOR ACOUSTIC NEUROMA REMOVAL

Fred G. Barker, MD (presenter), Michael McKenna, MD, Dennis Poe, MD, Joseph Nadol, MD, Robert Martuza, MD, Robert G. Ojemann, MD (Boston, USA)

Introduction: Bacterial meningitis is an uncommon but potentially devastating complication of acoustic neuroma surgery. We reviewed a consecutive patient series to identify risk factors for postoperative meningitis after acoustic neuroma resection. Results. During a 5 year period beginning July 1995, 205 patients underwent initial surgery for acoustic neuromas through a suboccipital approach with drilling of the internal auditory canal and no pre- or postoperative ventriculoperitoneal shunt. Of these, 3 (1.5%) developed postoperative bacterial meningitis. Causative organisms were Enterobacter (2 cases) and E. coli. A fourth patient developed clinical symptoms of bacterial meningitis that resolved rapidly after broad-spectrum antibiotic treatment; although CSF cultures obtained after the first antibiotic dose were sterile, this was classified as "probable" bacterial meningitis. Fever started 3 to 6 days postoperatively. Three patients made good recoveries and one had persistent disability. Risk factors tested for association with meningitis included sex, age, tumor side and size, transtympanic electrode placement for hearing monitoring, and postoperative CSF leak. Transtympanic electrode placement for hearing monitoring or transtympanic middle ear obliteration for perceived high CSF leak risk were associated with a higher rate of postoperative definite or probable bacterial meningitis (Fisher p = 0.025). No other risk factor was significant.

Conclusions: Transtympanic instrumentation during suboccipital acoustic neuroma resections appears to be a risk factor for postoperative bacterial meningitis, especially with gram negative organisms. Careful aseptic preparation of the external ear canal and addition of prophylactic antibiotics active against gram negative organisms may be warranted when transtympanic electrode hearing monitoring is planned.

ENDODERMAL SINUS TUMOR OF THE PARANASAL SINUSES: A CASE REPORT

Daphne Ayn Bascom, MD (presenter), Ricardo Carrau, MD, E. Leon Barnes, MD, Amin Kassam, MD (Pittsburgh, USA)

Introduction: Endodermal sinus tumor is an uncommon malignant germ cell tumor that occurs in both gonadal and extragonadal tissues.

Purpose: We present a case of endodermal sinus tumor arising from the ethmoid sinuses in a 44 year old man.

Treatment: Combined treatment with anterior craniofacial resection and post-operative radiation therapy.

Conclusions: Endodermal sinus tumors of the head and neck, exclusive of the central nervous system, are rare. Combined treatment with surgery, radiation therapy and/or chemotherapy may result in complete tumor regression.

COMBINED SURGICAL APPROACHES THROUGH THE TEMPORAL BONE: SURGICAL ANATOMY, PITFALLS AND COMPLICATIONS. LESSONS LEARNED IN A SERIES OF 36 PATIENTS

Mustafa K. Baskaya, MD (presenter), Imad A. Abumeri, MD, Ernesto Coscarella, MD, Fred F. Telischi, MD, Craig Buchman, MD, Jacques J. Morcos, MD, FRCS (Miami, USA)

Objective: "Combined" surgical approaches through the temporal bone provide access to more than one intra/extra cranial fossa or compartment. Though their general usefulness has not been questioned, their safety and specific applications have varied widely. Our aim is to discuss the surgical anatomy, pitfalls and complications of those approaches.

Methods and Results: A retrospective analysis of a total of 36 patients who had undergone combined surgical approaches through the temporal bone between November 1995 and October 2000 under the neurosurgical care of the senior author (JJM) were reviewed. Ages range from 18 to 71 years with a mean age of 50 years. Male to female ratio was 18 to 18. Pathologies included 14 meningiomas, 6 chondrosarcomas, 4 dural arteriovenous malformations, 3 aneurysms, 2 acoustic neuromas, 2 glomus jugulare tumors, 1 trigeminal schwannoma, 1 craniopharyngioma, 1 epidermoid tumor, 1 hemangiopericytoma, and 1 mucocele of the petrous apex. Surgical approaches were divided into the following groups: a) anterior petrosal or Kawase approach (n=4); b) posterior petrosal combined with subtemporal approach (n=21); c) combined posterior and anterior petrosal approach (n=3); d) other combinations (n=8). Posterior petrosal combined with subtemporal approach included retrolabyrinthine, partial translabyrinthine, translabyrinthine, transcochlear and transotic approaches. The "other combinations" included the following approaches: combined retrolabyrinthine or translabyrinthine with jugular foramen, combined-combined, and total petrosectomy. Clinical outcome and complications are analyzed and presented in detail as they relate to specific approaches. Anatomical dissections in the laboratory were also performed to rationalize the use of specific approaches for specific pathologies at specific location.

Conclusion: Combined surgical approaches through the temporal bone enable surgical treatment of various pathologies in the petroclival region in a safe and effective manner. A better understanding of the interaction of surgical anatomy with nature and extent of the lesion, along with refinements of each approach are of great importance in improving outcome and complication avoidance.

THE EXACT MORPHOMETRY OF THE SUPRAORBITAL FORAMEN AND THE FRONTAL SINUS AND CERTAIN ANATOMIC RELATIONS FOR SKULL BASE APPROACH: AN ANATOMICAL AND CEPHALOMETRIC STUDY

Funda Batay, MD (presenter), Mustafa Kazkayasi, MD, Osman Bengi, MD, Ibrahim Tekdemir, MD, Haluk Deda, MD (Kirikkale, TURKEY)

A detailed understanding of the complex anatomy of the face and midline skull base is the foundation for successful surgical intervention. To planning and deciding to the convenient approach, we aimed to standardize some specific dimensions among the supraorbital foramen, the frontal sinus and the fronto-zygomatic fissure.

The study consisted of two main steps, namely the anatomical examination and the cephalometric analysis of the skulls. In this study, 35 adult skulls (70 sides) were used and first of all, anatomical measurements were made according to the anatomical position of the supraorbital notch, the frontal sinus and the fronto-zygomatic fissure, then the cephalometric graphics were done and same distances were measured and compared with each other. To planning safe skull base approach and to avoid from postoperative complications, these anatomic measurements will be helpful for basic anterior midline skull base approaches.

ALTERNATIVE TECHNIQUES OF OCCIPITOCERVICAL FUSION FOLLOWING RESECTION OF CRANIAL BASE TUMORS

Christopher A. Bogaev, MD (presenter), Dennis G. Vollmer, MD (San Antonio, USA)

Instability of the occipitocervical junction is suspected after resection of cranial base tumors involving removal of the occipital condyle anterior to the hypoglossal canal, resection of the C1 lateral mass, or disruption of the attachments of the alar or transverse ligaments of the odontoid process from the anterior one-third of the occipital condyle or C1 lateral mass. The majority of the techniques for occipitocervical fusion involve a posterior bilateral construct from the occiput to C2 or C3, often performed as a second stage. These techniques provide good bilateral fixation, but the area of the defect is often left devoid of bone and is not involved in the fusion, potentially compromising the reconstruction. The following three cases illustrate alternative techniques.

In the first case, fibular strut grafts were used to bridge a defect from the clivus to C3 at the end of the resection of a large clival chordoma. This was followed by a traditional posterior occiput to C3 fusion. In the second case, a tumor had destroyed the occipital condyle, lateral mass of C1, and the superior facet of C2. At the end of the resection, a Harms cage filled with autologous iliac crest bone graft was used to bridge the defect. External fixation with a halo vest was then used instead of a posterior fusion, due to a microvascular free-flap reconstruction being present over the posterior midline. Finally, a case of fixation of a traumatic atlanto-occipital dislocation is presented, which was repaired in two stages. In the first stage, bilateral occipitocervical plates were placed with screws in the occiput bilaterally and in each C1 lateral mass with a posterior autologous bone strut from the occiput to the C1 posterior arch. In the second stage, bilateral arthrodeses of the atlanto-occipital joints were performed through modified bilateral extreme lateral approaches with placement of tricortical iliac crest bone grafts between the occipital condyles and the lateral masses of C1. This resulted in a 360-degree fusion of a severely unstable defect while preserving the atlanto-axial joint.

These unusual cases illustrate principles of occipitocervical fixation that can be used to augment more traditional techniques, potentially resulting in more stable fixation across fewer motion segments

COMBINED SUBFRONTAL-TRANSSPHENOIDAL APPROACH TO GIANT PITUITARY ADENOMAS

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

Giant pituitary adenomas with large extensions into both suprasellar area and sphenoid sinus pose difficult surgical challenge. With transnasal-transsphenoidal approach suprasellar extensions may be difficult to reach. Subfrontal intracranial approach does not provide access to sphenoid sinus. In 13 (3 prolactinomas, 3 acromegaly, 7 non-secreting adenomas) out of 52 patients with giant pituitary adenomas operated upon via fronto-orbital approach, wide removal of planum sphenoidale and tuberculum sellae was done in order to remove both parts in a single step. Reconstruction of opening into paranasal sinuses was accomplished with fascia lata, fat graft and periosteal flap. Tumor was totally removed in 10 operations. All the patients had severe visual disturbances before operation and postoperatively visual acuity remained stable in 5 and improved in 8. Endocrinological normalization was achieved in 3 acromegaly patients and in 2 of 3 prolactinomas. One patient developed CSF rhinorrhea that ceased on lumbar drainage. This combined approach allows for safe one-stage removal of giant pituitary adenoma.

APPLICATION OF SKULL BASE SURGERY TECHNIQUES AND SOMATOSTATIN ANALOGUE IN SURGICAL TREATMENT OF PATIENTS WITH ACROMEGALY

Wieslaw Bonicki, MD (presenter), Romuald Krajewski, MD, Andrzej Sobieraj, MD, Wojciech Zgliczynski, MD, Witold Olszewski, MD, Maria Maksymowicz, PhD (Warsaw, POLAND)

Somatostatin analogue reduces growth hormone (GH) levels and is supposed to make removal of GH-secreting adenoma easier. Among 342 pituitary adenomas operated upon during last 2 years there were 102 patients with acromegaly (6 microadenomas, 93 macroadenomas and 3 giant). Somatostatin analogue was used in 18 patients in whom radioisotope scan confirmed presence of somatostatin receptors. Tumor size diminished after somatostatin administration in 9 out of 18 cases, GH level was reduced in 15 and in these patients tumor was soft and easier to remove. In 3 patients with giant adenomas fronto-orbital approach combined with removal of planum sphenoidale and tuberculum sellae was used. Biopsy material was evaluated under light and electron microscopy. There was no operative mortality. Transitory diabetes insipidus occurred in 12%. Endocrinological normalization was achieved in 63%. Preparation with somatostatin analogue is beneficial in macroadenomas treated with transsphenoidal approach as well as in giant adenomas operated upon with skull base surgery approach.

THE USE OF DELAYED CRANIOTOMY IN SELECTIVE PATIENTS FOR PRE-RESECTION EMBOLIZATION OF MENINGIOMAS

Alan S. Boulos, MD (presenter), Andrew J. Ringer, MD, Demetrius K. Lopes, MD, Lee R. Guterman, MD, L. Nelson Hopkins, MD (Buffalo, USA)

Introduction: Preoperative embolization of meningiomas may safely reduce

blood loss and improve ease of resection. By delaying the craniotomy for resection from the time of embolization, necrosis occurs making the tumor easier to resect. Preoperative MRI was analyzed to predict tumors amenable to embolization. Methods: Imaging studies from 1988 through 1999 were reviewed to determine characteristics of susceptible tumors. Patients treated between 1997 to 2000 were reviewed to determine the time of embolization to craniotomy, symptoms of increased mass effect, evidence of necrosis, and ease of tumor removal.

Results: 102 meningiomas were evaluated. 58 tumors were embolized. 37 tumors lacked accessible feeding arteries or significant vascular blush. 7 were unsuccessfully attempted. When available, preoperative MRI/MRA were evaluated to predict angiographic criteria for success. From 1997 to 2000, 11 patients underwent craniotomy within 3 days of embolization (Group A) and 9 patients had surgery at least 5 days after embolization (Group B). Neither group had evidence of increased mass effect , but group B had higher incidence of necrosis and shortened length of operation.

Conclusion: Embolization was performed successfully in a majority of patients. MRI/MRA characteristics help predict susceptible tumors. By delaying craniotomy at least 5 days, tumor necrosis and decreased operative time may be gained without losing hemostatic effect.

CEREBROSPINAL FLUID LEAK IN ACOUSTIC NEUROMA SURGERY: INFLUENCE OF TUMOR SIZE AND SURGICAL APPROACH ON INCIDENCE AND RESPONSE TO TREATMENT.

Jeffrey W. Brennan, MD, FRACS (presenter), David Rowed, FRCSC, Julian Nedzelski, FRCSC, Joseph Chen, FRCSC (Toronto, CANADA)

Objective: To review the incidence of cerebrospinal fluid (CSF) leak complicating the removal of acoustic neuroma, and to identify factors that may influence its occurrence and treatment.

Method: Prospective information on consecutive patients operated on for acoustic neuroma was supplemented by a retrospective review of the medical records identifying cases of CSF leak complicating tumor removal.

Results: In 24 years of practice, 624 cases of acoustic neuroma had an overall incidence of CSF leak of 10.7%. The rate of leak was significantly lower in the last 9 years compared to the first 15, most likely due to the abandonment of the combined translabyrinthine middle fossa exposure. There was no significant difference in leak rate between translabyrinthine (TL) and retrosigmoid (RS) approaches, although there were differences in site of leak. Tumor size had a significant effect on leak rate overall and for RS cases but not for TL procedures. The majority of leaks ceased with nonoperative treatments. However, TL leaks (especially rhinorrhea) needed surgical repair significantly more frequently than RS leaks.