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Vol 10 No 1 Archive

Presentation Abstracts: Presenting Authors G-H

MICROVASCULAR DECOMPRESSION ELIMINATED TRIGEMINAL NEURALGIA REFRACTORY TO FIVE DESTRUCTIVE PROCEDURES - A CASE REPORT

Ramsis F. Ghaly, MD (presenter) (Chicago, USA)

Refractory trigeminal Neuralgia (TN) to medical and destructive treatment is difficult to cure. The following case is unique in demonstrating the efficacy of microvascular decompression (MVD) for treatment of refractory TN.

A 61-year-old female presented with right typical and atypical trigeminal pain in the distribution of V2 and V3. Over a decade, she underwent radiofrequency, glycerol, balloon compression, alcohol injection, and thermocoagulation rhizotomies. These procedures provided temporary or no relief and left the patient with atypical facial pain with permanent numbness and burning. She was receiving a combination of Carbazepine, Gapabentin, Elavil, and Topomax.

Right occipital craniotomy for MVD was performed. A total of 3 offending vessels were causing drez root compression; superior cerebellar artery (SCA) from above anterior inferior cerebellar artery (AICA) laterally and aberrant trigeminal vein from below. The latter was sacrificed and two pieces of Ivolin sponges were used to separate the SCA and AICA.

Immediate relief with permanent recovery of the typical and atypical facial pain was achieved. Currently, the patient is under no medication and returned to work with an open social personality.

Anesthesia delarosa, atypical facial pain, and refractory TN are disabling neuropathic pain syndromes with limited options for treatment. Some of the current options may include stereotactic radiosurgery, caudaulis, neucleous lesioning and sensory root sacrifice. A non-destructive MVD provided permanent cure despite the prior five destructive procedures. It supports the theory that TN is caused by neurovascular compressions. Once neurovascular compressions were released, TN was eliminated.

REAPPRAISAL OF THE ETIOLOGY OF ABDUCENS NERVE PALSY: AN ANATOMIC AND DEVELOPMENTAL STUDY

Sanjay Ghosh, MD (presenter), Rebecca Hanson MD, Ignacio Gonzalez MD, Floyd Gilles MD, and Michael Levy MD (Los Angeles, USA)

Introduction: Of the three cranial nerves that mediate ocular motility, the abducens nerve (cranial nerve 6) is most commonly affected by disease and increased intracranial pressure with herniation. Furthermore, this nerve is the most frequently affected cranial nerve in a number of disorders including skull base chordomas, intracranial chondrosarcomas, skull base fractures, and hydrocephalus. Several authors (including Gray's Anatomy and Greenberg Handbook of Neurosurgery) have attributed the vulnerability of the sixth nerve to its long intracranial course. In order to test the validity of this hypothesis, we performed a two part anatomic study of the sixth cranial nerve. The first part of the study involved measurement of the length of the sixth cranial nerves at the time of autopsy amongst 12 pediatric patients. The second part of the study involved surgical exposure of the sixth cranial nerve in a preserved human cadaver head to identify the anatomic substrate for sixth nerve palsy.

Results: The children's ages ranged from three months to 14 years. We found the sixth nerve to range from 11 to 15 mm in length. The fourth cranial nerve (trochlear) was 3 to 3.3 times as long as the sixth nerve. An extended middle fossa craniotomy was then performed on an injected human cadaver head to expose the sixth cranial nerve in its entire course. Endoscopic analysis of the in situ course of the nerve demonstrated the vertical course of the nerve, its tethering at its arachnoidal penetration and Dorello's canal, as well as extreme proximity of the nerve to the clival dura, basilar artery, and anterior inferior cerebellar artery.

Conclusions: The abducens nerve is significantly shorter than the trochlear nerve through all stages of pediatric development as well as in adults. The frequency of abducens nerve palsies has nothing to do with the absolute length of the nerve, but rather, its specific anatomic location, its anchors at the pontomedullary junction caudally and at Dorello's canal rostrally, and its course within the cranial vault.

UNSUCCESSFUL FRACTIONATED RADIOSURGERY FOR CYSTIC ACOUSTIC NEUROMA: A CASE REPORT

Sanjay Ghosh, MD (presenter), Rick Friedman, MD, PhD, John Diaz Day MD (Los Angeles, USA)

Objective and Importance: Gamma knife radiosurgery has traditionally involved the precise delivery of radiation in a single session. Single dose radiosurgery has been found to have a high failure rate in the management of cystic acoustic neuromas. Recently, some neurosurgeons have begun to fractionate the radiation treatments in the interest of reducing the incidence of cranial nerve injury when treating acoustic neuromas. The experience of fractionated radiosurgery with cystic acoustic neuromas has not been described. We report the first case of a cystic acoustic neuroma treated with fractionated radiosurgery.

Clinical Presentation: A 55-year-old man with a history of unilateral sensorineural hearing loss was found to have a left 2.5 cm cystic acoustic neuroma by magnetic resonance imaging.

Intervention: The patient was initially managed at an outside facility with fractionated radiosurgery. He received 4 Gray of radiation in 5 sessions over 5 days for a total dose of 20 Gray to the 90 percent isodose curve. A frameless guidance system was used to deliver the radiation. The patient had serial magnetic resonance imaging obtained at 6 and 8 months after radiosurgery. These images revealed a progressive increase in both the solid and cystic components of the tumor with compression of the pons and hydrocephalus. In order to relieve the pontine compression and hydrocephalus, the tumor was managed with surgical resection by a translabyrinthine craniotomy. The patient recovered uneventfully from surgery with House-Brackmann grade I (normal) facial nerve function.

Conclusions: Like single dose radiosurgery, fractionated radiosurgery in its current form appears to be ineffective in treating cystic acoustic neuromas. Patients with cystic vestibular schwannomas are at significant risk of experiencing sub-acute expansion of the cyst after either single or fractionated dose radiosurgery. The consequences of such cyst expansion include cranial nerve palsy, brainstem compression, and hydrocephalus. Therefore, cystic acoustic neuromas are best managed by surgical resection.

EXTRACANALICULAR VESTIBULAR SCHWANNOMA: WHAT CAN BE ACHIEVED WITH THE ENLARGED MIDDLE FOSSA APPROACH?

Mislav Gjuric, MD, PhD (presenter) (Frankfurt, GERMANY)

Objective: Whereas intracanalicular vestibular schwannoma (VS) is ideally removed with the enlarged middle fossa approach (EMFA), extracanalicular tumor protruding into the cerebellopontine angle (CPA) poses special challenges on the surgeon.

Patients: 608 VS patients with an extracanalicular tumor growth between 0.1-3 cm.

Results: The tumor was completely removed in 96% of cases, and the postoperative facial nerve function was normal and near-normal in 83-94%, depending on the tumor size. Serviceable hearing was preserved in 24-56% of patients with preoperative class A hearing. Hearing at or near the preoperative level was preserved in 17.6-48.2%.

Conclusion: The EMFA is an excellent low-morbidity approach for VS removal with limited CPA extension. Specific advantages are the superior internal auditory canal exposure resulting in an extremely low tumor recurrence rate, best capability for hearing preservation, and minimal incidence of cerebrospinal fluid leaks. Postoperative facial function outcome compares with that of other surgical approaches.

THE CAVERNOUS SINUS AND MIDDLE FOSSA TRIANGLES: CONTENTS AND CLINICAL IMPORTANCE EXPANDED IN 3 DIMENSIONS

Fernando Gonzalez, MD (presenter), Pushpa Deshmukh, PhD, Mauro A. Ferreira, MD, Joseph M. Zabramski, MD, Mark C. Preul, MD, Robert F. Spetzler, MD (Phoenix, USA)

Introduction: Cavernous sinus and the middle fossa contain neurovascular structures of vital importance for the neurosurgeon. Relations among the cranial nerves and vascular structures have been described, resembling triangular shapes.

Material and methods: Five cadaver heads injected with silicone were dissected. We measured the medial, lateral and basal aspects of the anteromedial (Dolenc's Triangle), medial, superior, lateral (Parkinson's triangle), posterolateral (Glasscock's triangle), posteromedial (Kawase's triangle), anteromedial and anterolateral triangles. We focused attention to the structures that can be exposed through these areas. Stages of the dissections were recorded with 3-dimensional (3D) photography.

Results: We found that dividing the cavernous sinus and the middle fossa in triangular areas is a useful concept to understand the relations among nerves and vascular structures. Most of the triangles can be extended into 3-dimensional polygons, which may allow for refinements in skull base surgical approaches. For example the posteromedial (Kawase) triangle may be extended into a polygon which enhances the space to work in the posterior fossa from a lateral approach. 3D photography adds to the ability to recognize and use the anatomical relationships in the triangles.

Conclusion: Knowledge of the anatomy of the cavernous sinus and middle fossa can be gained using triangular figures among the structures. This knowledge can be further enhanced using a 3 dimensional or 3D polygonal approach to the anatomy.

THE OCCIPITAL CONDYLE: A MICROANATOMICAL STUDY AND ITS SURGICAL RELEVANCE

Fernando Gonzalez, MD (presenter), Mauro A. Ferreira, MD, Pushpa Deshmukh, PhD, Joseph M. Zabramski, MD, Mark C. Preul, MD, Robert F. Spetzler, MD (Phoenix, USA)

Introduction: The importance of the atlanto-occipital joint is often neglected. The anatomical relationships of the occipital condyle are critical for craniovertebral junction, posterior fossa, and the far lateral surgical exposures.

Material and Methods: Five cadaver heads with silicone-injected vasculature were dissected. Far lateral exposures were performed bilaterally. Attention was focused on the region of the occipital condyle, including dimensions; bony relations with the atlas; relations with the vertebral artery and surrounding venous plexus; and neural relations, including the hypoglossal nerve. Stages of the dissections were recorded with stereoscopic (3D) photography.

Results: The occipital condyle presents variations in size; its position overshadows the content of the antero-lateral margin of the foramen magnum. Extradural removal of the occipital condyle provides a wider exposure of the antero-lateral region of the foramen magnum. The variable position of the hypoglossal nerve is crucial to the integrity of the occipital condyle. The occipital condyle provides a potential bony anchorage for occipitocervical screw fixation.

Conclusions: Removal of the occipital condyle provides extra space when accessing the antero-lateral margin of the foramen magnum. 3D photography allowed for the reexamination and study of the anatomical relationships in a more thorough and accurate manner. Further anatomical exploration may indicate the biomechanical efficacy of occipitocervical fixation that includes the occipital condyle in the construction.

RETRO-MANDIBULAR SUBFACIAL APPROACH TO HIGH GLOMUS VAGALE TUMORS WITHOUT FACIAL NERVE MOBILIZATION: CLINICAL PRESENTATION AND ANATOMIC STUDY

Murali Guthikonda, MD (presenter), Jaechon Park, MD, Colleen Duffy, RN, BSN, CNRN (Detroit, USA)

Glomus vagale tumors can arise any where along the course of the vagus nerve in the upper cervical area. As the vagus nerve lies in the antero-medial compartment of the jugular foramen, the tumors arising it extend medial to the jugular bulb and along the upper cervical area posterior to the internal carotid artery. They can also extend in cephalad direction into the infratemporal fossa (ITF). The exposure of such tumors reaching the jugular foramen or growing into then infra-temporal fossa require facial nerve mobilization/dissection resulting in a high incidence of facial paralysis, temporary or permanent. We present our experience with retromandibular subfacial approach without facial nerve mobilization in such tumors and support the approach with anatomical studies.

TREATMENT OF POSTERIOR FOSSA CEREBROVASCULAR PATHOLOGY USING THE FAR-LATERAL APPROACH: ANEURYSMS, CAVERNOUS MALFORMATIONS, ARTERIOVENOUS MALFORMATIONS, AND ISCHEMIA

Patrick P. Han, MD (presenter), Jeffrey S. Henn, MD, and Robert F. Spetzler, MD (Phoenix, USA)

Introduction: Posterior fossa cerebrovascular pathology remains technically challenging for neurosurgeons. We report our experience with the treatment of 44 posterior fossa aneurysms, 14 brain stem cavernous malformations, 6 arteriovenous malformations, and 2 patients with ischemia using the far-lateral approach.

Methods: Between 1994 and 1998, 66 patients with cerebrovascular pathology underwent a far-lateral craniotomy.

Results: Approach-related morbidity was minimal. Complications from the approach as well as treatment-related morbidity and mortality will be discussed in detail.

Conclusions: The far-lateral approach provides excellent exposure for the treatment of posterior inferior cerebellar artery or vertebrobasilar aneurysms, pontomedullary cavernous malformations, and select arteriovenous malformations. Exposure of the intradural vertebral artery is optimal for direct ligation or endarterectomy when needed in select cases. It can be performed with minimal approach-related morbidity.

MULTIMODALITY MANAGEMENT OF VESTIBULAR SCHWANNOMAS

Carl B. Heilman, MD (presenter), Nikolas Blevins, Dennis Poe, MD, David Vernick, MD (Boston, USA)

The optimal management of patients with a vestibular schwannoma is controversial. Treatment options include watchful waiting with serial imaging, radiation therapy, radiosurgery, and surgical excision. The surgical options include the retromastoid approach (RM), translabyrinthine approach (TL) and the middle fossa (MF) approach. The management of 108 consecutive patients with a vestibular schwannoma, treated over a six year period will be presented. 84 patients were treated surgically (56 RM, 22 TL, 6 MF). In 21 patients, the initial management was watchful waiting with serial imaging studies - 17 patients continue to be followed. 7 patients were treated by radiosurgery (1 Linac, 6 Gamma Knife). Total tumor removal was performed in 94% (79/84) of the patients treated surgically. In patients with tumors <3 cm, total tumor removal was performed in 98% (60/61) of the patients. 58 of the 61 surgically treated patients with tumors <3 cm had post operative facial function of House Brackmann Grade 1 (52 pts.) or 2 (6 pts.). Although 26% (22/84) of the surgical patients suffered a temporary complication of some kind, there were only 5 permanent complications (other than cranial nerve 7 or 8) in the surgically treated group (3 chronic headaches, 1 contralateral lower cranial nerve palsy, 1 corneal scar). Preoperative trigeminal nerve sensory loss was present in 20 patients and resolved completely postoperatively in 15. Preservation of Gardner Robertson Grade 1 or 2 hearing in the surgical group was possible in 38% overall (13/34), 41% in tumors < 2.0 cm and 75% (6/8) in intracanalicular tumors. There were no cases of post operative cerebellar ataxia, no strokes, no cerebellar hemorrhages and no deaths. The advantages and disadvantages of surgery versus radiosurgery/radiation therapy will be discussed.

OUR SERIES OF SKULL BASE SURGERY LESIONS - LESS FREQUENT EXPANSIONS OF MIDDLE PART OF SKULL BASE

Jan Hemza, MD (presenter), Zdenek Novak, MD, Petr Krupa, MD, Jan Bucek, MD, Eva Lzicarova, MD (Brna, CZECH REPUBLIC)

Between 9/96-9/2000 have 272 operations of the skull base lesions. We have 8 less frequent from these, the different diagnosis: chondrom et chordom. of clivus, paragangliom sphenoidal sinus, cyst of Rathke cleft epidermoid retrosellar to CT angle, neoplasmatic transformation of epidermoid to the spincellular carcinoma. Author discussed different approaches in this middle part and divided 4 from these lesions: midfacial degloving, pterional approach, retrosigmoid and subfrontal. Mortality in our series are 0, morbidity 12% temporary. The anatomy-topographical relations with philosophy of the minimal invasive neurosurgery show rational types of approaches and our experiences with them.

TRAUMA AND SKULL BASE SURGERY-OPEN FRACTURES OF ANTERIOR AND MIDDLE FOSSA

Jan Hemza, MD (presenter), Tomas Zeman, MD, Petr Krupa, MD, Zdenek Novak, MD (Brna, CZECH REPUBLIC)

During 8 years we have experiences with acute surgery intervention of open fractures of anterior and middle fossa. During technic we used vascular flap, toast technic, microsurgery technic with protection of olfactory structures. We have 112 cases in series, 21 middle fossa open fractures and 91 anterior fossa open fractures. We have in our series only 1 case with liquorhoea recurrence. Author show the pathology on the olfactory structures after trauma. He discussed timing of surgery, surgery technic, problems of radiology examine (CT, MRI, MRI and CT cisternography Le.), clinical problems of open trauma and active approach to the therapy. We preferred acute surgery after open fracture of skull base.

THE ANATOMICAL STRUCTURES OF THE LAMINA CRIBROSA OF THE ANTERIOR SKULL BASE FOSSA

Jan Hemza, MD (presenter), Jitka Hanzlova, MD (Brna, CZECH REPUBLIC)

Our first study of the lamina cribriform we show this oss as labyrinth type. Now we study histological structures and we look at, that into labyrinth oss are veins, which have specific structures of the wall. This structures are very similar as cavernous vein or vein into the lien. The vein wall is very thin and endothelial cells are discontinuous on basal membrane. We hope, that this veins have very important role in resorption of cerebrospinal fluid.

THE FAR-LATERAL CRANIOTOMY: NOVEL APPLICATION OF STEREOSCOPIC VIRTUAL REALITY

Jeffrey S. Henn, MD (presenter), G. Michael Lemole, Jr, MD, Mauro Ferreira, MD, Fernando Gonzales, MD, Mark Preul, MD, and Robert F. Spetzler (Phoenix, USA)

The far-lateral craniotomy has become a standard skull-base approach for accessing the anterior clivus, foramen magnum, and anterolateral brainstem. The success of this approach is contingent upon mastery of complex three-dimensional anatomy. Our objective was to evaluate whether advances in computer-based virtual reality could be applied to improve demonstration of these intricate anatomic relationships.

Cadaveric dissection was performed following the steps of a far-lateral craniotomy. At each stage of the dissection, stereoscopic images were obtained. These images were combined into interactive virtual reality "movies." The result is an extremely useful computer-based interface for studying or teaching the techniques and anatomy of the far-lateral craniotomy.

Computer-based stereoscopic virtual reality can be used to improve neurosurgical education and has several advantages over other available tools. These include the benefits of interactive learning, the ability to communicate information in a multimedia format, and improved demonstration of complex three-dimensional relationships.

AGGRESSIVE MULTISPECIALTY TREATMENT IMPROVES SURVIVAL IN SINONASAL

Jason Heth, MD (presenter), Vincent C. Traynelis, MD, Timothy M. McCulloch, MD, Robert A. Robinson, MD, PhD, Gerry F. Funk, MD, and Henry T. Hoffman, MD (Iowa City, USA)

Introduction: Patient prognosis in sinonasal undifferentiated carcinoma, a recently described neoplasm, has poor reported survival rates, ranging from 4 to 15 months. On the contrary, aggressive multidisciplinary treatment at the UIHC resulted in substantially improved survival.

Methods: The UI Oncology registry was queried for patients diagnosed with SNUC from 1986 to the present. Demographic and treatment data were recorded.

Results: Nine patients, mean age 39.9 years, were reviewed; all were histologically confirmed. Eight underwent surgical resection. All patients received radiation therapy; eight received chemotherapy. Two patients had invasion into the orbit or anterior cranial fossa. Three patients died of disease, while six patients are alive, five without recurrence. Average survival for all patients was 52.1 months, for patients dying of disease was 26.0 months, and for surviving patients was 65.2 months.

Discussion: These data demonstrate improved SNUC patient survival. These results likely reflect the relative confinement of tumors at presentation and reinforce the need for aggressive multispecialty treatment of this neoplasm.

LIPOMAS OF THE MIDDLE EAR AND POSTERIOR FOSSA

Drew M. Horlbeck, MD (presenter), Michael J. Holliday, MD, Matthew Ng, MD (Baltimore, USA)

Lipomas of the intracranial cavity and the middle ear are rare tumors. There have been only 4 cases of lipomas of the middle ear described in the English literature. A small subset of intracranial lipomas occurs within the internal auditory canal and the cerebellopontine angle. In this location, these tumors account for 9% of intracranial lipomas. Historically, removal of these tumors is difficult due to adherence to adjacent cranial nerves, brainstem and incorporation of vessels and nerve fascicles within the tumor. This has led to a high rate of postoperative neurologic deficits and incomplete resection. In a recent review of all of posterior fossa lipomas to date, only 33% of lipomas could be completely resected. With complete tumor resection hearing was preserved in 12%. Hearing was preserved in 23% of CPA lipomas with partial resections. Review of hearing preservation rates reported for complete removal of tumors limited to the IAC is 40%.

We present three cases: a cerebellopontine angle lipoma, a lipoma of the internal auditory canal and a middle ear lipoma. Interestingly, we observed no change in audiometric thresholds after a middle fossa resection of the internal auditory canal lipoma. Specifically looking at small lipomas limited to the internal auditory canal, this case illustrates hearing preservation may be possible.

CRANIAL NEUROPATHIES: PITFALLS IN DIAGNOSIS AND MANAGEMENT

Michael B. Horowitz, MD (presenter), Amin B. Kassam, MD, Michael Soso, MD, Misha Pless, MD, Ricardo Carrau, MD, Carl Snyderman, MD, Barry Hirch, MD, Mark Ochs, DDS, Lois Burkhart, RN (Pittsburgh, USA)

Despite the fact that cranial neuropathies affect a small portion of the population, the Center for Cranial Nerve Disorders at the University of Pittsburgh Medical Center evaluates approximately 1,000 patients annually with cranial nerve complaints. There can be many pitfalls in making the correct diagnosis. We have attempted to minimize incorrect diagnoses by employing a multidisciplinary team. A variety of differential diagnoses must be considered when evaluating patients with: trigeminal neuralgia, hemifacial spasm, glossopharyngeal neuralgia, tinnitus, vertigo, and geniculate neuralgia. The common and not so common alternate etiologies for cranial neuropathies will be discussed.

MYOFIBROMA OF THE BASE OF SKULL

John R. Houck, MD (presenter) (Oklahoma City, USA)

Myofibroma is a rare, low-grade sarcoma with a confusing spectrum of histopathologic findings and clinical courses. A case is presented of a 6-year-old boy with a series of skull base myofibromas. He initially presented with proptosis and decreased vision in the left eye. Multiple skull base lesions were seen on scans. A biopsy of the left ethmoid sinuses revealed a neoplasm with controversial histologic characteristics. Multiple pathologists throughout the United States could not agree on a definitive diagnosis. The case was presented to two well-known base of skull surgeons, who recommended debulking. With no treatment, the original lesions have regressed and vision has improved, although not to normal. New lesions have been noted on scans, but have not been symptomatic. Multiple family members have also had manifestations of the disease, although not at the base of skull. Clinical variations, genetics, and treatment options will be discussed.

EFFECTS OF CLOSURE TECHNIQUES ON POST-OPERATIVE HEADACHE FROM SUBOCCIPITAL CRANIECTOMY.

Frank P.K. Hsu, MD, PhD (presenter), Jeffrey Adams, MD, Johnny B. Delashaw, MD, Sean O. McMenomey, MD (Portland, USA)

Introduction: Post-operative headaches from suboccipital craniectomy are commonly reported in the literature (incidence 10-70%). The chronic headache starting immediately after surgery can be debilitating. Possible etiologies include neuroma or nerve entrapment at incision, bone dust irritation, or adhesion between scalp or nuchal musculature and dura. We examined whether the closure techniques influence the incidence and severity of post-craniectomy headaches.

Methods: Retrospective review was performed on patients undergoing suboccipital craniectomy for resection of acoustic neuromas at the Oregon Health Sciences University. The patients were divided into three groups according to the method of closures: (A) no cranioplasty, (B) titanium plate cranioplasty, and (C) Norian cranioplasty. Patients were excluded if they had cerebrospinal fluid leak, hydrocephalus, or shunt procedures. Headaches were quantitatively graded with grades: (0) no headache, (1) headache present but no medication needed, (2) headache controlled with over-the-counter medication, (3) headache controlled with prescription medication, (4) severe headache uncontrolled with medication.

Results: Ninety consecutive patients were identified from 1992 to 1999. Four patients were excluded and ten patients were lost to follow-up. Among the 76 patients, 38 patients had no cranioplasty (A), 18 patients had titanium plate cranioplasty (B), and 20 patients had Norian cranioplasty (C). The incidence of headache in each group was (A) 45%, (B) 33%, and (C) 5%. In group (A) there were 35% grade 2, 35% grade 3, and 30% grade 4 headaches. In group (B) there were 33% grade 2, 50% grade 3, and 17% grade 4 headaches. For the patients with at least one year follow-up, duration of headache was characterized: 95% (3 months), 84% (6 months), 79% (12 months), 68% (greater than 12 months).

Discussion/Conclusion: Titanium plate cranioplasty does not significantly reduce the incidence of headache following suboccipital craniectomy, Early results indicate that Norian calcium-phosphate cement cranioplasty does help prevent post-operative headache.