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The authors describe use of a flexible fiberoptic light source to guide the craniofacial resection of anterior skull base neoplasms. The light is introduced transnasally and serves to outline the perimeter of the tumor, helping to direct the safe placement of intracranial osteotomies and en bloc tumor removal.
Enhancement in the region of the jugular foramen on magnetic resonance imaging (MRI) is highly sensitive to the presence of a skull base neoplasm. Unfortunately, this imaging method lacks the specificity to be the sole criterion in the diagnosis of a lesion of the jugular foramen. Although well described in the radiological literature, the phenomenon of gadolinium enhancement of the relatively static blood in the jugular system continues to be erroneously diagnosed as glomus jugulare tumor. Instances of this phenomenon present in patients referred to our practice for surgical opinions before radiation therapy and/or definitive resection will be presented. The purpose of this communication is to bring this potential treatment pitfall to the attention of the neurotology community. Treatment planning for lesions of the lateral skull base cannot singularly be based on MRI findings but requires a healthy skepticism satisfied only by more complete evaluation.
Neoplasms located along the antero-lateral skull base, with probable involvement of the orbit and with extension into the pterygoid and/or infratemporal fossa can usually not be sufficiently exposed using standard neurosurgical or otosurgical approaches, which is why combined approaches to these skull base targets have been developed in the recent past. In this report we describe our experience, using a combined orbito-frontal, sub- and infratemporal fossa approach which, starting with a pre-auricular incision and a standard pterional craniotomy, is extended to an extensive osteoplastic enbloc resection of the orbito-zygomatic area allowing for direct visualisation of the antero-temporo-lateral skull base from the orbital cavity to the depth of the infratemporal and pterygoid fossa. The surgical technique as well as the clinical experiences accumulated with this approach are described.
The midfacial degloving approach to the midfacial orbital and anterior skull base structures is very versatile. It provides excellent access to a wide range of resections, such as medial maxillectomy, radical maxillectomy with and without orbital exenteration, anterior skull base cranifacial resection, and partial rhinectomy. This technique is useful for removal of benign and malignant lesions. The postoperative complications are rare. Because of absence of external skin incisions the cosmetic results are excellent.
Image-guided surgery of the cranial base requires a knowledge of both surgical anatomy and the technical aspects of the particular system being used. The authors report on their experience using the ISG Viewing Wand over the last two years, concentrating on the technical considerations for the use of the system and lessons learned. Image-guided surgical systems may well replace the current forms of intraoperative imaging used for anatomic orientation and localization and are considered a valuable addition to the armamentarium of the skull base surgeon.
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A high incidence of morbidity and mortality was related with skull-base neoplasm surgery. Several advances have permitted, in recent years, the total excision of such neoplasms with minimal patient morbidity. Due to an improved understanding of the surgical anatomy of the skull-base and to the collaboration of the neurosurgeon and maxillofacial surgeon and, moreover, to the improvements of imaging (CT and MR) in the past decades new combined approaches were planned and performed to allow en bloc resections of extensive lesions. Extensive exposure of the tumor, improved management of the internal carotid artery, preservation of cranial nerves not involved by tumors and improved cranial base reconstruction techniques (by free flaps) have resulted from this progress. The aim of the present work is to show the main anatomical landmarks of infratemporal fossa and medium skull base that help the surgeon to achieve an en bloc resection.
PURPOSE: To assess the accuracy of MR imaging in predicting dural, venous sinus, and perineural invasion by skull base tumors. METHODS: The preoperative MR images of 22 patients who had resection of skull base neoplasms were evaluated for the following characteristics: dural enhancement, pial enhancement, local perineural invasion by adjacent tumor, and venous sinus invasion by tumor. The greatest width of dural enhancement was measured, and the character of dural enhancement was noted. The pathologic and surgical reports were reviewed retrospectively with specific attention to dural, venous, and local perineural invasion. RESULTS: Of the 22 patients studied, dural invasion by tumor was confirmed in eight patients, vascular invasion in six patients, and perineural invasion in four patients. The sensitivity of dural enhancement in predicting invasion was 88%, the specificity 50%, and the accuracy 64%. When enhancement and focal nodularity were present, the sensitivity remained at 88%; however, specificity was 100% and accuracy 95%. If the dural enhancement was more than 5 mm thick, sensitivity, specificity, and accuracy were 75%, 100%, and 91%, respectively. Predicting tumor invasion of the dura by the presence of pial enhancement was 50% sensitive and 100% specific. Venous sinus/jugular vein invasion was predicted with 100% sensitivity, 94% specificity, and 95% accuracy. Local perineural invasion was predicted with 100% sensitivity, 50% specificity, and 59% accuracy. CONCLUSIONS: The presence of pial enhancement, focal dural nodules, or dural thickening of more than 5 mm is highly accurate in predicting the presence of neoplastic dural invasion. Linear enhancement of dura does not imply dural infiltration by tumor. Venous invasion by tumor can be predicted accurately with preoperative MR imaging.
BACKGROUND: The retinoblastoma (Rb) gene is a well characterized tumor suppressor gene in which loss of heterozygosity has been implicated in a number of malignancies including osteosarcoma and breast carcinoma. Chordomas and chondrosarcomas are rare skull base neoplasms with a propensity for local recurrences, resistance to conventional radiotherapy, and a 5%-30% incidence of metastases. Except for the so called "chondroid chordoma," histologic features do not correlate with the clinical behavior or growth patterns of these tumors. No study to date has investigated what role tumor suppressor genes or oncogenes play in the development and continued growth of these rare neoplasms. METHODS: In order to evaluate the role of the retinoblastoma tumor suppressor gene in chordomas and chondrosarcomas we screened seven chordomas and two chondrosarcomas located at the skull base for loss of heterozygosity (LOH) of the Rb gene. Genomic DNA was extracted from tumor specimens as well as matched control tissue and utilizing a polymerase chain reaction technique, intron 17 and 20 were amplified from each specimen. The intron 17 product was then digested with the restriction endonuclease X ba1 followed by electrophoresis on a 1% agrose gel. The intron 20 amplified products were electrophoresed on a nondenaturing 6% polyacrylamide gel. RESULTS: We demonstrated LOH at intron 17 of the retinoblastoma gene in 2/7 chordomas and in 0/2 chondrosarcomas. The two chordomas possessing LOH were particularly aggressive tumors demonstrating extensive involvement of the skull base and rapid recurrences following radical resections. CONCLUSIONS: Alterations of the Rb gene may play a role in the growth of skull base chordomas with LOH of the Rb gene serving as a marker for more aggressive tumors. This report represents the first study evaluating the Rb gene in chordomas or chondrosarcomas and is the first report of allelic loss of the Rb gene in skull base chordomas.
We studied the signal and enhancement characteristics of the central skull base prospectively in 40 children aged 13 days to 8 years, on a 1.5 T MRI system. Identical standard short TR/TE spin echo sequences in the sagittal plane were performed before and after intravenous gadolinium-DTPA. The sequences used for comparison were filmed at identical window and level settings. Three independent observers assessed (1) the intensity of contrast enhancement of the basisphenoid, basiocciput and presphenoid, (2) the signal intensity of the spheno-occipital synchondrosis, (3) the degree of pneumatization of the sphenoid sinus and (4) the uniformity of signal intensity reflecting fatty replacement of the marrow of the basisphenoid, basiocciput and presphenoid. In 16% and 28% respectively of cases there was no enhancement of the basisphenoid and basiocciput after gadolinium administration; in 42% and 44% there was mild enhancement, and moderate or intense enhancement was observed in 42% and 28% of cases. Even when there was irregular fatty replacement, residual hemopoietic clements could enhance intensely. When skull base neoplasms are being investigated, the normal signal irregularity and enhancement of the central skull base in children must not be confused with pathologic invasion of the marrow.
Primary tumors originating from cells of the glial lineage usually affect predominantly the white matter of the brain. Only rarely do gliomas destroy the surrounding bone by invasion of the extracellular matrix, especially without prior surgery. This paper describes the unusual case of a 66-year-old female patient with a left-sided intra- and extracranial tumor involving the temporal lobe, destroying the underlying skull base, and growing into the paranasal sinuses, orbit, and temporal bone. Biopsy revealed glioblastoma multiforme with strong GFAP positivity. Molecular biologic investigations of the p53, EGFR, and mdm2 genes showed functional inactivation of the p53 gene but no overexpression of oncogenes. Because the tumor was considered inoperable, palliative irradiation was carried out. The patient died 7 months after diagnosis. The causes of this phenomenon are discussed and the literature reviewed.
The resection of skull base neoplasms requires an intimate knowledge of basicranial vascular anatomy. Tumor distortion of surgical landmarks may increase the potential for inadvertent vascular injury with life-threatening intraoperative bleeding or delayed neurologic sequelae. Moreover, massive transfusion therapy may significantly alter the hemostatic mechanism in the perioperative period. On the basis of a review of hemorrhagic complications encountered in 154 consecutive skull base procedures, we describe techniques that are designed to avoid or efficiently control venous and arterial bleeding in extended skull base surgery. The management of complications resulting from blood replacement are reviewed.
Despite conventional multimodality treatment (surgery and fractionated radiation therapy), recurrence and clinical progression of cranial base chordomas and chondrosarcomas are common. The malignant behavior of these tumors is a result of their critical location, locally aggressive nature, and high recurrence rate. To explore the role of radiosurgery in the treatment of these skull base neoplasms, we assessed its use in four patients with chordoma and two with chondrosarcoma. In five of the patients, radiosurgery was used as adjuvant therapy for residual or recurrent tumors after surgical debulking, and in one patient with a chordoma, it was the primary treatment. No patient received fractionated external beam radiotherapy. All tumors were less than 30 mm in diameter and were treated with 20 Gy to the tumor margin. Skull base computed tomography and magnetic resonance images were essential to define the anatomic relationships between tumor and adjacent basal structures. During follow-up (mean, 22 mo; range, 8-36 mo), we found no progression of the treated tumor volume in any patient. Neurological deficits before treatment improved in three patients; the other three patients remained in stable neurological condition. Serial follow-up imaging studies demonstrated that two patients showed reduction in tumor size and four patients had no tumor growth. In one patient, a metastatic parietal lobe chondrosarcoma developed and was treated by microsurgery. Another patient showed tumor progression outside of the radiosurgical treatment volume. Our results attest to the value of stereotactic radiosurgery as an adjuvant or primary treatment for selected patients with chordoma or chondrosarcoma and demonstrate its potential advantages over standard fractionated irradiation. Analysis of the long-term clinical and imaging effects after radiosurgery is warranted.
Skull base tumour is rare and until recently was considered unresectable. The authors present a patient with skull base tumour of extra and intracranial compartment penetrating into parapharyngeal space and maxillary bone. Radiologic findings on CT, MRI, arteriography were studied. A surgical technique to expose the cranial base and intraoperative findings are described. Significant improvement occurred after incomplete tumour resection.
The surgical resection of skull base tumors often presents technically challenging problems and can result in major deformities. In planning the operation, each individual patient must be evaluated not only with respect to the extent of the disease, but also with respect to the functional losses, which may severely affect the patient's quality of life. The patient presented is an elderly woman with a malignant anterior skull base basal cell carcinoma and multiple recurrences. The tumor extended to the orbits bilaterally, resulting in blindness in the right eye. The objective was to resect the tumor from the skull base and the orbits, while preserving vision in the left eye. Utilizing intraoperative frozen sections, extensive tumor resection in the left orbit was accomplished without compromising vision. This was followed by the reconstruction of the eyelids and periorbital tissues. Exenteration of the right orbit, anterior craniectomy, and partial dural resection were also performed. Ten years later, the patient remains free of tumor recurrence and has good vision in her left eye.
A 60-year-old woman, who had undergone curettage of a mandibular ameloblastoma about 20 years before, presented with recurrence of an ameloblastoma in the mandibular symphysis. This tumor was removed by a marginal resection. About 2 years later, the tumor recurred in the right mandibular ramus, and the patient underwent right mandibulectomy. About 6 months later, the tumor again recurred. Radical resection was performed, but invasion of the infraorbital region and cranial base was noted. An anterior craniotomy was then performed and the lesion removed. Histologically, proliferation of squamous cells associated with atypia was seen, and ameloblastic features were no longer observed. Metastasis to the lung was noted 1 year later.
Three-dimensional imaging is a new digital technology which interpolates two-dimensional computer tomography information to render a "life-like" anatomic display of the diagnostic information. We have found that this new methodology significantly improves the assessment and therapy of patients undergoing surgical procedures of the head and neck. The technique has been used in cranial-facial and laryngeal pathology, and in preoperative planning of tumor resection, particularly skull-base neoplasms. The use of three-dimensional computer tomography improves the display of the location and volume of pathology and affords accurate therapeutic and surgical planning. The choice and extent of surgery is better defined, and precise bone removal can be performed. In reconstructive surgery, an accurate prefabricated model of the bony defect can be made to aid reconstruction. Representative cases demonstrating the use of three-dimensional computer tomography in head and neck surgery, and its benefits in saving operative time and improving the postoperative result, will be discussed.
Osteomas involving the anterior cranial base are quite rare lesions. Intracranial and orbital extension of these tumors, causing neurological and ophthalmological symptoms and signs is a rare event. Two such cases are reported. In the first one, the tumor arose from the frontal sinus and extended upward to the medial and superior wall of the right orbital cavity and the lower part of the right frontal convexity. In the second case the osteoma arose from the left orbital roof and extended to the lower part of the homolateral frontal convexity and the splenoid wing. After the operation the symptoms disappeared and the cosmetic deficits were corrected. Skull-films, CT and MR well define the bony extension and the displacement of the orbital and intracranial structures. Indications to the surgery include progressive ophthalmologic and neurologic signs and significant cosmetic deformations. The surgical techniques and the postoperative complications are briefly discussed.