The cavernous sinus is a very complex area, and surgical treatment requires detailed anatomical knowledge and familiarity with its relationship to surrounding structures. By exposing the lateral wall of the cavernous sinus with the extradural approach, it is possible to pass through the triangular corridor of the cavernous sinus and perform surgical treatment for diseases such as trigeminal schwannoma and meningioma inside and outside the cavernous sinus. In addition to the extradural infratemporal fossa approach, the extradural infratemporal fossa to the pterygoid fossa and the approach to the paranasal sinuses can be safely performed by inserting the endoscope into the bone corridor of the middle cranial fossa. Furthermore, in the last decade, transnasal endoscopic skull based approaches have further developed, facilitating surgical access to the cavernous sinus. The cavernous sinus is an unattachable site due to the complex structure of multiple nerves, veins, and internal carotid arteries, but if the anatomy of the cavernous sinus is known well we can treat this complex site. As for the choice of approach to the cavernous sinus, a better understanding of the anatomy surrounding the cavernous sinus will allow a rational choice between transcranial and transnasal approaches.
Pituitary adenomas are one of the most common brain tumors. They represent approximately 18% of all intracranial, and around 95% of sellar neoplasms. In recent years, our understanding of the pathophysiology and the behavior of these lesions has led to better control and higher curative rates. The treatment decision is largely dependent on type of the adenoma, clinical presentation, and the size of the lesion. In addition, incidental pituitary lesions add uncertainty in the decision-making process, especially for pituitary adenomas that can be medically managed. When surgery is indicated, the endoscopic endonasal transsphenoidal approach is the technique of choice, but open standard craniotomy approaches can also be the option in selected cases. The following chapter will review the classification, clinical presentation, pathophysiology, diagnostic work-up, selection of surgical approach, and treatment complications in pituitary adenomas.
Extended orbital exenteration is a highly disfiguring operation which entails complete removal of the orbital contents including periorbita, eyelids and involved surrounding bony walls with variations tailored to the specific clinical circumstances. The aim of such an extensive surgery is to achieve local control of the life-threatening progressive neoplasms, when other treatment modalities fail to achieve disease control. Eyelids can be preserved in posterior orbital pathology, while it may not be possible in neoplasms arising from the anterior eye tissues. Depending on the clinical circumstances, if the neoplasm is invading the surrounding bony orbit, the involved bony and soft tissue structures are removed en bloc to achieve complete resection (R0 resection). Although the steps of the orbital exenteration are well defined, the same is not true for extended orbital exenteration. We demonstrate the details of extended orbital exenteration in different clinical scenarios for the malignancy of orbit and periorbital tissues invading surrounding orbital walls.
Chordoma is a rare bone malignancy that influences the spine and cranium base. Once in a while, it includes bone and when it does, cranial bones are the favored location. Chordomas emerge from embryonic remnants of the primitive notochord and chondrosarcomas from primitive mesenchymal cells, otherwise from the embryonic rest of the cranial cartilaginous matrix. Chondrosarcomas constitute a heterogeneous group of essential bone malignancy characterized by hyaline cartilaginous neoplastic tissue. Both are characterized by invasion and pulverization of the neighboring bone and delicate tissue with higher locoregional reappearance frequency. Chordoma and chondrosarcoma, especially myxoid variation of chondrosarcoma of the cranium base, are as often as possible amalgamated because of similar anatomic location, clinical presentation, and radiologic sightings, and mixed up histopathological highlights. Chordoma and chondrosarcoma vary with respect to their origin, management strategy, and contrast particularly with respect to outcome. Ultimately, developing indication supports aberrant growth factor signaling as possible pathogenic mechanisms in chordoma. Here, we have shown such a location-based symptomatic predicament, understood effectively with ancillary immunohistochemistry. In this review, we summarize the most recent research findings and focus primarily on the pathophysiology and diagnostic aspects.
Benign skull base tumors include meningiomas, pituitary adenomas, craniopharyngiomas, and vestibular schwannomas. As an adjuvant therapy to surgery or when surgical treatment carries too high a risk of complications, a highly precise focused radiation, known as stereotactic radiosurgery or fractionated stereotactic radiation therapy, can be delivered to the tumor. The aim of this chapter is to systematically discuss benefits of the therapy, i.e., tumor control as well as complications and risk factors of the therapy relating to vision, hearing, hormone secreting regions, and cerebral vasculature. Meningiomas, pituitary adenomas, craniopharyngiomas, and vestibular schwannomas constitute the majority of primary skull base tumors amenable to stereotactic radiation therapy or radiosurgery and will be described in this chapter.
Sphenoid wing meningiomas account for 11%-20% of all intracranial meningiomas, whereas meningiomas of the anterior clinoid process comprise about 34.0–43.9%. Assignment of these cranio-basal tumors to a separate group is due to the parasellar location and challenges in their surgical removal, mainly because of its anatomical syntopy: compression of the optic nerve, carotid artery inclusion, and invasion to the cavernous sinus. This chapter consists of the combination of current knowledge and our experience in understanding, diagnosis, surgical strategy, and complication avoidance with these tumors.
Spheno-orbital meningiomas are mainly defined as primary en plaque tumors of the lesser and greater sphenoid wings, invading the underlying bone and adjacent anatomical structures. The patients, mostly women in their fifties, generally present with a progressive, unilateral, and nonpulsatile proptosis, often associated with cosmetic deformity and optic nerve damage. Surgical resection is currently the gold standard of treatment in case of optic neuropathy, significant symptoms, or radiological progression. The surgical strategy should take into account the morphology of the tumor, its epicenter at the level of the sphenoid wing, and the invasion of adjacent anatomical structures. Surgery stabilizes or improves visual function and oculomotricity in most cases but it is rare that the proptosis recovers completely. Gross total resection is hard to achieve considering the complex anatomy of the spheno-orbital region and the risk of inducing cranial nerve deficits. Rare cases of WHO grade II or III meningiomas warrant adjuvant radiotherapy. Tumor residues after subtotal resections of WHO grade I meningiomas are first radiologically monitored and then treated by stereotactic radiosurgery in case of progression.
This overview presents computer-based augmented reality (AR) and virtual reality (VR) tools, in-vitro and in-vivo models as useful teaching tools for neurosurgical training, especially in skull-base surgery. An easy set-up and practicable training model for ventricular drainage (VD) is demonstrated. The model allows to evaluate practices, pitfalls and traceability in a virtual but realistic set-up for simulating VD placement. Computer-assisted planning and simulation of skull-base approaches and integration within the daily neurosurgical routine with VR and AR models are discussed for neurosurgical education. A set-up for microvascular training on a plastic rat and a specific vascular anastomosis practice kit with different tube diameters of 1–3 mm of specific plastic vessels for the training of microvascular anastomoses is shown. End-to-end and end-to-side anastomoses were performed with different levels of difficulty, trying to simulate realistic conditions in bypass surgery. Additionally, the teaching strategy of experimental silicone aneurysm clipping in a 3D printed plastic skull and silicone brain model is demonstrated in video sequences. An experimental animal model with microsurgically created bifurcation aneurysms is discussed because this training model for clip occlusion of aneurysms on a living object, still has the greatest relevance to neurosurgical reality.
The objective of this article is to evaluate single-fraction or fractionated stereotactic radiotherapy of central nervous system (CNS) and head and neck lesions using intensity-modulated radiotherapy (IMRT) with a commercially available system (Peacock(TM), Nomos Corporation, Sewickley, PA). This system allows tomotherapeutic delivery of intensity-modulated radiation, that is, the slice-by-slice treatment of the volume of interest with an intensity-modulated beam, making the delivery of highly conformal radiation to the target possible in both single or multiple fractions mode. During an 18-month period, 43 (21 males and 22 females) patients were treated, using a removable cranial screw-fixation device. Ages ranged from 10 to 77 years (mean, 52.2; median, 53.5). Intra- and extra-axial lesions, including head and neck malignancies and spine metastases, were treated. Clinical target volume ranged from 0.77 to 195 cm(3) (mean, 47.8; median, 29.90). The dose distribution was normalized to the maximum and was prescribed, in most cases, at the 80% or 90% isodose line (range, 65 to 96%; median, 85%; mean, 83.4%) and ranged from 14 to 80 Gy (mean, 48; median, 50). The number of fractions ranged from 1 to 40 (mean, 23; median, 25). In all but one patient, 90% of the prescription isodose line covered 100% of the clinical target volume. The heterogeneity index (the ratio between the maximum radiation dose and the prescribed dose) ranged between 1.0 and 1.50, whereas the conformity index (the ratio between the volume encompassed by the prescription isodose line and the clinical target volume) ranged between 1.0 and 4.5. There were no complications related to the radiation treatment. With a median followup of 6 months, more than 70% of our patients showed decreased lesion size. Stereotactic IMRT of CNS and head and neck lesions can be delivered safely and accurately. The Peacock system delivers stereotactic radiation in single or multiple fractions and has no volume limitations. It has been used to treat intracranial, head and neck, and spinal lesions. The option of fractionation, the lack of volume constraint, and the capability of treating intracranial, head and neck, and spinal pathology make stereotactic IMRT a valuable adjunct to established stereotactic radiotherapy systems delivering convergent-beam irradiation using the Linac or Gamma Knife. In a clinical setting that offers Linac, Gamma Knife radiosurgery, and conformal stereotactic radiotherapy, the latter may have advantages for treating large (> 25-cm(3)) and irregular lesions, especially when fractionation is considered useful.
The translabyrinthine approach is familiar to most neurosurgeons and neuro-otologists and is frequently used to remove acoustic neuromas. Some of the complications associated with this surgery include cerebrospinal fluid (CSF) leaks, meningitis, and rarely fat graft prolapse. The authors report a 60-year-old woman who underwent a translabyrinthine approach and microsurgical resection of a right-sided 1-cm acoustic neuroma. Initially, she was discharged home after an uneventful postoperative course. Four days later, she sought treatment in the emergency room complaining of headaches, dizziness, and lethargy. A computed tomographic (CT) scan showed a large right-sided subdural hygroma and right temporal lobe edema. The patient underwent burr hole evacuation of the collection and placement of a subdural drain, after which the edema in the temporal lobe and hygroma resolved. We speculate that the underlying mechanism was the result of inadvertant damage to the venous drainage and an arachnoid tear that was not appreciated during surgery. Neurosurgeons and neuro-otogists should be aware of this unusual complication of translabyrinthine surgery and its possible underlying mechanisms.
In this study, 31 cases with different anterior skull base lesions mandating broad exposure, including the sphenoidal, parasellar, and clival region, were surgically treated using the frameless computer assisted surgery (CAS) system. The contribution of navigated surgery in relation to the broad exposure and direct visualization of this region rendered by the subcranial-subfrontal approach was evaluated. In group I, consisting of extensive tumors, the contribution of CAS was only given in five cases for the exposure of the tumor extensions located to the parasellar sphenoclival complex with concomitant distortion of the anatomic landmarks. No advantages were experienced in the more anterior locations along the ethmoidal compartment and frontal sinus. In the cases in group II, consisting of congenital anomaly implying fronto-orbital advancement and a meningoencephalocele as well as extensive mucoceles, the CAS was only helpful in those cases with an extremely aberrative anatomy in these regions.
Although craniopharyngiomas account for a large percentage of pediatric intracranial tumors, there is a bimodal age distribution. Most of these neoplasms are suprasellar or sellar in location. In this report we describe an unusual case of an infrasellar craniopharyngioma in a child. Only four previous cases of infrasellar craniopharyngiomas with no sellar involvement have been described. Infrasellar craniopharyngiomas are part of the continuum representing intracranial craniopharyngiomas and ameloblastomas of the jaw. A transnasal endoscopic biopsy was performed with a preliminary diagnosis of craniopharyngioma. The patient then underwent a radical resection of the infrasellar tumor via a subfrontal transbasal approach. This case illustrates a rare and unusual location for a craniopharyngioma. Craniopharyngiomas should be considered in the differential diagnosis of infrasellar neoplasms. Infrasellar craniopharyngiomas compromise part of the spectrum of tumors originating from enamel-forming neural crest cells.
A 60-year-old female with chronic lymphocytic leukemia sought treatment after experiencing double vision for 3 weeks. She also noted difficulty with her balance and ambulation. She was evaluated by her oncologist who referred her for magnetic resonance (MR) imaging (Fig. [1]). On physical examination, she was alert and oriented. Her speech was clear. Her extraocular muscles were intact, her tongue was midline, her hearing was grossly normal, and the remainder of her cranial nerves were intact. She had pronounced dysmetria on the right side. In addition, the patient had a positive Romberg's sign as well as an ataxic gait.
Non-Hodgkin's lymphoma (NHL) is a rare tumor of the skull base. As the incidence of primary central nervous system (CNS) lymphoma has increased, atypical presentations involving the skull or cranial base exclusively have been reported. In immunocompetent patients with no previous history or predisposing factors, the diagnosis of primary NHL of the skull base may be delayed. We present four cases of nasal and paranasal sinus NHL with both skull base and intracranial involvement in immunocompetent patients. Clinicopathologic correlation suggests that cranial base and intracranial involvement with NHL represents advanced-stage primary sinonasal disease. Surgical biopsy before definitive treatment is recommended. Radiation therapy provides local control; adjuvant chemotherapy after primary radiation therapy may be required for recurrent disease.
The incidence of cerebrospinal fluid (CSF) fistula after transtemporal skull base surgery can range from 4% to 19%. The risk of CSF leak may be related to tumor size and location, the extent of the dural defect, and the technical aspects of the wound reconstruction. Prevention of meningitis depends on the early detection and management of CSF leakage. Five hundred eighty-nine patients underwent a variety of transtemporal surgical approaches for the extirpation of skull base tumors at our institution from July 1988 to October 1999. The medical records were reviewed retrospectively to identify the tumor histology, size, and location, as well as the surgical approach, defect reconstruction technique, and the incidence of postoperative CSF leak. The risk of CSF fistulae was greatest in using the retrosigmoid approach (8%) and lowest in those who underwent a translabyrinthine approach (4%). Tumor size had no bearing on the incidence of the CSF leak and the overall incidence of meningitis was 1.0%. This article outlines our institutional objective for the prevention and management of CSF fistula after transtemporal skull base surgery. Illustrative cases will be presented.
Transverse-sigmoid sinus dural arteriovenous malformations (DAVM) are uncommon vascular lesions for which complete cure may be difficult to obtain. A wide variety of treatments for these lesions include observation, arterial compression, surgical resection, and endovascular embolization. We propose that transverse-sigmoid sinus DAVM can be completely cured by occluding the ipsilateral dural sinus with detachable balloon and Guglielmi detachable coils (GDC) coils before arterial feeder embolization with histoacryl. Three patients who presented with pulsatile tinnitus and normal magnetic resonance imaging (MRI) studies underwent angiography, which demonstrated transverse-sigmoid sinus DAVM. All three patients wer treated with retrograde transvenous sinus embolization with complete occlusion of the transverse-sigmoid sinus with detachable balloons and GDC coils with preservation of the vein of Labbé. Subsequently, the various feeders from the external carotid artery were embolized. The tentorial arteries arising from the ipsilateral internal carotid arteries were not embolized in any of the cases, which were still contributing to the DAVM. Complete cure with thrombosis of the tentorial branch of the internal carotid artery (ICA) was seen on follow-up angiogram 1 day after embolization in one patient and on 4-week and 6-week follow-up angiograms in the other two patients. Complete occlusion of the transverse sinus proximal to the vein of Labbé, in spite of incomplete arterial feeder embolization, can result in complete cure of the transversesinus dural AVF if adequate time is given for the remaining feeders to occlude, once the fistula is obliterated.
The authors review their experience with endoscopic repair of skull base defects associated with cerebrospinal fluid (CSF) rhinorrhea involving the paranasal sinuses. A total of 22 patients was treated endoscopically between 1992 and 1998. The repair method consisted of closure of the CSF fistula with a free autologous abdominal fat graft and fibrin glue, supported with a sheet of silastic. The primary closure rate was 82% (18/22), and the overall closure rate was 95.5% (21/22) without recurrence or complications within an average follow-up of 5 years (14-83 months). A single patient still complains of cerebrospinal rhinorrhea, although this was never proved by any clinical, endoscopic, or biological (beta(2)-transferrin) examination. The repair of ethmoidal-sphenoidal cerebrospinal fluid fistulae by endonasal endoscopic surgery is an excellent technique, both safe and effective. Fat is a material of choice, as it is tight and resists infection well. The technique and indications for endoscopic management of cerebrospinal fluid leaks are discussed.
Papillary tumors of the middle and inner ear have been interpreted histogenetically in many ways. In 1989 Heffner proposed the endolymphatic sac epithelium as a possible origin. These rare tumors are clinically aggressive and can cause extensive temporal bone destruction. Because of this behavior, endolymphatic sac tumors (ELST) were classified as low-grade adenocarcinomas, although metastasis has not yet been documented. Two papillary neoplasms of the temporal bone are presented, which we believe are examples of adenomatous tumors arising from the epithelium of the endolymphatic sac. One was associated with a pituitary adenoma. A third case of a papillary middle ear neoplasm is described that shows histologic features similar to the other two, but it was located in the tympanum and had no connection to the endolymphatic sac. This report focuses on clinical, radiologic, and histologic findings of papillary tumors of the temporal bone with additional emphasis on modern concepts of histogenesis and aspects of differential diagnosis.
This study was performed to determine if the arcuate eminence can be drilled down without opening the semicircular canal to obtain a flatter operative field during an anterior or posterior transpetrosal approach. The depth of the superior semicircular canal from the top of the arcuate eminence was measured in 43 dry temporal bones. We found that the arcuate eminence was situated approximately 20 mm from the petrosigmoid intersection, and the superior semicircular canal was located 2.0 mm deep from the top of the arcuate eminence (range, 0.2 mm to 4.2 mm). The arcuate eminence consists of either (1) the otic capsule and additional overlying bone, (2) the naked otic capsule of normal thickness, or (3) the thinned otic capsule. In cases strictly selected by preoperative computed tomography, it may be possible to drill down the arcuate eminence with meticulous manipulation. The relationship between opening the semicircular canal and hearing preservation is also discussed.
The authors report on their experience with the trans-sinusal frontal approach in removing olfactory groove meningiomas. Six tumors were operated on by the trans-sinusal frontal approach, using a bicoronal incision; two tumors developed on one side, and there were four bilateral olfactosellar tumors. Osteotomy of the anterior wall of the frontal sinus was performed with an oscillating saw without any burr hole. The posterior wall of the sinus was resected and the tumor was attacked through a real subfrontal route along the plane of the anterior skull base. Ethmoidal blood supply was controlled at the initial stages of the operation, allowing avascular tumor debulking. Olfactory nerves, invaded by the tumor, were removed along with the tumor. Tumor extensions toward the sella and the optic canals were removed without brain retraction, opening of the Sylvian fissure, or dissection of the carotid arteries. All patients made a good neurologic recovery; intellectual impairment disappeared within 1 month, and visual acuity normalized within 2 weeks. Olfactory nets were preserved on the contralateral side in unilateral tumors. The trans-sinusal frontal approach is technically easy and safe to achieve. Osteotomy and replacement of the anterior wall of the frontal sinus are rapidly performed. When the frontal sinus is small, image-guided surgery allows precise deliniation of its limits and the free bone flap, including the calvarial outer layer, tangentially cut from one supraorbital canal to the other. The cosmetic result is perfect, as the normal contour of the forehead is maintained without any scar or visible burr hole. The trans-sinusal frontal approach gives access to the orbital roofs and to the central anterior skull base from the crista galli to the tuberculum sellae and the anterior clinoid processes. The trans-sinusal frontal approach represents an alternative to conventional craniotomies for tumors developed in the central anterior skull base, especially for olfactory groove meningiomas, whatever their size.
