18 Extracranial Anterior Cranial Base Surgery for Vascular Tumors

Vascular tumors of the head and neck include both benign and malignant neoplasms. In the head and neck region, paragangliomas are the most common vascular tumors and are discussed in Chapter 19 given their involvement of the lateral cranial base. In the sinonasal region, the most common vascular tumor is the angiofibroma. Whereas paragangliomas prominently involve the temporal bone and lateral skull base, angiofibromas more commonly affect the sinonasal region and ventral skull base. Angiofibromas are the focus of this chapter and provide a good model for discussion of principles of management of all vascular tumors.¹ These include preoperative assessment of tumor vascularity, tumor staging based on vascularity, preoperative devascularization, surgical strategy including role of endoscopy, hemostatic surgical techniques, and prevention of complications. Other benign and malignant tumors that are associated with increased vascularity are also discussed.

Keywords: Endoscopic endonasal surgery, juvenile nasopharyngeal angiofibroma, embolization, ethmoidal arteries, sphenopalatine artery, sinonasal malignancy

18.1 Key Learning Points

●For vascular tumors such as angiofibroma, intraoperative bleeding is a major risk factor for complications and oncologic control.

●The University of Pittsburgh Medical Center staging system for angiofibroma incorporates tumor vascularity as a significant prognostic factor.²

●Angiography with embolization provides useful information regarding the vascular supply of a tumor and devascularization of the extracranial component of the vasculature.

●Large tumors can be divided into vascular territories to facilitate stepwise surgical removal.

●Intraoperative sacrifice of the ethmoidal arteries further devascularizes a tumor prior to dissection.

●Patient positioning, specialized hemostatic instruments, and warm saline irrigation are useful adjuncts in managing intraoperative hemorrhage.

●Staging of surgery is sometimes necessary with highly vascular tumors.

●Endoscopic and open approaches may be combined in a complementary fashion to optimize access and minimize morbidity.

●A team-based approach including a surgical team facilitates more effective management of highly vascular tumors.

18.2 Introduction

The sinonasal tissues naturally have a rich blood supply due to bilateral contributions of the external carotid artery (ECA) and internal carotid artery (ICA) with abundant anastomoses. Some tumor types are particularly characterized by increased vascularity and pose additional challenges. Vascular tumors of the sinonasal region may extend to the ventral skull base through direct tissue invasion or erosion and may be in close proximity to major vessels and nerves. Traditional surgical management required open approaches with wide exposure to provide necessary control of the blood supply. With advances in endovascular techniques and improved management strategies with surgical innovation, the majority of these tumors can be successfully managed using less invasive endoscopic techniques.

18.3 Vascular Challenge

Bleeding is the greatest challenge during surgery for sinonasal tumors, especially vascular tumors such as angiofibroma. Poor visualization due to bleeding obscures landmarks, increasing the odds of injury to the orbit, optic nerve, dura/brain, or a major vessel or cranial nerve. Poor visualization compromises oncologic resection, increasing the risk of positive resection margins and residual tumor. Excessive intraoperative blood loss may require transfusion of blood products and contribute to perioperative morbidity such as infection, and pulmonary and cardiac problems. There is also an increased risk of bleeding complications postoperatively due to inadequate replacement of coagulation factors. In some cases, surgery may need to be staged due to excessive blood loss.

The challenges of surgical treatment of vascular tumors are maintaining visualization during tumor dissection and minimizing intraoperative blood loss. Widespread adoption of endoscopic techniques introduces new challenges in dealing with tumor vascularity. A variety of hemostatic tools and techniques have greatly improved the ability to control intraoperative hemorrhage.

18.4 Injury Avoidance

Avoidance of bleeding complications starts with a thorough preoperative assessment. Clues to the vascularity of a tumor are often provided by the history and physical examination. A history of mild intermittent epistaxis is a common presentation for vascular sinonasal tumors such as angiofibromas or sinonasal malignancies. A history of other malignancies such as renal cell carcinoma, prostate cancer, or breast cancer raises the possibility of metastasis to the skull base. Associated nonspecific symptoms include nasal obstruction, headache, nasal discharge, loss of olfaction, epiphora, and eustachian tube dysfunction. Extension beyond the nasal cavity may result in orbital symptoms (diplopia, proptosis, and visual loss), facial hypesthesia (V₂), and trismus. Nasal endoscopy often reveals a hypervascular tumor with blood clots, but tumor may be hidden from view within the sinuses or submucosally.

A proper preoperative diagnosis is essential to avoid untoward consequences. A preoperative biopsy in an outpatient setting is not always possible due to inaccessibility of the tumor or is ill-advised due to risk of bleeding. In such cases, radiologic imaging can narrow the range of possibilities and may offer a near-definitive diagnosis. Computed tomography (CT) and magnetic resonance imaging (MRI) provide complementary information and are often obtained in concert. Brisk enhancement with contrasted CT and evidence of flow voids with MRI from large vascular channels are indicators of increased vascularity. Masses that are in proximity to a major vessel need to be considered carefully since they may represent an aneurysm or pseudoaneurysm; diagnostic biopsy is to be avoided in such situations. A CT angiogram (image guidance protocol) is often obtained in anticipation of surgery to provide precise localization of the ICA relative to the tumor.

Neurophysiological monitoring should be employed in all cases where there is potential for vascular injury. Monitoring of cortical function with somatosensory evoked potentials provides an early warning system for global ischemia and can guide intraoperative decision-making in the event of ICA injury. Intraoperative navigation with a CT angiogram improves identification of the course of the ICA relative to the tumor. Intraoperative Doppler and indocyanine green fluoroscopy provide additional confirmation of the course of the ICA during tumor dissection.3

18.5 Related Pathologies

Benign vascular lesions include arteriovenous malformations, aneurysms, and pseudoaneurysms. True vascular tumors of the extracranial anterior cranial base region are rare and include both benign and malignant pathologies (Table 18.1).

Table 18.1 Vascular pathologies of the anterior cranial base

18.5.1 Fibro-osseous Tumors

Fibro-osseous tumors include osteoma, ossifying fibroma, and fibrous dysplasia.⁴ Of these, ossifying fibroma and fibrous dysplasia may be hypervascular. Juvenile ossifying fibroma (JOF) is seen in younger patients and is a locally aggressive tumor that can be quite extensive with skull base involvement and optic nerve compression (Fig. 18.1). Recurrence is common in the absence of complete surgical excision.

With fibrous dysplasia, normal bone marrow and cortical bone are replaced by immature fibro-osseous tissue intermixed with woven bone (Fig. 18.2). Fibrous dysplasia exists as monostotic or polyostotic forms. Patients may present with painless swelling and facial asymmetry, but it is often discovered incidentally when imaging is obtained for other reasons. Rarely, visual loss due to nerve compression occurs. Rapid growth may be observed during adolescence and may indicate cystic degeneration. Rarely, malignant transformation can occur. Surgery is performed for relief of compressive symptoms or cosmesis.

Aneurysmal bone cysts are nonneoplastic expansile bone lesions characterized by cystic cavities, usually filled with blood (Fig. 18.3). They occur predominantly in children and may be associated with JOF, fibrous dysplasia, and giant cell tumors. Complete surgical excision is necessary to prevent further cystic expansion and destruction of bone.

In all of these fibro-osseous lesions, distortion of anatomy with loss of surgical landmarks in association with increased bleeding increases the risks of surgery.

18.5.2 Angiofibroma

Angiofibromas are benign highly vascular tumors arising from the basisphenoid region in proximity to the sphenopalatine foramen. They occur almost exclusively in adolescent males. Nasal obstruction and epistaxis are the most common presenting symptoms. Due to their location and nonspecific symptoms, tumors are often advanced at presentation. Tumors grow through existing foramina and fissures to extend to the nasopharynx and paranasal sinuses, pterygopalatine space and infratemporal fossa, and the orbit and middle cranial fossa.

The vascularity of these tumors is derived from branches of both the external and internal carotid arteries. The predominant blood supply is typically from the internal maxillary artery. In large tumors, blood supply from the ICA is derived from the vidian artery in the pterygoid canal and other small branches from the cavernous ICA.

The preferred treatment for angiofibroma is complete surgical excision.1 ^{,​ 5 ,​ 6} The greatest operative challenge with these tumors is hemorrhage due to residual vascularity. Intraoperative bleeding and proximity to the ICA increase the risk of vascular injury.

18.5.3 Glomangiopericytoma

Glomangiopericytoma is a highly vascular tumor of borderline or low malignant potential that can occur in the nasal cavity.⁷ These indolent tumors should not be confused with solitary fibrous tumor, previously called hemangiopericytoma, which has greater malignant potential. Surgical excision is the treatment of choice.

18.5.4 Solitary Fibrous Tumor

Similar to glomangiopericytoma, solitary fibrous tumors are rare fibroblastic tumors that may be highly vascular.⁷ Complete surgical excision is usually curative.

18.5.5 Sinonasal Malignancy

Malignancies of the sinonasal region include a wide variety of pathologies, including squamous cell carcinoma, adenocarcinoma, olfactory neuroblastoma, neuroendocrine carcinoma, sinonasal undifferentiated carcinoma, adenoid cystic carcinoma, melanoma, lymphoma, plasmacytoma, and sarcoma. Although not vascular tumors, there is risk of increased bleeding due to their invasive nature, friability, and proximity to major vessels. Intraoperative blood loss is understandably greater with advanced stage tumors.

18.5.6 Metastasis

Metastatic tumors to the nasal cavity and sinuses include tumors that metastasize to bone such as cancers of the prostate, thyroid, breast, and kidney.⁸ In particular, metastatic renal cell carcinoma is notorious for its hypervascularity. Metastasis to the sinonasal cavity may be the first presentation. When surgery is considered, preoperative embolization may help minimize blood loss.

18.6 Case Examples

A 14-year-old boy presented with complaints of left nasal congestion and left hearing loss. Visual acuity was 20/40 OS and 20/20 OD. He had no complaints of diplopia, facial hypesthesia, or trismus. Physical examination including nasal endoscopy revealed an obstructive left nasal mass with displacement of the nasal septum to the contralateral side (Fig. 18.4). CT and MRI revealed an obstructive tumor filling the left nasal cavity/ nasopharynx, and sphenoid sinus with extension to the masticator space and middle cranial fossa (Fig. 18.5). Based on the presentation, endoscopic appearance, and radiographic appearance, a presumptive diagnosis of angiofibroma was made.

Related posts:

Bypass in the Treatment of Skull Base Tumors Endovascular Options to Treat Iatrogenic Vascular Injury and Tumor Involvement of the Skull Base Posterior Fossa During Open Skull Base Surgery Simulation and Training—Preparing for Vascular Injury Perforator Injury During Endoscopic Endonasal Skull Base Surgery Extracranial Lateral Cranial Base Vascular Tumor Surgery

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