21.1 Introduction

A large variety of benign and malignant tumors affect the temporal bone. Benign tumors are far and away more common than malignant tumors. Excluding cholesteatoma, the most common benign tumors that affect the temporal bone are schwannomas (trigeminal, facial, vestibular, vagal), paragangliomas, and meningiomas. Entire textbooks are dedicated to the evaluation and management of these tumors. Additionally, because tumors of the petrous apex, cerebellopontine angle, and jugular foramen are covered in other chapters, this chapter concentrates on tumors of the temporal bone.

This chapter will discuss the evaluation and management of benign and malignant tumors of the temporal bone. The primary benign tumors of the temporal bone are paragangliomas, meningiomas, and schwannomas. Temporal bone cancer is mainly squamous cell carcinoma (SCC). Primary temporal bone cancers are rare. However, given the temporal bone’s anatomical relationship to the parotid and sun-exposed skin of the ear and face, it is frequently involved by primary tumors from these locations. Primary temporal bone tumors make up about 2% of all head and neck cancers. Primary temporal bone cancers occur at a rate of 1/1,000,000 persons per year. SCC accounts for more than 60% of primary temporal bone cancers. The remainder are primary ear canal cancers (ceruminous adenoid cystic carcinoma, ceruminous adenocarcinoma), middle ear cancers (middle ear adenocarcinoma, neuroendocrine carcinoma), and primary temporal bone tumors (chondrosarcoma, osteosarcoma, rhabdomyosarcoma).

Emphasis is placed on the surgical management of these tumors, but properly speaking, these tumors demand multidisciplinary care. Postoperative radiotherapy (PORT) is given for malignant tumors stage T2 or higher on the Pittsburgh scale. Chemotherapy has emerged as an important treatment for T4 tumors. Several recent reports have demonstrated the efficacy of chemotherapy—usually a taxane, a platinum compound, and 5-FU—and radiotherapy for these large unresectable tumors.

21.2 Surgical Anatomy

The temporal bone is situated in the center of the skull base and is roughly pyramidal. It has six bony processes: zygomatic, mastoid, styloid, tympanic, squamous, and petrous (Fig. 21.1). It articulates with the sphenoid bone, along its squamous and petrous portion; with the maxilla, along its zygomatic process; with the occipital bone posteriorly; and with the clivus medially. Extracranially, the squamosal portion is covered by the temporalis muscle. The sternocleidomastoid muscle attaches at the mastoid tip. The digastric muscle attaches at the digastric grove, medial to the mastoid tip. The medial surface communicates with the infratemporal fossa. The mandible articulates at the glenoid fossa, which is on the anteroinferior surface.

Intracranially, the temporal bone has two surfaces: a superior surface that makes up the majority of the middle cranial fossa and a posterior surface that makes up part of the posterior cranial fossa (Fig. 21.2). Accordingly, the temporal bone is closely related to the temporal lobe on its superior surface and to the cerebellum on its posterior surface.

The bony ear canal (external auditory canal) is made up the tympanic portion anteriorly and inferiorly. This bony process joins with the squamous portion superiorly (tympanosquamous suture line) and mastoid portion posteriorly (tympanomastoid suture line). The bony ear canal is covered with thin skin (0.2 mm average thickness) and does not contain hair follicles or cerumen glands. The ear canal ends at the tympanic membrane. The cartilaginous canal makes up a third to half of the length of the ear canal and is covered with thicker skin containing hair follicles and cerumen glands.

The internal auditory canal (IAC) is located at the medial petrous portion of the posterior surface of temporal bone. The facial nerve (and its nervus intermedius) and cochleovestibular nerve enter through the IAC. The cochlear portion occupies the anteroinferior quadrant of the IAC and terminates at the perforated area of the cochlea. The vestibular nerve occupies the posterior half of the IAC and divides into a superior and an inferior branch to terminate in the vestibular organs.

The facial nerve is located in the anterosuperior quadrant of the IAC and has a long and complicated course through the temporal bone. It emerges out of the IAC and travels anteriorly through a short labyrinthine segment to reach the geniculate ganglion. The greater superficial petrosal nerve (GSPN) branches from the geniculate ganglion to supply preganglionic parasympathetic axons to the pterygopalatine (also called sphenopalatine) ganglion. The facial nerve continues posteriorly, superior to the cochleariform process (tendon of the tensor tympani muscle), and continues as the tympanic portion inferior to the horizontal semicircular canal and superior to the oval window and stapes. The nerve makes a gentle turn inferiorly (the second genu) to continue in its mastoid portion; here the nerve gives off a small branch to the stapedius muscle and a larger branch, the chorda tympani nerve, which contains special sensory afferents for taste on the anterior two-thirds of the tongue and preganglionic parasympathetic fibers for the submandibular ganglion. From there, the nerve exits the temporal bone at the stylomastoid foramen and continues its extratemporal course to the muscles of facial expression.

The petrous portion of the temporal bone contains the cochlea and vestibular organs. This portion of the temporal bone is quite dense. The otic capsule is surrounded by aerated bone. This aeration is highly variable.

The internal carotid artery enters the temporal bone medial to the tympanic process. It has a short intratemporal vertical segment that closely approximates the cochlea, after which it turns anteromedially underneath the Eustachian tube. The carotid continues in its horizontal petrous portion, which is closely marked by the GSPN, until it reaches the cavernous sinus.

The sigmoid sinus is the continuation of the transverse sinus and is the major venous outflow from the brain. This sinus lies in a deep grove along posterior portion of the temporal bone. Its serpentine tract continues underneath the temporal bone to exit at the jugular foramen (pars vasculosa). Cranial nerves IX, X, and XI exit the skull base in the anteromedial portion of the jugular foramen (pars nervosa).

Cranial nerves V and VI are closely related to the petrous apex. The trigeminal nerve is bounded by Meckel’s cave at the petrous apex. This nerve passes over the most medial aspect of the petrous apex and its divisions pass through their respective foramina of the sphenoid bone: V₁ (ophthalmic) through the superior orbital fissure, V₂ (maxillary) through the foramen rotundum, and V₃ (mandibular) through the foramen ovale. Located close to the foramen ovale is the foramen spinosum, which is in the temporal bone and admits the middle meningeal artery from the internal maxillary artery. Cranial nerve VI passes through a meningeal tunnel, Dorello’s canal, which is also closely applied to the petrous apex.

21.3 Regional Pathology and Differential Diagnosis

A wide range of benign and malignant tumors affect the temporal bone. Entire textbooks are dedicated to the evaluation and management of these tumors. Additionally, because tumors of the petrous apex, cerebellopontine angle, and jugular foramen are covered in other chapters, this chapter concentrates on primary cancers of the temporal bone.

Half the tumors that involve the temporal bone arise from sites outside the temporal bone. Parotid gland and periauricular skin account for 25% apiece of tumors that invade the temporal bone.1 Periauricular skin cancers are particularly bad players, because they tend to follow along embryologic fusion and often invade the temporal bone. Large neglected external ear cancers can grow into the ear canal (Fig. 21.3). Ear canal, middle ear and mastoid, and temporal bone tumors are rare. Finally, tumors from the temporomandibular joint can grow into the ear canal (Fig. 21.4).

SCC is by far the most common tumor type seen in the ear canal and temporal bone. Basal cell carcinoma, adenoid cystic carcinoma, adenocarcinoma, and melanoma are the next most common tumors of the ear canal. In the middle ear and mastoid, adenocarcinoma and neuroendocrine carcinoma are the next most common tumors in that location. Excluding SCC, most common temporal bone primary tumors include endolymphatic sac tumors (ELSTs) and adenocarcinomas. Unusual tumors that occur within the temporal bone include plasmacytoma and metastatic tumors. Tumors that grow from the temporomandibular joint to involve the ear canal and middle ear include giant cell tumor, chondrosarcoma, and pigmented villonodular synovitis.

Tumors of the ear canal and temporal bone generally present with ear blockage, pain, or drainage. These tumors are nonspecific and often occur with chronic otitis externa or chronic otitis media. Because chronic ear infections are so common and temporal bone cancers so rare, many patients are treated for infection (sometimes for months or years) before a definitive diagnosis of cancer is made.

Any unusual tissue in the ear canal that does not respond within a few weeks to standard treatment for otitis externa (ear cleaning and antibiotics drops) should be biopsied.

21.4 Clinical Assessment

The clinical assessment of the patients who have skull base tumors is covered in detail in Chapter 4 of this book. Some of these tumors have typical appearances that help in formulating the diagnosis (Fig. 21.5). Because benign ear canal tumors arise from cerumen glands, these tumors are usually subcutaneous and present as an external auditory meatus obstruction. Benign tumors, such as paragangliomas, are easily seen as a retrotympanic mass or as vascular engorgement of ear canal vessels. SCC of the ear canal appears as a reddish, friable tissue that can be confused for granulation tissue and often obscures the view of the tympanic membrane. Basal cell carcinoma appears as a raised ulcerated lesion. Adenoid cystic carcinoma is frequently subcutaneous.

Tumors of the ear canal are examined under the operative microscope. Care is taken to note the extent of disease with respect to the bony–cartilaginous junction. Tumors solely within the cartilaginous canal can be excised with wide local excision. Tumors that involve the bony canal are removed with a lateral temporal bone resection (LTBR).

All patients who undergo temporal bone surgery undergo an audiogram. This test measures the preoperative hearing level. Occasionally, the tumor is in the better (or only) hearing ear. These patients need appropriate counseling about hearing outcomes and rehabilitation. Patients who have significant preoperative hearing loss should have appropriate amplification for the uninvolved ear, for surgery will produce at least a maximum conductive hearing loss.

Patients who have T2 or higher-staged SCC, recurrent tumors, and tumors that have cervical lymph node involvement or perineural spread are referred to radiation oncology for a preoperative evaluation.2 ^,​ 3

Late-stage SCC, T3 and T4, are referred to medical oncology for consideration of preoperative or neoadjuvant chemotherapy.4 ^,​ 5 ^,​ 6 ^,​ 7 ^,​ 8 ^,​ 9 Patients who respond to therapy are then considered for surgical resection. Patients who do not respond to therapy can still undergo surgery, but long-term results for these patients are very poor.

21.5 Diagnostic Imaging

Cross-sectional imaging is needed to understand the extent of temporal bone disease. CT is used as the primary technique for imaging, because it offers excellent soft tissue and bony definition. CT will generally demonstrate aggressive bony erosion with cancers of the ear canal and mastoid (Fig. 21.6a,b). Soft tissue invasion and lymph node metastasis are also well defined on CT. MRI adds improved resolution when the dura is involved or for perineural invasion (Fig. 21.6c,d).

The differential diagnosis of ear canal and temporal bone lesions is long and includes benign and malignant processes.10 ^,​ 11 ^,​ 12 Benign processes include skull base osteomyelitis, histiocytosis, tuberculosis, Wegener’s granulomatosis, osteoradionecrosis, paragangliomas, and ELSTs. SCC is the most common malignant process, but other cancers in the temporal bone include basal cell carcinoma, adenoid cystic carcinoma, adenocarcinoma, melanoma, lymphoma, myeloma, chondrosarcoma, osteosarcoma, and metastatic lesions (Table 21.1).

Arriaga et al examined CT scans systematically in patients who had temporal bone cancer.13 They identified 12 important areas to evaluate for extent of disease: the four quadrants of the ear canal, middle ear, otic capsule, mastoid, jugular fossa, carotid canal, tegmen for middle fossa, posterior fossa, and infratemporal fossa. In comparing the CT findings to histopathologic slides, they concluded that CT accurately diagnosed the extent of disease.

Leonetti et al retrospectively reviewed stage III and IV SCC cases and compared intraoperative findings with radiographic analysis.14 They identified five invasion patterns: superiorly through the tegmen, anteriorly through the glenoid fossa and infratemporal fossa, inferiorly through the hypotympanum and jugular foramen, posteriorly though the mastoid air cells, and medially though the middle ear and carotid canal. They found that CT and MRI underestimated disease in the tegmen tympani, middle fossa dura, and intradural extension of disease.

Accurate assessment of imaging is required for staging of these tumors. A number of staging systems have been proposed for SCC.15 ^,​ 16 ^,​ 17 ^,​ 18 ^,​ 19 ^,​ 20 Although there is not an American Joint Committee on Cancer (AJCC) approved staging system, the Pittsburgh staging system has been widely used in the literature (Table 21.2).21 ^,​ 22

21.6 Preoperative Preparation

Patients who have temporal bone cancer are thoroughly questioned about their underlying medical history and carefully examined. Because temporal bone surgery usually requires several hours under general anesthetic, these patients must be of good general health. All underlying medical illnesses must be identified and optimized to minimize the chance of postoperative complications. When patients have multiple medical problems, a consultation with an internist is indicated to help manage these issues.

21.7 Surgical Technique: Benign Tumors

The most common benign tumor affecting the temporal bone is paraganglioma. Small paragangliomas that are found only within the middle ear (so-called glomus tympanicum) are easily excised via a transcanal approach (Fig. 21.7). A postauricular incision is made, and the ear canal is entered medially to the bony–cartilaginous junction. An incision is made anteriorly, and a large tympanomeatal flap is elevated to expose the inferior tympanic ring. The drill can be used to remove the inferior tympanic ring to expose the inferior extent of the tumor, if necessary. The tumor is carefully dissected away from the ossicular chain and out of the Eustachian tube. Bipolar cautery or CO₂ laser is used to coagulate the feeding vessels into the tumor. The tumor is then removed. Bleeding is easily controlled using absorbable gelatin sponge and thrombin solution. The tympanomeatal flap is repositioned and the ear canal filled with packing material. The postauricular wound is closed in layers.

Larger tumors that extend beyond the tympanic ring will require either a tympanomastoid approach or an infratemporal fossa approach (Fisch type C).23 For the tympanomastoid approach, a postauricular incision is made and a complete mastoidectomy performed. A tympanomeatal flap, as already described, is elevated to expose the tumor in the middle ear. Standard techniques are used to identify the facial nerve. The fallopian canal can be skeletonized to create an “intact fallopian bridge” (Fig. 21.8).24 Tumor resection is performed by working through both the middle ear and mastoid. Hemostasis is achieved using gelatin packing and thrombin. The tympanomeatal flap is replaced and the ear canal is packed. The postauricular wound is closed in layers.

Larger tumors that invade the jugular bulb require an infratemporal fossa approach. These larger tumors are evaluated with angiography preoperatively. Feeding vessels are embolized or coiled to help reduce blood loss. Because these patients are at high risk of developing lower cranial nerve deficits, all patients are evaluated preoperatively by a speech and swallowing therapist. Intraoperative nerve monitoring is employed for the facial and vagus nerves.

This approach requires removal of the ear canal and overclosure of the external auditory meatus. As a result, conductive hearing loss is an expected outcome. Furthermore, the facial nerve is elevated out of its canal, and temporary facial weakness is common.

A large postauricular C-shaped incision is made and elevated over the temporalis muscle, sternocleidomastoid muscle, and parotid gland. A palva flap is elevated, and the ear canal is divided medial to the bony–cartilaginous junction. After the canal is divided, the skin flap can be elevated over the parotid gland and held with a fishhook retractor. The skin of the external auditory meatus is undermined, everted, and sewn shut. The palva flap is sewn to the undersurface of the ear as a second layer.

Neck dissection is performed to identify the lower cranial nerves (IX–XII), the internal carotid artery, and the internal jugular vein. Vascular loops are placed around the great vessels (Fig. 21.9).

The skin of the bony canal, tympanic membrane, incus, and malleus are removed. A radical mastoidectomy is performed. The sigmoid sinus is skeletonized and 1 to 2 cm of retrosigmoid dura is exposed. The mastoid tip is removed, unifying the temporal bone with the neck. The facial nerve is skeletonized for 270° of its circumference from the second genu to the stylomastoid foramen (Fig. 21.10). Fisch instruments are used to remove the last thin shell of bone on the nerve and to open the periosteal cuff at the stylomastoid foramen. Blunt dissection along the nerve with a fine hemostat and sharp dissection with a no. 12 blade are used to dissect the extratemporal portion of the nerve until the pes anserinus is reached. The nerve is then gently elevated out of its canal. The digastric muscle is divided and grasped to avoid injuring the nerve, and the nerve is sewn up to the parotid gland.

Bone over the jugular bulb is then removed to expose the entire tumor. The styloid process and its muscular attachments are removed. The digastric is reflected anteriorly. Resection of the tumor requires ligation of the sigmoid. Suture ligatures are placed around the sigmoid and the sinus is divided (Fig. 21.11). The jugular vein is then ligated and divided in the neck. Tumor removal is then performed. Bleeding from the petrosal sinuses is controlled with packing.

Once the tumor is removed, reconstruction begins by harvesting an abdominal fat graft to fill in the mastoid defect. The dura can be repaired with a temporalis fascia graft, and strips of fat are packed on top of this.