Malignant Tumors of the Temporal Bone

Since temporal bone cancer is so rare, measuring specific etiologic factors for cancers in this area is very difficult. However, fair-skinned whites are more prone to nonmelanomatous skin cancers in other areas, especially areas exposed to ultraviolet radiation. A genetic predisposition to skin cancer may also exist, manifested as the development of skin cancers in sites not exposed to sunlight as well as sun-exposed areas. Chronic otitis media and cholesteatoma are common in patients with temporal bone cancers and have been implicated as etiologic factors. ^{[6, 7]} Chronic suppurative otitis media and the resulting chronic inflammation may lead to squamous metaplasia. Human papillomavirus has been implicated in squamous cell carcinomas of the middle ear. ^[8] Lim et al (2000) reported a series of temporal bone cancers in 7 patients who had undergone radiotherapy for nasopharyngeal carcinoma. ^[9] These patients had a particularly poor outcome.

The complex anatomy of the temporal bone makes tumor spread difficult to predict. Tumors of the skin around the auricle may extend along the soft tissues of the neck and ear. The soft tissues are a poor barrier against tumor spread, and eventually the tumors may extend along the conchal bowl and into the EAC. The cartilage of the EAC provides minimal resistance to tumor spread. The fissures of Santorini, foramen of Huschke, and bony-cartilaginous junctions are a source of direct access to the periparotid tissues and temporomandibular joint.

Cancer in the external auditory meatus can invade posteriorly through the soft tissue into the retroauricular sulcus over the mastoid cortex. The bony canal is more resistant to cancer extension; however, erosion through the posterior bony canal provides access to the mastoid cavity. Tumor growth medially along the EAC can extend through the tympanic membrane and bony tympanic ring, allowing invasion into the middle ear. Once a tumor enters the middle ear, the hard bone of the otic capsule provides a more effective barrier against tumor spread.

In the middle ear or mastoid, tumors spread easily via the eustachian tube, round and oval windows, neurovascular structures, and extensive air spaces of the mastoid cavity. The eustachian tube and neurovascular structures of the middle ear are potential means of tumor spread beyond the temporal bone to the infratemporal fossa, nasopharynx, or neck.

Aggressive tumors can erode through the tegmen tympani or mastoid into the middle or posterior fossa. The sigmoid sinus may become involved. The dura, although somewhat resistant to invasion, portends a grave prognosis if involved. The facial nerve and the stylomastoid foramen are metastatic routes to the soft tissues of the neck and the parotid. Proximal extension along the facial nerve leads toward the inner ear and posterior fossa. Leonetti et al (1996) offer an excellent review of the invasion patterns of temporal bone cancer. ^[10]

Nodal metastasis is uncommon in early disease but may occur in 10-20% of cases of advanced disease. ^{[11, 6]} The lymphatic drainage of the auricle and EAC extends anteriorly to the periparotid lymph nodes and parotid gland. ^[12] Drainage may also occur to the jugular chain or nodes overlying the mastoid. Lymphatic drainage of the medial EAC and middle ear is to the retropharyngeal nodes or deep jugular nodes. The lymphatic drainage of the inner ear is unknown.

Distant metastasis is rare.

Patients with cancer of the temporal bone most often present when aged 60 years or older, although any age group, including children, can be affected. Common presenting symptoms include chronic otalgia, otorrhea, bleeding, and hearing loss. Physical findings include otorrhea, a mass lesion, facial swelling, facial paresis, and other cranial nerve (CN) deficits. Patients often present after many years of symptoms. In a series from the authors' institution, the average time from the onset of symptoms to the time of primary treatment for cancer was 3.9 years. ^[11] Nodal disease is present in 10-20% of patients. ^{[11, 6]} Symptoms and signs of temporal bone lesions are summarized as follows:

• Otalgia (80-85%)

• Otorrhea (40-75%)

• Facial paralysis (25%)

• Hearing loss (45-80%)

• Tinnitus (8-10%)

• Vertigo

• Auricular lesion

• External canal mass (10%)

• Parotid mass (19%)

• Skin lesions

• CN V, IX, I, XI deficits (30%)

The aforementioned study by Song et al found that in cases of temporal bone metastasis, facial palsy and hearing loss were the most frequent otologic symptoms, with each occurring in 30.5% of patients. ^[3]

Physical examination in cases of temporal bone cancer should include inspection of the pinna, EAC, and middle ear for ulcers, mass lesions, soft tissue swelling or induration, old scars (eg, previously excised skin cancers may have been forgotten by the patient), and otorrhea. Perform a thorough CN examination. Close inspection for facial weakness is crucial. Perform audiography if hearing loss is suspected. As always, perform a complete head and neck examination. The patient's general medical condition should also be evaluated because it may greatly impact treatment options and outcome.

In general, all patients who are medically able should undergo surgical treatment. Primary radiation is ineffective for curative treatment; however, in the most extreme cases in which contraindications to surgery are serious deterrents to surgery, palliative radiation and chemotherapy may be offered.

The temporal bone is a complex structure comprised of 3 parts: the squamous, tympanic, and petrous portions. The squamous portion of the temporal bone forms a small portion of the bony EAC, the zygomatic process (and mandibular fossa), and a portion of the mastoid process. It has a superior portion that protects the temporal lobe and articulates with the parietal and occipital bones. The tympanic portion forms most of the bony canal and the posterior wall of the mandibular fossa. The middle ear is a space between the squamous and temporal portions laterally and the petrous portion medially. The petrous portion of the temporal bone contains the otic capsule and the internal auditory canal.

The EAC extends from the concha to the tympanic membrane. The lateral cartilaginous portion meets the bony portion at a bony-cartilaginous junction located about one third of its total length from the lateral aspect. The anterior cartilaginous wall contains small cartilage defects filled with connective tissue called fissures of Santorini, which are direct routes of tumor spread into the periparotid tissues. Within the bony portion is another potential route for tumor extension at the foramen of Huschke, a defect of the tympanic ring located inferiorly. The anterior wall of the canal is closely associated with the temporomandibular joint, and the anterior-inferior wall is close to the parotid gland.

The temporal bone contains or abuts many vital structures, including the internal carotid artery, jugular bulb, cavernous sinus, and sigmoid sinus. A thin layer of bone separates the middle ear and mastoid cavities from the middle and posterior fossae dura. Other important structures that lie within the temporal bone include the ossicles, the cochlea, and the eustachian tube and the cochlear, vestibular, facial, trigeminal, caroticotympanic, chorda tympani, and petrosal nerves.

In general, no contraindications specific to tumors of the temporal bone exist; all patients who are medically able should undergo surgical treatment. However, advanced tumors with intracranial invasion have a grave prognosis, and treatment should probably be limited to palliation with less extensive (and less morbid) surgical procedures.