The anatomy
The temporal bone is one of the most anatomically dense regions in the body. Within a few cubic centimeters it contains the ear canal, eardrum, and middle ear bones; the cochlea and the balance organs; the facial nerve; the internal carotid artery; the jugular bulb; and the internal auditory canal carrying the hearing and balance nerves toward the brainstem.
The lateral skull base is the boundary zone where this structure meets the intracranial cavity. Tumors arising here are uncommon individually, and their management is defined less by the tumor’s size than by which of these structures it touches.
Types of tumors
Benign tumors make up the majority:
- Vestibular schwannoma — the most common, arising from the balance nerve
- Facial nerve schwannoma — arising from the facial nerve itself, and presenting with gradual facial weakness or twitching, or with hearing loss
- Meningioma — arising from the coverings of the brain and extending toward or into the temporal bone
- Paraganglioma — glomus tympanicum and glomus jugulare tumors
- Endolymphatic sac tumor — a rare, locally aggressive tumor associated with von Hippel–Lindau disease
- Cholesterol granuloma — an expansile cystic lesion, most often at the petrous apex
Malignant tumors are less common but require prompt, coordinated treatment:
- Squamous cell carcinoma of the ear canal, the most frequent malignancy of this region, which may present as a chronically draining, painful ear that does not respond to treatment
- Basal cell carcinoma and other skin cancers extending inward from the auricle or surrounding skin
- Adenoid cystic carcinoma and other tumors of the ceruminous glands
- Metastatic disease from a primary tumor elsewhere
Symptoms that warrant evaluation
Because these tumors are rare and their early symptoms overlap with common ear problems, the following are worth investigating when they persist:
- A chronically draining ear that does not improve with appropriate treatment, particularly when accompanied by pain
- Deep or persistent ear pain, especially out of proportion to the examination findings
- Progressive facial weakness, or facial twitching — gradual onset is more concerning than sudden onset for a tumor
- Asymmetric hearing loss or one-sided tinnitus
- A mass in the ear canal or behind the eardrum
- Bleeding from the ear canal
- Hoarseness, swallowing difficulty, or shoulder weakness, suggesting lower cranial nerve involvement
- New numbness of the face
Evaluation
Assessment begins with a detailed history, microscopic examination of the ear, and a complete cranial nerve examination — the pattern of which nerves are affected often localizes the tumor before imaging confirms it. An audiogram documents hearing.
Imaging generally requires both high-resolution CT of the temporal bone for bony detail and MRI with contrast for soft tissue extent, nerve involvement, and intracranial spread. Vascular imaging is added when the carotid artery or jugular system may be involved.
Biopsy is appropriate for accessible lesions when malignancy is suspected, but is specifically avoided for vascular tumors such as paragangliomas.
Treatment
Treatment is individualized and frequently multidisciplinary, involving neurotology, neurosurgery, head and neck surgical oncology, radiation oncology, and medical oncology depending on the diagnosis. Options span observation with serial imaging, stereotactic radiosurgery, fractionated radiation, and microsurgical resection — alone or in combination.
For malignant tumors, treatment typically combines surgical resection with radiation, and sometimes chemotherapy, with reconstruction planned alongside the resection.
Central to planning in every case is the balance between complete treatment of the tumor and preservation of function: hearing, facial movement, swallowing, and voice. Which of these are at risk, and to what degree, depends entirely on the individual tumor and is the substance of the treatment discussion.