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Tumors of the Ear

Tumors of the ear are classified by anatomic location (external, middle, or inner ear/temporal bone/cerebellopontine angle), tissue of origin, and biological behavior (benign vs. malignant). The following is a systematic overview.

Classification Overview

Primary Benign Tumors

Paraganglioma (glomus tympanicum, glomus jugulare)
Schwannoma / Neurofibroma
Meningioma
Adenoma / Ceruminous adenoma
Hemangioma
Osteoma / Exostosis
Choristoma / Lipoma
Middle ear adenomatous neuroendocrine tumor

Primary Malignant Tumors

Squamous cell carcinoma (SCC) — most common
Basal cell carcinoma
Adenocarcinoma / Ceruminous adenocarcinoma
Adenoid cystic carcinoma
Mucoepidermoid carcinoma
Rhabdomyosarcoma
Chondrosarcoma / Chordoma
Melanoma
Angiosarcoma, fibrosarcoma, others

Metastatic Tumors (prostate, breast, renal cell, lung, lymphoma, multiple myeloma)

— Cummings Otolaryngology Head and Neck Surgery, Box 178.1

I. BENIGN TUMORS

1. Paraganglioma (Glomus Tumors)

Paragangliomas of the temporal bone are the most frequently encountered temporal bone neoplasms after acoustic neuromas. They arise from neural crest elements associated with the jugular bulb adventitia and Jacobson's and Arnold's nerves.

Two main subtypes:

Feature	Glomus Tympanicum	Glomus Jugulare
Origin	Glomus bodies of the middle ear	Jugular bulb adventitia
Presentation	Pulsatile tinnitus + conductive hearing loss (early, small)	Late presentation after bony destruction; cranial nerve IX–XII dysfunction
MRI hallmark	Enhancing mass behind TM	"Salt and pepper" T1/T2 appearance; arborizing flow voids
CT	Limited to middle ear; tympanic/hypotympanic location	Irregular destruction of jugular foramen; absent bony septum between ICA and IJV

1–3% of glomus jugulare tumors secrete catecholamines → preoperative 24-hour urine metanephrines required before surgery
MRI complements CT; angiography needed if embolization planned pre-operatively
Exam: if all borders visible through the TM → glomus tympanicum; if borders incomplete → may be glomus jugulare extending into hypotympanum

Classification systems used: Fisch classification and Glasscock-Jackson classification

Treatment:

Fisch class A/B (limited to middle ear): surgical resection preferred
Fisch class C/D (extensive): stereotactic radiosurgery (SRT) is favored — lower complication rates and similar/better local control vs. surgery
SRT achieves 90–95% tumor control; preserves lower cranial nerve function better than surgery

— Cummings Otolaryngology, pp. 3404–3436; K.J. Lee's Essential Otolaryngology, p. 488

2. Vestibular Schwannoma (Acoustic Neuroma)

Most common tumor of the internal auditory canal (IAC) and cerebellopontine angle (CPA)
8–10% of all intracranial tumors; incidence ~1 per 100,000
Arises most commonly from the vestibular nerve (though any cranial nerve may be involved)
Benign, slow-growing: average growth 1–2 mm/year; some never grow

Histology: Antoni A fibers (fibrillary, polar, elongated tissue) + Antoni B fibers (loosely reticulated tissue)

Clinical Features:

Asymmetric sensorineural hearing loss (SNHL)
Tinnitus and imbalance
Audiogram: poor speech discrimination score out of proportion to pure-tone loss; rollover (decline in discrimination at higher presentation levels)
ABR historically used; MRI with gadolinium is now the gold standard

Treatment (three options):

Approach	Indications	Notes
Observation	Small tumors, serviceable hearing, older age	Serial MRI; many tumors never grow
Radiosurgery	Tumors <2.5 cm, enlarging; 12–13 Gy	90–95% control; does NOT preserve hearing. Facial nerve dysfunction <1%; rare malignant transformation (1:1000 over 30 years)
Microsurgery	All sizes depending on hearing goals	Three approaches (below)

Surgical Approaches:

Translabyrinthine: causes profound SNHL; no brain retraction; removes any size tumor; facial nerve identified at fundus before tumor removal
Retrosigmoid: hearing preservation possible for tumors <1.5 cm in medial IAC; requires cerebellar retraction; higher rate of chronic headaches
Middle fossa: hearing preservation 60–70%; tumors in IAC <1.5 cm; temporal lobe retraction required

— K.J. Lee's Essential Otolaryngology, p. 488

3. Facial Nerve Schwannoma

Most common facial nerve tumor (followed by hemangioma)
Geniculate ganglion most commonly affected
MRI: enhancement with gadolinium
CT: smooth bony remodeling (vs. ground-glass appearance + erosion of hemangioma)

Treatment:

Normal/near-normal facial function → observe
House-Brackmann Grade 3 or worse → surgical removal + nerve grafting
Early/mild paresis → tumor decompression may be considered

4. Meningioma

Second most common CPA tumor after vestibular schwannoma
Arises from arachnoid cap cells

Imaging features distinguishing from schwannoma:

Dural tail
Eccentric location relative to the IAC
Calcifications, hyperostosis of adjacent bone
More homogenous enhancement with gadolinium

Symptoms: SNHL, tinnitus, imbalance, facial paresthesia, diplopia, ataxia

WHO Classification:

Grade 1 (Benign): meningiothelial, fibrous, transitional, psammomatous, angiomatous, secretory
Grade 2 (Atypical): chordoid, clear cell, atypical
Grade 3 (Anaplastic/malignant): papillary, rhabdoid, anaplastic

Histology: Psammoma bodies
Hearing preservation (or even improvement) more common than with vestibular schwannomas.

5. Middle Ear Adenomatous Neuroendocrine Tumor

Both neuroendocrine and glandular features
Symptoms: hearing loss, aural fullness, tinnitus, otalgia
CT similar to tympanic paraganglioma; may appear in atypical locations
Male predominance (2:1 ratio)
IHC: positive for pan-cytokeratins, chromogranin, synaptophysin, insulinoma-associated protein 1
Rare metastatic potential
Treatment: surgical resection + long-term follow-up (risk of recurrence)

6. Choristoma (Lipochoristoma / Middle Ear Lipoma)

Rare middle ear or IAC mass
Defined as histologically normal tissue in an abnormal location
Most common type: salivary gland tissue; less common: glial choristoma
Middle ear: conductive hearing loss + effusion
IAC: SNHL, tinnitus, imbalance
MRI: hyperintense on T1 without contrast; no enhancement with fat-saturation gadolinium sequences (unlike schwannoma)
Treatment: observation with serial imaging — removal from facial nerve usually not feasible

II. MALIGNANT TUMORS

1. Squamous Cell Carcinoma (SCC) of the Temporal Bone

Most common primary malignancy of the temporal bone, followed by basal cell carcinoma, adenocarcinoma, adenoid cystic carcinoma, mucoepidermoid carcinoma, ceruminoma, melanoma, and sarcoma.

Risk factors: Chronic irritation or inflammation (e.g., chronic otitis media)

Symptoms (in decreasing frequency):

Otalgia
Otorrhea
Hearing loss
Facial palsy
Parotid mass

Preoperative Evaluation:

Audiogram
CT temporal bone and neck (with IV contrast) — lymph node assessment
CT chest / PET scan — distant metastases

Staging — Modified University of Pittsburgh System:

T Stage	Extent of Disease
T1	Tumor limited to EAC; no bony erosion or soft tissue involvement
T2	Limited bony erosion (not full thickness) or <0.5 cm soft tissue involvement
T3	Erosion through bony EAC with limited (<0.5 cm) soft tissue; or middle ear/mastoid involvement
T4	Medial wall erosion (cochlea, labyrinth, petrous apex, jugular foramen, carotid canal, dura); >0.5 cm soft tissue; facial paresis

Treatment:

Low-grade EAC (no bone involvement): sleeve resection
Bone involvement: lateral temporal bone resection (LTBR) minimum
Middle ear extension: subtotal temporal bone resection (STBR)
Total temporal bone resection: no proven survival benefit; rarely performed
T3/T4 disease: parotidectomy ± neck dissection considered

— K.J. Lee's Essential Otolaryngology, pp. 491–492

2. Rhabdomyosarcoma

Most common soft-tissue sarcoma in children
Temporal bone is a parameningeal site → classified Stage II/III based on nodal status
Types: embryonal (most common in children), alveolar, pleomorphic

Treatment:

Wide surgical resection with clear margins
Most pediatric high-grade cases: surgery + 50–70 Gy external beam radiation + multidrug chemotherapy
SRS indicated for residual/recurrent disease at jugular foramen or perineurial invasion

Prognosis (5-year survival by risk group):

Low risk: ~90%
Intermediate risk: 60–80%
High risk: 20–40%

Caution in children: External beam radiation to skull base can cause Eustachian tube dysfunction, osteoradionecrosis, SNHL, cataract development, impaired cranial bone/tooth development, pituitary dysfunction.

3. Chondrosarcoma

Rare; 1% occur at the skull base — typically at spheno-occipital or petroclival synchondroses
WHO Grades 1 and 2: low grade, more common
WHO Grade 3 / mesenchymal subtype: high grade

Imaging: Similar to chordoma; eccentric location; no hallmark differentiating low from high grade

Pathology: Non-reactive for keratin and EMA (helps distinguish from chordoma)

Treatment: Surgery followed by radiation (proton beam / carbon ion preferred)

Prognosis (SEER): 5-year and 10-year survival: 87% and 68% (better in younger patients, females, smaller tumors)

4. Chordoma

Derived from notochord remnants; 33% of all chordomas occur at the skull base
Median age at presentation: 60 years (also occurs in children)
Metastases rare at presentation; morbidity from local growth

Imaging:

Hyperintense T2-MRI, hypointense T1-MRI (classic)

Treatment: Surgery followed by radiation; proton beam and carbon ion therapy preferred (5-year local control >70%)

Prognosis:

Median overall survival: 7.7 years (SEER)
Under 40 years: 68% 10-year survival
Over 40 years: 43% 10-year survival
Gross/near-total resection: 6× higher 5-year survival vs. subtotal resection

5. Adenoid Cystic Carcinoma and Other Ceruminous Gland Malignancies

Ceruminous gland tumors are a spectrum arising from the specialized apocrine glands of the external auditory canal:

Ceruminous adenoma (benign)
Ceruminous adenocarcinoma — low and high grade
Adenoid cystic carcinoma — perineural invasion characteristic
Mucoepidermoid carcinoma

All require surgical resection; adenoid cystic carcinoma has propensity for perineural spread and late recurrence.

III. Key Imaging Summary

Tumor	CT	MRI
Glomus jugulare	Irregular jugular foramen destruction	"Salt and pepper"; flow voids
Vestibular schwannoma	IAC widening (smooth)	Enhances with gadolinium; centered on IAC
Meningioma	Hyperostosis, calcification	Dural tail; homogenous enhancement
Chordoma	Bone destruction at skull base	Hyperintense T2
Chondrosarcoma	Eccentric, calcified; petroclival	Similar to chordoma
Choristoma/lipoma	—	Hyperintense T1; no enhancement with fat sat
Facial nerve schwannoma	Smooth bony remodeling	Gadolinium enhancement

IV. Metastatic Tumors to the Temporal Bone

Common primary sites: prostate, breast, gastrointestinal, renal cell carcinoma, lung, also multiple myeloma, lymphoma, and leukemia (chloroma). Always consider metastatic disease in patients with known malignancy presenting with new unilateral hearing loss or facial palsy.

Sources:

Cummings Otolaryngology Head and Neck Surgery, Box 178.1, pp. 3404–3436
K.J. Lee's Essential Otolaryngology, pp. 488–493

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Here is the fully expanded, comprehensive reference on tumors of the ear, integrating all available textbook data with clinical imaging.

Tumors of the Ear — Comprehensive Reference

Anatomic Classification Table

Location	Benign	Malignant
External Auditory Canal (EAC)	Osteoma, Exostosis, Adenoma (ceruminous)	SCC, BCC, Ceruminous adenocarcinoma, Melanoma, Direct extension
Middle Ear / Mastoid	Glomus tympanicum, Hemangioma, Lipoma/Choristoma, Endolymphatic sac tumor, Adenomatous neuroendocrine tumor	SCC, Adenoid cystic carcinoma, Acinic cell carcinoma, Rhabdomyosarcoma
IAC / CPA / Skull Base	Vestibular schwannoma, Facial nerve schwannoma, Meningioma, Choristoma/Lipoma	Chondrosarcoma, Chordoma, Metastases

— K.J. Lee's Essential Otolaryngology, Table 24-1; Cummings Otolaryngology, Box 178.1

PART I — BENIGN TUMORS

1. Paraganglioma (Glomus Tumor / Chemodectoma)

Epidemiology & Biology

Most common neoplasm of the middle ear and second most common temporal bone tumor overall
Also called chemodectoma; three types: Glomus tympanicum (GT), Glomus jugulare (GJ), Glomus vagale (GV)
Sex ratio: M:F = 1:5 (predominantly female); Caucasians more frequently affected
10% are multicentric
Majority sporadic; up to 30% familial
Rarely malignant: 2–4% (highest risk in vagal paragangliomas); diagnosis of malignancy requires metastasis to non-neuroendocrine tissue; most common sites: lymph nodes, bone, lung, liver, spleen
Rarely functional: 5% or less secrete neuroactive peptides → palpitations, sweating, flushing, syncope, hypertension, headaches; may cause catastrophic hypertension at anesthesia induction if unrecognized
- If secretory: treat with phentolamine (nonselective reversible α-adrenergic blocker)
Arise from chemoreceptor (Type I chief) cells and Type II sustentacular cells of parasympathetic paraganglia associated with:
- Jugular dome adventitia
- Tympanic promontory
- Along Jacobson's nerve (branch of CN IX) and Arnold's nerve (branch of CN X)

Genetics — Familial Paraganglioma Syndromes

Gene	Syndrome	Locus	Inheritance	Head & Neck	Adrenal	Malignancy Risk	Notes
SDHD	PGL1	11q23	AD (imprinted)	91–98%	16–21%	8%	Multiple tumors
SDHAF2	PGL2	11q13.1	AD (imprinted)	70–91%	0%	0%	Imprinting
SDHC	PGL3	1q21	AD	88%	<10%	<10%	Single tumors
SDHB	PGL4	1p35-36	AD	27–31%	18–28%	13–23%	Malignancy risk
SDHA	PGL5	5p15.33	AD	<3%	<10%	<10%	—

Mutations in mitochondrial complex II (succinate dehydrogenase subunits); involved in the electron transport chain. SDHB carries the highest malignancy risk.

Tumor Classification

Fisch Classification:

Type	Extent
A	Limited to the middle ear
B	Limited to the tympanomastoid area; no infralabyrinthine involvement
C1	Infralabyrinthine/petrous apex; limited carotid canal involvement
C2	Invasion of vertical carotid canal
C3	Invasion of horizontal carotid canal (not foramen lacerum)
C4	Entire intrapetrous carotid
De1	Extradural intracranial extension <2 cm
De2	Extradural extension >2 cm
Di1	Intradural extension <2 cm
Di2	Intradural extension >2 cm
Di3	Intradural, unresectable

Glasscock-Jackson — Glomus Tympanicum:

Type I: Limited to promontory
Type II: Completely filling the middle ear
Type III: Fills middle ear, extends into mastoid
Type IV: Extends into EAC; may extend anterior to ICA

Clinical Presentation

GT: Pulsatile tinnitus + conductive hearing loss (symptoms when tumor is still small due to proximity to TM and ossicles)
GJ: Late presentation — often sizeable when first identified; bony destruction of jugular foramen; cranial nerve IX–XII dysfunction; facial paresis (mastoid extension); SNHL (labyrinthine erosion); pulsatile tinnitus
Either type may erode TM and appear as a bleeding mass in the EAC

Diagnosis

Otoscopy: Reddish-blue/vascular pulsatile retrotympanic mass ("rising sun" sign inferiorly); if all borders visible through TM → GT; if borders not fully visible → GJ must be excluded
CT (bone windows): GT shows soft tissue on promontory; GJ shows irregular destruction of jugular foramen; absent bony septum between ICA and IJV
MRI: "Salt and pepper" appearance on T1/T2 (arborizing flow voids from prominent vascularity); low signal flow voids on T1/T2 reflecting large vessels
Angiography: Hypervascular pattern; essential before preoperative embolization
Preoperative 24-hour urine metanephrines: Mandatory — 1–3% secrete catecholamines (GJ > GT)
If arterial invasion suspected: preoperative balloon occlusion testing (99mTc-HMPAO SPECT or Xenon CT) of ipsilateral carotid

Endoscopic Images — Paraganglioma

Composite endoscopic views of paraganglioma (Fisch A1, B1, B2) showing increasing tumor size and vascularity behind the tympanic membrane

Endoscopic views of paraganglioma at different Fisch stages: A1 (small localized deep-red mass), B1 (larger pinkish-red mass filling most of middle ear), B2 (multi-lobulated mass with increased vascularity).

CT and MRI multimodal imaging of glomus tympanicum showing soft tissue mass on cochlear promontory

CT (axial bone windows) + MRI (T1+contrast, T2 coronal) of glomus tympanicum on the cochlear promontory with no bony erosion.

Treatment

Surgical:

Fisch A/B (GT and small GJ): Transcanal or anterior tympanotomy for small GT limited to promontory; mastoidectomy + extended facial recess for larger GT
Fisch A infratemporal fossa (Fisch type A) approach is standard for GJ — requires proximal control of great vessels and sigmoid sinus
Large tumors: may need facial nerve transposition for anterior exposure
Blood supply: ascending pharyngeal and stylomastoid arteries (branches of external carotid); contributions from ICA or vertebral possible
Preoperative embolization significantly reduces intraoperative blood loss (well-documented benefit)
Intraoperative vessel ligation: ascending pharyngeal, stylomastoid, caroticotympanic, superior tympanic arteries
Lower cranial nerve preservation paramount: morbidity from CN IX–XII resection may require tracheostomy and gastrostomy
Very large tumors: may need staged surgery (if blood loss >3 L during neck/temporal bone phase, intracranial resection proceeds at a later date)

Radiation:

Both IMRT and stereotactic radiotherapy achieve 90–100% tumor control
Mechanism: obliterative endarteritis
Doses: single fraction SRS 15 Gy; external beam 40–45 Gy
SRS preferred for Fisch C/D and GJ — fewer complications, better cranial nerve preservation vs. surgery
Risks of SRS: radiation-induced malignancy, osteoradionecrosis of skull base, temporal lobe necrosis, cranial nerve injury

2. Vestibular Schwannoma (Acoustic Neuroma)

Epidemiology

Most common tumor of the IAC and CPA
8–10% of all intracranial tumors; incidence ~1/100,000
Arises predominantly from the superior or inferior vestibular nerve; less commonly from cochlear, facial, or other cranial nerves
Bilateral schwannomas = Neurofibromatosis Type 2 (NF2)

Pathology

Benign; average growth 1–2 mm/year; up to 50% show no growth on serial imaging
Histology: Two cell populations:
- Antoni A: Dense, fibrillary, bipolar spindle cells in palisading arrangement (Verocay bodies)
- Antoni B: Loosely arranged, hypocellular, myxoid, reticulated stroma

Clinical Features

Asymmetric sensorineural hearing loss (SNHL) — most common presentation
Tinnitus (usually unilateral, high-pitched)
Imbalance / unsteady gait
Rollover on audiogram: speech discrimination score paradoxically worsens at higher presentation levels
Larger tumors: facial paresthesia (CN V compression), facial weakness (CN VII compression), ataxia (brainstem/cerebellar compression), hydrocephalus

Diagnosis

MRI with gadolinium — gold standard; shows strongly enhancing mass centered on IAC/CPA
CT: smooth, funnel-shaped widening of the IAC
ABR: prolonged Wave V latency or absent Wave V — historically used as screening test, now replaced by MRI

Koos Grading:

Grade 1: Intracanalicular
Grade 2: Small CPA component (<2 cm)
Grade 3: Large CPA component without brainstem contact
Grade 4: Large CPA component with brainstem displacement

Vestibular Schwannoma — MRI Images

MRI axial T1 gadolinium: Koos Grade 1 intracanalicular vs Grade 3 CPA extension with brainstem displacement

Left: Small intracanalicular (Koos 1) vestibular schwannoma. Right: Large CPA mass with brainstem displacement (Koos 3–4).

MRI + audiogram showing 23 mm vestibular schwannoma with profound SNHL and ABR changes

Heterogeneously enhancing IAC mass with associated profound SNHL and abnormal ABR waveforms.

Treatment

Modality	Indications	Key Points
Observation	Small tumors, serviceable hearing, older patients, initial diagnosis	Serial MRI; ~50% never grow
Stereotactic Radiosurgery (SRS)	Tumors <2.5 cm; enlarging tumor; patient preference	12–13 Gy; 90–95% control rate; does NOT preserve hearing; facial nerve dysfunction <1%; trigeminal paresthesia possible; malignant transformation 1:1000 at 30 years
Microsurgery	All sizes depending on hearing goals and tumor extent	Three approaches (below)

Surgical Approaches — Detailed Comparison:

Approach	Hearing	Tumor Size	Brain Retraction	Special Notes
Translabyrinthine	Destroys hearing (profound SNHL)	Any size	None required	Facial nerve identified at IAC fundus BEFORE tumor removal; safest facial nerve approach
Retrosigmoid (suboccipital)	Preservation possible if <1.5 cm, medial IAC	All sizes	Cerebellar retraction required	Higher rate of chronic postoperative headaches; supplemental endoscopy may be needed for lateral IAC tumor
Middle Fossa	60–70% hearing preservation	IAC tumors <1.5 cm	Temporal lobe retraction	Rare: memory changes, seizure; ideal for purely intracanalicular or small CPA with serviceable hearing

Most common surgical risks: CSF leak, meningitis, facial paralysis Cochlear schwannomas (rare, within cochlea): usually observed unless intractable dizziness or growth

3. Facial Nerve Schwannoma

Most common facial nerve tumor (hemangioma is second)
Geniculate ganglion most commonly affected
May involve any segment: tympanic, mastoid, labyrinthine, IAC
Present with progressive facial weakness (House-Brackmann grade increasing over months–years); rarely: sudden onset

Imaging:

CT: Smooth bony remodeling of facial nerve canal
MRI: Gadolinium enhancement; tubular shape following facial nerve course

Differential from hemangioma on CT:

Schwannoma → smooth remodeling
Hemangioma → infiltrative erosion + stippled/honeycomb calcifications at geniculate ganglion

Treatment algorithm based on facial function:

Facial Function	Management
Normal or near-normal	Observation with serial imaging
Mild early paresis	Tumor decompression
House-Brackmann Grade 3+	Tumor removal + nerve grafting (improved outcome with shorter preoperative weakness duration)
Surgical approaches based on hearing	Hearing preserved → middle fossa or transmastoid; no serviceable hearing → translabyrinthine

4. Hemangioma

0.7% of all temporal bone neoplasms; peak in 5th–6th decade
Almost exclusively associated with the facial nerve at the geniculate ganglion; rarely IAC or tympanic/mastoid segments
Key clinical pearl: Produces facial weakness out of proportion to tumor size (unlike schwannoma)
Rarely causes hearing loss or vestibular symptoms
Locally aggressive — bony destruction via nerve compression, nerve infiltration, or vascular steal
Cochlear erosion → SNHL; middle ear extension → CHL

Imaging:

CT: Infiltrative erosive lesion at geniculate ganglion with intratumoral stippled (honeycomb) calcifications — characteristic
MRI: Hypo- to isointense on T1; avid enhancement with contrast; may erode cochlea or labyrinth

Treatment:

Small lesions: Meticulous dissection from nerve — full facial function preservation possible
Early intervention maximizes chance of anatomic and functional nerve preservation
IAC lesions (non-paralyzed): Decompression of IAC canal (resection requires grafting)
Large lesions / complete paralysis: Resection + nerve grafting (outcome better with short duration of preoperative weakness)
Subtotal resection acceptable if facial function preserved — mandatory postoperative surveillance imaging

5. Endolymphatic Sac Tumor (ELST)

Locally aggressive, slow-growing neoplasm of the endolymphatic sac or duct
Histologic description: destructive papillary cystic adenomatous tumor of the temporal bone
IHC profile: Positive: cytokeratin, vimentin, S-100; Negative: chromogranin (↔ paraganglioma), thyroglobulin (↔ metastatic thyroid), transthyretin/prealbumin (↔ choroid plexus tumor)

Association with Von Hippel-Lindau (VHL):

11% of VHL patients develop ELST; 30% of those bilateral
VHL: loss-of-function mutation at chromosome 3p25.5 (ubiquitin ligase → fails to degrade HIF-1α → uncontrolled angiogenesis)
VHL-associated: 3rd–4th decade, more common in females
Sporadic: 5th–6th decade, no gender predilection
Screening: cranial MRI every 1–3 years in VHL patients

Clinical Presentation:

Dysfunction of the otic capsule — most common
Symptoms mimic endolymphatic hydrops: SNHL (most common), tinnitus, vertigo, aural fullness
Sudden SNHL — from intralabyrinthine hemorrhage
Middle ear extension: mimics Eustachian tube dysfunction or otitis media
Late: facial paralysis, brainstem compression, lower cranial neuropathies
No distant metastases reported; rare drop metastasis into thecal sac

Imaging:

CT: Bony destruction of posterior fossa plate at the operculum; central calcifications; may extend into mastoid
MRI T1: Heterogeneous; hyperintense areas (intralesional hemorrhage — methemoglobin, hemosiderin, cholesterol); hypointense areas (calcifications, residual bone)
MRI T2: Heterogeneous (highly vascular)
MRI T1+Gad: Heterogeneous enhancement
Angiography: Hypervascular; blood supply from inferior tympanic artery + dural stylomastoid branch (ascending pharyngeal and postauricular arteries); may also receive ICA or vertebral contributions

Differential: Paraganglioma, choroid plexus tumor, metastasis, eosinophilic granuloma, meningioma, arachnoid granulation, aneurysmal bone cyst

Treatment:

Surgery — method of choice; must remove both surfaces of the dura for complete resection
Hearing-sparing approaches (retrolabyrinthine–transdural) for small tumors
Translabyrinthine for nonserviceable hearing
Preoperative embolization for large tumors to minimize blood loss

6. Meningioma (CPA/Temporal Bone)

Second most common CPA tumor (after vestibular schwannoma)
Arises from arachnoid cap cells
WHO Grade classification:
- Grade 1 (Benign): Meningothelial, fibrous, transitional, psammomatous, angiomatous, secretory, lymphoplasmacyte-rich, metaplastic
- Grade 2 (Atypical): Chordoid, clear cell, atypical (mitoses, brain invasion)
- Grade 3 (Anaplastic/Malignant): Papillary, rhabdoid, anaplastic
Histology: Psammoma bodies (concentric calcified lamellae) — characteristic but not pathognomonic

Imaging features distinguishing meningioma from vestibular schwannoma:

Dural tail (enhancing dural thickening extending from tumor)
Eccentric location relative to IAC (does not funnel into it)
Calcifications
Hyperostosis of adjacent bone
More homogeneous enhancement
Bone algorithm CT essential

Symptoms: SNHL, tinnitus, imbalance, facial paresthesia/numbness, diplopia, ataxia — depending on location and size

Clinical note: Hearing preservation (or even improvement) more likely with meningioma than with vestibular schwannoma.

7. Osteoma and Exostosis of the EAC

Both are benign bony outgrowths of the external auditory canal and are histopathologically identical but clinically distinct:

Feature	Osteoma	Exostosis
Cause	Spontaneous / idiopathic	Cold water exposure ("surfer's ear")
Laterality	Unilateral	Bilateral
Shape	Pedunculated (on a stalk)	Broad-based
Location	Lateral to bony isthmus	Multiple; closer to TM
Multiplicity	Usually single	Multiple outgrowths

Clinical significance: May cause sufficient narrowing of the EAC to require surgery (conductive hearing loss, recurrent otitis externa from trapped keratin)

Radiology questions to answer on CT (HRCT/CBCT):

Maximum depth and transverse diameter of the exostosis
Exact site of origin of the osteoma
Distance between the medial aspect of exostosis and TM and between the deep aspect and facial nerve canal
Obstructed secretions medial to the exostosis?
Is the middle ear cleft normally pneumatized?

Treatment: Surgical canaloplasty (meatoplasty) when symptomatic

8. Middle Ear Adenomatous Neuroendocrine Tumor

Dual neuroendocrine + glandular differentiation
Sex ratio: M:F = 2:1
Symptoms: hearing loss, aural fullness, tinnitus, otalgia
CT: similar to tympanic paraganglioma; may occur in atypical positions
IHC: Positive: pan-cytokeratins, chromogranin, synaptophysin, insulinoma-associated protein 1 (INSM1)
Rare regional and distant metastatic potential
Treatment: surgical resection + long-term follow-up (recurrence risk)

9. Choristoma (Middle Ear / IAC Lipoma)

Histologically normal tissue in abnormal location (definition of choristoma)
Most common type: salivary gland tissue; less common: glial choristoma
Middle ear location → conductive hearing loss + effusion
IAC location → SNHL, tinnitus, imbalance
MRI: Hyperintense on T1 without contrast; no enhancement on fat-saturation gadolinium sequences (key distinction from schwannoma)
Unlike ELST or schwannoma: no surgical removal possible (inseparable from facial nerve in most cases)
Treatment: serial imaging and observation

PART II — MALIGNANT TUMORS

1. Squamous Cell Carcinoma (SCC) of the Temporal Bone

Epidemiology

Most common primary malignancy of the temporal bone
Frequency order: SCC > BCC > Adenocarcinoma > Adenoid cystic carcinoma > Mucoepidermoid carcinoma > Ceruminoma > Melanoma > Sarcoma
Risk factors: chronic otitis media, chronic irritation/inflammation, prior radiation, cholesteatoma

Clinical Presentation (in decreasing frequency):

Otalgia
Otorrhea (often blood-stained)
Hearing loss
Facial palsy
Parotid mass

Preoperative Evaluation

Audiogram
CT temporal bone + neck with IV contrast (assess bony erosion and lymph nodes)
CT chest with IV contrast / PET-CT (distant metastases)

Staging — Modified University of Pittsburgh System

T Stage	Extent of Disease
T1	Tumor limited to EAC; no bony erosion or soft tissue involvement
T2	Limited bony erosion (not full-thickness) OR <0.5 cm soft tissue involvement
T3	Erosion through bony EAC with <0.5 cm soft tissue; OR middle ear/mastoid involvement
T4	Medial wall erosion (cochlea, labyrinth, petrous apex, jugular foramen, carotid canal, dura); >0.5 cm soft tissue (TMJ, styloid, parotid); facial paresis/paralysis

Surgical Resection Types

Surgery	Tissues Removed	Medial Limit
Sleeve resection	EAC skin, cartilaginous EAC portion, ± TM	Leaves bony EAC intact
LTBR (Lateral Temporal Bone Resection)	En bloc: cartilaginous + bony EAC, TM, malleus, incus ± parotidectomy, neck dissection, mandibular condyle	Medial: stapes
STBR (Subtotal TBR)	LTBR + middle ear/mastoid contents, otic capsule, medial wall ± facial nerve, dura, sigmoid	IAC, petrous apex with neurovascular structures
TTBR (Total TBR)	STBR + petrous apex + neurovascular bundle ± ICA, clivus	No proven survival benefit; rarely performed

Adjuvant Treatment

Postoperative radiation (50–60 Gy) offered to all T2, T3, T4 disease
Chemotherapy considered for T4 tumors, residual disease, or metastatic disease
Parotidectomy + neck dissection performed for locoregional spread; prophylactic parotidectomy ± neck dissection for T3/T4

Survival by T Stage

T1: ~90% 5-year
T2: ~70–80% 5-year
T3: ~50–60% 5-year
T4: <30% 5-year

SCC Temporal Bone — Imaging

Preoperative axial CT and intraoperative views of subtotal temporal bone resection for EAC SCC

CT showing EAC SCC with mastoid involvement (left). Intraoperative exoscopic views showing IAC, cochlea, ICA, and jugular foramen during subtotal temporal bone resection.

Advanced Stage 4 SCC temporal bone — CT showing 'moth-eaten' bone destruction, MRI showing carotid encasement and dural involvement

Advanced T4 SCC: HRCT demonstrates 'moth-eaten' petrous apex erosion; MRI shows carotid encasement, sigmoid sinus involvement, and dural invasion.

2. Rhabdomyosarcoma (RMS)

Most common pediatric temporal bone malignancy; most common pediatric soft-tissue sarcoma overall
35–40% of all RMS are in the head and neck; only 5% in the temporal bone; temporal bone is a parameningeal site → unfavorable, minimum Stage II
Origin: embryologic skeletal muscle cells
Can arise from EAC, middle ear, or mastoid cavity

Symptoms

Otalgia, otorrhea, hearing loss, headache, aural polyp, facial nerve weakness, regional lymphadenopathy

Histological Classification

Type	Notes
Embryonal (most common in children)	Includes conventional, spindle cell, and botryoid subtypes
Alveolar	Worse prognosis than embryonal
Pleomorphic	Most common in adults

Spindle cell and botryoid: more favorable outlook
Alveolar > embryonal in aggressiveness

Staging — Children's Oncology Group (COG) System

Stage	Site	T	N	M
I	Orbit, HN (non-parameningeal), GU non-bladder	T1 or T2a/b	N0 or N1	M0
II	Bladder/prostate, extremity, cranial/parameningeal	T1 or T2a/b	N0	M0
III	Same	T1 or T2a/b	N1	M0
IV	All sites	Any T	N0/N1	M1

T2 = tumor invades structures outside EAC/tympanomastoid space; "a" = <5 cm, "b" = >5 cm

Surgical group assigned after resection (Groups 1–4: complete resection to distant metastasis)

Treatment

Debate: Upfront resection vs. biopsy → primary chemoradiation
Many advocate wide surgical resection — extent of resection determines prognosis
Most pediatric high-grade: Surgery + 50–70 Gy EBRT + multidrug chemotherapy
SRS for residual/recurrent disease at jugular foramen or perineural invasion into IAC/Meckel cave/cavernous sinus

Radiation risks in children: Eustachian tube dysfunction, osteoradionecrosis, SNHL, cataract, impaired cranial bone/tooth development, pituitary dysfunction, chronic headache

Prognosis

Low risk: ~90% 5-year survival
Intermediate risk: 60–80%
High risk: 20–40%

3. Chondrosarcoma

Rare cartilaginous malignancy; 1% occur at skull base, typically at spheno-occipital or petroclival synchondroses
Rarely metastasizes; morbidity from local growth
WHO Grades 1–2 (low grade): significantly more frequent; better prognosis
WHO Grade 3 / mesenchymal subtype (high grade): worse prognosis
IHC: Non-reactive for keratin and EMA (contrast with chordoma which is keratin+)

Imaging: Similar to chordoma; tends to be eccentrically located; calcifications common; no hallmark to distinguish low from high grade

Treatment: Surgery + radiation (proton beam / carbon ion preferred)

Prognosis (SEER):

5-year survival: 87%; 10-year: 68% (substantially higher for low-grade alone)
Better prognosis: younger age, female sex, smaller tumor

4. Chordoma

Derived from notochord remnants; 33% of all chordomas occur at the skull base
Median age of presentation: 60 years (also in children)
Metastases rare at presentation; morbidity/mortality from local progressive growth
Frequent presenting symptom: headache

Imaging (classic):

T1-MRI: Hypointense
T2-MRI: Hyperintense (key characteristic)
Bone destruction at skull base on CT

Treatment:

Surgery + radiation; proton beam / carbon ion therapy most commonly recommended
5-year local control rates: >70%

Prognosis (SEER):

Median overall survival: 7.7 years
Age <40 years: 68% 10-year survival
Age >40 years: 43% 10-year survival
Gross or near-total resection: 6× higher 5-year survival vs. subtotal

5. Ceruminous Gland Tumors (EAC)

Arising from the specialized apocrine ceruminous glands of the outer EAC:

Tumor	Behavior	Notes
Ceruminous adenoma	Benign	Well-circumscribed; local excision curative
Ceruminous adenocarcinoma	Malignant	Low or high grade; wide excision required
Adenoid cystic carcinoma	Malignant	Perineural invasion characteristic; late recurrence common; may occur decades later
Mucoepidermoid carcinoma	Malignant	Intermediate behavior
Sebaceous adenocarcinoma, papillary cystadenocarcinoma	Malignant	Rare

All ceruminous gland malignancies require wide surgical resection; adenoid cystic carcinoma specifically requires long-term follow-up given propensity for late, perineural recurrence.

6. Skull Base Malignancies Extending to the Ear

Jugular Foramen Schwannomas (Lower CN)

Originate from CN IX, X, or XI at jugular foramen
May be intracranial, infraforaminal, cervical, or combined
CT: Smooth symmetric enlargement of jugular foramen (vs. paraganglioma's irregular destruction)
Treatment: suboccipital approach for intracranial component; Fisch infratemporal fossa approaches for infraforaminal

Metastatic Tumors to the Temporal Bone

Common primaries:

Prostate (most common)
Breast
Renal cell carcinoma
Lung, GI, multiple myeloma, lymphoma, leukemia (chloroma)
Always suspect in patients with known malignancy presenting with new unilateral hearing loss or facial palsy

Key Imaging Differentiation Summary

Tumor	CT Appearance	MRI Appearance
Glomus tympanicum	Soft tissue on cochlear promontory; no bony erosion	Enhancing vascular mass
Glomus jugulare	Irregular jugular foramen destruction; absent ICA-IJV septum	"Salt and pepper" T1/T2; flow voids
Vestibular schwannoma	Smooth funnel-shaped IAC widening	Enhancing mass centered on IAC/CPA; isointense T1, hyperintense T2
Meningioma	Hyperostosis; calcification; eccentric to IAC	Dural tail; homogeneous enhancement
Hemangioma	Infiltrative erosion at geniculate; honeycomb calcifications	Avid enhancement; T1 hypo- to isointense
Endolymphatic sac tumor	Posterior fossa plate destruction; central calcifications	Heterogeneous T1 (hyperintense hemorrhage); heterogeneous T2; heterogeneous enhancement
Facial nerve schwannoma	Smooth remodeling of facial nerve canal	Tubular enhancement along CN VII
Cholesteatoma	Bony erosion of ossicular chain/tegmen/EAC	Restricted diffusion on DWI (non-EPI)
SCC temporal bone	Soft tissue mass ± bony erosion ± mastoid involvement	Enhancing soft tissue; perineural spread along CN VII/V
Chordoma	Midline/skull base bone destruction	Hyperintense T2 — characteristic
Chondrosarcoma	Eccentric; calcifications; petroclival	Similar to chordoma but off-midline
Choristoma/Lipoma IAC	Normal bony canal	Hyperintense T1; no fat-sat enhancement

Primary Sources:

K.J. Lee's Essential Otolaryngology, Ch. 24 "Tumors of the Temporal Bone", pp. 481–493
Cummings Otolaryngology Head and Neck Surgery, Ch. 178 (Temporal Bone Neoplasms), pp. 3404–3436; Ch. 179 (Glomus Tumors), pp. 3436–3489
Grainger & Allison's Diagnostic Radiology, Ch. 61 (Temporal Bone), pp. 1589–1590

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