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GLOMUS TUMOR (Paraganglioma of the Temporal Bone / Neck)

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1. INTRODUCTION AND NOMENCLATURE

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2. ORIGIN / ANATOMY

• Along Jacobson's nerve (branch of CN IX - tympanic branch) - in the middle ear
• Along Arnold's nerve (auricular branch of CN X) - in the middle ear
• In the adventitia of the jugular bulb - at the jugular foramen
• Along the vagus nerve in the neck

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3. HISTOLOGY / PATHOLOGY

• Predominate in the tumor
• Contain dense-core granules filled with catecholamines
• Part of the amine precursor and uptake decarboxylase (APUD) system
• Polygonal, with abundant granular eosinophilic cytoplasm
• Stain positively for: neuron-specific enolase (NSE), chromogranin A, synaptophysin
• Arranged in a characteristic nested pattern = Zellballen

• Elongated, closely resemble Schwann cells
• Peripherally surround the Type I cells
• Difficult to see on light microscopy (spindle-shaped, basophilic)
• Stain with S-100 and focally with GFAP

Important: Nuclear pleomorphism and cellular hyperchromatism are common in PGLs and should NOT be taken as evidence of malignancy. - Cummings Otolaryngology

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4. EPIDEMIOLOGY

• Most common benign neoplasm of the middle ear
• Predominantly affects women (F:M ratio ~6:1 for jugulotympanic)
• Peak incidence: 5th and 6th decades
• Can be sporadic or familial
• Rule of 10s (K.J. Lee's Essential Otolaryngology):
  • 10% bilateral
  • 10% familial
  • 10% malignant

• Autosomal dominant inheritance
• Associated with mutations in succinate dehydrogenase (SDH) subunit genes (SDHB, SDHC, SDHD)
• Higher rates of bilateral and multicentric tumors in familial cases

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5. VASOACTIVE PROPERTIES

• Catecholamines
• Norepinephrine, dopamine
• Somatostatin
• Vasoactive intestinal polypeptide (VIP)
• Calcitonin

• Order 24-hour urine VMA (vanillylmandelic acid) and serum catecholamine levels
• If elevated, get abdominal CT to rule out pheochromocytoma
• Treat adrenergic symptoms before surgery

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6. CLINICAL FEATURES

A. Glomus Tympanicum

B. Glomus Jugulare

C. Glomus Vagale

• Arises from vagus body high in neck at C1-C2 level
• May extend superiorly to mimic glomus jugulare
• Anterior displacement of the high cervical ICA on imaging

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7. OTOSCOPIC / CLINICAL SIGNS

• If all borders of the mass are visible through the TM → Glomus tympanicum (small, contained)
• If borders are not all visible → could be large glomus tympanicum or glomus jugulare extending into middle ear
• If cranial nerve deficits are present → more likely glomus jugulare

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8. INVESTIGATIONS

Radiology

• Glomus jugulare: destruction of the bony septum between ICA and IJV (highly specific finding)
• Irregular permeative ("moth-eaten") pattern of bone destruction
• Erosion of the jugular foramen
• Separates from aberrant ICA (which lacks this bony destruction)

• Classic "salt and pepper" appearance on T1/T2
  • "Pepper" (black) = flow voids from enlarged vessels (high vascular flow)
  • "Salt" (white) = areas of slow flow or subacute hemorrhage
• Intense post-gadolinium enhancement
• Defines intracranial extension

• Gold standard for vascular mapping
• Identifies feeding vessels for preoperative embolization
• Shows characteristic intense tumor blush
• Main feeders: ascending pharyngeal artery, posterior division of middle meningeal artery
• Less common: stylomastoid branch of occipital artery, posterior auricular artery

1. 24-hour urine metanephrines / VMA
2. Serum catecholamines (if secreting suspected)
3. Abdominal CT (to rule out pheochromocytoma)
4. Preoperative angiography with embolization

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9. STAGING / CLASSIFICATION

Fisch Classification (1978)

Glasscock-Jackson Classification (1982)

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10. DIFFERENTIAL DIAGNOSIS

Important: Never biopsy a suspected glomus tympanicum without proper imaging, to exclude aberrant ICA or high-riding jugular bulb.

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11. MANAGEMENT

Preoperative Preparation

1. Screen for secreting tumor (24-hr urine metanephrines)
2. Preoperative embolization 24-48 hours before surgery for sizeable tumors:
   • Significantly reduces intraoperative blood loss and operative time
   • Uses particles like Embospheres (100-500 μm) or PVA
   • Avoid embolizing stylomastoid artery (CN VII risk) - use lidocaine provocative test
3. Anesthesiology team coordination if secreting tumor

Surgical Treatment

• Most commonly approached by the Fisch Type A infratemporal fossa approach
• This involves: transposition of the facial nerve, closure of EAC, and wide exposure of the jugular foramen
• Staging may be necessary for large tumors with extensive intracranial extension
• Cranial nerves VII-XII may be involved at the skull base
  • Superficial involvement: segmental removal of epineurium
  • Frank neural invasion: may require segmental neurectomy (with caution)
  • Priority: nerve preservation due to significant morbidity of lower cranial nerve resection (may need tracheostomy + gastrostomy)
• ICA involvement: Preoperative balloon occlusion test or stenting if tumor infiltrates horizontal petrous ICA

• Intraoperative ligation of feeding vessels (ascending pharyngeal, stylomastoid, caroticotympanic, internal maxillary, superior tympanic arteries) before tumor removal to reduce bleeding.

Radiotherapy

• Elderly or medically unfit patients
• Bilateral tumors (to spare the contralateral side)
• Residual tumor after surgery
• Unresectable disease
• Patient preference (avoiding surgical morbidity)

Observation (Watch and Wait)

• Small, incidentally found, asymptomatic tumors in elderly patients
• Slow-growing nature justifies close surveillance with MRI

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12. COMPLICATIONS

• CN VII palsy (facial nerve injury)
• CN IX, X, XI, XII deficits (dysphagia, hoarseness, aspiration, shoulder weakness)
• Cerebrospinal fluid leak
• Significant intraoperative hemorrhage
• Sensorineural hearing loss
• Need for tracheostomy / gastrostomy (in severe lower CN palsy)

• Worsening facial nerve function
• Hearing loss
• Hoarseness
• Ataxia (rare)

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13. MALIGNANCY

• Rare: ~3-5% of paragangliomas are malignant
• Malignancy is defined by presence of distant metastases (lymph nodes, bone, lung, liver) - NOT histological appearance
• Local invasion alone does not mean malignancy
• SDHB mutations are associated with higher risk of malignancy

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14. QUICK MEMORY AID

GLOMUS TUMOR - KEY POINTS

Origin:      Neural crest → paraganglia cells
Location:    Jugular bulb (jugulare) / Middle ear (tympanicum)
Type:        Most common benign tumor of middle ear
Histology:   Zellballen pattern; Chief cells + Sustentacular cells
Symptoms:    Pulsatile tinnitus + Conductive hearing loss
Sign:        Reddish-blue mass behind TM (pulsatile)
Brown's sign: Blanching on pneumatic otoscopy
MRI:         "Salt and Pepper" appearance
CT:          Permeative bone erosion; absent bony septum (jugulare)
Angio:       Gold standard; intense tumor blush
Rule of 10s: 10% bilateral, 10% familial, 10% malignant
Surgery:     Fisch Type A (jugulare); transcanal (small tympanicum)
Pre-op:      Embolization 24-48h before; urine VMA screening
Radiotherapy: 90-100% tumor control rates

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REFERENCES

• Cummings Otolaryngology Head and Neck Surgery, 7th Ed - Chapters 136 & 178 (Paragangliomas of Temporal Bone)
• K.J. Lee's Essential Otolaryngology, 11th Ed - Chapter: Paragangliomas
• Shambaugh Surgery of the Ear - Glomus Tumor Section