How does a cholesteatoma (abnormal skin growth in the middle ear) spread to other areas?

Cholesteatoma Routes of Spread

Cholesteatomas spread through bone erosion, following paths of least resistance along pneumatized spaces, and can invade critical structures including the inner ear, facial nerve, and intracranial compartments. Understanding these pathways is essential for early detection and prevention of serious complications.

Anatomical Routes of Spread

Primary Expansion Pathways

• Middle ear cavity: Initial growth typically begins in the epitympanum or attic region
• Mastoid antrum and air cells: Expansion follows pneumatized spaces
• Ossicular chain: Early erosion commonly affects the incus and malleus
• Scutum: Erosion of this bony prominence is an early radiographic sign

Critical Invasive Routes

• Tegmen tympani/mastoideum: Upward spread can lead to:

  • Dural exposure
  • Brain herniation
  • Cerebrospinal fluid leakage
  • Intracranial complications 1

• Lateral semicircular canal: Erosion causes:

  • Vertigo
  • Sensorineural hearing loss
  • Labyrinthine fistula 2

• Facial nerve canal: Dehiscence leads to:

  • Facial nerve exposure
  • Potential facial paralysis 2

• Vascular structures:

  • Sigmoid sinus invasion (seen in 25% of extensive cases)
  • Jugular bulb involvement (8.33% of extensive cases)
  • Internal carotid artery (rare but dangerous) 1

Imaging Characteristics of Spread

CT Findings

• Provides excellent anatomic detail of both bony and soft tissue structures
• Reveals extent of disease and bone erosion patterns
• Essential for surgical planning and identifying anatomical variations 2

MRI Findings

• Diffusion-weighted imaging (DWI) differentiates cholesteatoma from:
  • Scar tissue
  • Inflamed granulation tissue
  • Other middle ear pathologies 2
• Non-echoplanar DWI in the coronal plane offers high sensitivity and specificity 2

Complications by Route of Spread

Intratemporal Complications

• Ossicular destruction leading to conductive hearing loss
• Labyrinthine fistula causing vertigo and sensorineural hearing loss
• Facial nerve paralysis from canal erosion

Intracranial Complications

• Meningitis
• Brain abscess (particularly cerebellar)
• Sigmoid sinus thrombosis (16.66% of extensive cases)
• Petrositis (8.33% of extensive cases) 1

Clinical Manifestations by Spread Pattern

• Foul-smelling purulent discharge (100% of extensive cases)
• Otalgia (75%)
• Hard of hearing (83.33%)
• Vertigo (58.33%)
• Temporal headache (33.33%) 1

Management Considerations Based on Spread

• Canal wall down mastoidectomy is typically required for extensive disease
• Neurosurgical intervention may be necessary when intracranial structures are involved
• Blind sac closure for severe cases with extensive spread (25% of extensive cases) 1

Pitfalls in Diagnosis

• Cholesteatoma may be mistaken for acute otitis externa or chronic external otitis
• Unlike these conditions, cholesteatoma is typically painless in early stages
• Associated with tympanic membrane abnormalities including perforation, retraction pockets, and granulation tissue 2
• Non-specific symptoms can delay diagnosis, particularly in atypical locations like paranasal sinuses 3

Early recognition of cholesteatoma spread patterns is crucial for preventing serious complications. High-resolution CT without contrast and MRI with DWI sequences are complementary imaging modalities that together provide the most comprehensive assessment of disease extent and invasion of critical structures.