Chapter 11: Labyrinthectomy

Introduction

Post-auricular labyrinthectomy is a surgical technique designed to eradicate labyrinthine vertigo by removing the semicircular canals and soft tissues of the vestibule. It is also a common approach for accessing the internal auditory canal (IAC) and managing conditions such as Ménière’s disease, translabyrinthine vestibular neurectomy, and acoustic neuroma surgery. This guide outlines the procedural steps, anatomical landmarks, and clinical considerations for successful execution ( 1, 2, 3, 4, 5, 12).

Surgical Objectives

1. Eradicate vestibular function by removing neuroepithelium in the semicircular canals and vestibule.
2. Provide access to the IAC for surgical interventions.
3. Preserve critical anatomical structures such as the facial nerve and dura ( 1, 2, 4, 5).

Key Anatomical Landmarks

• Posterior Canal Wall: Important for orientation during mastoidectomy ( 1, 4).
• Horizontal Semicircular Canal: Initial structure for opening the labyrinth ( 1, 2).
• Superior Semicircular Canal: Extends medially and is followed to the common crus ( 1, 3, 12).
• Posterior Semicircular Canal: Traced inferiorly and anteriorly under the descending facial nerve ( 1, 2, 3).
• Tegmen Tympani: Landmark for drilling near the middle fossa plate ( 1, 2).
• Facial Nerve: Critical for preservation, with segments at risk in proximity to canals ( 1, 4, 12).
• Sigmoid Sinus: Exposed during mastoidectomy and posterior dissection ( 1, 2).
• Endolymphatic Duct: Identified at the anterior end of the common crus, leading into the vestibule ( 1, 3, 5).

Surgical Steps

1. Mastoidectomy and Canal Identification

• Perform an extended mastoidectomy while preserving the posterior canal wall (Source 12).
• Drill the sinodural angle to expose the vestibule, ensuring thinning of the middle fossa dura for access to the superior semicircular canal ( 1, 3).
• Delineate the sigmoid sinus and retrofacial air cells to provide adequate exposure ( 1, 5).

2. Sequential Canal Opening

1. Lateral Semicircular Canal:
   • Open posteriorly using a cutting burr.
   • Progress anteriorly, preserving bony protection for the facial nerve ( 1, 2).
   • Use “blue lines” (shadows of the canal lumen) as orientation (Source 5).
2. Posterior Semicircular Canal:
   • Trace anteriorly to the common crus, noting its proximity to the descending facial nerve ( 1, 3, 5).
3. Superior Semicircular Canal:
   • Drill from the ampulla to the common crus, under the middle fossa plate ( 2, 4).

3. Vestibule Opening and Cleaning

• Open the vestibule widely by following the common crus.
• Remove all soft tissue, including neuroepithelium, from the vestibule and canals ( 1, 5, 12).
• Note specific structures:
  • Macula of Utricle and Saccule: Elliptical recess (utricle) posteriorly and spherical recess (saccule) anteriorly ( 1, 4).
  • Stapes Footplate: Palpated medially for orientation ( 1, 5).
  • Endolymphatic Duct: Recognized as a pearly, thread-like structure ( 1, 3, 5).

Clinical Considerations

• Vertigo Management: Labyrinthectomy is effective for refractory Ménière’s disease without serviceable hearing ( 2, 5).
• Translabyrinthine Access: Offers a direct route to the vestibular nerve for neurectomy or acoustic neuroma excision ( 5, 12).
• Anatomical Risks:
  • Facial nerve injury at the external genu or descending segment ( 1, 3).
  • Over-drilling of vestibular floor, risking damage to the fundus of the IAC ( 3, 12).

Technical Tips

1. Use Large Burrs: Reduces bone dust accumulation, minimizes frictional heat, and speeds dissection ( 1, 4).
2. Profuse Irrigation: Essential to clear debris and prevent thermal injury (Source 1).
3. Systematic Approach: Follow canals meticulously to maintain orientation and avoid “snake eyes” (confusion from non-sequential transection) ( 1, 3).
4. 3D Conceptualization: Visualize spatial relationships between structures for accurate dissection ( 1, 5).

Advanced Applications

• Endolymphatic Sac Decompression: Offers therapeutic potential in certain Ménière’s cases (Source 5).
• Translabyrinthine IAC Exposure: Facilitates vestibular nerve sectioning while preserving cochlear nerve integrity ( 5, 12).
• Surgical Education: Provides a foundation for understanding complex temporal bone anatomy ( 3, 12).

Conclusion

Post-auricular labyrinthectomy is a highly technical procedure requiring mastery of temporal bone anatomy and surgical precision. A systematic approach, guided by anatomical landmarks and careful preservation of critical structures, ensures optimal outcomes for patients and valuable learning for surgical trainees ( 1-5, 12).