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Defining the Access Routes to Intracochlear Drug Delivery Based on Temporal Bone Histology 3-Dimensional Models.

Zohar Hovev1,2,3,4, Daniel Moverman5,6, Alicia M Quesnel7,8

  • 1Otopathology Laboratory, Massachusetts Eye and Ear, Boston, Massachusetts, USA, zhovev@meei.harvard.edu.

Audiology & Neuro-Otology
|December 10, 2025
PubMed
Summary
This summary is machine-generated.

Optimizing inner ear drug delivery requires precise needle trajectories through the round window. This study defines optimal needle form and dimensions for minimally invasive access, preserving inner ear structures and function.

Keywords:
Crista fenestraGene therapyInner ear drug deliveryMicroneedleRound window membraneTrans-tympanic

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Area of Science:

  • Otolaryngology
  • Regenerative Medicine
  • Pharmacology

Background:

  • Effective genetic and regenerative treatments for sensorineural hearing loss depend on optimized inner ear access.
  • Minimally invasive transcanal approaches to the scala tympani via the round window are crucial for inner ear drug delivery.

Purpose of the Study:

  • To determine optimal needle trajectories and dimensions for minimally invasive transcanal access to the scala tympani.
  • To provide anatomical data for designing injection needles for structure- and function-preserving inner ear drug delivery.

Main Methods:

  • Three-dimensional modeling of eight human temporal bone histological sections.
  • Measurement of key anatomical relationships and optimal needle trajectories for transcanal access.
  • Analysis of needle bend angles and lengths for effective scala tympani penetration.

Main Results:

  • The optimal needle trajectory involves leaning and bending the needle at the superiormost point of the round window niche operculum.
  • Optimal needle medial part length ranges from 1.375 mm to 3.49 mm, with a bend angle of 147°.
  • Penetration at the round window membrane's vertical axis center minimizes damage, avoiding the crista fenestra.

Conclusions:

  • The study provides critical form and size factors for optimal transcanal inner ear access.
  • These findings facilitate the development of improved needles for structure- and function-preserving inner ear drug delivery.