Anatomy of the Round Window and Implications for Intratympanic Drug Delivery

By June 7, 2019

Pollak, Natasha1; Shariat-Madar, Bahbak1
1 Department of Otolaryngology-Head and Neck Surgery, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, USA.

Intratympanic injection therapy has become a widely utilized modality for localized drug delivery targeting the inner ear, particularly with an increasing role of intratympanic injections in the management of sudden sensorineural hearing loss.  Once a solution is injected into the middle ear space, the drug enters the inner ear primarily by absorption through the semipermeable round window membrane.  Prior studies have described the variable anatomy of the round window niche, most of them focusing on the round window as the access point for cochlear implant or other implantable hearing device placement.  This study investigates the anatomical variability of the round window niche, specifically focusing on features relevant to intratympanic injection therapy.

This retrospective review study was completed in a tertiary care referral center.  We reviewed the operative reports, photographs and videos of ear surgeries done by the senior author during the last 4 years, examined the variability of anatomy of the round window niche, and compared our findings to those of other researchers when possible.  Included in the study were adult patients who underwent ear surgery for a variety of conditions, both inflammatory and non-inflammatory.

Both the bony and membranous anatomy of the round window niche shows significant variability in our patient population.  Different patterns of variability are seen in patients with inflammatory vs. non-inflammatory conditions.

Round window anatomy is variable and predictable patterns of variability are seen.  These anatomic variations may have significant implications for intratympanic injection as a targeted drug delivery method.