Endoscopic Approach to the Round Window in Infants and Toddlers: Electrical Stimulation of the Cochlea

By June 7, 2019

Germiller, John1,2; Javia, Luv1,2
1 Division of Otolaryngology, Children’s Hospital of Philadelphia, Philadelphia PA, USA;
2 Department of Otorhinolaryngology, University of Pennsylvania, Philadelphia, PA, USA.

Endoscopic techniques facilitate access to the posterior mesotympanum, including the round window (RW) niche.  At our center, children with cochlear nerve hypoplasia undergo electrically-evoked ABR (EABR) testing, to determine candidacy for cochlear implantation vs. ABI.  We have begun employing endoscopic tympanotomy to access the RW directly, and deliver noninvasive electrical stimulation to elicit EABR responses.  Most patients are infants and toddlers, a population rarely undergoing endoscopic ear surgery.

Study Design: Prospective observational
Setting: Tertiary center
Patients/Interventions: Endoscopic RW EABR was performed unilaterally in 5 children and bilaterally in 8 (total 21 ears; median age 23 mo).  The youngest patient was 8 months of age.   Standard 3mm, 14-cm, 0- and 30-degree endoscopes were used.  Under endoscopic visualization, the posterior TM was elevated and a 1-mm ball-tip probe was placed directly on the RW membrane and stimulation applied.  The promontory was also stimulated for comparison. Nerve responses were measured by ABR.

Main Outcome Measures: successful RW access, complications.

Endoscopic access, stimulation of the RW, and EABR measurement were successful in all 21 ears.  A slightly modified tympanomeatal flap was needed to accommodate the very short ear canals in these patients.  No bone removal was necessary.  No injuries to the RW membrane occurred and all tympanic membranes healed.  One patient experienced transient facial weakness due to the electrical stimulation.

Endoscopic tympanotomy is a safe and effective technique to access the inner ear via the round window.  Access is straightforward even in young infants.  This approach may facilitate future therapies requiring access to the inner ear in infants and toddlers.