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Published on: February 29, 2020
Reversible electrocochleographic abnormalities in superior canal dehiscence
H Alexander Arts1, Meredith E Adams, Steven A Telian
1Department of Otolaryngology-Head and Neck Surgery, University of Michigan School of Medicine, Ann Arbor, Michigan 48109-0312, USA. aarts@umich.edu
Summary
Abnormal electrocochleography (ECoG) findings, specifically an elevated summating potential to action potential (SP/AP) ratio, are common in superior semicircular canal dehiscence (SSCD). Surgical correction of SSCD normalizes these ECoG results.
Area of Science:
- Neuroscience
- Otolaryngology
- Audiology
Background:
- Electrocochleography (ECoG) is a diagnostic tool for episodic vertigo, often indicating endolymphatic hydrops.
- Superior semicircular canal dehiscence (SSCD) is increasingly recognized as a cause of vestibular and auditory symptoms.
- This study investigates the relationship between SSCD and ECoG findings.
Purpose of the Study:
- To examine electrocochleographic (ECoG) findings in patients diagnosed with superior semicircular canal dehiscence (SSCD).
- To determine if ECoG abnormalities in SSCD patients normalize after surgical intervention.
Main Methods:
- A retrospective case series of 11 adult patients (7 unilateral SSCD, 4 bilateral SSCD) was conducted.
- Patients underwent audiometry, tympanic electrocochleography (ECoG), vestibular-evoked myogenic potentials (VEMPs), and high-resolution CT imaging.
- Five patients had superior canal obliteration, with pre- and post-operative ECoG and VEMP assessed in four.
Main Results:
- Fourteen of 15 ears with confirmed SSCD showed an elevated summating potential to action potential (SP/AP) ratio (>0.40).
- In patients who underwent superior canal obliteration, the SP/AP ratio normalized post-surgery.
- Intraoperative ECoG in one patient demonstrated immediate normalization of the SP/AP ratio upon canal occlusion.
Conclusions:
- An elevated SP/AP ratio on ECoG is a consistent finding in SSCD.
- These findings suggest that SSCD should be considered in the differential diagnosis of abnormal ECoG, previously attributed mainly to endolymphatic hydrops.
- Normalization of the SP/AP ratio after surgical correction supports the link between SSCD and ECoG abnormalities.
