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Posterior semi-circular canal electrode misplacement in Goldenhar's syndrome
Ashish Castellino1, Pabina Rayamajhi1, Rahul Kurkure1
1Madras ENT Research Foundation (P) Ltd, Chennai, India.
Insights
Electrode misplacement in cochlear implants, though rare, can occur. This case highlights posterior semicircular canal (SCC) misplacement in a Goldenhar syndrome patient, successfully corrected with HRCT guidance.
Area of Science:
- Otolaryngology
- Neurosurgery
- Medical Imaging
Background:
- Electrode misplacement in cochlear implant surgery ranges from 0.2% to 5.8%.
- The superior semicircular canal (SCC) is the most common site for misplacement.
- Congenital anomalies can complicate surgical landmark identification.
Observation:
- A child with Goldenhar syndrome and bilateral profound sensorineural hearing loss (SNHL) underwent cochlear implantation.
- Intraoperative findings revealed absent key landmarks, necessitating a subtotal petrosectomy.
- Initial electrode insertion into the posterior SCC was confirmed by post-operative HRCT, despite normal impedance but absent Neural Response Telemetry (NRT).
Findings:
- Post-operative HRCT identified cochlear implant electrode misplacement in the posterior SCC.
- Revision surgery successfully repositioned the electrode via a new cochleostomy.
- Corrected placement was confirmed by robust NRT tracings.
Implications:
- Accurate identification of surgical landmarks is crucial for cochlear implant electrode insertion.
- Intraoperative impedance testing and NRT are vital for confirming device integrity and correct placement.
- Post-operative HRCT serves as a valuable tool for diagnosing and guiding corrective action for electrode malposition, especially in resource-limited settings.
Abstract:
Literature documents the incidence of electrode misplacement within the range of 0.2% to 5.8% with the superior SCC as the most common site, followed by the vestibule. In this report, we present the finding of electrode misplacement in the posterior SCC in a child with Goldenhar syndrome which was subsequently corrected. This child with bilateral congenital profound SNHL presented for unilateral cochlear implant surgery. Intraoperatively, the lateral SCC bulge, stapes, oval window, round window niche and pyramid were noted absent, leading to a surgical decision in favour of a subtotal petrosectomy. Using the aberrant facial nerve and jugular bulb as critical landmarks, a cochleostomy was performed in the posteroinferior aspect of the promontory bulge. Although electrode insertion was smooth and complete, NRT was absent in the presence of normal electrode impedance. A post-operative HRCT scan showed the electrodes in the posterior SCC. Repositioning of the electrodes was carried out by creating a new cochleostomy anteroinferior to the previous one. Complete correct electrode insertion was accomplished via this cochleostomy complimented by robust NRT tracings. Cochlear implant electrode insertion should be supported by correct identification of surgical landmarks. Intraoperative impedance testing and NRT help confirm device integrity and correct placement, the absence of which may raise the suspicion of malposition. In the presence of such a suspicion, the post-operative HRCT scan is a useful retrospective guide to corrective action, in a low-cost setting lacking intra-operative imaging facilities like X-ray, Fluoroscopy, Flat Panel CT & CBCT. Abbreviations, BERA: Brainstem Evoked Response Audiometry; CBCT: Cone Beam Computed Tomography; EAC: External Auditory Canal; ITD: Insertion Test Device; LSCS: Lower Segment Caesarean Section; MDT: Multi-Disciplinary Team; NICU: Neonatal Intensive Care Unit; NRT: Neural Response Telemetry; OAE: Oto-Acoustic Emissions; PIH: Pregnancy Induced Hypertension; SCC: Semi-Circular Canal; SNHL: Sensori-Neural Hearing Loss.
