Electrocochleography (EcoG): Electrocochleography (EcoG) measures the summated intracellular potentials of the outer hair cells seen in response to an auditory stimulus. The electrical response is either due to cochlear microphonic potentials(electrical activity in the cochlea), summating potentials(a complex measurement of many electrophysiological parameters taken together) or electrical activity due to action potential of 8th nerve. It is an objective test that provides a reasonably accurate measurement of the hearing threshold between 1000 to 8000 Hz. No masking in the contralateral ear is required.
A schematic illustration of the placement of the transtympanic needle electrode and the electrocochleographic waveforms.
Procedure: The electrical activity can be detected by inserting a needle-like thin, active recording electrode through the tympanic membrane and placing onto the promontory or round window. The reference and ground electrodes are placed on the mastoid process and on the forehead respectively. It is usually done under sedation or local anaesthesia.
Uses of EcoG:
- To diagnose Meniere’s disease.
- To detect hearing threshold in the young infants and children within 5–10 dB
- To differentiate cochlear lesions from eighth nerve lesions.
- To monitor cochlea and cochlear nerve during neurotological surgical procedure.
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Learning resources.
- Scott-Brown, Textbook of Otorhinolaryngology Head and Neck Surgery.
- Glasscock-Shambaugh, Textbook of Surgery of the Ear.
- P L Dhingra, Textbook of Diseases of Ear, Nose and Throat.
- Hazarika P, Textbook of Ear Nose Throat And Head Neck Surgery Clinical Practical.
- Mohan Bansal, Textbook of Diseases of Ear, Nose and Throat Head and Neck surgery.
- Anirban Biswas, Textbook of Clinical Audio-vestibulometry.
- Ganong’s Review of Medical Physiology.
Author:
Dr. Rahul Kumar Bagla
MS & Fellow Rhinoplasty & Facial Plastic Surgery.
Associate Professor & Head
GIMS, Greater Noida, India
msrahulbagla@gmail.com
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