A 45-year-old woman presents with episodic vertigo lasting 20-30 minutes, fluctuating low-frequency sensorineural hearing loss, aural fullness, and tinnitus over 2 years. Electrocochleography (ECochG) is performed. The diagnostic finding most supportive of endolymphatic hydrops is:
- A Prolonged Wave V latency on ABR
- B SP/AP ratio (summating potential to action potential ratio) greater than 0.4 ✓
- C Absent otoacoustic emissions bilaterally
- D Type B tympanogram on the affected side
Correct answer: B. SP/AP ratio (summating potential to action potential ratio) greater than 0.4
Explanation
Electrocochleography (ECochG) measures cochlear electrical potentials. In endolymphatic hydrops (Meniere's disease), basilar membrane distension increases the summating potential (SP) relative to the compound action potential (AP). An elevated SP/AP ratio greater than 0.35-0.40 is the diagnostic criterion for endolymphatic hydrops on ECochG, reflecting distortion of the traveling wave on the hydropic basilar membrane. ABR Wave V latency tests retrocochlear function; absent OAEs suggest outer hair cell damage; Type B tympanogram indicates middle ear effusion.
Reference: Dhingra Diseases of Ear, Nose and Throat, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.