A 62-year-old man presents with progressive bilateral hearing loss over 10 years. Pure tone audiometry shows bilateral symmetrical sensorineural hearing loss with bone conduction thresholds better than air conduction thresholds at all frequencies. Otoscopy is normal. Which investigation is most appropriate to confirm the diagnosis of age-related hearing loss and rule out retrocochlear pathology?

## Investigation of Choice for Suspected Sensorineural Hearing Loss ### Clinical Context The patient presents with bilateral symmetrical sensorineural hearing loss (bone conduction better than air conduction) with normal otoscopy. While the history suggests presbycusis (age-related), retrocochlear pathology (acoustic neuroma, brainstem lesion) must be excluded. ### Why ABR is the Gold Standard **Key Point:** Auditory brainstem response (ABR) is the investigation of choice for: - Confirming sensorineural hearing loss - Detecting retrocochlear pathology (acoustic neuroma, brainstem lesions) - Assessing neural synchrony and transmission time - Evaluating asymmetrical hearing loss **High-Yield:** ABR measures electrical activity from CN VIII and brainstem nuclei in response to clicks. Abnormal findings include: - Prolonged latency of waves I, III, V - Increased I–V interpeak interval (>4 ms suggests retrocochlear lesion) - Absent waves (severe hearing loss or neural dysfunction) ### Differential Investigation Table | Investigation | Purpose | Sensitivity for Retrocochlear | Best Used For | |---|---|---|---| | **ABR** | Assess neural transmission, detect retrocochlear pathology | High (>95% for acoustic neuroma) | Asymmetrical SNHL, suspected retrocochlear lesion | | Speech discrimination score | Assess speech understanding | Low | Hearing aid candidacy, functional assessment | | Acoustic reflex | Assess stapes and CN VII function | Moderate | Conductive loss, CN VII palsy | | Tympanometry | Assess middle ear pressure and compliance | None | Conductive loss, eustachian tube dysfunction | | Electrocochleography | Assess cochlear microphonic and action potential | Low | Ménière's disease, endolymphatic hydrops | **Clinical Pearl:** In a patient with sensorineural hearing loss and normal otoscopy, ABR is mandatory to exclude acoustic neuroma before attributing the loss to presbycusis. ### Mnemonic: ABR Indications **"SCAN"** — **S**ymmetry assessment, **C**ochlear vs retrocochlear, **A**coustic neuroma screening, **N**eural transmission evaluation. **Tip:** ABR is also used for objective hearing assessment in patients who cannot cooperate with conventional audiometry (infants, malingerers).