Which finding is most indicative of retrocochlear pathology in unilateral hearing loss?

Which finding is most indicative of retrocochlear pathology in unilateral hearing loss?

• A. Normal WRS
• B. Absent contralateral acoustic reflex at 2 kHz
• C. Normal tympanometry
• D. Symmetric mild SNHL

Answer: (B)

Understanding retrocochlear pathology helps explain why the acoustic reflex findings matter. The acoustic reflex involves a pathway through the eighth nerve and brainstem that triggers the stapedius muscle to contract in response to loud sounds. If there is a lesion along this reflex arc beyond the cochlea (retrocochlear), especially on the side with hearing loss, the reflex can fail to occur when testing on the contralateral side. So, an absent contralateral acoustic reflex at 2 kHz in someone with unilateral hearing loss points to a retrocochlear issue, such as a lesion on the affected eighth nerve or nearby brainstem structures. Normal tympanometry suggests the middle ear is functioning, which makes a middle-ear source less likely. A symmetric mild sensorineural loss is more consistent with a cochlear or bilateral process rather than a retrocochlear lesion on one side. A normal word recognition score, while possible in some cases, does not specifically indicate retrocochlear pathology, because WRS can be variable and is not as sensitive a sign as an absent contralateral reflex for this purpose.

Understanding retrocochlear pathology helps explain why the acoustic reflex findings matter. The acoustic reflex involves a pathway through the eighth nerve and brainstem that triggers the stapedius muscle to contract in response to loud sounds. If there is a lesion along this reflex arc beyond the cochlea (retrocochlear), especially on the side with hearing loss, the reflex can fail to occur when testing on the contralateral side. So, an absent contralateral acoustic reflex at 2 kHz in someone with unilateral hearing loss points to a retrocochlear issue, such as a lesion on the affected eighth nerve or nearby brainstem structures.

Normal tympanometry suggests the middle ear is functioning, which makes a middle-ear source less likely. A symmetric mild sensorineural loss is more consistent with a cochlear or bilateral process rather than a retrocochlear lesion on one side. A normal word recognition score, while possible in some cases, does not specifically indicate retrocochlear pathology, because WRS can be variable and is not as sensitive a sign as an absent contralateral reflex for this purpose.