How is conductive hearing loss different from sensory loss?
Conductive hearing loss and sensorineural hearing loss are two main types of hearing loss with distinct causes and characteristics. Here's how they differ:
Conductive Hearing Loss:
1. Cause: Conductive hearing loss occurs when sound waves are not efficiently conducted from the outer ear to the inner ear. This can be due to issues in the outer ear (e.g., earwax blockage, foreign objects, otitis externa) or the middle ear (e.g., otitis media, tympanic membrane perforation, ossicular chain abnormalities).
2. Sound Transmission: In conductive hearing loss, sound waves are either partially or completely blocked from reaching the inner ear, resulting in a reduction in the overall volume of sounds.
3. Speech Understanding: Conductive hearing loss typically does not significantly affect the clarity or intelligibility of speech. Individuals may have difficulty hearing faint sounds, but they can usually understand speech in quiet environments.
4. Rinne Test: The Rinne test is used to differentiate between conductive and sensorineural hearing loss. In conductive hearing loss, air conduction (using a vibrating tuning fork held near the ear) is better than bone conduction (placing the vibrating tuning fork on the mastoid bone behind the ear).
5. Weber Test: The Weber test is another useful test. When a vibrating tuning fork is placed on the forehead, individuals with conductive hearing loss perceive the sound as louder or equal in both ears.
Sensorineural Hearing Loss:
1. Cause: Sensorineural hearing loss arises from damage to the inner ear structures, including the cochlea, hair cells, and auditory nerve. It can result from genetic factors, aging (presbycusis), noise exposure, certain medications, infections, autoimmune disorders, and other underlying medical conditions.
2. Sound Perception: In sensorineural hearing loss, the inner ear and nerve pathways are affected, impairing the proper reception and transmission of sound signals to the brain. Individuals may experience a reduced perception of loudness and difficulty understanding speech, especially in noisy environments.
3. Speech Understanding: Sensorineural hearing loss often affects the clarity of speech, making it difficult to understand conversational speech, even at a normal volume.
4. Rinne Test: In sensorineural hearing loss, bone conduction is usually better than air conduction in the Rinne test.
5. Weber Test: Individuals with sensorineural hearing loss may experience lateralization of sound to the better-hearing ear during the Weber test.
Conductive hearing loss can often be treated medically or surgically, whereas sensorineural hearing loss is typically permanent and may require assistive devices like hearing aids or cochlear implants for effective management.