boneconduction

Bone conduction refers to a process of hearing where sound is transmitted to the inner ear primarily through vibrations of the skull bones, bypassing the outer and middle ear. This pathway can stimulate the cochlea directly via the cranial bones, producing neural signals that are interpreted as sound by the brain.

Mechanism and pathways: A transducer converts electrical signals into mechanical vibrations applied to the skull, typically at the mastoid bones or temples. The vibrations spread through the skull to the cochleae of both ears, causing hair cells to initiate neural impulses along the auditory nerve. Because the signal reaches both cochleae, bone conduction can produce bilateral auditory input, though the effectiveness depends on device type, placement, and individual anatomy.

Devices and implementations: External bone conduction devices rest on the skull and transmit sound through the bones, suitable for temporary or non-surgical use. Implanted bone conduction devices include osseointegrated implants (bone-anchored devices) and active transcutaneous systems that couple a surgically implanted component to an external or percutaneous transducer. These are used to treat various forms of hearing loss and can be advantageous when the outer or middle ear is diseased, blocked, or absent. They are also employed in some cases of single-sided deafness.

Indications and outcomes: Bone conduction methods are indicated for conductive hearing loss, mixed hearing loss, single-sided deafness, and certain anatomical ear conditions. They can provide functional hearing when conventional air-conduction aids are unsuitable. Outcomes vary with device type, skin and tissue condition, skull characteristics, and user adaptation.

Limitations: Efficacy depends on skull properties, transducer coupling, and surgical factors for implanted systems. High-frequency transmission may be less efficient than low-frequency transmission, and external devices require proper fit and hygiene. Cost and maintenance, including potential surgical considerations, are also factors.