Ossicular chain disruption: damage to the middle ear bones and hearing loss

Sound reaches the ear as vibrations that move the eardrum. Behind the eardrum, in the air-filled middle ear, three small bones, the malleus (hammer), incus (anvil) and stapes (stirrup), form a chain that carries those vibrations to the inner ear. Sint-Trudo Hospital explains that damage to one or more of these bones can lead to hearing loss.

Disruption means that the chain is broken, dislocated or fractured at one or more points. The Journal of Audiology and Otology case report categorises traumatic ossicular injuries as incudostapedial separation, malleoincudal separation or dislocation, dislocation of the malleus or incus, stapediovestibular dislocation and fracture of the ossicles. It says incudostapedial dislocation is the most frequent form following head trauma, and that the malleus is more firmly attached and more resistant than the incus.

Because sound can no longer be passed efficiently across the middle ear, the typical result is a conductive hearing loss, in which the inner ear itself may be healthy. This is why hearing aids or surgery to restore the chain can help.

The Journal of Audiology and Otology report says trauma to the temporal bone, with or without fracture, remains the predominant cause of ossicular injury, and that injuries from objects such as ear picks are rare, although among injuries caused by foreign objects, ear-pick injury is the most common. Penetrating injuries through the ear canal can damage the bones directly, even when the eardrum later heals and looks normal.

Sint-Trudo Hospital lists chronic ear infection, a previous ear operation in which the chain was disrupted, congenital abnormalities and ear trauma as situations in which an ossiculoplasty may be needed.

The NHS advises not to put fingers or objects such as cotton buds in the ears, even if you think they might be blocked, which is relevant to preventing penetrating ear injuries.

The main symptom is hearing loss, usually in one ear, often noticed after an injury. The case report says other symptoms such as vertigo, nausea and tinnitus may also occur, and that facial nerve damage and dizziness can follow penetrating middle ear injuries. In one of the cases it describes, a patient had hearing loss from childhood after being stabbed in the ear with an ear pick, and no evaluation had been done at the time. The eardrum was intact on examination, yet hearing tests showed a conductive hearing loss with an air-bone gap of 48 dB.

The NHS lists general signs of hearing loss: difficulty hearing other people clearly, especially in noisy places, asking people to repeat themselves, turning the volume up, and finding it hard to keep up with a conversation.

The NHS says to ask for an urgent GP appointment or get help from NHS 111 if you have sudden hearing loss in one or both ears, if your hearing has been getting worse over the last few days or weeks, or if you have hearing loss along with other symptoms such as earache or discharge from the ear. It says to see a GP if you think your hearing is getting gradually worse or if your hearing has not come back after treatment for an ear infection or earwax.

After a head injury with hearing loss, vertigo, bleeding from the ear, clear fluid from the ear or nose, or weakness of the face, urgent assessment in A&E is needed; the NHS head injury advice lists problems with vision or hearing, clear fluid from the ears or nose and bleeding from the ears among reasons to call 999.

The case report describes pure-tone audiometry showing a conductive hearing loss with an air-bone gap, followed by CT of the temporal bone, which revealed partial ossicular destruction. It states that high-resolution CT of the temporal bone is crucial in identifying loss of normal ossicular articulation. It also says that ossicular dislocation should be considered if hearing loss does not improve after blood in the middle ear (haemotympanum) has been absorbed or an eardrum perforation has been repaired.

The NHS explains that where hearing loss cannot be treated by a GP, they may refer to a hearing specialist for further tests. In practice, assessment is by ENT and audiology, with imaging as needed. Sometimes the diagnosis is confirmed only at surgery, when the middle ear is explored.

Sint-Trudo Hospital describes an ossiculoplasty as an ear operation in which the ossicles are repaired or replaced to improve hearing. It is done under general anaesthetic through a small incision behind or above the ear to reach the middle ear, and the damaged ossicles are repaired or replaced with a prosthesis made of plastic or metal. It says you can usually go home the same day and that hearing typically improves gradually over several weeks to months, and that you should avoid pressure on the ear by straining, lifting or blowing your nose.

The case report says the choice of reconstruction, using the person's own incus, a partial ossicular replacement prosthesis or a total ossicular replacement prosthesis, depends on the type and location of the injury. In its two cases a titanium total prosthesis was used and hearing outcomes were satisfactory even though surgery was delayed years after injury.

Surgery is not the only option. The NHS says that for permanent hearing loss a specialist will often recommend hearing aids, which make sounds louder and clearer but will not make hearing perfect, and some people need a hearing implant.

Results vary with the type of injury and the health of the middle ear. The case report suggests reconstruction results in stable and better hearing outcomes even in delayed cases, though it is a small report of two patients, and individual results should be discussed with an ENT surgeon.

In the NHS the route is GP, then ENT and audiology; ear surgery is carried out in hospital ENT departments. Private ENT services can arrange the same assessments and surgery. Whichever route is used, protecting the ear from further injury and getting any sudden hearing change checked promptly are the key points.