Complex conductive hearing loss

When to call it complex

An air-bone gap is easy to measure. Deciding what causes it is not always. A conductive or mixed loss deserves a slower look when:

• the eardrum is normal and there is no history that fits otosclerosis;
• the stapedial reflex is present despite a clear gap;
• the gap is confined to the low frequencies with better-than-expected bone conduction;
• there are sound- or pressure-induced dizziness, pulsatile tinnitus or hearing one’s own eye movements;
• a previous operation did not produce the expected result, or the result faded;
• imaging shows an abnormality that does not match the audiogram;
• the loss is mixed, and it is unclear how much of it is truly conductive;
• the ear is the only hearing ear.

Causes that are easy to miss

Third-window lesions. A dehiscence of the superior semicircular canal, or a large vestibular aqueduct, creates an extra opening in the inner ear that shunts sound energy away from the cochlea. The audiogram mimics otosclerosis; the reflexes do not. Operating on the stapes in these ears does not help and risks the inner ear. Superior canal dehiscence is explained for patients at grolman-orl.fr.

Malleus fixation. Often coexists with stapes fixation and explains a residual gap after an otherwise correct stapedotomy.

Partial ossicular discontinuity. Fibrous union across an eroded incudostapedial joint can pass unnoticed at surgery.

Round-window obliteration, congenital anomalies, tympanosclerosis and, occasionally, a middle-ear tumour (glomus, facial nerve schwannoma) presenting only as a conductive loss.

Not conductive at all. Poorly masked bone conduction can create an apparent gap; so can collapsing ear canals under headphones. Repeating the audiogram with insert earphones and careful masking is sometimes the whole answer.

The point of all this

The goal of the reassessment is not to find a reason to operate. It is to make sure that if an operation is proposed, it is aimed at the actual problem, that the benefit is realistic, and that the inner ear and the future are protected. Sometimes the conclusion is that a well-fitted hearing device is the best treatment available for this particular ear — and that is a good result, not a failure.

A second opinion is most valuable in exactly these situations.

This page provides general educational information. It cannot replace an individual assessment, which depends on a full history, examination, audiometry and, where relevant, imaging. If you have sudden hearing loss, severe pain, facial weakness, severe dizziness or discharge with fever, seek medical care promptly.