Is hearing loss due to a ruptured eardrum conductive or sensorineural?

Hearing Loss Due to Ruptured Eardrum is Conductive

Hearing loss due to a ruptured eardrum is primarily conductive in nature, as the perforation disrupts the normal sound transmission pathway through the middle ear. 1

Understanding Types of Hearing Loss

Hearing loss is classified into three main categories:

• Conductive hearing loss (CHL): Results from abnormalities of the external ear, tympanic membrane (eardrum), middle ear space, or ossicles that impede the conduction of sound waves to the cochlea 1
• Sensorineural hearing loss (SNHL): Results from abnormalities of the cochlea, auditory nerve, or higher aspects of central auditory perception or processing 1, 2
• Mixed hearing loss: Combination of both conductive and sensorineural components 1

Mechanism of Hearing Loss with Tympanic Membrane Perforation

When the eardrum is ruptured:

1. The normal sound transmission pathway through the middle ear is disrupted
2. Sound waves cannot be effectively transmitted from the external ear to the middle ear ossicles
3. This creates an impedance mismatch that reduces the efficiency of sound transfer to the inner ear
4. The result is primarily a conductive hearing loss 1, 3

Evidence from Clinical Studies

Research on non-explosive blast injuries to the ear demonstrates that:

• 47.5% of patients with tympanic membrane perforations had pure conductive hearing loss
• The severity of conductive hearing loss correlates with the size of the perforation
• Perforations involving the posterior-inferior quadrant were associated with the largest air-bone gap
• Healing of the perforation was accompanied by closure of the air-bone gap, indicating resolution of the conductive component 3

Diagnostic Differentiation

To distinguish between conductive and sensorineural hearing loss:

• Tuning fork tests (Weber and Rinne) can help differentiate CHL from SNHL 1, 2
• Audiometric testing will typically show an air-bone gap in conductive hearing loss 3
• In a ruptured eardrum, otoscopic examination will reveal the perforation 4

Potential Complications

While the primary hearing loss from a ruptured eardrum is conductive, it's important to note that:

• In some cases of traumatic perforation, a mixed hearing loss pattern may develop if the inner ear is also affected by the trauma 3
• Only 0.8% of patients with non-explosive blast injuries had pure sensorineural loss 3
• Sudden sensorineural hearing loss can occur with diving injuries due to rupture of the round or oval window membrane, but this is distinct from the conductive loss caused by tympanic membrane perforation 4

Management Implications

Understanding that the hearing loss is conductive has important treatment implications:

• Most traumatic perforations heal spontaneously within weeks to months 4
• If the perforation doesn't heal on its own, tympanoplasty (surgical repair) may be needed 4
• Hearing typically returns to normal once the perforation heals 3
• Patients should keep the ear dry until healing occurs to prevent infection 4

Key Pitfalls to Avoid

• Misdiagnosis: Failing to distinguish between conductive and sensorineural hearing loss can lead to inappropriate treatment 2
• Incomplete evaluation: Not assessing for additional injuries that might cause sensorineural components 2
• Infection risk: Not advising patients to keep the ear dry during healing, which can lead to otitis externa or media 4

In summary, a ruptured eardrum primarily causes conductive hearing loss due to the disruption of the sound transmission pathway, and this hearing loss typically resolves with healing of the perforation.