Middle ear pathologies leading to conductive hearing loss include acute otitis media and otitis media with effusion (commonly known as adhesive ear). Otitis media with effusion is the most common cause of acquired hearing loss in children. [6] In most cases, this is a temporary problem that often recovers spontaneously, and no management other than monitoring is required. However, in some children, hearing loss can have catastrophic consequences on speech and language development. Middle ear effusions in adults should suspect a nasopharyngeal tumour (especially unilateral effusion or refractory effusion) and be investigated as such. [7] Another serious cause of conductive hearing loss is cholesteatoma. These occur due to the presence of squamous epithelium in the middle ear or other ventilated areas in the temporal bones. Although they are not tumors, they can be locally destructive and therefore require surgical removal. [8] Restoring hearing is a secondary goal behind forming a safe, dry ear.
For basic screening, conductive hearing loss can be identified with the Rinne test with a tuning fork of 256 Hz. The Rinne test, in which a patient is asked whether a vibrating tuning fork near the ear canal is heard louder (air conduction) or touches the bone behind the ear (bone conduction), is negative, indicating that bone conduction is more efficient than air conduction. A normal or positive result is when air conduction is more efficient than bone conduction. Often, the specific etiology underlying hearing loss defies diagnosis, and the mechanism leading to hearing loss may be more therapeutically relevant than specific diagnostic labeling. However, some conditions can be diagnosed by the classic clinical presentation, such as episodic vertigo associated with fluctuating hearing loss and tinnitus in Meniere`s disease and unilateral progressive hearing loss associated with tinnitus in acoustic neuroma. Conductive and neural hearing loss can often be associated with tinnitus. In addition, pathology of the inner ear and eighth nerve can lead to symptoms of imbalance. In the central nervous system, the auditory and vestibular pathways diverge, so healing symptoms of central origin may not be associated with vestibular symptoms, but often with other neurological abnormalities. Conductive hearing loss is a type of hearing loss that is different from sensorineural hearing loss, in which the causes of hearing loss are found in the inner ear.
Conductive hearing loss is significantly less common in adults than sensorineural hearing loss, although it is the most common type of hearing loss in children due to a middle ear infection with effusion. In the elderly population, collapse of the wax and ear canal can lead to conductive hearing loss, while in the general adult population, conductive hearing loss can occur after head trauma or other trauma resulting from perforation of the tympanic membrane, ossicular discontinuity, or adhesion to the middle ear. Unilateral or asymmetrical conductive hearing loss that develops in adulthood with normal middle ear pressure and tympanic membrane compliance should suggest otosclerosis, while negative middle ear pressure or serous otitis media should suggest nasopharyngeal cancer with middle ear involvement. Vascular malformations such as glomus tumors or, rarely, primary or secondary malignant tumors may also be associated with conductive hearing loss. There are several causes of sensorineural hearing loss (Table 1). Conduction dust results from any obstruction of the passage of sound waves from the external environment to the spiral organ. The obstacles are the airways of the external acoustic meatus, the eardrum and the bony path of the ossicles through the middle ear and the liquid medium of the perilymph in the cochlea. The receptor is always functional and responds to vibrations induced in the petrosal part of the temporal bone with a tuning fork, but not to sound waves that are prevented from reaching the receptor organ. The use of a tuning fork in animals is not reliable.