What factors can cause conductive hearing loss?

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Conductive hearing loss means that the structures of the middle ear and outer ear of human hearing that conduct hearing have lesions, resulting in the inability of external sounds to pass into the inner ear. This type of hearing loss is called conductive deafness. For example, the external auditory canal is covered with cerumen, etc. Conductive deafness can be caused by things such as obstruction, otitis media, perforation of the tympanic membrane, damage to the ossicles, etc. In addition, for example, some congenital middle ear malformations of the ossicles have this disease, causing hearing loss. If it cannot be transmitted to the inner ear, it is classified as conductive deafness.


What factors can cause conductive hearing loss?


1. Congenital diseases: congenital external auditory canal malformation or atresia, middle ear malformation
Congenital external ear and middle ear malformation Ear deformities often occur at the same time. The former is caused by the dysplasia of the first and second branchial arches and the developmental disorder of the first branchial groove during the embryonic period. The latter is accompanied by hypoplasia of the first pharyngeal pouch, which can lead to developmental malformations of the tympanic cavity, facial nerve, Eustachian tube, and mastoid, and can also be combined with inner ear malformations. Clinically it is often called "congenital microtia".

Generally divided into 3 levels according to the location and degree of deformity:
Level 1: The auricle is small and deformed, and its parts can still be distinguished; the external auditory canal is narrow or partially atretic; the tympanic membrane is present; hearing Basically normal.
Level 2: The auricle presents a cord-like protrusion, which is equivalent to the helix or only the earlobe; the external auditory canal is atretic; the tympanic membrane and malleus handle are not developed, half of the cases have fusion of the malleus and incus, and the stapes is present or not developed ; Presenting conductive hearing loss. This is a common clinical type, with an incidence rate approximately twice that of grade 1.
Level 3: The auricle is incomplete, with only sporadic and irregular protrusions; external auditory canal atresia; severe deformity of the ossicular chain; inner ear dysfunction. The incidence rate is the lowest, about 2%.
Grade 2 and 3 deformities are accompanied by maxillofacial hypoplasia, which manifests as deformities of the eyes, zygomatica, maxilla, mandible, mouth, nose, etc., accompanied by microtia, atresia of the external auditory canal, and ossicular deformities, which are called mandibular and facial bones. hypoplasia.


2. Acquired diseases: foreign body in the external auditory canal, otitis externa, cerumen embolism, traumatic tympanic membrane perforation, acute and chronic otitis media, middle ear cholesteatoma, tympanosclerosis, external auditory canal tumors, middle ear cancer, ossicular chain interruption, etc.

Foreign bodies in the external auditory canal: This behavior is more common in children. Children insert various foreign objects into the external auditory canal while playing. In adults, foreign objects are left behind during ear picking or trauma, or insects accidentally enter the ears. Foreign matter can be divided into three categories according to type: animal (such as insects, etc.), plant (such as grains, beans, small fruit stones, etc.) and non-biological (such as stones, iron filings, glass beads, etc.)


Otitis externa: Otitis externa can be divided into localized otitis externa (also known as external auditory canal furuncle) and diffuse inflammation of the skin of the external auditory canal (also known as diffuse otitis externa). Furuncle of the external auditory canal is a localized purulent inflammation of the hair follicles or sebaceous glands of the skin of the external auditory canal. The main pathogenic bacteria is Staphylococcus aureus, and a common cause is ear picking. The pathogenic bacteria of diffuse otitis externa are mostly Staphylococcus aureus, Streptococcus, Pseudomonas aeruginosa and Proteus. The triggers are ear picking, water in the external auditory canal while swimming, and long-term pus in chronic suppurative otitis media

Traumatic tympanic membrane perforation: tympanic membrane trauma is often caused by direct or indirect external force and can be divided into instrument injuries. ,

Such as digging the ear with a matchstick to puncture or puncture the tympanic membrane, or puncture or burn due to slag, sparks, etc.; iatrogenic injuries, such as removal of cerumen or foreign bodies in the external auditory canal; barotrauma, such as Ear slaps, blasting, firecrackers, high diving and diving, etc. stimulation.

Cerumen embolism: Excessive secretion of cerumen or obstruction of removal; inflammation and irritation of the external auditory canal; stenosis of the external auditory canal or poor self-cleaning effect, such as muscle relaxation in the elderly, weakness of mandibular joint movement, etc. These reasons will hinder the cerumen The cerumen is discharged, causing cerumen embolism.

Acute and chronic otitis media: Acute otitis media caused by pneumococci, Haemophilus influenzae, hemolytic streptococci and staphylococci through the Eustachian tube route, acute upper respiratory tract infection, etc., as well as acute otitis media that is not treated in time, Chronic otitis media that is not completely prolonged can cause conductive hearing loss.

Middle ear cholesteatoma: The so-called cholesteatoma is not a true tumor. It is the stratified squamous epithelium of the tympanic membrane and external auditory canal that grows and accumulates into the middle ear cavity through perforation to form a mass, which is covered with fibrous tissue and The adjacent bone walls or tissues are closely connected and contain exfoliated epithelium, keratinized material, and cholesterol-containing crystals.

Tympanosclerosis: This is the result of long-term chronic inflammation or repeated acute infections of the middle ear.Tympanosclerosis, also known as tympanic glass degeneration, is caused by the deposition of plaque-like collagen tissue under the epithelium of the tympanic mucosa. It mostly occurs on the tympanic mucosa and ossicles. Those that occur on the tympanic membrane are still called calcified plaques. It can involve the ossicles, oval window and their surroundings.

External auditory canal tumors:

(1) External auditory canal papilloma: The cause is unknown, but it is generally believed to be related to papilloma virus infection. It is a benign tumor that occurs in the cartilage skin of the external auditory canal. It is the most common benign ear tumor.

(2) Cerumen gland tumor of the external auditory canal: This is caused by cerumen gland hyperplasia, and its tissue structure is similar to hidradenoma. Benign tumors include cerumen adenoma and mixed tumor, and malignant tumors include cerumen adenocarcinoma and adenoid cystic carcinoma. Malignant tumors are more common.

Middle ear cancer: This is a relatively rare malignant tumor in clinical practice. It can originate in the middle ear, or it can invade the middle ear from tumors originating in the external auditory canal, nasopharynx or parotid gland. . Squamous cell carcinoma is the most common, with the most common age group being 40-60 years old. Most patients have a history of chronic suppurative otitis media.


Ossicular chain injury: Ossicular chain injury is a variety of violent effects on the outer ear, middle ear and head, resulting in structural damage or dysfunction of the ossicular chain . The ossicular chain is located deep and there is little chance of injury alone. Ossicular chain injuries often occur simultaneously with severe external auditory canal injuries or temporal bone fractures. A few may be caused by blast injuries and slap injuries.