Unilateral conductive deafness after head injury is due to all EXCEPT:
**Core Concept**
Unilateral conductive deafness after head injury involves damage to the middle ear structures, leading to a disruption in sound conduction. This can result from trauma to the tympanic membrane, ossicular chain, or the eustachian tube.
**Why the Correct Answer is Right**
The correct answer involves understanding the common causes of conductive deafness in the context of head injury. Conductive deafness is characterized by a reduced ability to conduct sound waves to the inner ear due to a problem in the middle ear. In the case of head injury, the most common cause of conductive deafness is a fracture of the ossicles, particularly the stapes. This can occur due to direct trauma to the middle ear or as a result of a temporal bone fracture. Additionally, a head injury can also cause a hemotympanum, which is the accumulation of blood in the middle ear, leading to a conductive hearing loss.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect as a fracture of the ossicles is a common cause of conductive deafness after head injury. The correct answer is not a fracture of the ossicles, as this is a known cause of conductive deafness.
* **Option B:** This option is incorrect as a temporal bone fracture is a common cause of conductive deafness after head injury. Temporal bone fractures can result in damage to the middle ear structures, leading to conductive hearing loss.
* **Option D:** This option is incorrect as a tympanic membrane perforation can also cause conductive deafness after head injury. A perforated tympanic membrane can disrupt sound conduction, leading to a conductive hearing loss.
**Clinical Pearl / High-Yield Fact**
In the context of head injury, it is essential to differentiate between conductive and sensorineural hearing loss. Conductive hearing loss is typically unilateral and associated with a history of head trauma, whereas sensorineural hearing loss is often bilateral and associated with a history of noise exposure or age-related decline.
**Correct Answer: A.**