Types of Deafness
- Conductive Deafness is caused by a defect in the conducting mechanism of the ear, namely the external and the middle ear. Any defect in the external auditory canal, ear drum, ossicular chain and tympanic cavity upto the oval window results in conductive deafness.
- Sensory–neural Deafness (Perceptive Deafness) is caused by lesions in the labyrinth, eight nerve and central connections. It includes psychogenic deafness.
- Mixed Deafness: If conductive as well as sensory–neural deafness are present, it is called mixed deafness.
|Site of lesion||External ear and middle ear.||Inner ear, eight erve and central connection.|
|Rinse test||Bone conduction better then air conduction.||Air conduction better ear.|
|Weber test||Liberalized to the worse ear.||Liberalized to the better ear.|
|Pure tone Audiometry||Bone conduction threshold normal. Air conduction threshold increased.||Both air and bone conduction thresholds are increased.|
|Hearing loss||Not more then 60 dB.||May be more than 60 dB.|
|Speech||Speaks in a low voice.||Speaks loudly.|
|Recruitment||Absent.||Present in cochlear deafness.|