This cause of deafness is prevented by adding iodine to salt. Brain stroke
Brain stroke in a region affecting auditory function such as a posterior circulation infarct has been associated with deafness. Pathophysiology
Sensory hearing loss is caused by abnormal structure or function of the hair cells of the organ of Corti in the cochlea. Neural hearing impairments are consequent upon damage to the eighth cranial nerve (the vestibulocochlear nerve) or the auditory tracts of the brainstem. If higher levels of the auditory tract are affected this is known as central deafness. Central deafness may present as sensorineural deafness but should be distinguishable from the history and audiological testing. Cochlear dead regions in sensory hearing loss
Hearing impairment may be associated with damage to the hair cells in the cochlea. Sometimes there may be complete loss of function of inner hair cells (IHCs) over a certain region of the cochlea; this is called a "dead region". The region can be defined in terms of the range of characteristic frequencies (CFs) of the IHCs and/or neurons immediately adjacent to the dead region. Cochlear hair cells
Outer hair cells (OHCs) contribute to the structure of the Organ of Corti, which is situated between the basilar membrane and the tectorial membrane within the cochlea (See Figure 3). The tunnel of corti, which runs through the Organ of Corti, divides the OHCs and the inner hair cells (IHCs). OHCs are connected to the reticular laminar and the Deiters’ cells.
major concern
pregnancy and childbirth information
medical history
development history
family history

Otoscopy
Direct examination of the external canal and tympanic membrane (ear drum) with an otoscope, a medical device inserted into the ear canal that uses light to examine the condition of the external ear and tympanic membrane, and
middle ear through the semi-translucent membrane. Differential testing
Differential testing is most useful when there is unilateral hearing loss, and distinguishes conductive from sensorineural loss. These are conducted with a low frequency tuning fork, usually 512 Hz, and contrast measures of air and bone conducted sound transmission. Weber test, in which a tuning fork is touched to the midline of the forehead, localizes to the normal ear in people with unilateral sensorineural hearing loss. Rinne test, which tests air conduction vs. bone conduction is positive, because both bone and air conduction are reduced equally. less common Bing and Schwabach variants of the Rinne test. absolute bone conduction (ABC) test.Table 1. A table comparing sensorineural to conductive hearing loss

Other, more complex, tests of auditory function are required to distinguish the different types of hearing loss. Bone conduction thresholds can differentiate sensorineural hearing loss from conductive hearing loss. Other tests, such as oto-acoustic emissions, acoustic stapedial reflexes, speech audiometry and evoked response audiometry are needed to distinguish sensory, neural and auditory processing hearing impairments. Tympanometry
A tympanogram is the result of a test with a tympanometer. It tests the function of the middle ear and mobility of the eardrum.