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.

In case of infection or inflammation, blood or other body fluids may be submitted for laboratory analysis.

Hearing loss is generally measured by playing generated or recorded sounds, and determining whether the person can hear them. Hearing sensitivity varies according to the frequency of sounds. To take this into account, hearing sensitivity can be measured for a range of frequencies and plotted on an audiogram.

Another method for quantifying hearing loss is a speech-in-noise test. As the name implies, a speech-in-noise test gives an indication of how well one can understand speech in a noisy environment. A person with a hearing loss will often be less able to understand speech, especially in noisy conditions. This is especially true for people who have a sensorineural loss – which is by far the most common type of hearing loss. As such, speech-in-noise tests can provide valuable information about a person's hearing ability, and can be used to detect the presence of a sensorineural hearing loss. A recently developed digit-triple speech-in-noise test may be a more efficient screening test.

Otoacoustic emissions test is an objective hearing test that may be administered to toddlers and children too young to cooperate in a conventional hearing test. The test is also useful in older children and adults.

Auditory brainstem response testing is an electrophysiological test used to test for hearing deficits caused by pathology within the ear, the cochlear nerve and also within the brainstem. This test can be used to identify delay in the conduction of neural impulses due to tumours or inflammation but can also be an objective test of hearing thresholds. Other electrophysiological tests, such as cortical evoked responses, can look at the hearing pathway up to the level of the auditory cortex.

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.

Learning of the central nervous system by "plasticity" or biological maturation over time does not improve the performance of monaural listening. In addition to conventional methods for improving the performance of the impaired ear, there are also hearing aids adapted to unilateral hearing loss which are of very limited effectiveness due to the fact that they don't restore the stereo hearing ability.

- Contralateral Routing of Signals (CROS) hearing aids are hearing aids that take sound from the ear with poorer hearing and transmit to the ear with better hearing. There are several types of CROS hearing aid:

- conventional CROS comprises a microphone placed near the impaired ear and an amplifier (hearing aid) near the normal ear. The two units are connected either by a wire behind the neck or by wireless transmission. The aid appears as two behind-the-ear hearing aids and is sometimes incorporated into eyeglasses.

- CIC transcranial CROS comprises a bone conduction hearing aid completely in the ear canal (CIC). A high-power conventional air conduction hearing aid fits deeply into the patient’s deaf ear. Vibration of the bony walls of the ear canal and middle ear stimulates the normal ear by means of bone conduction through the skull.

- BAHA transcranial CROS Bone Anchored Hearing Aid (BAHA): a surgically implanted abutment transmits sound from the deaf ear by direct bone conduction and stimulates the cochlea of the normal hearing ear.

- SoundBite Intraoral bone conduction which uses bone conduction via the teeth. One component resembles a conventional behind-the-ear hearing aid that wirelessly connects to a second component worn in the mouth that resembles a conventional dental appliance.

In Germany and Canada, cochlear implants have been used with great success to mostly restore the stereo hearing ability, minimizing the impacts of the SSD and the quality of life of the patient.

School-age children with unilateral hearing loss tend to have poorer grades and require educational assistance. This is not the case with everyone, however. They can also be perceived to have behavioral issues.

People afflicted with UHL have great difficulty locating the source of any sound. They may be unable to locate an alarm or a ringing telephone. The swimming game Marco Polo is generally impossible for them.

When wearing stereo headphones, people with unilateral hearing loss can hear only one channel, hence the panning information (volume and time differences between channels) is lost; some instruments may be heard better than others if they are mixed predominantly to one channel, and in extreme cases of sound production, such as complete stereo separation or stereo-switching, only part of the composition can be heard; in games using 3D audio effects, sound may not be perceived appropriately due to coming to the disabled ear. This can be corrected by using settings in the software or hardware—audio player, OS, amplifier or sound source—to adjust balance to one channel (only if the setting downmixes sound from both channels to one), or there may be an option to outright downmix both channels to mono. Such settings may be available via the device or software's accessibility features. As hardware solutions, stereo-to-mono adapters may be available to receive mono sound in stereo headphones from a stereo sound source, or some monaural headsets for cellphones and VOIP communication may combine stereo sound to mono (though headphones for voice communication typically offer lower audio quality than headphones targeted for listening to music). From the standpoint of sound fidelity, sound information in downmixed mono channel will, in any case, differ from that in either of the source channels or what is perceived by a normal-hearing person, thus technically some audio quality is lost (for example, the same or slightly different sound occurrences in two channels, with time delay between them, will be merged to a sound in the mono channel that unavoidably cannot correspond to the intent of the sound producer); however, such loss is most probably unnoticeable, especially compared to other distortions inherent in sound reproduction, and to the person's problems from hearing loss.

Treatment is supportive and consists of management of manifestations. User of hearing aids and/or cochlear implant, suitable educational programs can be offered. Periodic surveillance is also important.

About 1 in 1,000 children in the United States is born with profound deafness. By age 9, about 3 in 1,000 children have hearing loss that affects the activities of daily living. More than half of these cases are caused by genetic factors. Most cases of genetic deafness (70% to 80%) are nonsyndromic; the remaining cases are caused by specific genetic syndromes. In adults, the chance of developing hearing loss increases with age; hearing loss affects half of all people older than 80 years.

Audiometry (measuring ability to hear sounds of a particular pitch) is usually abnormal, but the findings are not particularly specific and an audiogram is not sufficient to diagnose Pendred syndrome. A thyroid goitre may be present in the first decade and is usual towards the end of the second decade. MRI scanning of the inner ear usually shows widened or large vestibular aqueducts with enlarged endolymphatic sacs and may show abnormalities of the cochleae that is known as Mondini dysplasia. Genetic testing to identify the pendrin gene usually establishes the diagnosis. If the condition is suspected, a "perchlorate discharge test" is sometimes performed. This test is highly sensitive, but may also be abnormal in other thyroid conditions. If a goitre is present, thyroid function tests are performed to identify mild cases of thyroid dysfunction even if they are not yet causing symptoms.

Auditory perception can improve with time.There seems to be a level of neuroplasticity that allows patients to recover the ability to perceive environmental and certain musical sounds. Patients presenting with cortical hearing loss and no other associated symptoms recover to a variable degree, depending on the size and type of the cerebral lesion. Patients whose symptoms include both motor deficits and aphasias often have larger lesions with an associated poorer prognosis in regard to functional status and recovery.

Cochlear or auditory brainstem implantation could also be treatment options. Electrical stimulation of the peripheral auditory system may result in improved sound perception or cortical remapping in patients with cortical deafness. However, hearing aids are an inappropriate answer for cases like these. Any auditory signal, regardless if has been amplified to normal or high intensities, is useless to a system unable to complete its processing. Ideally, patients should be directed toward resources to aid them in lip-reading, learning American Sign Language, as well as speech and occupational therapy. Patients should follow-up regularly to evaluate for any long-term recovery.

In cases where the causes are environmental, the treatment is to eliminate or reduce these causes first of all, and then to fit patients with a hearing aid, especially if they are elderly. When the loss is due to heredity, total deafness is often the end result. On the one hand, persons who experience gradual deterioration of their hearing are fortunate in that they have learned to speak. Ultimately the affected person may bridge communication problems by becoming skilled in sign language, speech-reading, using a hearing aid, or accepting elective surgery to use a prosthetic devices such as a cochlear implant.

In some cases, the loss is extremely sudden and can be traced to specific diseases, such as meningitis, or to ototoxic medications, such as Gentamicin. In both cases, the final degree of loss varies. Some experience only partial loss, while others become profoundly deaf. Hearing aids and cochlear implants may be used to regain a sense of hearing, with different people experiencing differing degrees of success. It is possible that the affected person may need to rely on speech-reading and/or sign language for communication.

In most cases the loss is a long term degradation in hearing loss. Discrediting earlier notions of presbycusis, Rosen demonstrated that long term hearing loss is usually the product of chronic exposure to environmental noise in industrialized countries (Rosen, 1965). The U.S. Environmental Protection Agency has asserted the same sentiment and testified before the U.S. Congress that approximately 34 million Americans are exposed to noise pollution levels (mostly from roadway and aircraft noise) that expose humans to noise health effects including the risk of hearing loss (EPA, 1972).

Certain genetic conditions can also lead to post-lingual deafness. In contrast to genetic causes of pre-lingual deafness, which are frequently autosomal recessive, genetic causes of post-lingual deafness tend to be autosomal dominant.

Prelingual hearing loss can be either acquired, meaning it occurred after birth due to illness or injury, or it can be congenital, meaning it was present at birth. Congenital hearing loss can be caused by genetic or nongenetic factors. The nongenetic factors account for about one fourth of the congenital hearing losses in infants. These factors could include: Maternal infections, such as rubella, cytomegalovirus, or herpes simplex virus, lack of oxygen, maternal diabetes, toxemia during pregnancy, low birth weight, prematurity, birth injuries, toxins including drugs and alcohol consumed by the mother during pregnancy, and complications associated with the Rh factor in the blood/jaundice. Genetic factors account for over half of the infants with congenital hearing loss. Most of these are caused by an autosomal recessive hearing loss or an autosomal dominant hearing loss. Autosomal recessive hearing loss is when both parents carry the recessive gene, and pass it on to their child. The autosomal dominant hearing loss is when an abnormal gene from one parent is able to cause hearing loss even though the matching gene from the other parent is normal.

Each year in the United States, approximately 12,000 babies are born with hearing loss. Profound hearing loss occurs in somewhere between 4 to 11 per every 10,000 children.

No specific treatment exists for Pendred syndrome. Speech and language support and hearing aids are important. Cochlear implants may be needed if the hearing loss drops to severe to profound levels and can improve language skills. If thyroid hormone levels are decreased, thyroid hormone supplements may be required. Patients are advised to take precautions against head injury.

Diagnosis is based on clinical findings.

'Clinical findings'

- Profound congenital sensorineural deafness is present

- CT scan or MRI of the inner ear shows no recognizable structure in the inner ear.

- As michel's aplasia is associated with LAMM syndrome there will be Microtia and microdontia present(small sized teeth).

Molecular genetic Testing

1. "FGF3" is the only gene, whose mutation can cause congenital deafness with Michel's aplasia, microdontia and microtia

Carrier testing for at-risk relatives requires identification of mutations which are responsible for occurrence of disease in the family.

Cortical deafness is a rare form of sensorineural hearing loss caused by damage to the primary auditory cortex. Cortical deafness is an auditory disorder where the patient is unable to hear sounds but has no apparent damage to the anatomy of the ear (see auditory system), which can be thought of as the combination of auditory verbal agnosia and auditory agnosia. Patients with cortical deafness cannot hear any sounds, that is, they are not aware of sounds including non-speech, voices, and speech sounds. Although patients appear and feel completely deaf, they can still exhibit some reflex responses such as turning their head towards a loud sound.

Cortical deafness is caused by bilateral cortical lesions in the primary auditory cortex located in the temporal lobes of the brain. The ascending auditory pathways are damaged, causing a loss of perception of sound. Inner ear functions, however, remains intact. Cortical deafness is most often cause by stroke, but can also result from brain injury or birth defects. More specifically, a common cause is bilateral embolic stroke to the area of Heschl's gyri. Cortical deafness is extremely rare, with only twelve reported cases. Each case has a distinct context and different rates of recovery.

It is thought that cortical deafness could be a part of a spectrum of an overall cortical hearing disorder. In some cases, patients with cortical deafness have had recovery of some hearing function, resulting in partial auditory deficits such as auditory verbal agnosia. This syndrome might be difficult to distinguish from a bilateral temporal lesion such as described above.

Degrees of vision loss vary dramatically, although the ICD-9 released in 1979 categorized them into three tiers: normal vision, low vision, and blindness. Two significant causes of vision loss due to sensory failures include media opacity and optic nerve diseases, although hypoxia and retinal disease can also lead to blindness. Most causes of vision loss can cause varying degrees of damage, from total blindness to a negligible effect. Media opacity occurs in the presence of opacities in the eye tissues or fluid, distorting and/or blocking the image prior to contact with the photoreceptor cells. Vision loss often results despite correctly functioning retinal receptors. Optic nerve diseases such as optic neuritis or retrobulbar neuritis lead to dysfunction in the afferent nerve pathway once the signal has been correctly transmitted from retinal photoreceptors.

Partial or total vision loss may affect every single area of a person's life. Though loss of eyesight may occur naturally as we age, trauma to the eye or exposure to hazardous conditions may also cause this serious condition. Workers in virtually any field may be at risk of sustaining eye injuries through trauma or exposure. A traumatic eye injury occurs when the eye itself sustains some form of trauma, whether a penetrating injury such as a laceration or a non-penetrating injury such as an impact. Because the eye is a delicate and complex organ, even a slight injury may have a temporary or permanent effect on eyesight.

Presence of inner ear abnormalities lead to Delayed gross development of child because of balance impairment and profound deafness which increases the risk of trauma and accidents.

- Incidence of accidents can be decreased by using visual or vibrotactile alarm systems in homes as well as in schools.

- Anticipatory education of parents, health providers and educational programs about hazards can help.

Many types of sense loss occur due to a dysfunctional sensation process, whether it be ineffective receptors, nerve damage, or cerebral impairment. Unlike agnosia, these impairments are due to damages prior to the perception process.

The diagnostic criteria as of 2015 define definite MD and probable MD as follows:

Definite

1. Two or more spontaneous episodes of vertigo, each lasting 20 minutes to 12 hours

2. Audiometrically documented low- to medium-frequency sensorineural hearing loss in the affected ear on at least 1 occasion before, during, or after one of the episodes of vertigo

3. Fluctuating aural symptoms (hearing, tinnitus, or fullness) in the affected ear

4. Not better accounted for by another vestibular diagnosis

Probable

1. Two or more episodes of vertigo or dizziness, each lasting 20 minutes to 24 hours

2. Fluctuating aural symptoms (hearing, tinnitus, or fullness) in the reported ear

3. Not better accounted for by another vestibular diagnosis

A common and important symptom of MD is hypersensitivity to sounds. This hypersensitivity is easily diagnosed by measuring the loudness discomfort levels (LDLs).

Symptoms of MD overlap with migraine-associated vertigo (MAV) in many ways, but when hearing loss develops in MAV is usually in both ears, and this is rare in MD, and hearing loss generally does not progress in MAV as it does in MD.

People who have had a transient ischemic attack (TIA) and stroke can present with symptoms similar to MD, and in people at risk for stroke magnetic resonance imaging (MRI) should be conducted to exclude TIA or stroke, and as TIA is often a precursor to stroke, that risk should be managed.

Other vestibular conditions that should be excluded include vestibular paroxysmia, recurrent unilateral vestibulopathy, vestibular schwannoma, or a tumor of the endolymphatic sac.

From 3% to 11% of diagnosed dizziness in neuro-otological clinics are due to Meniere's. The annual incidence rate is estimated to be about 15/100,000 and the prevalence rate is about 218/100,000, and around 15% of people with Meniere's disease are older than 65. In around 9% of cases a relative also had MD, signalling that there may be a genetic predisposition in some cases.

The odds of MD are greater for people of white ethnicity, with severe obesity, and women. Several conditions are often comorbid with MD, including arthritis, psoriasis, gastroesophageal reflux disease, irritable bowel syndrome, and migraine.

Beat deafness is a form of congenital amusia characterized by a person's inability to distinguish musical rhythm or move in time to it.

Sign language therapy has been identified as one of the top five most common treatments for auditory verbal agnosia. This type of therapy is most useful because, unlike other treatment methods, it does not rely on fixing the damaged areas of the brain. This is particularly important with AVA cases because it has been so hard to identify the causes of the agnosia in the first place, much less treat those areas directly. Sign language therapy, then, allows the person to cope and work around the disability, much in the same way it helps deaf people. In the beginning of therapy, most will work on identifying key objects and establishing an initial core vocabulary of signs. After this, the patient graduates to expand the vocabulary to intangible items or items that are not in view or present. Later, the patient learns single signs and then sentences consisting of two or more signs. In different cases, the sentences are first written down and then the patient is asked to sign them and speak them simultaneously. Because different AVA patients vary in the level of speech or comprehension they have, sign language therapy learning order and techniques are very specific to the individual's needs.

Treating auditory verbal agnosia with intravenous immunoglobulin (IVIG) is controversial because of its inconsistency as a treatment method. Although IVIG is normally used to treat immune diseases, some individuals with auditory verbal agnosia have responded positively to the use of IVIG. Additionally, patients are more likely to relapse when treated with IVIG than other pharmacological treatments. IVIG is, thus, a controversial treatment as its efficacy in treating auditory verbal agnosia is dependent upon each individual and varies from case to case.