<unk>  <unk>  is a type of<unk>  loss in which the root cause lies in the inner ear or sensory organ (cochlea and associated structures) or the vestibulocochlear nerve (cranial nerve VIII).<unk>  accounts for about 90% of reported<unk>  loss .<unk>  is usually permanent and can be mild, moderate, severe, profound, or total. Various other descriptors can be used depending on the shape of the audiogram, such as high frequency, low frequency, U-shaped, notched, peaked, or flat. Sensory<unk>  loss often occurs as a consequence of damaged or deficient cochlear hair cells. Hair cells may be abnormal at birth or damaged during the lifetime of an individual. There are both external causes of damage, including infection, and ototoxic drugs, as well as intrinsic causes, including genetic mutations. A common cause or exacerbating factor in<unk>  is prolonged exposure to environmental noise, or noise-induced<unk>  loss. Exposure to a single very loud noise such as a gun shot or bomb blast can cause noise-induced<unk>  loss. Using headphones at high volume over time, or being in loud environments regularly, such as a loud workplace, sporting events, concerts, and using noisy machines can also be a risk for noise-induced<unk>  loss. Neural, or "retrocochlear",<unk>  loss occurs because of damage to the cochlear nerve (CVIII). This damage may affect the initiation of the nerve impulse in the cochlear nerve or the transmission of the nerve impulse along the nerve into the brainstem. Most cases of<unk>  present with a gradual deterioration of<unk>  thresholds occurring over years to decades. In some, the loss may eventually affect large portions of the frequency range. It may be accompanied by other symptoms such as ringing in the ears (tinnitus) and dizziness or lightheadedness (vertigo). The most common kind of<unk>  is age-related (presbycusis), followed by noise-induced<unk>  loss (NIHL). Frequent symptoms of<unk>  are loss of acuity in distinguishing foreground voices against noisy backgrounds, difficulty understanding on the telephone, some kinds of sounds seeming excessively loud or shrill, difficulty understanding some parts of speech (fricatives and sibilants), loss of directionality of sound (especially with high frequency sounds), perception that people mumble when speaking, and difficulty understanding speech. Similar symptoms are also associated with other kinds of<unk>  loss; audiometry or other diagnostic tests are necessary to distinguish<unk> . Identification of<unk>  is usually made by performing a pure tone audiometry (an audiogram) in which bone conduction thresholds are measured. Tympanometry and speech audiometry may be helpful. Testing is performed by an audiologist. There is no proven or recommended treatment or cure for<unk> ; management of<unk>  loss is usually by<unk>  strategies and<unk>  aids. In cases of profound or total deafness, a cochlear implant is a specialised<unk>  aid that may restore a functional level of<unk> .<unk>  is at least partially preventable by avoiding environmental noise, ototoxic chemicals and drugs, and head trauma, and treating or inoculating against certain triggering diseases and conditions like meningitis.
Sensorineural hearing loss
Conductive hearing loss
Prelingual deafness
Spatial hearing loss
Unilateral hearing loss
Hemifacial hypertrophy
Cortical deafness
Ocular dysmetria