Brainstem evoked response audiometry Health Dictionary

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Brainstem Evoked Response Audiometry: From 1 Different Sources

Audiometry

The testing of hearing.... audiometry

Brainstem

A stalk of nerve tissue that forms the lowest part of the brain and links with the spinal cord. The brainstem acts partly as a highway for messages travelling between other parts of the brain and spinal cord. It also connects with 10 of the 12 pairs of cranial nerves (which emerge directly from the underside of the brain) and controls basic functions such as breathing, vomiting, and eye reflexes. Brainstem activities are below the level of consciousness, and they operate mainly on an automatic basis.

The brainstem is composed of 3 main parts: the midbrain, pons, and medulla. The midbrain contains the nuclei (nervecell centres) of the 3rd and 4th cranial nerves. It also contains cell groups involved in smooth coordination of limb movements. The pons contains nerve fibres that connect with the cerebellum. It also houses the nuclei for the 5th–8th cranial nerves. The medulla contains the nuclei of the 9th–12th cranial nerves. It also contains the “vital centres” (groups of nerve cells that regulate the heartbeat, breathing, blood pressure, and digestion (information on which is relayed via the 10th cranial nerve (see vagus nerve). Nerve-cell groups in the brainstem, known collectively as the reticular formation, alert the higher brain centres to sensory stimuli that may require a conscious response. Our sleep/wake cycle is controlled by the reticular formation.

The brainstem is susceptible to the same disorders that afflict the rest of the central nervous system (see brain, disorders of). Damage to the medulla’s vital centres is rapidly fatal; damage to the reticular formation may cause coma. Damage to specific cranial nerve nuclei can sometimes lead to specific effects. For example, damage to the 7th cranial nerve (the facial nerve) leads to facial palsy. Degeneration of the substantia nigra in the midbrain is thought to be a cause of Parkinson’s disease.... brainstem

Immune Response

The body’s defensive reaction to microorganisms, cancer cells, transplanted tissue, and other substances or materials that are recognized as antigenic or “foreign”.

The response consists of the production of cells called lymphocytes, substances called antibodies, or immunoglobulins, and other substances and cells that act to destroy the antigenic material.

(See also immune system.)... immune response

Response Rate

The number of completed or returned survey instruments (questionnaires, interviews, etc) divided by the total number of persons who would have been surveyed if all had participated. Usually expressed as a percentage.... response rate

Visual Evoked Response

Stimulation of the retina of the EYE with light causes changes in the electrical activity of the cerebral cortex (see BRAIN). These changes can be measured from outside the skull and can give valuable information about the state of the visual pathway from the retinal ganglion cells to the occipital cortex. Not only can it determine that function is normal, it can also help to diagnose some causes of poor VISION.... visual evoked response

Evoked Responses

The tracing of electrical activity in the brain in response to a specific external stimulus. The procedure is similar to that for an EEG.

The technique is used to check the functioning of various sensory systems (such as sight, hearing, or touch). The information obtained can be used to reveal abnormalities caused by inflammation, pressure from a tumour, or other disorders, and to help confirm a diagnosis of multiple sclerosis.... evoked responses

Fight-or-flight Response

Arousal of the sympathetic part of the autonomic nervous system in response to fear but which also occurs in anxiety disorders. Adrenaline (epinephrine), noradrenaline (norepinephrine), and other hormones are released from the adrenal glands and nervous system, leading to a raised heart-rate, pupil dilation, and increased blood flow to the muscles. These effects make the body more efficient in either fighting or fleeing the apparent danger.... fight-or-flight response

Impedance Audiometry

A hearing test used to investigate the middle ear in cases of conductive deafness.... impedance audiometry

Auditory Brainstem Response Audiometry

(ABR audiometry, brainstem evoked response audiometry, BSER) an objective test of hearing that measures the electrical activity in the auditory nerve and *brainstem following sound stimulation using repeated clicks or brief tones.... auditory brainstem response audiometry

Auditory Steady State Response

(ASSR) an objective test of hearing that measures the electrical activity in the auditory nerve and *brainstem following sound stimulation using a modulated continuous tone.... auditory steady state response

Biological Response Modifier

(BRM) a therapeutic agent, such as *interferon or *interleukin, that influences the body’s defence mechanisms to act against infection and disease. In small amounts, these substances are produced naturally by the body; larger doses have been genetically developed for use against rheumatoid arthritis, hepatitis, and cancer (especially melanoma and renal cancer).... biological response modifier

Cortical Evoked Response Audiometry

(CERA) an objective test of hearing that measures the electrical activity in the *cerebral cortex following sound stimulation.... cortical evoked response audiometry

Immuno- Combining Form Denoting Immunity Or Immunological Response.

... immuno- combining form denoting immunity or immunological response.

Response

n. the way in which the body or part of the body reacts to a *stimulus. For example, a nerve impulse may produce the response of a contraction in a muscle that the nerve supplies.... response

Auditory Brainstem Implant

a device similar to a *cochlear implant except that the electrode stimulates the auditory parts of the *brainstem rather than the cochlea. It is used to restore hearing of profoundly deaf people who have had damage to both auditory nerves and are hence unsuitable for cochlear implantation. It consists of an electrode that is permanently implanted on the surface of the brainstem. An external device with a microphone and an electronic processing unit pass information to the electrode using radio-frequency waves. The implant is powered by batteries in the external part of the device. It is most commonly used in patients with *neurofibromatosis type II who have had bilateral *vestibular schwannomas.... auditory brainstem implant

Response Prevention

a form of *behaviour therapy given for severe *obsessions. Patients are encouraged to abstain from rituals and repetitive acts while they are in situations that arouse anxiety. For example, a hand-washing ritual might be treated by stopping washing while being progressively exposed to dirt. The anxiety then declines, and with it the obsessions.... response prevention

Systemic Inflammatory Response

see shock.... systemic inflammatory response

Vestibular Evoked Myogenic Potential Test

(VEMP) a test used to measure the response of the *saccule. It is used in the diagnosis of *superior canal dehiscence syndrome, *Ménière’s disease, and other disorders of the inner ear.... vestibular evoked myogenic potential test

Visual Reinforcement Audiometry

(visual reinforced audiometry, VRA) a behavioural test of hearing for children aged approximately 6 to 30 months in which the subject sits between two calibrated loudspeakers. A sound is generated from one loudspeaker. Children who turn towards the sound are rewarded by brief illumination of a toy adjacent to the loudspeaker. Older children can be tested with headphones, rather than using the loudspeakers, to enable each ear to be tested separately. The test can be adapted for use with older subjects who have learning disabilities.... visual reinforcement audiometry

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