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Acoustic Immittance
The primary purpose of impedance audiometry is to determine the status of the tympanic membrane and middle ear via
tympanometry. The secondary purpose of this test is to evaluate acoustic reflex pathways, which include cranial nerves
(CN) VII and VIII and the auditory brainstem. This test does not directly assess auditory sensitivity, although results are interpreted in conjunction with other threshold measures.
Tympanometry measures sound reflection from the tympanic membrane, while the operator varies air pressure in the ear canal. Tympanometry aids assessment of the outer and middle ear system, including the eustachian tube.
Acoustic Reflex Threshold is a middle ear measurement of stapedius muscle response to higher intensity and adequate duration sounds for individual frequencies.
Acoustic reflex decay test assesses the integrity of CN VIII. A contralateral continuous tone is presented for 10 seconds at a stimulus level 10 dB above the acoustic reflex threshold for that stimulus frequency in that ear.
ACOUSTIC NEUROMA
benign tumor of the eighth cranial nerve
ANASTOMOSIS
the surgical joining of two organs - can be muscles, nerves, or
blood vessels.
ARTERIOGRAM (ANGIOGRAM)
a type of X-ray which demonstrates the vascular system after an
injection of dye - used in some patients to determine type, size, and
exact location of cranial tumor
Air Conduction
This test assesses sensitivity when the signal is transmitted through the outer, middle, and inner ear and then through the brain to the cortex. Testing may be performed using headphones, insert earphones, or sound fields.
Audiologist
Audiologists are health care and education professionals who identify, assess, and manage disorders of auditory, balance, and other neural systems. Audiologists provide audiological (aural) rehabilitation to children and adults across the entire life span. Audiologists select, fit, and dispense amplification systems such as hearing aids and related devices. Audiologists prevent hearing loss through the provision and fitting of hearing protective devices, consultation on the effects of noise on hearing, and consumer education. Audiologists are involved in auditory and related research pertinent to the prevention, identification, and management of hearing loss,
tinnitus, and balance system dysfunction. Audiologists serve as expert witnesses in litigation related to their areas of expertise.
Audiogram
The audiogram is a chart of hearing sensitivity with frequency (tone pitch) charted on the x-axis (horizontal axis) and intensity (loudness) on the y-axis (vertical axis). Intensity is the level of sound power measured in decibels (dB); loudness is the perceptual correlate of intensity.
Audiology
Audiology is the study of hearing, hearing disorders, and habilitation/rehabilitation for individuals who have hearing loss. It encompasses the study of how the hearing mechanism works; the assessment of hearing; hearing and listening disorders; and the rehabilitation of individuals who have hearing loss
Auditory
Refers to the sense of hearing.
Auditory Brainstem Response Testing
(ABR) or Evoked Potentials (EP) Testing
Sometimes referred to as BAER (Brainstem Auditory Evoked Response) Testing or AER (Auditory Evoked Response) Testing.
Electrodiagnostic test procedures give information about the status of neural pathways. These procedures are used with individuals who are difficult to test by conventional behavioral methods. They are also indicated for a person with signs, symptoms or complaints suggesting a nervous system disease or disorder.
Auditory brainstem response
(ABR) is an auditory evoked potential that originates from the auditory nerve. It is often used with babies. Electrodes are placed on the head (similar to electrodes placed around the heart when an electrocardiogram is run), and brain wave activity in response to sound is recorded.
BENIGN
not malignant - does not spread to other parts of the body
BILATERAL
pertaining to both sides of the body
BRAINSTEM
connects the upper brain to the spinal cord - less than three inches
(7.6cm) long (The pons is one part of the brainstem.)
Bone Conduction
This technique assesses sensitivity when the signal is transmitted through the bones of the skull to the cochlea and then through the auditory pathways of the brain. This type of testing bypasses the outer and middle ear.
CENTIMETER (cm)
.394 inch (2.54 cm equals one inch)
CEREBELLOPONTINE ANGLE
space bounded by the petrous bone, brain stem, and cerebellum, and
through which cranial nerves six (VI), seven (VII), eight (VIII), nine
(XI), ten (X), and eleven (XI) pass
CEREBELLUM
located behind the brain stem, extending from the brain stem out
toward each mastoid bone - carries 11% of the brain's weight and
controls muscular coordination
Cochlea
Portion of the inner ear concerned with hearing.
Conductive hearing loss
Hearing loss produced by abnormalities of the outer ear (ear canal and pinna) or middle ear (tympanic membrane and
ossicles). These abnormalities create a hearing loss by interfering with the transmission of sound from the outer ear to the inner ear (cochlea).
CRANIAL NERVES
There are two set each of twelve cranial nerves. Each set involves
one side of the body. The cranial nerves control the sensory and muscle
functions around the eyes, face, and throat.
CROS HEARING AID (Contralateral Routing of Sound)
A CROS aid is used with one-sided deafness. It receives sound on the
deaf side, amplifies it, and carries it to the good ear.
CSF (cerebrospinal fluid)
a watery fluid, continuously being produced and absorbed, which
flows in the ventricles (cavities) within the brain and around the
surface of the brain and spinal cord
Disequilibrium
Refers to unsteadiness, imbalance or loss of equilibrium; often is accompanied by spatial disorientation (a sensation of not knowing where one's body is in relation to the vertical and horizontal planes).
Electronystagmography (ENG)
Test used clinically to evaluate patients with dizziness, vertigo, or balance dysfunction.
Electrocochleography
(ECoG)
ECoG testing is conducted to assist in the diagnosis of Meniere's Disease. The primary recording electrode is a Tiptrode , however a tympanic membrane electrode is used at times.
Electrocochleography: ECoG is a method of measuring intracochlear electrical potential changes associated with hearing.
Eustachian tube
Connects the middle ear space with the throat; maintains equal air pressure on both sides of the tympanic membrane (eardrum).
GADOLINIUM
a contrast material given, at the time of MRI, which concentrates in
the tumor and makes it more visible
Hearing Testing /
Hearing Evaluation
Purpose - to determine the type, degree and shape of hearing (loss). Includes - Pure tone testing, Speech Reception Threshold, Word Recognition, Performance Intensity Function of Phonetically Balanced Words, and Acoustic Immittance Testing.
HYDROCEPHALUS
enlargement of the normal CSF - containing cavities (ventricles) within
the brain due to impairment of flow or absorption of the CSF
Labyrinth
The complex system of chambers and passageways of the inner ear; includes both the hearing and balance portions of the inner ear. An inflammation of the labyrinth is called
labyrinthitis.
MAGNETIC RESONANCE IMAGING (MRI)
a body imaging system employing a magnet which surrounds the patient
- A magnetic field causes small harmless movement of atoms in the area
of the body being studied. A low energy radio wave is then passed
through the same area and the minute change this imparts to the atoms in
the magnetic field causes signals to be emitted which are picked up and
analyzed by modern computer technology. An image of the tissue is
produced in clear detail.
Middle ear
An air-filled cavity containing the ossicles and tympanic membrane, the function of which is to transfer sound energy from the outer ear to the inner ear (cochlea).
Mixed hearing loss
Hearing loss produced by abnormalities in both the conductive and sensorineural mechanisms of hearing.
NEUROMA
benign growth originating on a nerve
NEUROFIBROMATOSIS
a familial condition characterized by developmental changes in the
nervous system, muscles, bones, and skin - The central form
(Neurofibromatosis Type 2) may produce bilateral acoustic neuromas.
PONS
located at the base of the brain in the front of the cerebellum -
This section of the cranium is a mass of nerve tissue which coordinates
the activities of the various lobes of the brain.
POSTERIOR POSSA
the cavity in the back part of the skull which contains the
cerebellum, and cranial nerves V - XII
Nystagmus
Involuntary, alternating, rapid and slow movements of the eyeballs.
Ossicles (incus, malleus, stapes)
The three tiny bones of the middle ear that conduct sound from the tympanic membrane to the oval window of the inner ear.
Otoliths
Calcium carbonate crystals found in the utricle and saccule of the inner ear. Sometimes also called "ear rocks."
Oval window
Oval-shaped opening into the inner ear. The footplate of the stapes fits into the oval window.
Perilymph fistula or "leak"
Abnormal opening that permits perilymph from the inner ear to leak into the middle ear.
PIPB (Performance Intensity of Phonetically Balanced Words)
Word recognition testing performed at a level significantly above he previous level utilized for word recognition testing. This open set of monosyllabic words is presented at an elevated level and the score is compared back to that of the previous word recognition test. If a decline of 20% or greater is noted, the PIPB evaluation is considered abnormal (suggests "rollover"). This would suggest that additional diagnostic testing might be required to rule out retrocochlear pathology.
Pinna
The external, visible portion of the ear. Its primary function is to carry sounds to the middle ear. Also called the auricle.
Pure-tone Audiometry
Pure-tone audiometry is a behavioral test measure used to determine hearing sensitivity. This measure involves the peripheral and central auditory system. Pure-tone thresholds
(PTTs) indicate the softest sound audible to an individual at least 50% of the time. Hearing sensitivity is plotted on an audiogram, which is a graph displaying intensity as a function of frequency.
Round window
Membrane-covered opening between the inner ear and the middle ear.
Saccule
Sac-like inner ear organ containing otoliths; senses vertical motion of the head.
Shunt
a tube implanted in the cranium to balance the flow of cerebrospinal
fluid - used in the treatment of hydrocephalus
Sensorineural hearing loss
Hearing loss produced by abnormalities of the cochlea or the auditory nerve or of the nerve pathways that lead beyond the cochlea to the brain.
Speech-reception Threshold
The SRT is the softest intensity spondee word that an individual may repeat at least 50% of the time.
Spondees
Bisyllabic words equally emphasizing both syllables.
Temporal bone
The part of the skull in which the inner ear is located.
Tinnitus
Noise or ringing in the ears; also referred to as "head noise."
TRANSLABYRINTHINE
surgical approach to an acoustic neuroma through the mastoid bone and inner
ear (labyrinthine)
Tympanic membrane
Eardrum; separates the external ear canal from the middle-ear air cavity.
UNILATERAL
involving only one side
Utricle
Sac-like inner ear organ containing otoliths; senses forward and backward motion of the head.
Vertigo
Perception of movement, either of yourself or of objects around you, that is not actually occurring or is occurring differently from what you perceive.
VESTIBULAR
associated with the balanced system
Vestibulo-cochlear nerve
Nerve that carries information to the brain from the inner ear. Also called the eighth cranial nerve, auditory nerve, or acoustic nerve.
(Peripheral) vestibular system
The part of the inner ear concerned with balance and body orientation; consists of the semicircular canals, utricle, and
saccule.
Word Recognition
Word recognition (formerly called speech discrimination) is the ability to repeat correctly an open set of monosyllabic words at suprathreshold intensity. Word lists are phonetically balanced
(PB), meaning that the speech sounds they use occur with the same frequency as in the whole language.
Portions above authored by Peter S Roland, MD, Chair, Professor, Department of Otolaryngology, University of Texas Southwestern
Coauthored by William L Meyerhoff, MD, PhD, Chair, Professor, Department of Otolaryngology, University of Texas Southwestern Medical School
Other material was provided by the Acoustic Neuroma Association as a public
service. They provide an excellent source of information on acoustic neuroma,
as well as coordinating patient support groups and informational sessions.
Please visit their home page at: neurosurgery.mgh.harvard.edu/ana/
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