Magnetic resonance imaging (MRI): A system of visualizing the inside of the body without the use of X rays. The body is placed in a magnetic field and bombarded with radio waves, some of which are re-emitted and resolved by computer, which allows for viewing soft tissues and various abnormalities.
Mainstreaming: Integrating children with hearing impairments (or other disabilities) into the "least restrictive" educational setting. This often implies placement in a regular school classroom with special educational assistance, where necessary.
Maintaining cause: The perpetuating cause that keeps a problem from self-correcting; for example, parents of an eight-year-old considering a lisp "cute."
Maintenance: Carryover.
Malar hypoplasia: Underdevelopment of the cheek bones.
Malingering: The conscious, willful, and deliberate act of feigning or exaggerating a disability (such as hearing loss) for personal gain or exemption.
Malleus: The first and largest bone in the ossicular chain of the middle ear, connected to the tympanic membrane and the incus; so named because of its resemblance to a hammer.
Malocclusion: Improper alignment of the maxillary (upper) and mandibular (lower) dental arches.
Mandible: Lower jaw.
Mandibular processes: Primitive embryological tissue that gives rise to the mandible.
Manner of production: In describing consonant production, the mode of articulation; for example, continuant or stop.
Manual communication method: An approach to teaching communication skills to individuals with hearing impairment that emphasizes the use of some sort of signing system as the means for receptive and expressive communication.
Manubrium: A process of the malleus embedded in the fibrous layer of the tympanic membrane.
Masking: The introduction of a noise into the nontest ear in an attempt to eliminate cross-hearing.
Masking: The process by which the threshold of a sound is elevated by the simultaneous introduction of another sound.
Masking-level difference (MLD): The binaural threshold for a pure tone is lower when a binaural noise is 180 degrees out of phase than when the noise is in phase between the two ears.
Mass reactance: The quantity that results from the formula 2pfM (two times pi times frequency times mass).
Mass: The quantity of a body as measured in terms of its relationship to inertia The weight of a body divided by its acceleration due to gravity.
Mastoid process: A protrusion of the temporal bone, one portion of which is pneumatized (filled with air cells).
Mastoidectomy: An operation to remove infected cells of the mastoid. Mastoidectomies are termed as simple, radical, and modified radical, depending on the extent of surgery.
Mastoiditis: Infection of the mastoid.
Maternal rubella: German measles during pregnancy; may result in various disorders in the developing fetus.
Maxilla: Upper jaw.
Maxillary processes: Primitive embryological tissue that gives rise to the lateral aspects of the maxilla and palatal shelves.
Maximal contrast: A minimal pair in which the differing phonemes differ in more than one distinctive feature; for example, "say" (/se/) and "bay" (/be/).
Maximal opposition: See Maximal contrast.
Maximum masking: The highest level of noise that can be presented to one ear through an earphone before the noise crosses the skull and shifts the threshold of the opposite ear.
Mean length of utterance (MLU): The average length of utterances measured in morphemes. In English, this is an important measure of preschool development, because language becomes more complex as it becomes longer.
Meatus: A passage, such as the external auditory canal.
Medial geniculate body: The final subcortical auditory relay station, found in the thalamus on each side of the brain.
Medial: Toward the midline.
Medulla oblongata: A structure in the brain stem that connects the pons with the spinal cord and contains vital nerve cells that are involved in respiration, circulation, and sensation.
Mel: A unit of pitch measurement. One thousand mels is the pitch of a 1000 Hz tone at 40 dB SL, 2000 mels is the subjective pitch exactly double 1000 mels, and so on.
Mendelsohn maneuver: A swallowing technique in which the client manually holds the larynx at its highest point during the swallow.
Méniére disease: A disease of the inner ear, the symptoms of which include tinnitus, vertigo, and hearing loss (usually fluctuating and unilateral).
Meningitis: An inflammation of the meninges, or layers of tissue covering the brain, and frequently a cause of severe to profound hearing loss.
Meniscus: The curved surface of a column of fluid. A meniscus is sometimes seen through the tympanic membrane when fluids are present in the middle ear.
Mental retardation/developmental disabilities: A disorder characterized by substantial limitations in intellectual functioning, concurrent related limitations in adaptive skill areas, and manifestation before age eighteen.
Mesenchyme: A network of embryonic connective tissue in the mesoderm, which forms the connective tissue, blood vessels, and lymph vessels of the body.
Mesoderm: The middle-most of the three primary embryonic germ layers, lying between the ectoderm and the entoderm.
Metalinguistic skills: Abilities that enable a child to consider language in the abstract, to make judgments about its correctness, and to create verbal contexts, such as in writing.
Metaphon: An approach to phonological therapy that is based on the premise that phonological disorders in children are developmental language learning disorders.
Microbar (mbar): A pressure equal to one-millionth of standard atmospheric pressure (1 mbar equals 1 dyne/cm2).
Micrognathia: Underdeveloped mandible.
Microtia: A congenitally small, malformed pinna or ear canal that may result in a conductive hearing loss.
Midbrain: A structure in the brain stem. Also known as the Mesencephalon.
Middle ear space: A cubed-shaped area between the outer and inner ear containing the ossicles.
Middle ear: A small air-filled cavity separated from the outer ear by the eardrum; transmits sound waves from the eardrum to the partition between the middle and inner ears through a chain of small bones.
Middle-ear cleft: The space made up of the middle ear and the eustachian tube.
Minimal auditory deficiency syndrome (MADS): Changes in the size of neurons in the central auditory nervous system caused by conductive hearing loss in early life. The result is difficulty in language learning.
Minimal contrast: A minimal pair in which the differing phonemes differ in a single distinctive feature; for example, "lope" (/lop/) and "lobe" (/lob/).
Minimal pair: Two words that differ in a single phoneme; for example, "say" (/se/) and "bay" (/be/).
Minimum contralateral interference level: On the Stenger test, the lowest intensity of a signal presented to the poor ear that causes the patient to stop responding to the signal that is above threshold in the better ear.
Minimum response level (MRL): The lowest level of response offered by a child to an acoustic stimulus. Depending on a variety of circumstances, the signal responded to may be either barely audible or well above threshold.
Mismatch negativity (MMN): A small negative response evoked when subjects are instructed to attend to a set of stimuli in one ear, while different signals are presented to the other ear.
Mixed dysarthrias: Symptoms or areas of brain injury that cross several dysarthrias as a result of degenerative disorders, toxins, metabolic disorders, stroke, trauma, tumors, and infectious diseases.
Mixed hearing loss: The sum of the hearing losses produced by abnormalities in both the conductive and sensorineural mechanisms of hearing.
Modeling: Demonstrating the desired response.
Modified barium swallow study: An X-ray procedure that is used to visualize the swallowing process. Also known as videofluoroscopy.
Modiolus: The central pillar of the cochlea.
Monaural: Listening with one ear.
Monitored-live voice (MLV): Introduction of a speech signal (as in speech audiometry) through a microphone. The loudness of the voice is monitored visually by means of a VU meter (sometimes displayed as a series of light-emitting diodes).
Monoloudness: Voice lacks normal variations of intensity that occur during speech.
Monopitch: Voice that lacks normal inflection in tone.
Monosyllabic whole-word repetitions: Stuttering behavior in which whole words are repeated as in "hit-hit-hit-hit-hit me."
Monotone: Voice that is produced without varying the fundamental frequency.
Moro reflex: A sudden embracing movement of the arms and drawing up of the legs of infants and small children in response to sudden loud sounds.
Morpheme: The smallest meaningful unit of language.
Morphology: The study of word structure.
Morphophonemic contrasts: Changes in pronunciation as a result of morphological changes.
Most comfortable loudness (MCL): The hearing level designated by a listener as the most comfortable listening level for speech.
Motor neuron: A nerve coming from the spinal cord that controls muscle movement; injuries to these can result in paralysis.
MS: See Multiple sclerosis.
Mucosal tissue: Pinkish tissue lining the inside of the mouth.
Mucous membrane: A form of epithelium found in many parts of the body, including the mouth, nose, paranasal sinuses, eustachian tube, and middle ear. Its cells contain fluid-producing glands.
Mucous membrane: The moist lining of cavities of the body, such as the middle ear.
Multifactorial genetic considerations: Arising from the interaction of several genes and environmental factors.
Multiple sclerosis (MS): A progressive disease characterized by demyelinization of nerve fibers of the brain and spinal cord.
Multiview videofluoroscopy: Motion picture X-rays recorded from various angles.
Muscular dystrophy: A progressive degenerative disease resulting in muscles that may be unable either to contract or relax.
Music therapist: A professional who uses music such as listening, rhythmic clapping, or dance therapeutically.
Myasthenia gravis: A disorder characterized by fatigability and rapid weakening of muscles, a cause of flaccid dysarthria.
Myelination: Development of a protective myelin sheath or sleeve around the cranial nerves.
Myofunctional disorder: See Tongue thrust.
Myringitis: Any inflammation of the tympanic membrane.
Myringoplasty: Surgery for restoration or repair of the tympanic membrane.
Myringotomy: A surgical procedure in which a small tube is placed in the tympanic membrane to drain fluid from the middle ear.
Narrowband noise: A restricted band of frequencies surrounding a particular frequency to be masked; usually obtained by band-pass filtering a broadband noise.
Nasal alae: Lateral flaring of the nostrils.
Nasal cavity: Cavity above the oral cavity related to the nose.
Nasal emission: Air escaping through the nose during speech production.
Nasalance score: A numerical score that reflects the magnitude of hypernasality when measured by a nasometer.
Nasals: Phonemes that are produced with nasal resonance.
Nasogastric tube: A tube placed into the nose then through the pharynx and esophagus by which liquefied food may be fed.
Nasomedian processes: Primitive embryological tissue that gives rise to the anterior portion of the upper lip and premaxilla.
Nasometer: A commercially available device that is used to measure nasality.
Nasopharynx: The area where the back of the nose and the throat communicate.
Necrosis: The death of living cells.
Neologism: A novel word that does not exist in the language. Neologisms are created and used quite confidently by some individuals with aphasia.
Neonate: Newborn.
Neoplasm: Any new or aberrant growth, as a tumor.
Neurofibromatosis (NF): The presence of tumors on the skin or along peripheral nerves; also called von Recklinghausen disease.
Neurofibromatosis type 2: An hereditary disorder characterized by bilateral tumors along the cochleovestibular nerve; associated with hearing loss and other intracranial tumors.
Neurogenic stuttering: Disorder of fluency associated with some form of brain damage.
Neurolinguistics: Study of the anatomy, physiology, and biochemistry that are responsible for language processing and formulation.
Neurologist: A physician who specializes in disorders of the brain and nervous system.
Neuron: The basic unit of the nervous system, consisting of the cell body, axon, and dendrites. It is specialized as a conductor of nerve impulses.
Neurotransmission: The manner in which neurons communicate with one another neurochemically.
Neurotransmitter: A chemical substance that is released to bridge the gap between neurons so that neurotransmission can be facilitated.
Newton (N): The force required to give a 1 kg mass an acceleration of 1 m/sec2 (1 N equals 100,000 d).
NG tube: Nasogastric tube.
Nifedipine: A medication that may be useful in managing dysphagia.
Noise-induced hearing loss: Hearing impairment as a result of working around noisy equipment, listening to loud music, or a similar experience.
Nonfluent aphasia: A language disorder that is characterized by slow, labored speech and struggle to retrieve words and form sentences.
Nonorganic hearing loss: The exaggerated elevation of auditory thresholds.
Nonverbal: Without words.
Nonvocal: Without voice.
Norm referenced: A comparison that is usually based on others of the same gender and similar age.
Northwestern University Children's Perception of Speech (NUCHIPS): Test A picture-identification test for measuring the word-recognition abilities of small children.
NPO: No food by mouth.
Nystagmus: An oscillatory motion of the eyes.
