The Gale Encyclopedia of Neurological Disorders vol 2 - part 1 pot

Electromyography Empty sella syndrome Encephalitis and Meningitis S J Joubert syndrome Kennedy’s disease Klippel Feil syndrome Krabbe disease Kuru S L Lambert-Eaton myasthenic syndrome L

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LIBRARY OF CONGRESS CATALOGING-IN-PUBLICATION DATA

The Gale encyclopedia of neurological disorders / Stacey L Chamberlin, Brigham Narins, editors.

Includes bibliographical references and index.

ISBN 0-7876-9150-X (set hardcover : alk paper) — ISBN 0-7876-9151-8 (v 1) — ISBN

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1 Neurology—Encyclopedias.

[DNLM: 1 Nervous System Diseases—Encyclopedias—English 2 Nervous System Diseases—Popular Works WL 13 G151 2005] I Title: Encyclopedia of neurological disorders II Chamberlin, Stacey L III Narins, Brigham, 1962– IV Gale Group.

RC334.G34 2005

List of Entries vii

Introduction xiii

Advisory Board xv

Contributors xvii

Entries Volume 1: A–L 1

Volume 2: M–Z 511

Glossary 941

General Index 973

GALE ENCYCLOPEDIA OF NEUROLOGICAL DISORDERS v

Autonomic dysfunction

Back pain Bassen-Kornzweig syndrome Batten disease

Behçet disease Bell’s palsy Benign positional vertigo Benzodiazepines Beriberi Binswanger disease Biopsy

Blepharospasm Bodywork therapies Botulinum toxin Botulism Brachial plexus injuries Brain anatomy Brain and spinal tumors Brown-Séquard syndrome

Canavan disease Carbamazepine Carotid endarterectomy Carotid stenosis Carpal tunnel syndrome Catechol-O-methyltransferase inhibitors

Central cord syndrome Central nervous system Central nervous system stimulants Central pain syndrome

Cerebellum Cerebral angiitis Cerebral cavernous malformation Cerebral circulation

Cerebral dominance Cerebral hematoma Cerebral palsy Channelopathies Charcot-Marie-Tooth disorder Cholinergic stimulants Cholinesterase inhibitors Chorea

Chronic inflammatory demyelinating polyneuropathy

Clinical trials Congenital myasthenia Congenital myopathies Corpus callosotomy Corticobasal degeneration Craniosynostosis Craniotomy Creutzfeldt-Jakob disease

CT scan Cushing syndrome Cytomegalic inclusion body disease

Dandy-Walker syndrome Deep brain stimulation Delirium

Dementia Depression Dermatomyositis Devic syndrome Diabetic neuropathy disease Diadochokinetic rate Diazepam

Dichloralphenazone Dichloralphenazone, Isometheptene, and Acetaminophen

Diencephalon Diet and nutrition Disc herniation Dizziness Dopamine receptor agonists Dysarthria

Dysesthesias Dysgeusia Dyskinesia Dyslexia Dyspraxia Dystonia

Electromyography

Empty sella syndrome

Encephalitis and Meningitis

S J

Joubert syndrome

Kennedy’s disease Klippel Feil syndrome Krabbe disease Kuru

S L

Lambert-Eaton myasthenic syndrome Laminectomy

Lamotrigine Learning disorders Lee Silverman voice treatment Leigh disease

Lennox-Gastaut syndrome Lesch-Nyhan syndrome Leukodystrophy Levetiracetam Lewy body dementia Lidocaine patch Lissencephaly Locked-in syndrome Lupus

Lyme disease

Machado-Joseph disease Magnetic resonance imaging (MRI) Megalencephaly

Melodic intonation therapy Ménière’s disease

Meninges Mental retardation Meralgia paresthetica Metachromatic leukodystrophy Microcephaly

Mitochondrial myopathies Modafinil

Moebius syndrome Monomelic amyotrophy Motor neuron diseases Movement disorders Moyamoya disease Mucopolysaccharidoses Multi-infarct dementia Multifocal motor neuropathy

Multiple sclerosis Multiple system atrophy Muscular dystrophy Myasthenia, congenital Myasthenia gravis Myoclonus Myofibrillar myopathy Myopathy

Myotonic dystrophy

Narcolepsy Nerve compression Nerve conduction study Neurofibromatosis Neuroleptic malignant syndrome Neurologist

Neuromuscular blockers Neuronal migration disorders Neuropathologist

Neuropsychological testing Neuropsychologist Neurosarcoidosis Neurotransmitters Niemann-Pick Disease

Occipital neuralgia Olivopontocerebellar atrophy Opsoclonus myoclonus Organic voice tremor Orthostatic hypotension Oxazolindinediones

S P

Pain Pallidotomy Pantothenate kinase-associated neurodegeneration Paramyotonia congenita Paraneoplastic syndromes Parkinson’s disease Paroxysmal hemicrania Parsonage-Turner syndrome Perineural cysts

Periodic paralysis Peripheral nervous system Peripheral neuropathy Periventricular leukomalacia Phantom limb

Pharmacotherapy Phenobarbital Pick disease Pinched nerve Piriformis syndrome Plexopathies Poliomyelitis

viii GALE ENCYCLOPEDIA OF NEUROLOGICAL DISORDERS

Social workers Sodium oxybate Sotos syndrome Spasticity Speech synthesizer Spina bifida Spinal cord infarction Spinal cord injury Spinal muscular atrophy Spinocerebellar ataxia Status epilepticus Stiff person syndrome Striatonigral degeneration Stroke

Sturge-Weber syndrome Stuttering

Subacute sclerosing panencephalitis Subdural hematoma

Succinamides Swallowing disorders Sydenham’s chorea Syringomyelia

S T

Tabes dorsalis Tay-Sachs disease Temporal arteritis Temporal lobe epilepsy Tethered spinal cord syndrome Third nerve palsy

Thoracic outlet syndrome Thyrotoxic myopathy Tiagabine

Todd’s paralysis Topiramate Tourette syndrome Transient global amnesia Transient ischemic attack Transverse myelitis Traumatic brain injury

Tremors Trigeminal neuralgia Tropical spastic paraparesis Tuberous sclerosis

Ulnar neuropathy Ultrasonography

Valproic acid and divalproex sodium

Vasculitic neuropathy Vasculitis

Ventilatory assistance devices Ventricular shunt

Ventricular system Vertebrobasilar disease Vestibular schwannoma Visual disturbances Vitamin/nutritional deficiency Von Hippel-Lindau disease

Wallenberg syndrome West Nile virus infection Whiplash

Whipple’s Disease Williams syndrome Wilson disease

Zellweger syndrome Zonisamide

GALE ENCYCLOPEDIA OF NEUROLOGICAL DISORDERS ix

PLEASE READ—IMPORTANT INFORMATION

The Gale Encyclopedia of Neurological Disorders is

a medical reference product designed to inform and

edu-cate readers about a wide variety of diseases, syndromes,

drugs, treatments, therapies, and diagnostic equipment

Thomson Gale believes the product to be comprehensive,

but not necessarily definitive It is intended to supplement,

not replace, consultation with a physician or other

health-care practitioner While Thomson Gale has made

sub-stantial efforts to provide information that is accurate,

comprehensive, and up-to-date, Thomson Gale makes norepresentations or warranties of any kind, including with-out limitation, warranties of merchantability or fitness for

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GALE ENCYCLOPEDIA OF NEUROLOGICAL DISORDERS xi

The Gale Encyclopedia of Neurological Disorders

(GEND) is a one-stop source for medical information that

covers diseases, syndromes, drugs, treatments, therapies,

and diagnostic equipment It keeps medical jargon to a

minimum, making it easier for the layperson to use The

Gale Encyclopedia of Neurological Disorders presents

au-thoritative and balanced information and is more

compre-hensive than single-volume family medical guides

SCOPE

Almost 400 full-length articles are included in The Gale Encyclopedia of Neurological Disorders Articles

follow a standardized format that provides information at

a glance Rubrics include:

va-ABOUT THE CONTRIBUTORS

The essays were compiled by experienced medicalwriters, physicians, nurses, and pharmacists GEND med-ical advisors reviewed most of the completed essays to in-sure that they are appropriate, up-to-date, and medicallyaccurate

GALE ENCYCLOPEDIA OF NEUROLOGICAL DISORDERS xiii

HOW TO USE THIS BOOK

The Gale Encyclopedia of Neurological Disorders

has been designed with ready reference in mind:

• Straightalphabetical arrangement allows users to

lo-cate information quickly

• Bold faced terms function as print hyperlinks that point

the reader to full-length entries in the encyclopedia

• A list of key terms is provided where appropriate to

de-fine unfamiliar words or concepts used within the text of the essay

con-•Cross-references placed throughout the encyclopedia

di-rect readers to where information on subjects without theirown entries can be found Cross-references are also used toassist readers looking for information on diseases that arenow known by other names; for example, there is a cross-

reference for the rare childhood disease commonly known

as HallervordSpatz disease that points to the entry titled Pantothenate kinase-associated neurodegeneration

en-• A Resources section directs users to sources of further

information, which include books, periodicals, websites,and organizations

• A glossary is included to help readers understand

unfa-miliar terms

• A comprehensive general index allows users to easily

target detailed aspects of any topic

GRAPHICS

The Gale Encyclopedia of Neurological Disorders isenhanced with over 100 images, including photos, tables,and customized line drawings

xiv GALE ENCYCLOPEDIA OF NEUROLOGICAL DISORDERS

ADVISORY BOARD

Laurie Barclay, MD

Neurologist and Writer

Tampa, FL

F James Grogan, PharmD

Pharmacist, Clinician, Writer,

Editor, and Consultant

Swansea, IL

Joel C Kahane, PhD

Professor, Director of the

Anatomical Sciences Laboratory

The School of Audiology and

Speech-Language PathologyThe University of Memphis

Memphis, TN

Brenda Wilmoth Lerner, RN

Nurse, Writer, and Editor

London, UK

Yuen T So, MD, PhD

Associate Professor

Clinical NeurosciencesStanford University School ofMedicine

Stanford, CA

Roy Sucholeiki, MD

Professor, Director of the Comprehensive Epilepsy Program

Department of NeurologyLoyola University Health SystemChicago, IL

Gil I Wolfe, MD

Associate Professor

Department of NeurologyThe University of TexasSouthwestern Medical CenterDallas, TX

GALE ENCYCLOPEDIA OF NEUROLOGICAL DISORDERS xv

An advisory board made up of prominent individuals from the medical and healthcare communities provided invaluable tance in the formulation of this encyclopedia They defined the scope of coverage and reviewed individual entries for accu-racy and accessibility; in some cases they contributed entries themselves We would therefore like to express our greatappreciation to them:

Lisa Maria Andres, MS, CGC

Certified Genetic Counselor and

Bruno Verbeno Azevedo

Espirito Santo University

of MedicineColumbia, SC

Michelle Lee Brandt

Francisco de Paula Careta

Espirito Santo UniversityVitória, Brazil

Rosalyn Carson-DeWitt, MD

Physician and Medical Writer

Durham, NC

Stacey L Chamberlin

Science Writer and Editor

Fairfax, VA

Bryan Richard Cobb, PhD

Institute for Molecular and HumanGenetics

Georgetown UniversityWashington, D.C

Adam J Cohen, MD

Craniofacial Surgery, Eyelid and Facial Plastic Surgery, Neuro-Ophthalmology

L Fleming Fallon, Jr., MD, DrPH

Professor

Department of Public HealthBowling Green State UniversityBowling Green, OH

Antonio Farina, MD, PhD

Department of Embryology,Obstetrics, and GynecologyUniversity of Bologna

Sandra Galeotti, MS

Science Writer

Sao Paulo, Brazil

GALE ENCYCLOPEDIA OF NEUROLOGICAL DISORDERS xvii

Medical Genetics Department

Indiana University School of

MedicineIndianapolis, IN

Alexander I Ioffe, PhD

Senior Scientist

Geological Institute of the Russian

Academy of SciencesMoscow, Russia

Holly Ann Ishmael, MS, CGC

The School of Audiology and

Speech-Language PathologyThe University of Memphis

Memphis, TN

Kelly Karpa, PhD, RPh

Assistant Professor

Department of PharmacologyPennsylvania State UniversityCollege of MedicineHershey, PA

Adrienne Wilmoth Lerner

University of Tennessee College ofLaw

Knoxville, TN

Brenda Wilmoth Lerner, RN

Nurse, Writer, and Editor

Peter T Lin, MD

Research Assistant

Member: American Academy ofNeurology, AmericanAssociation of ElectrodiagnosticMedicine

Department of BiomagneticImaging

University of California, SanFrancisco

Nicole Mallory, MS, PA-C

Michael Mooney, MA, CAC

University of OxfordOxford, England

Marcos do Carmo Oyama

Espirito Santo UniversityVitória, Brazil

Greiciane Gaburro Paneto

Espirito Santo UniversityVitória, Brazil

Toni I Pollin, MS, CGC

Research Analyst

Division of Endocrinology,Diabetes, and NutritionUniversity of Maryland School ofMedicine

Robert Ramirez, DO

Medical Student

University of Medicine and

Dentistry of New JerseyStratford, NJ

Stephanie Dionne Sherk

Freelance Medical Writer

Department of NeurologyLoyola University Health SystemChicago, IL

Kevin M Sweet, MS, CGC

Cancer Genetic Counselor

James Cancer Hospital, Ohio StateUniversity

Resident in Neurology

Department of Neurology andNeurosciences

Stanford UniversityStanford, CA

Bruno Marcos Verbeno

Espirito Santo UniversityVitória, Brazil

Beatriz Alves Vianna

Espirito Santo UniversityVitória, Brazil

GALE ENCYCLOPEDIA OF NEUROLOGICAL DISORDERS xix

GALE ENCYCLOPEDIA OF NEUROLOGICAL DISORDERS 511

A M

Machado-Joseph diseaseDefinition

Machado-Joseph disease (MJD), also known as ocerebellar ataxia Type 3 (SCA 3), is a rare hereditary

spin-disorder affecting thecentral nervous system, especially

the areas responsible for movement coordination of limbs,

facial muscles, and eyes The disease involves the slow and

progressive degeneration of brain areas involved in motor

coordination, such as the cerebellar, extrapyramidal,

py-ramidal, and motor areas Ultimately, MJD leads to

paral-ysis or a crippling condition, although intellectual

functions usually remain normal Other names of MJD are

Portuguese-Azorean disease, Joseph disease, Azorean

disease

Description

Machado-Joseph disease was first described in 1972among the descendants of Portuguese-Azorean immi-

grants to the United States, including the family of

William Machado In spite of differences in symptoms and

degrees of neurological degeneration and movement

im-pairment among the affected individuals, it was suggested

by investigators that in at least four studied families the

same gene mutation was present In early 1976,

investi-gators went to the Azores Archipelago to study an existing

neurodegenerative disease in the islands of Flores and São

Miguel In a group of 15 families, they found 40 people

with neurological disorders with a variety of different

symptoms among the affected individuals

Another research team in 1976 reported an inheritedneurological disorder of the motor system in Portuguese

families, which they named Joseph disease During the

same year, the two groups of scientists both published

in-dependent evidence suggesting that the same disease was

the primary cause for the variety of symptoms observed

When additional reports from other countries and ethnic

groups were associated with the same inherited disorder,

it was initially thought that Portuguese-Azorean sailors

had been the probable disseminators of MJD to other ulations around the world during the sixteenth century pe-riod of Portuguese colonial explorations and commerce.Presently, MJD is found in Brazil, United States, Portugal,Macau, Finland, Canada, Mexico, Israel, Syria, Turkey,Angola, India, United Kingdom, Australia, Japan, andChina Because MJD continues to be diagnosed in a vari-ety of countries and ethnic groups, there are current doubtsabout its exclusive Portuguese-Azorean origin

pop-Causes and symptoms

The gene responsible for MJD appears at some 14, and the first symptoms usually appear in earlyadolescence Dystonia (spasticity or involuntary and

chromo-repetitive movements) or gait ataxia is usually the initial

symptoms in children Gait ataxia is characterized by stable walk and standing, which slowly progresses withthe appearance of some of the other symptoms, such ashand dysmetria, involuntary eye movements, loss of handand superior limbs coordination, and facial dystonia (ab-normal muscle tone) Another characteristic of MJD isclinical anticipation, which means that in most families theonset of the disease occurs progressively earlier from onegeneration to the next Among members of the same fam-ily, some patients may show a predominance of muscletone disorders, others may present loss of coordination,some may have bulging eyes, and yet another sibling may

un-be free of symptoms during his/her entire life In the latestages of MJD, some people may experience delirium or dementia.

According to the affected brain area, MJD is classified

as Type I, with extrapyramidal insufficiency; Type II, withcerebellar, pyramidal, and extrapyramidal insufficiency;and Type III, with cerebellar insufficiency Extrapyramidaltracts are networks of uncrossed motor nerve fibers thatfunction as relays between the motor areas and corre-sponding areas of the brain The pyramidal tract consists

of groups of crossed nerves located in the white matter ofthe spinal cord that conduct motor impulses originated in

512 GALE ENCYCLOPEDIA OF NEUROLOGICAL DISORDERS

Key Terms

Autosomal Relating to any chromosome besides

the X and Y sex chromosomes Human cells tain 22 pairs of autosomes and one pair of sex chro-mosomes

con-Cerebellar Involving the part of the brain

(cere-bellum) that controls walking, balance, and dination

coor-Dysarthria Slurred speech.

Dystonia Painful involuntary muscle cramps or

spasms

Extrapyramidal Refers to brain structures located

outside the pyramidal tracts of the central nervoussystem

Genotype The genetic makeup of an organism or

a set of organisms

Mutation A permanent change in the genetic

ma-terial that may alter a trait or characteristic of an dividual, or manifest as disease This change can betransmitted to offspring

in-Penetrance The degree to which individuals

pos-sessing a particular genetic mutation express thetrait that this mutation causes One hundred per-cent penetrance is expected to be observed in trulydominant traits

Phenotype The physical expression of an

individ-ual’s genes

Spasticity Increased mucle tone, or stiffness,

which leads to uncontrolled, awkward ments

move-Trinucleotide A sequence of three nucleotides.

the opposite area of the brain to the arms and legs

Pyra-midal tract nerves regulate both voluntary and reflex

mus-cle movements However, as the disease progresses, both

motor systems tracks will eventually suffer degeneration

Diagnosis

Diagnosis depends mainly on the clinical history ofthe family Genetic screening for the specific mutation that

causes MJD can be useful in cases of persons at risk or

when the family history is not known or a person has

symptoms that raise suspicion of MJD Initial diagnosis

may be difficult, as people present symptoms easily

mis-taken for other neurological disorders such as Parkinson

and Huntington diseases, or even multiple sclerosis.

Treatment

Although there is no cure for Machado-Joseph ease, some symptoms can be relieved, The medicationLevodopa or L-dopa often succeeds in lessening musclerigidity and tremors, and is often given in conjunction

dis-with the drug Carbidopa However, as the disease gresses and the number of neurons decreases, this pallia-tive (given for comfort) treatment becomes less effective.Antispasmodic drugs such as baclofen are also prescribed

pro-to reduce spasticity Dysarthria, or difficulty to speak, and

dysphagia, difficulty to swallow, can be treated withproper medication and speech therapy Physical therapycan help patients with unsteady gait, and walkers andwheelchairs may be needed as the disease progresses.Other symptoms also require palliative treatment, such asmuscle cramps, urinary disorders, and sleep problems

Clinical Trials

Further basic research is needed before clinical trials

become a possibility for MJD Ongoing genetic and lecular research on the mechanisms involved in the geneticmutations responsible for the disease will eventually yieldenough data to provide for future development and design

mo-of experimental gene therapies and drugs specific to treatthose with MJD

Prognosis

The frequency with which such genetic mutationstrigger the clinical onset of disease is known as pene-trance Machado-Joseph disease presents a 94.5% pene-trance, which means that 94.5% of the mutation carrierswill develop the symptoms during their lives, and less than5% will remain free of symptoms Because the intensityand range of symptoms are highly variable among the af-fected individuals, it is difficult to determine the progno-sis for a given individual As MJD progresses slowly, mostpatients survive until middle age or older

Resources

BOOKS

Fenichel, Gerald M Clinical Pediatric Neurology: A Signs and

Symptoms Approach, 4th ed Philadelphia: W B Saunders

Company, 2001.

OTHER

National Institute of Neurological Disorders and Stroke.

Machado-Joseph Disease Fact Sheet May 5, 2003

<http://www.dystonia-foundation.org>.

GALE ENCYCLOPEDIA OF NEUROLOGICAL DISORDERS 513

Technician conducting an MRI (Will & Deni McIntyre/Photo

Researchers, Inc Reproduced by permission.)

International Machado-Joseph Disease Foundation, Inc P.O.

Box 994268, Redding, CA 96099-4268 (530) 246-4722.

MJD@ijdf.net <http://www.ijdf.net>.

National Ataxia Foundation (NAF) 2600 Fernbrook Lane,

Suite 119, Minneapolis, MN 55447-4752 (763) 0020; Fax: (763) 553-0167 naf@ataxia.org.

553-<http://www.ataxia.org>.

National Organization for Rare Disorders (NORD) P.O Box

1968 (55 Kenosia Avenue), Danbury, CT 06813-1968.

(203) 744-0100 or (800) 999-NORD (6673); Fax: (203) 798-2291 orphan@rarediseases.org <http://www.

rarediseases.org>.

Worldwide Education & Awareness for Movement Disorders

(WE MOVE) 204 West 84th Street, New York, NY

10024 (212) 875-8312 or (800) 437-MOV2 (6682);

Fax: (212) 875-8389 wemove@wemove.org.

<http://www.wemove.org>.

Sandra Galeotti

Macrencephaly see Megalencephaly

Mad cow disease see Creutzfeldt-Jakob

strong magnetic fields and radio waves, MRI collects and

correlates deflections caused by atoms into images MRIs

(magnetic resonance imaging tests) offer relatively sharp

pictures and allow physicians to see internal bodily

struc-tures with great detail Using MRI technology, physicians

are increasingly able to make diagnosis of serious

pathol-ogy (e.g., tumors) earlier, and earlier diagnosis often

trans-lates to a more favorable outcome for the patient

Description

A varying (gradient) magnetic field exists in tissues inthe body that can be used to produce an image of the tis-

sue The development of MRI was one of several powerful

diagnostic imaging techniques that revolutionized

medi-cine by allowing physicians to explore bodily structures

and functions with a minimum of invasion to the patient

In the last half of the twentieth century, dramatic vances in computer technologies, especially the develop-

ad-ment of mathematical algorithms powerful enough to

allow difficult equations to be solved quickly, allowed

MRI to develop into an important diagnostic clinical tool

In particular, the ability of computer programs to eliminate

“noise” (unwanted data) from sensitive measurements hanced the development of accurate, accessible and rela-tively inexpensive noninvasive technologies

en-Nuclear medicine is based upon the physics of excitedatomic nuclei Nuclear magnetic resonance (NMR) wasone such early form of nuclear spectroscopy that eventu-ally found widespread use in clinical laboratory and med-ical imaging Because a proton in a magnetic field has twoquantized spin states, NMR allowed the determination ofthe complex structure of organic molecules and, ulti-mately, the generation of pictures representing the largerstructures of molecules and compounds (such as neuraltissue, muscles, organs, bones, etc.) These pictures wereobtained as a result of measuring differences between theexpected and actual numbers of photons absorbed by a tar-get tissue

Groups of nuclei brought into resonance, that is, clei-absorbing and -emitting photons of similar electro-magnetic radiation (e.g., radio waves), make subtle yet

nu-distinguishable changes when the resonance is forced tochange by altering the energy of impacting photons Thespeed and extent of the resonance changes permit a non-destructive (because of the use of low energy photons) de-termination of anatomical structures This form of NMR

514 GALE ENCYCLOPEDIA OF NEUROLOGICAL DISORDERS

Key Terms

Magnetic resonance imaging MRI An imaging

technique used in evaluation and diagnoses of thebrain and other parts of the body

Resonance A condition in which the applied

force (e.g., forced vibrations, forced magneticfield, etc.) becomes the same as the natural fre-quency of the target (e.g., tissue, cell structure, etc.)

became the physical and chemical basis of the powerful

diagnostic technique of MRI

The resolution of MRI scanning is so high that theycan be used to observe the individual plaques inmultiple

sclerosis In a clinical setting, a patient is exposed to short

bursts of powerful magnetic fields and radio waves from

electromagnets MRI images do not utilize potentially

harmful ionizing radiation generated by three-dimensional

x-ray computed tomography (CT) scans, and there are no

known harmful side effects The magnetic and radio wave

bursts stimulate signals from hydrogen atoms in the

pa-tient’s tissues that, when subjected to computer analysis,

create a cross-sectional image of internal structures and

Nobel Prize in Physiology or Medicine for their

discover-ies concerning the use of magnetic resonance to visualize

more accurate form of polygraph (lie detector) Current

polygraphs are of debatable accuracy (usually they are not

admissible in court as evidence) and measure observable

fluctuations in heart rate, breathing, perspiration, etc

In a 2001 University of Pennsylvania experimentusing MRI, 18 subjects were given objects to hide in their

pockets, then shown a series of pictures and asked to deny

that the object depicted was in their pockets Included was

a picture of the object they had pocketed and so subjects

were “lying” (making a deliberate false statement) if they

claimed that the object was not in their pocket An MRI

recorded an increase of activity in the anterior cinglate, a

portion of the brain associated with inhibition of responses

and monitoring of errors, as well as the right superior

frontal gyrus, which is involved in the process of paying

attention to particular stimuli

After the September 11, 2001, terrorist attacks, anumber of government agencies in the United States began

to take a new look at brain scanning technology as a

po-tential means of security screening Such activity, along

with an increase of interest in potential brain-wave

scan-ning by the Federal Bureau of Investigation (FBI), has

raised concerns among civil-liberties groups, which view

brain-wave scanning as a particularly objectionable

Paul Arthur

MegalencephalyDefinition

Megalencephaly (also called macrencephaly) scribes an enlarged brain whose weight exceeds the mean(the average weight for that age and sex) by at least 2.5standard deviations (a statistical measure of variation).Megalencephaly may also be defined in terms of volumerather than weight Hemimegalencephaly (or unilateralmegalencephaly) is a related condition in which brain en-largement occurs in one hemisphere (half) of the brain

de-Description

A person with megalencephaly has a large, heavybrain In general, a brain that weighs more than 1600grams (about 3.5 pounds) is considered megalencephalic.The heaviest brain on record weighed 2850 grams (about6.3 pounds) Macrocephaly, a related condition, refers to

an abnormally large head Macrocephaly may be due tomegalencephaly or other causes such as hydrocephalus

(an excess accumulation of fluid in the brain), and brainedema Megalencephaly may be an isolated finding in anotherwise normal individual or it can occur in associationwith neurological problems (such as seizures or mental retardation) and/or somatic abnormalities (physical

GALE ENCYCLOPEDIA OF NEUROLOGICAL DISORDERS 515

Key Terms

Autosomal dominant A pattern of inheritance in

which only one of the two copies of an autosomal

gene must be abnormal for a genetic condition or

disease to occur An autosomal gene is a gene that is

located on one of the autosomes or non-sex

chro-mosomes A person with an autosomal dominant

dis-order has a 50% chance of passing it to each of their

offspring

Autosomal recessive A pattern of inheritance in

which both copies of an autosomal gene must be

ab-normal for a genetic condition or disease to occur

An autosomal gene is a gene that is located on one

of the autosomes or non-sex chromosomes When

both parents have one abnormal copy of the same

gene, they have a 25% chance with each pregnancy

that their offspring will have the disorder

Chromosome A microscopic thread-like structure

found within each cell of the human body and

con-sisting of a complex of proteins and DNA Humanshave 46 chromosomes arranged into 23 pairs Chro-mosomes contain the genetic information necessary

to direct the development and functioning of all cellsand systems in the body They pass on hereditarytraits from parents to child (like eye color) and de-termine whether the child will be male or female

Gene A building block of inheritance, which

con-tains the instructions for the production of a lar protein, and is made up of a molecular sequencefound on a section of DNA Each gene is found on aprecise location on a chromosome

particu-Inborn error of metabolism One of a group of rare

conditions characterized by an inherited defect in anenzyme or other protein Inborn errors of metabolismcan cause brain damage and mental retardation if leftuntreated Phenylketonuria, Tay-Sachs disease, andgalactosemia are inborn errors of metabolism

problems or birth defects of the body) Dysmorphic facial

features (abnormal shape, position or size of facial

fea-tures) may also be observed in an affected individual

According to the National Institute of NeurologicalDisorders and Stroke (NINDS), megalencephaly is one of

the cephalic disorders, congenital conditions due to

dam-age to or abnormal development of the nervous system

There have been various attempts to classify

megalen-cephaly into subcategories based on etiology (cause)

and/or pathology (the condition of the brain tissue and

cells) Dekaban and Sakurgawa (1977) proposed three

main categories: primary megalencephaly, secondary

megalencephaly, and hemimegalencephaly DeMyer

(1986) proposed two main categories: anatomic and

meta-bolic Gooskens and others (1988) modified these

classi-fications and added a third category: dynamic

megalencephaly The existence of different classification

systems highlights the inherent difficulty in categorizing a

condition that has a wide range of causes and associated

pathology

Demographics

The incidence of megalencephaly is estimated at tween 2% and 6% There is a preponderance of affected

be-males; megalencephaly affects males three to four times

more often than it does females Among individuals with

macrocephaly, estimates of megalencephaly are between

10 and 30% Hemimegalencephaly is a rare condition and

occurs less frequently than megalencephaly

Causes and symptoms

Both genetic and non-genetic factors may producemegalencephaly Most often, megalencephaly is a familialtrait that occurs without extraneural (outside the brain)findings Familial megalencephaly may occur as an auto-somal dominant (more common) or autosomal recessivecondition The autosomal recessive form is more likelythan the autosomal dominant form to result in mental re-tardation Other genetic causes for megalencephaly in-clude single gene disorders such as Sotos syndrome (an

overgrowth syndrome),neurofibromatosis (a

neurocuta-neous syndrome), and Alexander disease (a trophy); or a chromosome abnormality such as Klinefelter

leukodys-syndrome Non-genetic factors such as a transient disorder

of cerebral spinal fluid may also contribute to the opment of megalencephaly Finally, megalencephaly can

devel-be idiopathic (due to unknown causes)

The cells that make up the brain (neurons and othersupporting cells) form during the second to fourth months

of pregnancy Though the precise mechanisms behindmegalencephaly at the cellular level are not fully under-stood, it is thought that the condition results from an in-creased number of cells, an increased size of cells, oraccumulation of a metabolic byproduct or abnormal sub-stance due to an inborn error of metabolism It is possiblethat more than one of these processes may explain mega-lencephaly in a given individual

There is variability in age of onset, symptoms present,rate of progression, and severity of megalencephaly The

516 GALE ENCYCLOPEDIA OF NEUROLOGICAL DISORDERS

y disorder typically presents as a large head circumference

(distance around the head) either prenatally (before

birth), at birth, or within the first few years of life The

head circumference may increase rapidly in the span of a

few months or may progress slowly over a longer period

of time Head shape may be abnormal and skull

abnor-malities such as widened or split sutures (fibrous joints

be-tween the bones of the head) may occur There may also

be increased cranial pressure and bulging fontanels (the

membrane covered spaces at the juncture of an infant’s

cranial bones which later harden)

From a neurological standpoint, the clinical picture ofmegalencephaly varies widely Manifestations may range

from normal intellect, as with case of benign familial

megalencephaly, to severe mental retardation and seizures,

as with Alexander disease, an inherited leukodystrophy

(disease of the brain’s white matter) Neurological

symp-toms that may be present or develop in a person with

megalencephaly include:

• delay of motor milestones such as holding up head,

rolling over, or sitting

• abnormal or an excess amount of neurons

• abnormal or an excess amount of glia cells

Diagnosis

A diagnosis of megalencephaly is based on clinicalfindings and results of brain imaging studies Since mega-

lencephaly can be a benign condition, there may well be

many individuals who never come to medical attention

Though no longer used as a primary means of diagnosing

megalencephaly, an autopsy may provide additional

evi-dence to support this diagnosis The evaluation of a patient

with suspected megalencephaly will usually consist of

questions about medical history and family history, a

physical exam that includes head measurements, and a velopmental and/or neurological exam It may be neces-sary to obtain head circumference measurements forfirst-degree relatives (parents, siblings, children) De-pending upon the history and clinical findings, a physicianmay recommend imaging studies such as CT (computedtomography) scan or MRI (magnetic resonance imag- ing) Findings on CT scan or MRI consistent with a diag-

de-nosis of megalencephaly are an enlarged brain withnormal-sized ventricles and subarachnoid spaces The vol-ume (size) of the brain may be calculated or estimatedusing measurements from the CT or MRI A patient withmegalencephaly may be referred to specialists in neurol-ogy or genetics for further evaluation Laboratory testingfor a genetic condition or chromosome abnormality mayalso be performed

Treatment

There is no specific cure for megalencephaly agement of this condition largely depends upon the pres-ence and severity of associated neurological and physicalproblems In cases of benign familial megalencephaly, ad-ditional management beyond routine health care mainte-nance may consist of periodic head measurements andpatient education about the inheritance and benign nature

Man-of the condition For patients with neurological and/orphysical problems, management may include anti-epilep-tic drugs for seizures, treatment of medical complicationsrelated to the underlying syndrome, and rehabilitation forneurological problems such as speech delay, poor muscletone, and poor coordination Placement in a residentialcare facility may be necessary for those cases in whichmegalencephaly is accompanied by severe mental retar-dation or uncontrollable seizures

Treatment team

The types of professionals involved in the care of tients is highly individualized because the severity ofsymptoms varies widely from patient to patient For pa-tients with associated neurological and/or physical prob-lems, the treatment team may include specialists inneonatology, neurology, radiology, orthopedics, rehabili-tation, and genetics Genetic counseling may be helpful tothe patient and family, especially at the time of diagnosis.Participation in a support group may also be beneficial tothose families adversely affected by megalencephaly

pa-Recovery and rehabilitation

The optimal remedial strategies for individuals withmegalencephaly depend upon the presence and severity ofassociated neurological and physical problems Interven-tions such as speech, physical, and occupational therapy

GALE ENCYCLOPEDIA OF NEUROLOGICAL DISORDERS 517

may be indicated for individuals with megalencephaly

Early intervention services for young children and special

education or other means of educational support for

school-aged children may be recommended if

develop-mental delays, learning disabilities, or other barriers to

learning are present The goal of these therapies is to

max-imize the patient’s success in school, work, and life in

gen-eral A child with megalencephaly may be eligible to have

an Individual Education Plan (IEP) An IEP provides a

framework from which administrators, teachers, and

par-ents can meet the educational needs of a child with

learn-ing disabilities Dependlearn-ing upon severity of symptoms and

the degree of learning difficulties, some children with

megalencephaly may be best served by special education

classes or a private educational setting

Clinical trials

As of 2004, there were no active clinical trials

specifically designed to study megalencephaly Patients

with underlying syndromes that produce megalencephaly

may be candidates for clinical trials that relate to that

par-ticular syndrome For more information, interested

indi-viduals may search for that specific condition (for

example, neurofibromatosis) at www.clinicaltrails.gov

Prognosis

The prognosis for megalencephaly varies according

to the presence and severity of associated problems such

as intractable seizures, paralysis, and mental retardation

Hemimegalencephaly is often associated with severe

seizures, hemiparesis (paralysis of one side of the body),

and mental retardation and as such, it carries a poor

prog-nosis In the case of a fetus diagnosed with

megalen-cephaly, prediction of outcome remains imprecise

Resources

BOOKS

Greer, Melvin “Structural Malformations,” Chapter 78 In

Merritt’s Textbook of Neurology, 10th edition, edited by L.

P Rowland Baltimore, MD: Williams and Wilkins, 2000.

Graham, D I., and P L Lantos, eds Greenfield’s

Neuropathology, volume I, 7th edition London: Arnold,

2002.

Parker, James N., and Philip M Parker, eds The Official

Parent’s Sourcebook on Alexander Disease: A Revised and Updated Directory for the Internet Age San Diego,

CA: ICON Health Publications, 2003.

PERIODICALS

Bodensteiner, J B and E O Chung “Macrocrania and

mega-lencephaly in the neonate.” Seminars on Neurology 13

(March 1993): 84–91.

Cutting, L E., K L Cooper, C W Koth, S H Mostofsky,

W.R Kates, M B Denckla, and W E Kaufmann.

“Megalencephaly in NF1: predominantly white matter

contribution and mitigation by ADHD.” Neurology 59

(November 2002): 1388–94.

DeMyer, W “Megalencephaly: types, clinical syndromes and

management.” Pediatric Neurology 2 (1986): 321–28.

Gooskens, R H J M., J Willemse, J B Bijlsma, and P.

Hanlo “Megalencephaly: Definition and classification.”

Brain and Development 10 (1988): 1–7.

Johnson, A B., and M Brenner “Alexander’s disease: clinical,

pathologic, and genetic features.” Journal of Child

Neurology 18 (September 2003): 625–32.

Singhal, B S., J R Gorospe, and S Naidu “Megalencephalic

leukoencephalopathy with subcortical cysts.” Journal of

Child Neurology 18 (September 2003): 646–52.

WEBSITES

The National Institute of Neurological Disorders and Stroke

(NINDS) Megalencephaly Information Page.

<http://www.ninds.nih.gov/health_and_medical/

disorders/megalencephaly.htm>.

The National Institute of Neurological Disorders and Stroke

(NINDS) Cephalic Disorders Fact Sheet <http://

<http://www.nichd.nih.gov>.

National Institute of Neurological Disorders and Stroke (NINDS, Brain Resources and Information Network (BRAIN) P O Box 5801, Bethesda, MD (800) 352-

9424 <http://www.ninds.nih.gov>.

National Organization for Rare Disorders (NORD) PO Box

1968, 55 Kensonia Avenue, Danbury, CT 06813

(203) 744-0100 or 800-999-NORD (6673); Fax: (203) 798-2291 orphan@rarediseases.org <http://www.rare diseases.org>.

Dawn J Cardeiro, MS, CGC

Meige syndrome see Hemifacial spasm

Melodic intonation therapyDefinition

Melodic intonation therapy (MIT) uses melodic andrhythmic components to assist in speech recovery for pa-tients with aphasia.

518 GALE ENCYCLOPEDIA OF NEUROLOGICAL DISORDERS

y Purpose

Although MIT was first described in the 1970s, it isconsidered a relatively new and experimental therapy Few

research studies have been performed to analyze the

ef-fectiveness of treatment with large numbers of patients

Despite this, some speech therapists use the method for

children and adults with aphasia as well as for children

with developmental apraxia of speech.

The effectiveness of MIT derives from its use of themusical components melody and rhythm in the production

of speech A group of researchers from the University of

Texas have discovered that music stimulates several

dif-ferent areas in the brain, rather than just one isolated area

They also found a strong correlation between the right side

of the brain that comprehends music components and the

left side of the brain that comprehends language

compo-nents Because music and language structures are similar,

it is suspected that by stimulating the right side of the brain,

the left side will begin to make connections as well For

this reason, patients are encouraged to sing words rather

than speak them in conversational tones in the early phases

of MIT Studies using positron emission tomography

(PET) scans have shown Broca’s area (a region in the left

frontal brain controlling speech and language

comprehen-sion) to be reactivated through repetition of sung words

Precautions

Patients and caregivers should be aware that there islittle research to support consistent success with MIT The-

oretically, this form of therapy has the potential to improve

speech communication to a limited extent

Description

Melodic intonation therapy was originally developed

as a treatment method for speech improvements in adults

with aphasia The initial method has had several

modifi-cations, mostly adaptations for use by children with

apraxia The primary structure of this therapy remains

rel-atively consistent however

There are four steps, or levels, generally outlining thepath of therapy

• Level I: The speech therapist hums short phrases in a

rhythmic, singsong tone The patient attempts to followthe rhythm and stress patterns of phrases by tapping itout With children, the therapist uses signing while hum-ming and the child is not initially expected to participate

After a series of steps, the child gradually increases ticipation until they sign and hum with the therapist

par-• Level II: The patient begins to repeat the hummed phrases

with the assistance of the speech therapist Children at thislevel are gradually weaned from therapist participation

• Level III: For adults, this is the point where therapist ticipation is minimized and the patient begins to respond

par-to questions still using rhythmic speech patterns In dren, this is the final level and the transition to normal

chil-speech begins Sprechgesang is the technique used to

transition the constant melodic pitch used up to this pointwith the variable pitch in normal conversational speech

• Level IV: The adult method incorporates sprechgesang at

this level More complex phrases and longer sentencesare attempted

un-to be successful for patients who meet certain criteria such

as non-bilateral brain damage, good auditory aptitude,non-fluent verbal communication, and poor word repeti-tion The speech pathologist should be familiar with thedifferent MIT methodologies as they relate to either adults

Music Therapy Perspectives 18, no 2 (2000): 110–14

Belin, P., et al “Recovery from Nonfluent Aphasia After

Melodic Intonation Therapy: A PET Study.” Neurology

47, no 6 (December 1996): 1504–11

Bonakdarpour, B., A Eftekharzadeh, and H Ashayeri.

“Preliminary Report on the Effects of Melodic Intonation Therapy in the Rehabilitation of Persian Aphasic

GALE ENCYCLOPEDIA OF NEUROLOGICAL DISORDERS 519

Key Terms

Aphasia Loss of the ability to use or understand

language, usually as a result of brain injury or

dis-ease

Apraxia Loss of the ability to carry out a voluntary

movement despite being able to demonstrate

nor-mal muscle function

Pitch The property of sound that is determined by

the frequency of sound wave vibrations reaching

the ear

Patients.” Iranian Journal of Medical Sciences 25 (2000):

156–60

Helfrich-Miller, Kathleen “A Clinical Perspective: Melodic

Intonation Therapy for Developmental Apraxia.” Clinics

in Communication Disorders 4, no 3 (1994): 175–82

Roper, Nicole “Melodic Intonation Therapy with Young

Children with Apraxia.” Bridges 1, no 8 (May 2003)

Sparks R, Holland A “Method: melodic intonation therapy for

aphasia.” Journal of Speech and Hearing Disorders.

1976;41:287–297

ORGANIZATIONS

American Speech-Language-Hearing Association 10801

Rockville Pike, Rockville, MD 20852 (301) 897-5700 or (800) 638-8255; Fax: (301) 571-0457 action

center@asha.org <http://www.nsastutter.org>.

Music Therapy Association of British Columbia 2055 Purcell

Way, North Vancouver, British Columbia V7J 3H5, Canada (604) 924-0046; Fax: (604) 983-7559.

info@mtabc.com <http://www.mtabc.com>.

The Center For Music Therapy 404-A Baylor Street, Austin,

TX 78703 (512) 472-5016; Fax: (512) 472-5017.

info@centerformusictherapy.com <http://www.centerfor musictherapy.com>.

Stacey L Chamberlin

Ménière’s diseaseDefinition

Ménière’s disease is a disorder characterized by current vertigo, sensory hearing loss, tinnitus, and a feel-

re-ing of fullness in the ear It is named for the French

physician, Prosper Ménière, who first described the illness

in 1861 Ménière’s disease is also known as idiopathic

en-dolymphatic hydrops; “idiopathic” refers to the unknown

or spontaneous origin of the disorder, while

“endolym-phatic hydrops” refers to the increased fluid pressure in the

inner ear that causes the symptoms of Ménière’s disease

af-• Fluctuating loss of hearing

• Tinnitus This is a sensation of ringing, buzzing, or ing noises in the ear The most common type of tinnitusassociated with Ménière’s is a low-pitched roaring

roar-• A sensation of fullness, pressure, or discomfort in the ear.Some patients also experience headaches, diarrhea,

and pain in the abdomen during an attack.

Attacks usually come on suddenly and last from two

or three to 24 hours, although some patients experience anaching sensation in the affected ear just before an attack.The attacks typically subside gradually In most cases,only one ear is affected; however, 10–15% of patients withMénière’s disease are affected in both ears After a severeattack, the patient often feels exhausted and sleeps for sev-eral hours

The spacing and intensity of Ménière’s attacks varyfrom patient to patient Some people have several acuteepisodes relatively close together, while others may haveone or two milder attacks per year or even several yearsapart In some patients, attacks occur at regular intervals,while in others, the attacks are completely random Insome patients, acute attacks are triggered by psychologi-cal stress, menstrual cycles, or certain foods Patients usu-ally feel normal between episodes; however, they may findthat their hearing and sense of balance get slightly worseafter each attack

Demographics

The National Institute on Deafness and Other munication Disorders (NIDCD) estimates that, as of 2003,there are about 620,000 persons in the United States di-agnosed with Ménière’s disease Another expert gives afigure of 1,000 cases per 100,000 people About 46,000new cases are diagnosed each year; some neurologists,however, think that the disorder is underdiagnosed

Com-Ménière’s disease has been diagnosed in patients ofall ages, although the average age at onset is 35–40 years

of age The age of patients in several controlled studies ofthe disorder ranged from 49 to 67 years

Although Ménière’s disease has not been linked to aspecific gene or genes, it does appear to run in families.About 55% of patients diagnosed with Ménière’s have sig-nificant family histories of the disorder Women are slightly

520 GALE ENCYCLOPEDIA OF NEUROLOGICAL DISORDERS

more likely than men to develop Ménière’s; various

stud-ies report female-to-male ratios between 1.1:1 and 3:2

There is no evidence as of 2003 that Ménière’s ease occurs more frequently in some racial or ethnic

dis-groups than in others

Causes and symptoms

The underlying causes of Ménière’s disease arepoorly understood as of late 2003 Some geneticists pro-

posed in 2002 that Ménière’s disease might be caused by

a mutation in the COCH gene, which is the only human

gene known to be associated with inherited hearing loss

related to inner ear dysfunction In 2003, however, two

groups of researchers in Japan and the United Kingdom

reported that mutations in the COCH gene are not

re-sponsible for Ménière’s Other theories about the

under-lying causes of Ménière’s disease that are being

investigated include virus infections and environmental

noise pollution

One area of research that shows promise is the ble relationship between Ménière’s disease and migraine

possi-headache Dr Ménière himself suggested the possibility of

a link, but early studies yielded conflicting results A

rig-orous German study published in late 2002 reported that

the lifetime prevalence of migraine was 56% in patients

di-agnosed with Ménière’s disease as compared to 25% for

controls The researchers noted that further work is

nec-essary to determine the exact nature of the relationship

be-tween the two disorders

The immediate cause of acute attacks is fluctuatingpressure in a fluid inside the inner ear known as en-

dolymph The endolymph is separated from another fluid

called perilymph by thin membranes containing nerves

that govern hearing and balance When the endolymph

pressure increases, there is a sudden change in the rate of

nerve cells firing, which leads to vertigo and a sense of

fullness or discomfort inside the ear In addition, increased

endolymph pressure irritates another structure in the inner

ear known as the organ of Corti, which lies inside a

shell-shaped structure called the cochlea The organ of Corti

de-tects pressure impulses, which it converts to electrical

impulses that travel along the auditory nerve to the brain

The organ of Corti contains four rows of hair cells that

govern a person’s perception of the pitch and loudness of

a sound Increased pressure from the endolymph affects

the hair cells, causing loss of hearing (particularly the

abil-ity to hear low-pitched sounds) and tinnitus

Diagnosis

Diagnosis of Ménière’s disease is a complex processrequiring a number of different procedures:

• Patient history, including family history A primary care

physician will ask the patient to describe the symptoms

experienced during the attacks, their severity, the dates ofrecent attacks, and possible triggers

• Physical examination Patients often come to the doctor’soffice with signs of recent vomiting; they may be paleand sweaty, with a fast pulse and higher than normalblood pressure There may be no unusual findings duringthe physical examination, however, if the patient is be-tween episodes If the doctor suspects Ménière’s disease

on the basis of the patient’s personal or family history, he

or she will examine the patient’s eyes for nystagmus, orrapid and involuntary movements of the eyeball At thispoint, a primary care physician may refer the patient to

an audiologist or other specialist for further testing

• Hearing tests There are several different types of ing tests used to diagnose Ménière’s The Rinne andWeber tests use a tuning fork to detect hearing loss InRinne’s test, the examiner holds the stem of a vibratingtuning fork first against the mastoid bone and then out-side the ear canal A person with normal hearing orMénière’s disease will hear the sound as louder when it

is held near the outer ear; a person with conductive ing loss will hear the tone as louder when the fork istouching the bone In Weber’s test, the vibrating tuningfork is held on the midline of the forehead and the patient

hear-is asked to indicate the ear in which the sound seemslouder A person with conductive hearing loss on oneside will hear the sound louder in the affected ear, while

a person with Ménière’s disease will hear the soundlouder in the unaffected ear Other hearing tests measurethe person’s ability to hear sounds of different pitchesand volumes These may be repeated in order to detectperiodic variations in the patient’s hearing

• Balance tests The most common balance tests used todiagnose Ménière’s disease are the Romberg test, inwhich the patient is asked to stand upright and steadywith eyes closed; the Fukuda test, in which the patient isasked to march in place with eyes closed; and the Dix-Hallpike test, in which the doctor moves the patient from

a sitting position to lying down while holding the tient’s head tilted at a 45-degree angle Patients withMénière’s disease tend to lose their balance or movefrom side to side during the first two tests The Dix-Hallpike test is done to rule out benign paroxysmal po-sitional vertigo (BPPV), a condition caused by smallcrystals of calcium carbonate that have collected within

pa-a ppa-art of the inner epa-ar cpa-alled the utricle Some ppa-atientswith Ménière’s disease may have a positive score on theDix-Hallpike test, indicating that they also have BPPV

• Blood tests These are ordered to rule out metabolic orders, autoimmune disorders, anemia, leukemia, or in-fectious diseases (Lyme disease and neurosyphilis).

dis-• Transtympanic electrocochleography (ECoG) This testinvolves the placement of a recording electrode close to