Type II Probably the same as Apert syndrome
amorphosynthesis 1. A variant term for construc- construc-tional apraxia as a result of parietal lobe dysfunction
D. Progressive muscular atrophy with ALS An entity of uncertain validity, presenting as a combination of
hereditary motor and sensory neuropathy and py-ramidal features
E. Spastic paraplegia with amyotrophy of hands F. Focal motor neuron disease See monomelic spinal
muscular atrophy.
G. Amytrophic lateral sclerosis with ophthalmoplegia A rare variant in which there is extensive neuronal loss and gliosis in the nuclei of the third, fourth, and sixth cranial nerves2473
H. Forms with associated evidence of degeneration of the posterior columns or other tracts in the spinal cord, of tics, or of Luyso-pallidal-nigral atrophy VII. Forms with involvement of other body systems or with other
identified disease
A. Amyotrophic lateral sclerosis with hyperparathy-roidism A syndrome of corticospinal tract deficit and axonal motor polyneuropathy. In this syndrome weakness, intermittent dysphagia, weight loss, atro-phy and fasciculations of the distal muscles, pseudob-ulbar dysarthria, hyperactive reflexes, and up-going plantar responses are found without sensory loss in patients with hyperparathyroidism.1869
B. Paraneoplastic ALS Here the typical findings of ALS are associated with underlying bronchial carcinoma, and remit when the tumor is resected.3906 Carcino-matous motor neuron disease is only possibly a spe-cific syndrome but amyotrophy may be seen in para-neoplastic encephalomyelopathy and may improve after removal of the tumor.
C. Amytrophic lateral sclerosis with plasma cell dyscrasia and monoclonal paraproteinemia, such as Walden-strom macroglobulinemia, multiple myeloma, or chronic lymphatic leukemia. Both monoclonal and polyclonal gammopathies involving either IgM or IgG have been detected.3779See gammopathic neu-ropathy.
D. Amytrophic lateral sclerosis associated with adreno-corticotrophic hormone deficiency.2727
ALS-like syndromes resemble but are not ALS and in-clude spondylotic myelopathy, vascular, lymphoma, non-tumor endocrine abnormalities, hyperthyroidism, hyperparathyroidism, prior irradiation of the spinal cord, acute infection, postinfectious, monoclonal gam-mopathy, dysimmune states such as multifocal motor neuropathy with conduction block, exogenous toxins such as lead,881and genetic/acquired enzyme defects such as hexosaminidase A deficiency in younger pa-tients. (Adapted from the Scottish MND Register.5039) Amyotrophic Lateral Sclerosis and Other Motor Neu-ron Disorders The official publication of the World Federation of Neurology Research Group on Motor Neuron Disease, published by Martin Dunitz. Web site:
http://www.tandf.co.uk/journals/alphalist.html.
Amyotrophic Lateral Sclerosis Association See ALS Association.
Amyotrophic Lateral Sclerosis score A standardized method of assessment of motor functions in patients AMYOTROPHIC LATERAL SCLEROSIS SCORE 49
with ALS, which are rated as 3 (normal), 2 (impaired), 1 (trace), or 0.
Items assessed include holding up the head, chewing food, swallowing, speaking, turning in bed, sitting up, emptying the bowel and bladder, breathing and cough-ing. Subjects are also scored on writing their name, fas-tening buttons or zippers, feeding themselves, gripping objects, lifting themselves, lifting a book or a tray, lift-ing a fork or a pencil, changlift-ing arm position, climblift-ing one flight of stairs, walking one block, walking across a room, walking with assistance, standing up, and chang-ing position. Stretch reflexes in the arms and legs, the jaw jerk, and the plantar responses bilaterally are also assessed, as are fasciculations and wasting in the face, tongue, arms, shoulders, legs, and hips. Emotional la-bility, fatigala-bility, and leg rigidity are other factors ex-amined. The theoretical maximum score is 100.4164 Amyotrophic Lateral Sclerosis Society of Canada A charitable organization. Address: 90 Adelaide St. E., Ste.
B-101, Toronto, Ontario, Canada M5C 2R4. Tel: 416-362-0269.
amyotrophic syphilitic myelopathy See Erb syphilitic amyotrophy.
amyotrophy (from Lat, lack of muscle growth) Muscle atrophy. The word is used in the context of acute shoulder girdle pain and weakness (neuralgic amyotrophy), syphilitic amyotrophy, diabetic amy-otrophy, and various genetically determined malfor-mations; but as it is descriptive rather than definitive, its employment is properly limited. There is a conven-tion, however, that it is used when the seat of the pathology is in the anterior horn cells.
The word is an unfortunate neologism; while lack of muscle growth is indeed present in patients with amy-otrophy, the word atrophy is better known to us, and myoatrophy would have been a better construction. But since amyotrophy has been around for twice as long as has this author, he will not tilt at windmills.
anabolic GM3gangliosidosis See hematosidosis.
anaerobic threshold The level of muscular activity at which respiratory rate, plasma lactate levels, and other signs of anaerobic metabolic activity first appear.
anal reflex The superficial anal reflex is a (polysy-naptic) reflex contraction of the anal sphincter in re-sponse to stimulation of the perianal skin, mediated by the somatic fibers at S4–5, described by Rossimolo in 1891. It is lost in tabes dorsalis and with local lesions at these levels.
The deep (internal) reflex consists of the contraction of the internal anal sphincter muscle in response to muscle stretch, as by the gloved finger introduced, and is mediated by sympathetic fibers from L1–L2.
anal triangle An anatomical region, the two sides of which are formed by the gluteus maximus and the base
by the superficial transverse perineal muscles. The anus, along with the surrounding external anal sphincter, is in the middle. The entire area is covered by the levator ani.
analgagnosia Unawareness of the unpleasant quali-ties of painful stimuli, as shown by the subject’s lack of reactivity to them.
analgesia (Gr, lack of pain) 1. Insensibility to pain, or lack of pain sensation, without effects on con-sciousness. 2. Reduction or loss of sensitivity to a stim-ulus which would normally be painful. This meaning, however, is often included in the nonspecific term anesthesia.
analgesia panaris See hereditary sensory neuropa-thy type 2.
analgesic rebound headache (analgesic headache;
rebound headache; medication induced headache; er-gotamine headache) A headache syndrome with clini-cal characteristics of both migraine and tension-type headaches, occurring in chronic migraine or tension-type headache sufferers who have taken to consuming acetylsalicylic acid, acetaminophen, nonsteroidal anti-inflammatory agents, benzodiazepines, ergot com-pounds, caffeine, narcotics, barbiturates, or combina-tions of these agents in increasing doses and on a regular basis, usually daily.4595A headache with characteristics of hemicrania continua has also been reported as a variant.
The mechanism is unknown, but the morning ac-centuation of the symptom would support chemical de-pendence such that the headaches are triggered by falling analgesic levels. This perpetuates and worsens instead of alleviating the headaches. See rebound headache.
analphalipoproteinemia See Tangier disease.
anamnesia (Gr, anew memory) Recollection of phenomena prior to a given period in the disease.
anamnestic Recalling to memory. Thus as anamne-sis, the history of the disease.
anamnestic color blindness Difficulty in finding the correct word for a colored object, errors being made in which the patient may perseverate. This is probably a combination of a mild disorder of visual perception and minimal dysphasia.
anapeiratic (Gr, to do again, to repeat exercises) The term applied by Hammond to those pareses brought on by excessive use of a body part. See occupational cramps.
anaplastic meningioma See meningioma.
anarchic hand See alien hand.
anarithmia Inability to comprehend numeration and the principles of mathematics, as presumably is the case in Gerstmann syndrome. See also acalculia.
50 AMYOTROPHIC LATERAL SCLEROSIS SOCIETY OF CANADA
anarithmic acalculia See acalculia.
anarthria Complete inability to articulate speech sounds, due to local causes or to lesions of the medulla, pons, or bulbar cranial nerves. The original Greek der-ivation actually indicates a defect or absence of the limbs.
anastic aphasia See anomia.
anastomosis (Gr, to bring to a mouth) The commu-nication of the branches of vessels with one another, as if one mouth (or open end of a vessel) were joined to another.
anaudia (Gr, negative speech) See aphonia. The term has also been employed for catalepsy.
ancient change The presence of large, pleomorphic, scattered, hyperchromatic nuclei within Schwanno-mas, and particularly in long-standing acoustic neuro-mas.6
Ander disease See Dercum disease.
Andermann syndrome 1. See Landau-Kleffner syn-drome. 2. (agenesis of the corpus callosum) A con-genital dysmorphic syndrome characterized by hyper-telorism, strabismus, ptosis, nystagmus, facial and generalized weakness, scoliosis, pes cavus, callosal age-nesis, and mental and developmental delay.3277 Andersen brown forehead ring (linea fusca) A brown pigmentation on the forehead, found in some patients with chronic CNS diseases, especially posten-cephalitic parkinsonism and syphilis. The cause is un-known.3865
Andersen disease (glycogen storage disease type IV;
D-1,4 glucan 6-glucosyltransferase brancher enzyme de-ficiency). The major features are hepatic cirrhosis, splenomegaly, hypotonia with muscle atrophy (espe-cially in the legs), and delay in acquisition of motor skills.169See glycogen storage diseases.
Andersen, Dorothy (1901–1963) American pediatri-cian and pathologist.
Andersen syndrome (Klein-Lisak syndrome) A rare entity comprising potassium-ensitive periodic paralysis without myotonia, ventricular arrhythmias leading potentially to syncope or sudden death, and dysmor-phisms (clinodactyly, syndactyly, hypoplastic mandible, hypertelorism, low-set ears). A prolonged QTc interval is detected in many cases. Tubular aggregates may be found on muscle biopsy. A dominant variant has been reported.5500
Anderson, W. (1842–1900) English surgeon and anatomist at St. Thomas’ Hospital, where he was also a dermatologist.
Anderson-Fabry disease A rare X-linked lysosomal storage disorder due to deficiency of ␣-galactosidase A, which results in the deposition of neutral
glycosphin-golipids (mainly trihexosyl ceramide) in endothelial and smooth muscle cells.
The clinical features include a skin rash (angioker-atoma); pain and paresthesias in the extremities; ab-normalities of cutaneous thermal sensation; episodic painful crises, sometimes precipitated by exercise or other stress; acroparesthesias; and a tendency toward acute ischemic hemorrhagic brain lesions. Death is due to renal failure and cerebrovascular accidents.172,588,1728
Andes disease See altitude insomnia.
Andrade neuropathy (familial amyloid neuropa-thy, Portuguese neuropathy) A dominantly inherited acropathic sensorimotor and autonomic neuropathy with adult onset, complicating primary amyloidosis, in which gastrointestinal complaints (cyclic diarrhea and constipation) are common.174
André-Thomas (1867–1961) French neurologist, born in Paris, where he trained in Medicine, serving under Raymond, Bouchard, and Déjèrine. After grad-uation he worked as chef de laboratoire for Déjèrine, remaining at the Salpetrière until 1917, but was not accepted onto the staff. From 1911 until his death he was attached to the Hôpital Saint-Joseph. He assumed the hyphen between his Christian name and surname in order to distinguish himself from André Thomas, the contemporary physiologist.
His contributions to neurology extend over about 70 years, the greater part concerned with clinical and anatomical studies of the cerebellum and spinal cord, psychotherapy, and neurophysiology. He commenced his studies of the development of the newborn at the age of 78; these culminated in his landmark book, The Neurological Examination of the Infant (1954, in col-laboration).
André-Thomas sign (Springlike phenomenon) This is essentially the same as rebound.4723
anemic headache A frontal or generalized headache, once considered to be associated with increased blood flow in patients with severe anemia.
anencephaly (Gr, lack of brain) (acrania, exen-cephaly, craniorachischisis) A lethal defect due to fail-ure of the cephalad part of the neural tube to form, re-sulting in the complete absence of development of the cerebral hemispheres1351and of the vault of the skull.
This developmental aberration is commonly accompa-nied by failure of closure of the neural tube, presenting as myelocele or meningomyelocele.
It is suggested that anencephalics are capable of per-forming certain of those intellectual functions com-monly considered to require the presence of cerebral cortex, but they seldom live long enough for evidence of this to be detected.
anerethisia (Gr, lack of to excite) Lack of incen-tive or motivation.
ANERETHISIA 51
anergy (Gr, lack of energy) (anergia, anenergia) Lack of strength, vigor, or energy.
anesthesia (Gr, lack of sensation) Lack of feeling, though not necessarily of pain. The term was suggested by Oliver Wendell Holmes (1804–1894), the American physician and author, in a letter to Dr. William Mor-ton, an American dentist who pioneered the use of pain-relieving agents in his practice. Holmes used the diphthong.
anesthesia dolorosa 1. Painful anesthesia or dyses-thesia, often related to surgical trauma of the trigemi-nal ganglion, evoked most frequently after rhizotomy or thermocoagulation has been performed for treat-ment of idiopathic trigeminal neuralgia.
Anaesthesia dolorosa may also follow upon trauma to the trigeminal complex and, rarely, after vascular le-sions of the central trigeminal pathways. This defini-tion and the following diagnostic criteria are suggested by the Headache Classification Committee of the In-ternational Headache Society and are reproduced by kind permission.
A. Pain or dysesthesia is limited to the distribution of one or more divisions of the trigeminal nerve.
B. Sensation to pinprick is diminished over the affected area.
C. Symptoms follow a lesion of the trigeminal nerve or its central projections.1051
2. Painful insensitivity of a body part, occurring as a result of incomplete nerve injury, usually traumatic or postherpetic.
anesthetic leprosy (Danielsson-Boeck disease) A form of leprosy in which hyperesthesia gives way to anesthesia with mutilation.1274See leprosy.
aneurysm (Gr, a widening) An expansion of the di-ameter of a blood vessel, usually an artery, due to dis-ease of its wall. Various forms occur:
Berry (“saccular”) aneurysms (naturalistic, not eponymic) are focal “blowouts” at points where arter-ies bifurcate, at which sites there is attenuation of the medial muscular and of the elastic layers of the arterial wall. They are found on the vessels of the anterior cir-culation in 85% of cases; in 25% of cases, more than one aneurysm is present.
Cirsoid (Gr, enlargement of a vein likeness) or racemose (Lat; clusters) aneurysms are irregular dilata-tions of arteries, causing to many sinuous bulges.
Dissecting aneurysms are those occurring in both in-tracranial and exin-tracranial arteries in which there is a tear in the media, the blood under pressure rupturing and splitting the media before tracking back into the true lumen of the vessel at a higher level.
Fusiform aneurysms (dolichoectasia, atherosclerotic aneurysm) are dilatations of the whole circumference over a length of the vessel, mainly caused by atheroma.
They are found most commonly in the vertebrobasilar and internal carotid arteries in elderly people, and
pro-duce symptoms mainly by compression of adjacent structures.1818
Mycotic aneurysms are focal dilatations of cerebral ar-teries resulting from inflammation of the walls of the vessels, tending distally and usually occurring as a com-plication of bacteremia.
aneurysm of the great vein of Galen Aneurysmal di-latation of this vein as a result of the shunting of ex-cessive amounts of arterial blood into it, seen in infants with developmental cerebrovascular anomalies such as arteriovenous malformations.
In early infancy, the usual presentation is with high-output cardiac failure, accompanied by a cranial bruit,5193while in later months the aneurysm may act as a mass lesion causing aqueductal compression and re-sulting hydrocephalus; seizures and dilated scalp veins are other features of note. When the presentation is not until later childhood, seizures, the effects of intracranial bleeding, and both brainstem and cerebellar findings are commonly noted, but usually no bruit is audible.
anfracta cerebri The cerebral fissures.
anfractuosity (Lat, a turning or bending around) Applied to the sulci between the cerebral convolutions.
Angelman syndrome (happy puppet syndrome;
OMIM 105830) A congenital neurobehavioral disorder characterized by brachycephaly, microcephaly, and a horizontal depression in the occipital bone; cerebral at-rophy and primary optic atat-rophy; multifocal seizures with hypsarrhythmia; ataxic, jerky (puppet-like) limb movements (hence the alternative name); prognathism;
unusually protrusive tongue; easily provoked and pro-longed paroxysms of laughter but no speech; hypopig-mentation; and mental and developmental delay.182A microdeletion at chromosome 15q11–q13 is present, almost always of maternal inheritance.
See also Prader-Willi syndrome, in which the same deletion is of paternal inheritance.
Angelucci syndrome (allergic conjunctivitis syn-drome) A syndrome of recurrent conjunctivitis, often associated with dermal and mucosal pruritic lesions and occasionally with signs of proximal myopathy.183The cause is unknown.
angiectasia (Gr, a blood vessel dilation) Patholog-ical widening of the blood vessels, usually applied to di-latation of the capillaries (telangiectasis).
angioblastic meningioma See meningioma.
angiodysgenetic myelomalacia See subacute necrotic myelopathy (Foix-Alajouanine syndrome).
angioendotheliomatosis Invasion of cerebral and other blood vessels by anaplastic malignant cells.
angiographically occult CNS vascular malformation Slow-flow vascular lesions within the brain which ap-pear avascular on angiography. They include venous
52 ANERGY
angioma, telangiectasis, thrombosed arteriovenous an-gioma, and cavernous angioma.
angiography A series of techniques for visualizing the anatomy and pathology of the arterial system by means of the injection of radio-opaque dyes with X-ray imaging; ultrasound (Doppler studies; or magnetic resonance imaging).
The first of these was introduced by the Portuguese surgeon Egaz Moniz in 1936, providing the first op-portunity for physicians to obtain even an indirect rep-resentation of the intracranial structures. A history of angiography has been written by Gurdjian.2336 angioid streaks (Knapp syndrome) Brown or gray lines visible on the retinae. They represent defects in Brusch’s membrane or other retinal degenerative changes, and resemble blood vessels except that they are not usually directed radially.
Angioid streaks are typically seen in pseudoxan-thoma elasticum but also occur in other diseases of the retinal vessels3094and are occasionally found in normal subjects.
angiokeratoma Warty growths in the skin with telangiectasia, the skin lesion clustered in the swimming trunk area, characteristic of Anderson-Fabry disease and in Mibelli disease, described first in 1877 by Dr.
E.W. Cottle (d. 1919), an English physician.4979 angiokeratoma corporis diffusum (universale) (Fabry disease) See Anderson-Fabry disease.
angiolipoma A rare benign tumor composed of adi-pose tissue and abnormal vascular elements, usually in the posterior epidural space of the spinal canal and sometimes infiltrating local bone.1919
angioma A common vascular malformation (rather than a true neoplasm), comprising four types:
Arteriovenous malformations Capillary telangiectases
Cavernous angiomas (cavernomas) Compact aggregations of sinusoidal blood vessels with minimal or no neural tis-sue between the vessels, most common within the brain-stem and in Sylvian regions and sometimes multiple. Cal-cification may occur. Clinically, bleeding is uncommon, but seizures may occur.
Venous angiomas (developmental venous anomalies) Com-mon malformations consisting of loose collections of ve-nous channels with intervening neural tissue, situated anywhere in the nervous system and often multiple. They are seldom symptomatic.
angioma capillare et venosum calcificans See Sturge-Weber syndrome.
angiomatosis meningo-oculofacialis See Sturge-Weber syndrome.
angiomatosis retinae (cystica) See von Hippel–
Lindau disease.
angiomatosis retino-cerebellaris See von Hippel–
Lindau disease.
angiomatous malformation See arteriovenous malformation.
angiomatous meningioma See meningioma.
angioparalytic hemicrania See hemiplegic migraine.
angiopathia retinae juvenalis See Eales disease.
angiopathic myopathy An ischemic myopathy com-plicating polyarteritis nodosa or giant-cell arteritis.3301 angiopathic neuropathy Typically, a multiple mono-neuropathy causing pain, weakness, and sensory loss in the distribution of a number of nerves as a result of numerous nerve microinfarcts in small-vessel occlusive diseases, causing both axonal damage and demyelina-tion. Diabetes and polyarteritis are the more common causes.1572
angiophrasia The repetitive insertion of a meaning-less sound into otherwise normal speech, as in “hem-ming and hawing.”
angiosarcoma A vascular sarcoma.
angiosclerotic paroxysmal myasthenia (Determan) See Charcot.
angiostrongyliasis An infestion by Angiostrongylus cantonensis, acquired through the ingestion of inade-quately cooked snails, prawns or frogs, or the vegetable matter upon which they have resided. Both sensory radiculopathies and CNS infestation are complications.
Anglade, Dominique (b. 1867) French neurologist who first demonstrated the value of Victoria Blue as a staining technique for neuroglia, according to Lasègue.3285
angle tumors Conventionally synonymous with cerebellopontine angle tumors. The typical syndrome was first described in accurate detail by Cushing,1229 who noted that there had been reports as far back as 1830 but based his account on a personal series of 30 such cases. Tinnitus; deafness; vertigo; suboccipital dis-comfort; frank cerebellar signs; involvement of the fifth, sixth, seventh, and bulbar cranial nerves; features of raised intracranial pressure; and “cerebellar crises” (ex-treme suboccipital pain with neck retraction and re-duction in consciousness, angor animi, bradycardia and apnea, indicating intermittent increases in intracranial pressure) occurred, generally in that order.
angular gyrus syndrome The clinical effects of dam-age to the heteromodal cortex adjacent to Wernicke area, including any combination of anomia, alexia, acalculia, constructional deficits, dysgraphia, defects in finger identification, and left/right naming difficulties.
See also Gerstmann syndromes, alexia.
anhedonia A term used mainly in psychiatry, signi-fying the inability to experience pleasure and loss of the power of enjoyment. By extension, it represents a telling symptom of depressed affect.
ANHEDONIA 53
anhidrosis (Gr, lack of sweat) Absence of sweat-ing; a local phenomenon with damage to specific sym-pathetic cholinergic pathways, or a generalized prob-lem as a result of degenerative or chemically induced sympathetic failure.
The condition may occur congenitally as a recessively inherited trait in which there is a failure of differentia-tion of sweat glands.3569See also Riley-Day syndrome, multiple system atrophy, familial amyloid neuropa-thy.
anhidrotic ectodermal dysplasia (Christ-Siemens-Touraine syndrome) An X-linked recessive syndrome comprising anhidrosis, hypotrichosis, saddle nose, den-tal anomalies, periorbiden-tal pigmentation, and sometimes mental delay.5690
anhydromyelia (Gr, lack of water marrow) De-ficiency of CSF.
anima (derivative of Lat; soul or spirit) The soul or vital life-force, applied also to the intellectual principle of humans.
aniridia A dominantly inherited congenital malfor-mation characterized by absence of the iris, usually bi-laterally, associated with photophobia, amblyopia, nys-tagmus, and sometimes ataxia.5105Other anomalies are also described in a few of the patients.
In a variant form (aniridia, mental retardation, geni-tal abnormalities), these features and nystagmus, cataract, and glaucoma are found in association with abnormalities of chromosome 11p13.4137 See also Gillespie syndrome.
aniseikonia Perception of one object viewed by the two eyes as having two different sizes or shapes.
anismus Constipation due to functional obstruction of the pelvic outlet by paradoxical contraction of the striated sphincter muscles during defecation straining.
This may represent a focal dystonia.3693
anisocoria (Gr, negative equal pupil) Inequal-ity of the diameter of the pupils of 0.4 mm or more, suggesting the presence of a lesion of the sympathetic pathway to the eye on one side or of the parasympa-thetic pathway on the other if any disease is present at all.
In this form, simple, essential, or central anisocoria, the pupils react to light and accommodation, the difference in their size is maintained under different conditions of illumination, and pharmacological responses are nor-mal. The condition is regarded as a normal variant.
anisometropia (Gr, negative equal measure eye) A difference in the refraction of the two eyes; or a difference in the anteroposterior diameter of the two eyes. In each case, it is a common cause of amblyopia.
anisomorphic gliosis The irregular orientation of the glial fibers in severely damaged neural tissues.
anisosthenic (Gr, negative the same strength) Inequality in the force of contraction of different mus-cles.
ankyloblepharon The presence of a variable degree of fusion of the lid margins, a malformation that may be dominantly or recessively inherited.
ankylosis (from Gr, the bend of the arm) A stiffen-ing of a joint by disease.
Annals of Neurology The journal of the Ameri-can Neurological Association (Web site: http://www.
aneuroa.org/) and of the Child Neurology Society (Web site: http://www.childneurologysociety.org/), publish-ing articles on all aspects of the human nervous system, both normal and abnormal is published by John Wiley
& Sons Inc. Wiley InterScience. Web site: http://www3.
interscience.wiley.com/cgi-bin/jtoc?ID76507645.
annectant gyri The convolutions passing from the parietal to the occipital lobes.2240
Annual Review of Neuroscience (Annu. Rev. Neu-rosci.) A neurological/neuroscience review book series.
Address: Annual Reviews Inc., 4139 El Camino Way, Palo Alto, CA 94303-0897. Web site: http://neuro.an-nualreviews.org/.
anodal block A local block of nerve conduction caused by membrane hyperpolarization under a stim-ulating anode. Does not occur in routine clinical stud-ies, since it is possible for the anode to routinely result in nerve depolarization if sufficient current intensities are used. (From the 2001 Report of the Nomenclature Committee of the American Association of Electro-myography and Electrodiagnosis.10 Used by permis-sion, copyright © 2001, AAEM.)
anode The positive terminal of an electric current source. cf. cathode.
anodyne (Gr, lack of pain) An analgesic medicine;
until the earliest part of this century the word was ap-plied to drugs such as opium, chloroform, and hemp, only the last of which is easily obtainable today.
anomalous reflex A reflex with no known survival value, e.g., vomiting with vertigo.
anomia (from Lat, deprivative a name) The inabil-ity to generate and utter names; a facilinabil-ity impaired in all forms of aphasia but also in many cerebral diseases not causing aphasia. Four forms are distinguished:468
Word-production anomia The patient knows the required name but is unable to produce it correctly without some form of cuing, because of difficulty in initiating articula-tion, or in evoking the word, or as a result of paraphasia.
Word-selection anomia A pure word-finding problem in which the patient can recognize and describe the func-tion of the object presented, but cannot evoke its name.
Semantic anomia A failure of both the comprehension and the use of the name of an object; a situation in which the word has lost its semantic meaning for the patient.
54 ANHIDROSIS