Australian X disease See Murray Valley encephalitis
7. Valsalva ratio. This is an expression of the maximum heart rate generated by a Valsalva maneuver (blowing
against 40 mmHg for 15 seconds) divided by the mini-mum rate occurring within 30 seconds of the maximini-mum rate. The ratio of the longest to the shortest R-R interval should be 1.45 in young people. This is more accurately measured invasively.
8. The bulbocavernosus reflex and anal sphincter tone can be assessed with specialized instrumentation.
Invasive tests, including measurements of skin blood flow during mental arithmetic or with an inspiratory gasp, hot/cold stimulation, or radiant heating, need a well-tuned autonomic laboratory. The tests currently most favored have been reviewed.8
autonomic hyperreflexia syndrome See Head-Riddoch syndrome.
autonomic nervous system (vegetative nervous sys-tem) A division of the nervous system responsible for the automatic regulation of all the other systems of the body. Its existence was known to Galen, who regarded the sympathetic chain and the ninth, tenth, and eleventh nerve complex as forming the sixth nerve in his classification. He was also aware of the superior cer-vical ganglion and the rami communicantes.
It was Eustachius (1524–1574) who differentiated the vagus from the sympathetic, but the relative functions of the two systems were not considered until Pourfour DuPetit (1644–1741) sectioned the sympathetic chain in a dog and observed the resulting features of Horner syndrome. Remak first described unmyelinated nerve fibers in 1838 and believed that they arose from the sympathetic chain. Kolliker, Claude Bernard, and Brown-Séquard each demonstrated sympathetic vaso-constrictor effects, while E.F. and E.H. Weber slowed the heart by vagal stimulation and introduced the con-cept of inhibition in the nervous system. Hering and Breuer discovered the pulmonary reflex resulting from inflation of the lung in 1868.
W.H. Gaskell (1874–1914) and John Newport Lan-gley (1852–1925), working in Cambridge, described pre- and postganglionic neurons, noted the antagonis-tic functions of the sympatheantagonis-tic and parasympatheantagonis-tic systems (respectively exciting and inhibiting glandular and smooth muscle activity), and divided the auto-nomic system between the cranial (bulbar) and sacral parasympathetic and thoracolumbar sympathetic out-flows. It was Langley who suggested the name auto-nomic nervous system.32
autonomic neuropathy 1. (acute autonomic neu-ropathy, acute pandysautonomia) The acute or
suba-cute onset of pandysautonomia occurring over several weeks, followed by recovery and usually unaccompa-nied by evidence of involvement of the central or pe-ripheral nervous systems, preceding infection and other systemic disease. The condition is possibly a variant form of acute inflammatory demyelinating polyneu-ropathy.
Clinically, lethargy, tiredness, postural hypotension, blurred vision with pupillary paresis, anhidrosis, dry mouth, abdominal pain, constipation, urinary reten-tion, and impotence are the usual features.5558 Pure cholinergic dysautonomia has also been described.3776
Ropper et al.4772have defined diagnostic criteria for the pure autonomic variant of acute inflammatory de-myelinating polyneuropathy as follows, reproduced here by kind permission of the authors and of F.A.
Davis, Inc.
Clinical Features
Progressive sympathetic and parasympathetic dysfunction over 1–3 weeks
No limb weakness, ophthalmoplegia, or ataxia Areflexia or hyporeflexia by 1 week
Improvement of some autonomic dysfunction by 2–4 months
Laboratory Abnormalities That Confirm the Diagnosis Elevated CSF protein concentration
Normal (or virtually normal) motor nerve conduction stud-ies, and abnormal sensory nerve conduction studies 2. Neuropathies affecting the autonomic nervous
sys-tem as part of a more generalized affection as with diabetes, amyloidosis, porphyria, and the heredi-tary sensory and autonomic neuropathies, etc.3776 Autonomic Neuroscience: Basic and Clinical (for-merly the Journal of the Autonomic Nervous System).
The official publication of The International Society for Autonomic Neuroscience. Web site: http://www.
isanweb.org.
autonomic storm See episodic autonomic dysre-flexia; diencephalic autonomic seizures.
Autonomic Symptom Profile A question bank as-sessing secretomotor function, male sexual dysfunc-tion, urinary, gastrointestinal, pupillomotor, vasomo-tor and sleep functions, and reflex syncope.5401 autonomous bladder 1. (reflex neurogenic bladder) The state of the bladder following loss of all supraspinal inhibitory influences; the volume tolerated is reduced and reflex emptying occurs through a contracted sphinc-ter. 2. (autonomous or paralytic neurogenic bladder) The state of the bladder deprived of lower motor neu-ron innervation or in the early stages of spinal shock; the bladder is flaccid and dilated, with dribbling inconti-nence through a lax sphincter and loss of voluntary con-trol of the initiation or termination of voiding.
autophagy The localization of intracellular debris and organelles within membranes of the endoplasmic reticulum.
AUTOPHAGY 83
autoregulation The ability of the brain to maintain a constant cerebral blood flow despite changes in per-fusion pressure by variation in size of precapillary re-sistance vessels (arterioles). A metabolic mechanism is likely, perhaps based on the release of adenosine or other vasodilator metabolites with incipient hypoxia.
With fully relaxed smooth muscle, increases in trans-mural pressure cause passive widening of the lumen. If the smooth muscle is normally responsive, increased transmural pressure causes constriction and decreased pressure, dilatation. Maximum dilatation occurs below 60 and above 160 mmHg. (Below or above those lev-els, the perfusion rate follows the perfusion pressure—
i.e., autoregulation is lost.)
With severe hypertension, the arterioles dilate max-imally and the blood–brain barrier breaks down. Sub-stances such as protein cross as a result of increased vesicular transport and endothelial disruption, not by opening of the tight junctions. The result is edema.
autosomal dominant cerebellar ataxia (ADCA, olivopontocerebellar atrophy) A group of spinocerebel-lar degenerations including what were once known as Sanger-Brown and Marie ataxias and olivopontocere-bellar, “primary” parenchymatous cerebellar cortical, and cerebellopontine atrophies, with onset in young adult life. In these conditions, cerebellar and corti-cospinal features coexist variously with optic atrophy, in-voluntary movements (chorea, dystonia or Parkinsonian features), lower motor neuron lesions, ptosis, my-oclonus, bulbar palsy, pigmentary retinal degeneration, and/or ophthalmoplegia; sensory loss is not found.
Harding2438classified them as follows:
ADCA I Cerebellar ataxia associated with supranuclear ophthalmoplegia, optic atrophy, dementia, lower motor neurone lesions, and/or extrapyramidal features. Patho-logically, there is degeneration of the spinal cord, brain-stem nuclei and cerebellar afferent pathways. This class is genetically heterogeneous.
ADCA II Cerebellar ataxia, visual failure due to pigmentary retinal degeneration and sometimes dementia, and both pyramidal and extrapyramidal features
ADCA III A rare pure cerebellar ataxia with onset over the age of 50 years
ADCA IV Cerebellar ataxia with photosensitive myoclonus and deafness
A few rare, dominantly inherited forms remain: one with periodic ataxic manifestations, another associated with essential tremor, and others still whose various manifestations demonstrate that these disorders are es-sentially multiple system degenerations, potentially involving almost any part of the nervous system.
Variant forms are autosomal or X-linked recessively inherited or occur sporadically.
autosomal dominant cerebellar atrophy with optic atrophy, progressive external ophthalmoplegia, de-mentia, extrapyramidal signs, and lower motor neu-ron lesions See Joseph disease.
autosomal dominant chin tremor See hereditary quivering of the chin.
autosomal dominant episodic ataxia A heteroge-nous condition characterized by episodic ataxia and clinical response to acetazolamide. In many cases nys-tagmus is also found. In various kindreds paroxysmal ataxia, paroxysmal choreoathetosis, and myotonia are also described.2016See episodic ataxia.
autosomal dominant juvenile amyotrophic lateral sclerosis See amyotrophic lateral sclerosis.
autosomal dominant muscular dystrophy with humeropelvic distribution and cardiomyopathy See myopathies.
autosomal dominant myopathy with myofibrillar in-clusions See myofibrillar myopathy.
autosomal dominant nocturnal frontal lobe epilepsy A dominantly inherited syndrome of brief clusters of nocturnal seizures preceded by an aura, lasting less than a minute, with onset in childhood. Tonic spasms or hy-perkinetic motor seizures are the usual phenotypes.
Partial awareness may be maintained. Linkage to both 20q (OMIM 600513) and 15q (OMIM 603204) have been established. The latter presents with tonic hyper-kinetic movements resembling parasomnias.
A diagnosis of parasomnia or of paroxysmal noc-turnal dystonia is often made if sleep EEGs are not available.4947
autosomal dominant partial epilepsy with variable foci A syndrome with onset in childhood in which heterogeneous complex partial or secondarily general-ized seizures occur in members of the same family, by day or night. Interictal EEGs are abnormal in the pa-tients and in some asymptomatic relatives.4947 autosomal dominant rolandic epilepsy with speech dyspraxia A syndrome with onset in early childhood of typical nocturnal rolandic seizures, centrotemporal spikes in the interictal EEG with the addition of speech dyspraxia, and cognitive deterioration becoming severe in subsequent generations as a result of anticipation.4947 autosomal dominant torsion dystonia See dopa-responsive dystonia.
autosomal recessive muscular dystrophy A severe and progressive recessively inherited muscular dystro-phy characterized by the onset in childhood of proxi-mal muscle weakness and atrophy affecting the girdle and truncal muscles predominantly. Joint contractures, pseudohypertrophy, scoliosis, cardiomyopathy, calf hy-pertrophy, and markedly raised serum creatine kinase levels are other features.
The best-recognized form, also known as ad-halinopathy, is characterized by at least near-complete absence of this muscle membrane protein with normal dystrophin staining. The gene responsible is located on chromosome 17q. The clinical disorders reported range 84 AUTOREGULATION
from severe childhood muscular dystrophy resembling Duchenne dystrophy (but seldom with cardiomyopa-thy and with a more benign course) to a late-onset syn-drome of mild myopathic muscle weakness.4437 An-other form is due to a mutation of a gene on 13q, which is hardly distinguishable from Duchenne dystrophy except for the absence here of mental retardation and the occurrence of the disorder mainly (so far) in Tunisian patients.447See also severe childhood auto-somal recessive muscular dystrophy.
There is marked variability in the intensity of symp-toms and severity of the course of the disease between siblings.2402See also limb-girdle muscular dystrophy, myopathies.
autosomal recessive sensory neuropathy See hereditary sensory neuropathy.
autotopagnosia Impairment in the localization and naming of one’s own body parts, described by Pick in 1908.
Avellis, Georg (1864–1916) German laryngologist.
Avellis syndrome (ambiguo-spinothalamic syn-drome) Paralysis of one vocal cord and the same side of the pharynx and soft palate (tenth cranial nerve) with contralateral hemianesthesia, due to a lesion of the medullary tegmentum affecting the vagal nuclei and the spinothalamic tract, or from a lesion at the jugular fora-men. Horner syndrome or contralateral spinothalamic tract deficits may be associated.269
In the original cases, only the ninth and tenth cra-nial nerves were affected, and the lesion was most likely at the jugular foramen; but the more generalized effects of a medullary lesion are now regarded as appropriately placed with the condition.
average potential reference (Goldman-Offner refer-ence) An average of the potentials of all or of many EEG electrodes, used as a reference.
averaging A method for extracting time-locked po-tentials from random background noise by sequentially adding traces and dividing by the total number of traces.
aviation neurology The branch of neurology con-cerning fitness to fly in an airplane as aircrew or pas-senger. Guidelines for fitness status were compiled by a committee of the American Medical Association and published in 1979.
Avicenna (980–1036) Persian physician and Islamic philosopher. His book on the laws of medicine was pub-lished in Arabic and, when translated into Latin, served as a basic textbook for medicine in Europe until the ei-thteenth century. In it he described facial palsy, trigem-inal neuralgia, and perhaps hemifacial spasm, and in-troduced the word epilepsy.139
AVM Support Group A charitable organization. 107 Bella Vista Way, San Francisco, CA 94127. Tel: 415-421-7330
awakening The return to the polysomnographically defined awake state from any non-rapid eye movement stage or from rapid eye movement sleep, characterized by the appearance of alpha and beta waves on the EEG, tonic EMG activity, voluntary eye movements, and eye blinking.249See also arousal.
awakening grand mal An epileptic syndrome, rep-resenting a form of primary generalized epilepsy of ado-lescence, characterized by the onset, after the age of 8 and usually in the mid-teen years, of primary general-ized seizures, occurring mainly in the half hour fol-lowing awakening but sometimes also during sleep.
Seizures are easily provoked by deprivation of sleep and by photic stimulation. See also juvenile myoclonic epilepsy.
Axelrod sensory neuropathy with skeletal dysplasia A congenital dysmorphic syndrome characterized by skeletal deformities, absent or sparse tears, seizures, sensory and autonomic neuropathy, and craniorachis-chisis.337
Axenfeld, Karl Theodor Paul Polycarpus (1867–
1930) German ophthalmologist.
Axenfeld-Schurenberg syndrome (cyclic oculomo-tor paralysis) A congenital unilateral third cranial nerve palsy with mydriasis alternating with phases of pupil-lary constriction and contraction of muscles supplied by the third nerve, and thus leading to elevation of the upper lid and nasal deviation of the eye (although lat-eral deviation is also described).275See also cyclic ocu-lomotor palsy.
axial dystonia Dystonia affecting the back and trunk, causing scoliosis, lordosis, tortipelvis, etc.
axial hyperkinesia Rocking at the hips in a to-and-fro movement, often with an element of pelvic thrust-ing. It is seen in some patients with dystonic states, such as tardive dyskinesia.
axial myopia Congenital increase in the anteropos-terior diameter of the eye, leading to the appearance of unilateral proptosis of up to 4 mm.4267
axial skeletal–neural dysraphic disorders Complex developmental malformations due to original paraxial mesodermal insufficiency affecting the formation of the axial basicranium, and the elevation of the neural folds interfering with their closure. Three fundamental types are recognized, in which the skeletal, neural, and oropharyngeal elements are partially or totally unclosed (e.g. anencephaly and occipital encephalocele) or are closed but abnormal (e.g., Chiari malformation).3624 axial tonic seizures Seizures in which stiffening of the posterior neck muscles produces an erect posture of the head. Opening of the eyes and mouth, rigidity of the paraspinal and abdominal muscles, and apnea are other common characteristics.2055
AXIAL TONIC SEIZURES 85
axilemma (axolemma, Mauthner’s sheath) The axon sheath. Ludwig Mauthner (1840–1894), a Bohemian ophthalmologist, described and so named it in 1882.
axilla (Gr, the point on which a wheel revolves arm) The armpit.
axillary nerve palsy (circumflex nerve palsy) A mononeuropathy occurring particularly as a result of dislocation of the shoulder, and leading to weakness and wasting of the deltoid and teres minor muscles and to a patch of numbness over the lateral aspect of the shoulder and upper arm.
axis The second cervical vertebra.
axis cylinder (axon, Remak’s band) The core and conducting element of the nerve fiber; the long exten-sion of a neuronal cell body containing microtubules, neurofilaments, and smooth endoplasmic reticulum.
Robert Remak (1815–1865), a German physiologist and neurologist, described and named it in 1838.4979 axon The conducting element of the nerve trunk. See axis cylinder.
axon reaction See chromatolysis.
axon reflex (axon response, axon wave) A late re-sponse recorded from nerves after peripheral stimula-tion and disappearing when the stimulus is supramax-imal. It may witness ephaptic transmission, and is detected in neuropathies or after nerve injury.1991See also A wave.
axon reflex test Local vasodilation with the produc-tion of a flare normally follows a prick delivered through one drop of 1% histamine solution placed on the skin, indicating that the axons in that region are in-tact. See also autonomic function tests.
axon response A triple response in the skin, consist-ing of local vasodilatation, formation of a wheal, and further surrounding vasodilatation (the flare) occur-ring after the intradermal injection of 1% histamine acid phosphate or a strong local tactile stimulus. See also axon reflex.
It is present normally and in areas in which dener-vation has occurred as a result of preganglionic nerve lesions. With postganglionic nerve lesions, the response is not present in anesthetic regions, when it thus rep-resents a hopeful prognostic sign.659
axon stains Histological enhancement methods used to demonstrate axons preferentially. These include the Bodian and Bielschowsky methods employing silver salts and a reducing agent. See also myelin stains.
axon wave See axon reflex.
axonal cross-talk See ephaptic transmission.
axonal degenerations Forms of neuropathy in which the basic fault is disruption of neuronal metabolism to the extent that axonal transport mechanisms fail. See also Wallerian degeneration.
axonal sheath Three concentric layers of tissue about the axon. From within outwards, these comprise the Schwann cells and two connective tissue membranes, the neurilemma and the endoneurium. In some nerves, a layer of myelin is interposed between the Schwann cell layer and the axon.
axonal transport (axoplasmic transport) The pro-cess whereby constituents of the axoplasm pass both centrifugally from and centripetally towards the perikaryon. Two systems exist: the slow transport sys-tem is that process whereby the constituents of axo-plasm such as neurofilaments and microtubules are delivered from the cell body down the axon to its ter-minal at rates of up to 3 mm/day; the fast system is bidi-rectional and carries substances of high molecular weight (small vesicles, mitochondria, and membrane-bound tubules) at speeds of up to 400 mm/day both to-wards and away from the cell body.
The existence of such a system was correctly surmised by Descartes, although he was unaware of the electrical properties of nerves.
axonopathy Disease of the axon, as opposed to dis-ease primarily affecting the neuronal cell body (which is called neuronopathy). In the dying-back form, there is initial degeneration of the longer fibers with pro-gression of the lesion from distal to proximal.
axonotmesis A lesion of a peripheral nerve produc-ing discontinuity of axons, while the supportproduc-ing struc-tures of the nerve (Schwann tubes, endoneurium, and perineurium) are more or less preserved. There is nev-ertheless such disturbance of the nerve fibers that true Wallerian degeneration occurs peripherally.
The condition represents one of the three types of nerve injury described by Seddon,5048the others being neurapraxia and neurotmesis.
axoplasm The circulating cytoplasm contained within the axonal tubes.
axorhizomelic tonic seizures A type of tonic seizure which begins in the same way as axial tonic seizures but which continues with tonic contraction of the proximal part of the contralateral arm, causing abduction and el-evation of the semiflexed arm and shoulder.
axotomy, axonotomy See axonotmesis.
Azorean disease (Azorean ataxia, Joseph disease). A dominantly inherited syndrome with cerebellar ataxia.
See Machado-Joseph disease.
86 AXILEMMA
B cells Type B lymphocytes which are the precursors of immunoglobulin-producing cells.
B waves Spontaneous oscillations of intracranial pressure of between 10 and 50 mmHg, occurring at 0.5-to 2-minute intervals during sleep and in patients with periodic (Cheyne-Stokes) respirations.
Baastrup disease The presence of lumbar pain due to soft tissue disease affecting the interspinous liga-ments and adjacent soft tissues.280
Babcock sentence “One thing that a nation must have to become rich and great is a large, secure supply of wood.” The inability to repeat exactly this rather pedestrian economic statement after three presenta-tions was once considered a strong indication of im-paired short-term memory, but three-item recall se-quences are now more fashionable.
Babes nodules Collections of microglia in the nerv-ous system, found in in rabies.
Babin´ski, Josef-Francois-Felix (1857–1932) French neurologist of Polish descent who became chef de clin-ique under Charcot, following Pierre Marie and pre-ceding Gilles de la Tourette. He did not succeed Char-cot as professor at the Salpétrière for internal political reasons, but instead led the neurology service at the Pitié, an adjacent Paris hospital, from 1895. He re-mained a bachelor, living with his older brother Henri, a gourmet of distinction.
Babin´ski regarded his work on spinal cord compres-sion to be his best, but today his most lasting legacy is considered to be the sign bearing his name, which he de-scribed in 1896 (in 28 lines). He is also remembered for his definition of many cerebellar signs and for the intro-duction of the terms dysdiadochokinesis and asynergia;
for the platysma, reinforcement, trunk-thigh, and prona-tor signs; and for the Babinski-Frölich (adiposo-geni-tal) syndrome, which he described in 1900, a year before Fröhlich. The Babinski-Nageotte and Anton-Babinski (anosognosia) syndromes also bear witness to his aston-ishing clinical perspicacity. It is also remembered that he pointed out that the hysterical symptoms of many pa-tients at the Salpétrière died with Charcot. He was an early proponent of the use of the reflex hammer.
Babinski attracted many important neurologists from abroad to his service, but his failure to gain ap-pointment at the Salpétrière reduced his influence within France, although he was a founder of the Société de Neurologie, edited the Revue Neurologique, and was elected to the Parisian Academy of Medicine in 1914.
In the end, dispassionately, from abroad, he was prop-erly regarded as the most outstanding of all the pupils of Charcot.2750Like Henry Head, he died from com-plications of Parkinson disease.
Babinski signs 1. Described by Babinski as “the phe-nomenon of the toes,” the sign consists of the upward (dorsiflexion or extension) movement of the hallux with uncomfortable or painful stimulation of the sole of the foot, while the normal response would be for the toes to move downwards. As he noted in his original283 or in later papers published between 1896 and 1903, flexion at the hip and knee, ankle dorsiflexion, and fan-ning of the toes (“signe de l’éventail”) may also occur.
The sign is present (upgoing toe) in the presence of a disturbance in the pyramidal system, regardless of its duration, intensity, or extent, and it represents a part of the flexion reflex in humans.
Marshall Hall, Vulpian, and Strumpell had previ-ously noted this phenomenon and Remak had de-scribed extension of the hallux on plantar stimulation in transverse myelitis 3 years before, but Babinski in-vestigated the phenomenon in depth, principally in an attempt to distinguish organic from hysterical weak-ness, and deserves the eponym. Some reports show him using a feather, but his words indicate that he elicited the sign by pricking the skin of the sole.283
Numerous other methods of eliciting the sign (Chaddock, Bing, Oppenheim, Gordon, Thomas, Stransky, etc.) have also been described, and are com-plementary but rather less useful.5729
2. Diminution or absence of the Achilles reflex in sciatica. Babinski introduced the preferred method of examining the reflex, with the patient kneeling.
3. Fanning of the toes on the side on which there is clinical evidence of a pyramidal lesion, when the supine patient attempts to sit up.
4. Greater contraction of the platysma on the healthy than on the affected side in hemiparesis, tested by getting the patient to open the mouth wide or to try to whistle.
5. (pronator sign) Increased pronation of the paretic arm in hemiparetic states, such that when the examiner places the patient’s hands in a position of supination, only the hand on the side affected returns to the pronated position.
6. Pupillary changes with aortic aneurysms.284See Horner syndrome.
7. Paradoxical raising of the eyebrow on the side of hemifacial spasm as a result of contraction of the frontalis muscle as well as the orbicularis oculi.286