Pyridoxine Vitamin B6

Pyridoxal phosphate is the active biochemical form of pyridoxine. It is a coenzyme of amino acid metabolism, particularly tryptophan and methionine. By inhibiting methionine metabolism, excessive S-adenosylmethionine accumulates, which inhibits nerve lipid and myelin synthesis. y Because tryptophan is required in the production of niacin, pyridoxine deficiency can produce a secondary niacin deficiency indistinguishable from primary pellagra. Pyridoxine is also involved in lipid and...

History And Definitions

In an attempt to distinguish the class of motor disturbances resulting from lesions of the basal ganglia, Kinnier Wilson coined the term extrapyramidal in his famous 1912 articled describing hepatolenticular degeneration, now known as Wilson's disease. This term was widely adopted thereafter and continues to be used today. The extrapyramidal system refers to the basal ganglia with their anatomical connections, and extrapyramidal disorders are hypokinetic and hyperkinetic states that ensue from...

Evaluation Guidelines

In virtually every patient who presents with overt or subtle manifestations of trigeminal nerve dysfunction, some form of laboratory evaluation is indicated ( Table 10-2 ). Careful and directed neurological examination dictates the most important tests to obtain. Neuroimaging. Once a lesion has been reasonably localized to the cortex, white matter pathways, thalamus, or brain stem, neuroimaging is essential to support a definitive clinical diagnosis (for complete text, see reference 'i )....

Associated Medical Findings

The skin should be checked for rashes, lesions, or evidence of insect bites. The head and neck should be examined for masses, signs of trauma, or postoperative scars. The auricle and ear canal should be examined thoroughly for vesicles, ulcers, or other lesions. The tympanic membrane should be checked for perforation, drainage, or cholesteatoma. Infections, neoplasms, and evidence of prior otological surgery should be sought while examining the middle ear. The oral cavity and pharynx should be...

Evaluation Guidelines Table132

Lesions of the medulla such as infarction or neoplasm, or extramedullary, intracranial lesions, are better visualized by magnetic resonance imaging (MRI) than by computer-assisted tomography (CT). Some lesions that involve bone, especially the skull base, may be detected by CT or radiographs, the latter usually requiring the neurologist to request special views of the base of the skull. Imaging should be employed to assist in defining lesion type when the clinical examination...

Evaluation Guidelines Table142

The following tests may aid in the diagnosis of problems affecting the eleventh and twelfth cranial nerves. Neuroimaging. Various neuroimaging studies may be useful. y y Plain films of the skull may provide diagnostic information in platybasia (flattening of the base of the skull so that the angle formed by an imaginary line connecting the anterior margin of the foramen magnum, the tuberculum sella, and the nasion is greater than 143 degrees), Paget's disease (areas of increased and decreased...

Clinical History

Because cranial nerves III, IV, and VI innervate the extraocular muscles that move the eyes, the striated muscles that elevate the upper eyelids, and the iris sphincters that constrict the pupils, several symptoms develop when damage occurs. In general, dysfunction of these nerves causes different combinations of binocular double vision from misalignment of the visual axes. Damage to cranial nerve III causes ptosis from weakness of the levator palpebrae muscle, as well as pupil mydriasis or...

Preferential Atrophy

Type 1 fibers Myotonic dystrophy (prominent), nemaline myopathy, centronuclear myopathy, congenital fiber type disproportion Type 2 (especially 2B) fibers Disuse, corticosteroid excess (exogenous, endogenous)* CYTOARCHITECTURAL ABNORMALITIES Type 1 fibers Target fibers, central cores (central core disease), rod bodies (nemaline myopathy), motichondrial abnormalities Type 2 fibers Tubular aggregates *Type fiber atrophy, especially if limited to type 2B fibers, is a nonspecific finding most...

Specific Indications

Categories of CNS disease amenable to diagnosis by brain biopsy or mimicking types of disease normally presenting as neurosurgical conditions are summarized in Table 25-8 . This disorder can be grouped into conditions that present with mass lesions, focal or multifocal nonmass TABLE 25-8 -- BRAIN AND MENINGEAL BIOPSY DIAGNOSES TABLE 25-8 -- BRAIN AND MENINGEAL BIOPSY DIAGNOSES Gliomas, metastatic tumors, CNS lymphoma HIV encephalitis, opportunistic infections (toxoplasma, cytomegalovirus,...

Laboratory Test

Morning ACTH Fasting am cortisol 24-hour urine free cortisol Dexamethasone suppression test a Test results may be altered by pharmacological agents.b Tests should be performed and related to normal values for timing of menstrual cycle. infectious causes of problems, including sarcoidosis, histiocytosis X, bacterial meningitis, tuberculosis, or abscess, are typically resolved by the presence of other findings of these diseases. Lymphocytic hypophysitis and Sheehan's syndrome often occur in the...

Types of Detectable Abnormalities

The use of water-soluble intrathecal contrast medium has markedly decreased over the past 10 to 15 years with the introduction of CT and, more recently, MRI. Before these more advanced imaging tools, water-soluble myelography was the gold standard in evaluating patients with back pain and had the ability to evaluate spinal stenosis, disc bulges and herniations, other extradural impressions on the thecal sac, spinal cord enlargement, and various inflammatory conditions. However, intrathecal...

Abetalipoproteinemia Bassen Kornzweig Syndrome

This autosomal recessive lipid disorder develops clinically in the first decade of life with steatorrhea, distal sensorimotor neuropathy, and retinitis pigmentosa. Ataxia, dysarthria, areflexia, and ophthalmoparesis may also develop. y Serum cholesterol levels are low, betalipoproteins are low or absent, and erythrocytes take on the appearance of acanthocytes. Ihe primary metabolic defect relates to the inability to synthesize betalipoprotein, the major protein of chylomicrons and very low...

Abnormal Findings and Clinical Uses of Repetitive Nerve Stimulation

Repetitive nerve stimulation is a useful technique for evaluating neuromuscular transmission. In diseases in which such transmission is impaired, the muscle response to repetitive nerve stimulation may show abnormal alterations in size or area. In myasthenia gravis, a progressive decrement in the response may occur with repetitive stimulation (especially at 2 to 3 Hz), or an initial decrement may be followed by a leveling off of the response at a reduced size. Abnormalities are more likely to...

Abnormal Findings and Clinical Uses of the BAEP

The BAEP is an important means of evaluating function of the eighth cranial nerve and the central auditory pathways in the brain stem. In infants, young children, and adults who are unable to cooperate for behavioral testing, BAEPs can be used to evaluate hearing. y The wave V component of the response is generated by auditory stimuli that are too weak to generate other components. As a screening test of hearing, then, the electrophysiological threshold for eliciting wave V is determined. An...

Abnormal Findings and Clinical Uses of the Blink Reflex

The blink reflex may be helpful in revealing the presence of a subtle trigeminal or facial nerve lesion. Ipsilateral trigeminal nerve lesions lead to responses that are either lost or have a prolonged latency bilaterally. A unilateral facial nerve lesion, by contrast, leads to a delayed or absent response on the affected side regardless of which side is stimulated. The blink reflex may be abnormal with polyneuropathies, thereby indicating the extent of the disorder. Abnormalities may also occur...

Abnormal Findings and Clinical Uses of the VEP

Visual evoked potentials are useful in evaluating the function of the anterior visual pathways. They are not useful in evaluating lesions posterior to the optic chiasm. In patients with an acute optic or retrobulbar neuritis, the P100 response is initially lost with time, it recovers and is then found to have a markedly prolonged latency that generally persists indefinitely (see Fig 24-12 ),y , y even if apparently complete clinical recovery occurs. The VEP is therefore an important means of...

Acute Intoxication

In the nervous system, alcohol acts as a depressant, and small doses may lead to disinhibition or a slight euphoria. The toxic effects of alcohol become more prominent with rising blood levels, yet through repeated consumption, humans can become habituated rapidly. Although blood levels of 100 mg dl typically cause drunkenness in occasional imbibers, chronic alcohol abusers can tolerate levels up to 500 mg dl without any apparent effects. The toxic effects of alcohol can be produced in any...

Additional Neurological Findings

The presence of accompanying cortical signs other than memory loss helps to localize the anatomical basis of an amnestic syndrome. Accompanying dyspraxia, aphasia, or agnosia indicates that the cortex is involved in the pathological process. An assessment of affect is also important, since depression can produce a picture of seeming dementia (pseudodementia). Emotional lability or poor voluntary control over emotional expression (pseudobulbar affect) can occur in patients with...

Adolescence

Leber's hereditary optic neuropathy (II) Kearns-Sayre syndrome (III) Chronic progressive external ophthalmoplegia (III) Others Leber's hereditary optic neuropathy plus multiple system degeneration (II) Inherited exertional myoglobinuria (I) ADULTHOOD Malignant migraine (III) Neuropathy, ataxia, retinitis pigmentosa syndrome (II) Hypertrophic cardiomyopathy and myopathy (II) Mitochondrial myopathy (II, IV) *Diseases are listed by order of most likely age presentation The molecular genetics class...

Affective Disorder Syndromes

When secondary causes have been sufficiently evaluated, treatment of depression can be initiated. Treatment may include psychological therapies (supportive psychotherapy and behavior therapy) as well as pharmacological agents. Nearly 80 percent of patients with major and most chronic minor depressions respond to drug therapy, including tricyclic antidepressants, specific serotonin reuptake inhibitors, and MAO inhibitors. Electroconvulsive therapy may be necessary if medications fail or their...

Alexias and Agraphias

Alexia without agraphia was first described by Dejerine in 1892 in a patient who suddenly lost the ability to read but had no other language disturbance. The only neurological finding of significance was a right homonymous hemianopia. Although the patient was unable to read except for some individual letters, he could write adequately. In patients with this syndrome, the patient can write but cannot read his or her own written output. If the letters of a word are read aloud, the patient can...

Altered Sexuality Syndromes

Brain MRI CT Epilepsy, Huntington's disease, CNS neoplasm, trauma, stroke, encephalitis Brain MRI CT Epilepsy, CNS neoplasms, stroke, trauma, carbon monoxide poisoning, hydrocephalus, encephalitis, Wernicke-Korsakoff syndrome Brain MRI CT CNS neoplasms, stroke, trauma Brain MRI CT Post-trauma, stroke, encephalitis, multiple sclerosis Brain MRI CT Degenerative disorders, CNS tumors, trauma, encephalitis Brain MRI CT Encephalitis, CNS tumors, hypothalamic lesions, trauma EEG Psychosis associated...

Aminoacidopathies and Organic Acidopathies

Disorders of Later Infancy with Recurrent Metabolic Crises Progressive Diseases of Infancy and Childhood Mitochondrial Enzyme Defects Subacute Necrotizing Encephalomyelopathy (Leigh's Disease) Progressive Infantile Poliodystrophy (Alpers' Disease) Lethal Infantile Mitochondrial Disease or Congenital Lactic Acidosis Myoclonic Epilepsy and Ragged Red Fibers Syndrome Mitochondrial Encephalopathy, Lactic Acidosis, and Strokelike Episodes Chronic Progressive External Ophthalmoplegia and Kearns-Sayre...

Anaplastic Astrocytoma and Glioblastoma Multiforme

Malignant tumors are thought to evolve from lower grade tumors, although they can evolve spontaneously, perhaps as the result of abnormalities of gene function. Alteration of one gene may lead to transformation to a low-grade glioma, and subsequent cell division leads to the accumulation of multiple genetic alterations that ultimately result in a tumor with the histological characteristics of a glioblastoma multiforme. Alternatively, a putative glioblastoma...

Anatomy of Declarative Memory

A broad convergence of human and animal research indicates that declarative memory depends on an interaction between domain-specific neocortical regions and domain-independent medial-temporal, diencephalic, and basal forebrain regions. Long-term memories are thought to be stored in the neocortex, the neocortical location reflecting the content of the memory. Thus, knowledge about the visual appearance of a tool may be stored separately, TABLE 5-1 -- CLINICO-ANATOMICAL CORRELATIONS OF MEMORY...

Anatomy of the Pursuit System

In contrast to the saccadic control, the conjugate pursuit system of each hemisphere controls binocular eye movements Figure 9-6 (Figure Not Available) Hypothetical cortical pathways involved in saccade control. The cortical relays of saccade pathways are represented by arrowheads. FEF, frontal eye field H, hippocampal formation OC, occipital cortex PEF, parietal eye field PFC, prefrontal cortex (i.e., area 46 of Brodmann) PPC, posterior parietal cortex SC and RF, superior colliculus and...

Anatomy of the Saccade System

Three important cortical areas are involved with saccade generation and include the frontal eye fields (FEF), the supplementary eye fields (SEF), and the parietal eye fields (PEF). Other zones of the association cortex that play a secondary, but important role in saccade generation are the prefrontal cortex (PFC) and posterior parietal cortex. The interrelationships of these structures are complex and are summarized with a clinical emphasis (Fig. 9-6 (Figure Not Available) ). y The FEF is...

Anosmia and Hyposmia

Loss or decreased olfactory function is estimated to be present in approximately 1 percent of the American population under the age of 60 and in more than half of the population over that age.y The causes of loss or decreased olfactory function are variable, and simply establishing the presence of olfactory loss per se provides little insight into the cause. Nearly two thirds of patients with chronic anosmia or hyposmia (i.e., those that are presumably permanent) are due to prior upper...

Antibacterial Agents

PENICILLINS, CEPHALOSPORINS, AND IMIPENEM Historically, radiculitis, paraplegia, hemiplegia, and convulsions occurred after penicillin was administered into the CSF, but because this route of administration has been abandoned, such reactions are exceedingly rare. The neurotoxic clinical manifestations of penicillins, cephalosporins, and imipenem include myoclonus, seizures, confusion, hallucinations, encephalopathy, nystagmus, and agitation. Imipenem, cefazolin, and benzyl penicillin are the...

Antimalarials

Chloroquine, once considered too toxic for humans, has been the antimalarial of choice for 40 years. Although a range of serious CNS effects has been documented during chloroquine therapy, the incidence is unclear. y Abnormal involuntary movements including torticollis, blepharospasm, and dystonic tongue protrusion have been reported during chloroquine therapy, especially in patients younger than 30 years of age. i Headache, nausea, and tinnitus with progressive hearing loss, optic nerve...

Arenavirus Lymphocytic Choriomeningitis Virus

The natural reservoir for the lymphocytic choriomeningitis virus (LCMV) is the common house mouse. Hamsters and laboratory animals can also be infected with this virus. Most human infections result from contact with house mice. y , y Four clinical syndromes due to infection with LCMV have been described (1) subclinical asymptomatic infection, (2) nonmeningeal influenza-like illness, (3) aseptic meningitis, and (4) meningoencephalomyelitis. y The LCMV was the first...

Associated Neurological Findings

With regard to CN XI or XII, bihemispherical lesions may result in significant weakness of the SCM, trapezeii, or extrinsic tongue muscles. Other features that confirm the presence of bihemispherical lesions are urinary incontinence, gait apraxia, pseudobulbar palsy (i.e., dysarthria, dysphagia, and emotional incontinence), cognitive deficits, and alterations in personality. Cranial Nerves. Dysfunction of neck or tongue musculature may be the result of lesions in the brain stem...

Autonomic Innervation of Specific Organs

The heart receives parasympathetic and sympathetic innervation. The cell bodies of the parasympathetic preganglionic neurons innervating the heart are located in the medulla (nucleus ambiguous and dorsal motor nucleus of the vagus). The axons of these neurons, which are part of the vagus nerve, join the cardiac neural plexus after entering the thorax to synapse with neurons in the intracardiac ganglia. y From these ganglia, short postganglionic parasympathetic neurons emerge to innervate the...

Autosomal Dominant Diseases

NEUROFIBROMATOSIS (VON RECKLINGHAUSEN'S DISEASE) Pathogenesis and Pathophysiology. Neurofibromatosis y is no longer considered a single clinical entity and has been divided into at least two distinct forms. y The common form, once known as peripheral neurofibromatosis (NF), is called NF-1, and the rare form, once termed central NF, is NF-2. Both are inherited as autosomal dominant traits, and the gene locus responsible for NF-1 is on chromosome 17 (17q11.2), whereas that for NF-2 is on...

Basic Mechanisms Of Epileptogenesis

To understand the mechanisms related to the development of epilepsy, some basic principles of normal neurophysiology must be reviewed. Electrical signals in neurons take two forms the action potential, which propagates down the axon of the neuron from the soma to the axon terminal translocating information within a neuron and transmission of information between neurons, which is accomplished primarily by chemical synapses. A complex series of events underlie these electrical signals. Central to...

Basic Principles and Technique

Disorders of sleep are common and often respond well to treatment. Polysomnography is important in diagnosing and characterizing such disorders. It involves recording the EEG on two or a few channels to characterize the stage of sleep while recordings are also made of eye movements, mentalis muscle activity (chin EMG), electrocardiogram, respiration, and oxygen saturation. Respiratory movements are recorded by measurement of air flow through the nasal passages and the mouth using thermistors...

Basic Principles and Techniques

Ultrasonography depends on the presence of sonographic windows, which allow sound wave propagation and detection of echo signals. These signals form the basic sonographic units for image generation. Therefore, as a general rule, US is indicated when visualization of the target object is not blocked by intervening bone or air, such as calvarium or bowel gas. This limitation does not completely negate the use of US in the evaluation of adult brain disorders, as discussed later. The usefulness of...

Carnitine Palmitoyl Transferase II Deficiency

In CPI II deficiency, long-chain acylcarnitines are transported across the inner mitochondrial membrane but cannot be converted to their corresponding long-chain acyl- CoAs. They accumulate in the mitochondrial matrix and are transported out into plasma. Ihese elevated levels may produce cardiac arrhythmias. Dicarboxylicaciduria is absent, because of the same explanation given for carnitine transport defect. Ihe exact incidence is unknown, but the adult form is more common than the infantile...

Carnitine Transport Defect Primary Generalized Carnitine Deficiency

Carnitine fails to be taken up in muscle, heart, and kidney but not liver, leading to insufficient carnitine to support fatty acid oxidation. Ihe kidney fails to conserve carnitine by reabsorption, resulting in very low plasma carnitine levels, which then causes decreased passive diffusion into liver, impairing ketogenesis. Accumulating acyl-CoA compounds become substrates for peroxisomal beta- oxidation, which produces medium-chain fatty acids and dicarboxylic acids, which do not require...

Cat Scratch Disease

Cat-scratch disease is caused by the bacterium Bartonella henselae and begins with a cutaneous papule or pustule at the site of inoculation, usually a kitten scratch or bite, within a week of the injury. A regional adenopathy involving the head, neck, and upper extremity follows in 1 to 7 weeks. Fever and malaise occurs in approximately one third of patients. The diagnosis is made by demonstrating pleomorphic bacilli by Warthin-Starry silver stain of a lymph node biopsy or by polymerase chain...

Central Autonomic Network

The ANS, like the somatic nervous system, is organized in segmental levels. Neurons in the cerebral cortex, basal forebrain, hypothalamus, midbrain, pons, and medulla participate in autonomic control. Autonomic neurons are reciprocally interconnected by neurochemically complex pathways and constitute a functional unit referred to as the central autonomic network (CAN).y , 4 The CAN integrates visceral, humoral, and environmental information to produce coordinated autonomic, neuroendocrine, and...

Central Connections

The olfactory tract, which contains both afferent and efferent fibers, is relatively flat posteriorly and becomes the olfactory trigone just rostral to the anterior perforated substance (so named because of the many small holes for blood vessels found throughout this region). At the edges of the trigone, the tract divides into the medial and lateral olfactory striae. The axons of the mitral and tufted cells arise from the caudolateral part of the olfactory bulb and form the olfactory tract at...

Chickpea Lathyrism

Lathyrism is related to a neurotoxin acting through the glutaminergic system. Spastic paraplegia has been observed in Europe and India following consumption of different varieties of chickpea. Development of human lathyrism is associated with two potent neurotoxins found in the peas alpha-amino beta oxalylaminopropionic acid and alpha-amino gamma oxalylaminobutyric acid.'39' Toxic neurological signs are seen when 30 percent or more of the diet consists of chickpeas. Men tend to be affected more...

Chronic Falsepositive Vdrl Test Lasting Longer Than 6 Months

Systemic lupus erythematosus and other connective tissue disorders Reproduced with pemmission from Roos KL Syphilitic meningitis. In Roos KL (ed) Meningitis 100 Maxims in Neurology London, Amold, 1997, pp 171-181. with neurosyphilis have a positive VDRL test. A CSF examination should be performed in patients with a reactive MHA-TP or FTA-ABS. The diagnosis of neurosyphilis is made in the presence of a reactive serological test with either neurological manifestations consistent with...

Clinical Syndromes Table115

The sensory examination aims to establish the sensory modality involved, the intensity of involvement, and the anatomical distribution of the sensory change. In combination, these patterns isolate the likely neurological location of disease and later suggest etiology. In lesions of the peripheral nervous system the sensory loss tends to be intense, with fixed, clearly defined zones. With central nervous system sensory deficits the boundaries are vague and the deficit is more mild as compared...

Clinical Uses of the EEG

The EEG is useful in the evaluation of patients with several types of neurological disorders, including seizures, encephalopathy, and focal cerebral abnormalities. It also provides an ancillary aid to the diagnosis of brain death and may suggest certain specific neurological diagnoses when characteristic EEG findings are recorded in patients with clinical disorders of uncertain nature. The EEG is important in the evaluation of patients with known or suspected epilepsy. The interictal occurrence...

Coagulation Disorders

Brain ischemia and hemorrhage often result from hematological disorders. Changes in the formed cellular constituents of the blood may be quantitative or qualitative. Polycythemia increases blood viscosity, decreases cerebral blood flow, and increases the risk of thrombosis. Sickle-cell disease and sickle-cell hemoglobin-C disease are examples of qualitative red blood cell abnormalities that affect blood flow. Sickle-cell disease causes occlusive changes in large intracranial arteries and small...

Colloid Cysts

Colloid cysts are benign tumors that are amenable to curative neurosurgical resection. They must be diagnosed promptly before symptoms develop that can lead to acute conditions and sudden death. They are rare tumors but, with the advent of neuroradiological imaging, can be identified incidentally when imaging is performed for other reasons. They typically present in midlife, although pediatric diagnoses are known. They are located most frequently in the third ventricle and can cause variable...

Conceptual Apraxia

Whereas patients with ideomotor apraxia make production errors (e.g., spatial and temporal errors), patients with conceptual apraxia make content and tool selection errors. These patients may not recall the type of actions associated with specific tools, utensils, or objects (tool-object action knowledge) and therefore make content errors.y , y For example, when asked to demonstrate the use of a screwdriver, either pantomiming or using the tool, the patient who has lost tool-object action...

Congenital Myasthenias

The onset of myasthenic symptoms at birth or in patients with a family history of this disease has always made congenital forms of myasthenia a diagnostic possibility. With the advent of the acetylcholine receptor (AChR) and the calcium channel antibody test as markers for myasthenia gravis and Lambert Eaton myasthenia, it has become apparent that congenital myasthenia, like the congenital myopathies, may present later in life and, in some cases, without a family history. Pathogenesis and...

Congenital Myopathies

The initial definition of the so-called congenital myopathies implied the onset at birth of a nonprogressive primary myopathy, that could not be explained on the basis of a dystrophic or metabolic abnormality. However, in some morphologically and genetically identical cases, no symptoms are not present at birth and instead occur later. Furthermore, some cases of congenital myopathies such as nemaline myopathy and centronuclear myopathy are characterized by progressive weakness with a fatal...

Craniopharyngioma

Craniopharyngiomas are thought to be congenitally derived and to arise from remnants of Rathke's pouch. Embryonic collections of epithelial cells remain after absorption of the hypophysealpharyngeal duct, from which the infundibulum tuber cinereum is derived ( Fig , 4.6. 8 ). The squamous cells are found to be metaplastic and may be present for a significant period before transformation occurs. Alternative proposals suggest that these tumors are derived from a...

Craniosynostosis

Craniosynostosis refers to the premature fusion of one or more of the cranial sutures. The premature fusion of one or more sutures results in abnormal and often asymmetrical growth of the cranium with resulting effects on both the underlying brain and the outward appearance of the head. In patients with craniosynostosis, the brain may show a nonprogressive hydrocephalus. Intracranial pressure may be elevated even in the absence of hydrocephalus and also in...

Critical Illness Polyneuropathy

The occurrence of muscle weakness in patients with sepsis and multiple organ failure managed in the intensive care unit has been recognized with increasing frequency in the last 15 years. This weakness is due to an axonal polyneuropathy, otherwise called critical illness polyneuropathy. It must be differentiated from myopathy or disturbance of the neuromuscular junction that can also occur in the intensive care setting. y Neither the cause nor the exact mechanism of critical illness...

Death by Brain Criteria

The ability to transplant organs successfully led to the need of criteria for brain death, and national and international definitions have been developed. Many now argue that current criteria are restrictive and should be expanded to include patients who have no reasonable chance of regaining consciousness. y If this change is to be made, a substantial shift in societal thinking about life and death may need to precede it. However, in North America, death by brain criteria is still considered...

Deficiency Amblyopia

This disorder is most likely related to the depletion of one or more B vitamins, although none has been specifically implicated. Deficiency amblyopia occurs only after severe and prolonged nutritional deprivation. The strict dietary deficiencies required to produce amblyopia are known to occur mainly in mistreated prisoners of war and alcoholics. Smoking tobacco was once considered another risk factor (hence, the alias tobacco-alcohol amblyopia), but this is no longer believed to be true....

Definitions

Cranial nerve I (CN I) constitutes the primary receptor cells for the sense of smell. This nerve monitors the intake of airborne agents into the human respiratory system and largely determines, along with the sense of taste, the flavor and palatability of foods and beverages. In addition to purveying esthetic pleasures, CN I warns of spoiled foods, leaking natural gas, polluted air, and smoke, and mediates elements of basic communication (e.g., mother-infant interactions). Of particular...

Degenerative Muscular Disorders

The muscular dystrophies are hereditary, degenerative dystrophinopathies and disorders of dystrophin-associated proteins. In 1987, with the identification of a defect in the dystrophin gene as the cause of Duchenne muscular dystrophy (DMD), Monaco and Kunkel opened the door TABLE 36-4 -- FAMILIAL SPASTIC PARAPLEGIA (SPG), GE AR, Autosomal recessive AD, autosomal dominant, LICAM, L1 cell adhesion molecule. for research into its role in muscle function and maintenance. Dystrophin is controlled by...

Dermoid Epidermoid and Teratoma

These rare embryonic remnant tumors may present anywhere in the CNS but most commonly occur in the posterior fossa and the cauda equina. They are congenital tumors and may be seen at any age however, they are more likely to occur in children or young adults of either sex. They are slow growing and present with symptomatology specific for compressive syndromes at their location within the central nervous system. These symptoms can be insidious, and blockage of cerebrospinal flow occurs rarely....

Diencephalic Dysfunction

Disorders of the diencephalon may affect consciousness either directly, by interfering with reticular system function, or indirectly, by producing endocrine disorders. These conditions may develop slowly, as with anterior pituitary syndromes resulting in hypothyroidism or cortisol deficiency, or rapidly, as with osmoregulatory disorders. The lesions producing these problems may also affect the cerebral cortex, as in the case of neoplasms, and produce seizures or other focal neurological...

Diffuse Autonomic Failure Pandysautonomia

Preganglionic autonomic failure central neurodegenerative diseases Multiple system atrophy (Shy-Drager syndrome) Parkinson's disease with autonomic failure Ganglionic and postganglionic disorders-peripheral neurodegeneranve disorders Pure autonomic failure Peripheral neuropathies and neuronopathies with autonomic failure Acute and subacute (preganglionic and postganglionic) Chronic small-fiber (postganglionic) neuropathies ) Hereditary (familial dysautonomia, Fabry's disease Subacute or chronic...

Diffuse Autonomic Failure Pandysautonomia Central Preganglionic Disorders

Multiple system atrophy (MSA, Shy-Drager syndrome) is a degenerative disorder of the CNS that affects the extrapyramidal, cerebellar, and autonomic neurons (see Chaptei 34,). Autonomic dysfunction in patients with MSA is due to the loss of preganglionic neurons in the brain stem and spinal cord. Patients with MSA typically present with diffuse autonomic failure and parkinsonian, cerebellar, or pyramidal deficits in different combinations. y Autonomic features include...

Directed General Examination

The general medical examination provides useful diagnostic information in patients with hypokinesia and hyperkinesia. The skin examination in patients with Parkinson's disease shows seborrhea, scaly skin, and often patches of excessive dryness. Increased salivation and drooling are typical. The eyes should be examined in patients with movement disorders to detect the presence of Kayser-Fleischer rings or copper deposits in the cornea (Wilson's disease), and proptosis and lid-lag suggests...

Directed Neurological Examination Assessment Of Muscle Bulk

The patient should be in a state of sufficient undress for the physician to be able to appreciate his or her general bodily habitus and especially the muscle bulk of the extremities. Before actual testing of muscle strength begins, simple observation may disclose asymmetries in muscle bulk of the extremities or more focal atrophy of specific muscles or muscle groups. The upper extremities should be inspected in both the pronated and supinated positions, which is especially important to...

Directed Neurological Examination Cranial Nerve Xi

The examination of cranial nerve (CN) XI consists of two parts observation (at rest and during action) and palpation. Abnormal findings include atrophy fasciculations neck or shoulder deviation and limitations in range, strength, or speed of motion. Examiners should observe the neck and back while the patient is seated or standing, paying particular attention to the SCM muscle and the upper portion of the trapezius muscle. Atrophy or asymmetry should be noted. Fasciculations may be present with...

Directed Neurological Examination MOTOR

First, the clinician should observe the patient at rest for symmetry and the presence of any involuntary movements (e.g., fasciculations, tics). Signs of facial weakness include flattening of the nasolabial groove, slower blinking, and loss of facial wrinkles. Next, clinicians should check the amount of voluntary motion in each of the five peripheral branches by having the patient perform the following (1) temporal--raise the eyebrows, wrinkle the brow (2) zygomatic--close the eyes gently, and...

Directed Neurological Examination Overview

The examination of the patient with altered consciousness begins by ensuring that the patient's vital signs and basic biochemistry are adequate to support brain function. It is essential to ensure that blood pressure, respiration, and oxygen saturation are adequate and that the patient is not hypoglycemic or thiamine deficient before proceeding with the examination outlined later. In many situations (e.g., emergency departments), naloxone is also administered at this point to reverse any...

Directed Neurological Examination

The examination of speech includes the assessment of speech volume, rate, articulation, prosody, and initiation. M , y Each component of speech can be affected differently in various disorders. The examiner should assess speech through spontaneous conversation or by having the patient read a standardized passage to elicit a wide range of sounds including labials, linguals, dentals, and gutturals. Speech volume may be increased with auditory perceptual problems. Reduced volume...

Directed Neurological Examination Sensory Function Of Cranial Nerve V

When assessing the trigeminal system, it is important to perform a directed and assiduous neurological examination because subtle alterations in function may provide clues to detect potentially serious neurological disease. Sensory and motor components should be tested separately, comparing right and left sides, and light touch, pin, and temperature sensation should be tested individually in V1 to V3. The cornea and sclera should be inspected for evidence of keratitis, which may be suggestive...

Disorders of Memory

A disorder of declarative memory is defined as amnesia. A pure amnesia refers to a relatively circumscribed disorder of declarative memory that cannot be accounted for by nonmnemonic deficits such as attention, perception, language, or motivation. Anterograde amnesia refers to the inability to acquire new declarative memories. Retrograde amnesia refers to the loss of memories acquired prior to the onset of the amnesia. Retrograde amnesias are described as flat when they extend back uniformly...

Druginduced

Tions in frequency and amplitude seen in patients with other myotonias. In phenotypically similar cases, in which the electrical activity closely resembles that noted in myotonia, the likely diagnosis is myotonia permanans.pl In all these conditions, muscle biopsy shows few abnormalities, although there may be variations in fiber size with fiber hypertrophy and increased central nuclei. In paramyotonia congenita with hyperkalemic periodic paralysis, vacuolated and necrotic fibers may occur. In...

Druginduced And Iatrogenic Neurological Disorders

ADCA, autosomal dominant cerebellar ataxia CNS, central ataxia. Alcoholic cerebellar degeneration (thiamine deficiency) 40 Chronic panencephalitis of congenital rubella 41 Varicella, measles, rubella, echo, coxsackie A B, polio, Epstein-Barr, herpes simplex Postinfectious disseminated encephalomyelitis Mumps, cytomegalic Mycoplasma pneumoniae Toxoplasmosis Lyme disease Plasmodium falciparum Cysticercosis Tuberculosis Cerebellopontine angle tumors (acoustic neurinoma, meningioma) Metastases lung...

Dysarthria

Dysarthria is the inability to form or produce understandable speech due to lack of motor control over peripheral -- USEFUL STUDIES IN THE EVALUA riON OF SPEECH AND LANGUAGE DISORDERS Mass lesion compressing the tenth cranial nerve, or on the vocal cords Abnormal decrement of CMAP with repetitive stimulation in myasthenia gravis. Single-fiber EMG showing jitter in NMJ defects Carcinoma of the vocal cords, carcinomatous meningitis Normal language and cognitive function Vocal cord pathology...

Dysosmia

Dysosmia (disordered smell perception) presents as either a distortion in the perceived quality of an odor ( parosmia, cacosmia) or as the presence of a strange odor in the absence of actual odor stimulation (phantosmia or olfactory hallucinations). Most dysosmias reflect dynamic elements associated with degeneration (or, more rarely, regeneration) of the olfactory epithelium and remit over time. However, it is common for patients with anosmia to report that prior to the onset of anosmia they...

Dyssynergy Synergy Syndromes

Although locomotor synergies, the basic patterns of muscle contraction and relaxation that produce coordinated rhythmic stepping, exist in the spinal cord, dyssynergies resulting from discrete spinal lesions are not recognized clinically. This is partly because spinal lesions that would disrupt the central pattern generators would probably affect TABLE 18-2 -- USEFUL STUDIES IN THE EVALUATION OF DISORDERS OF GAIT AND

Executive Function and Motor Performance

Traditionally, executive functions have been ascribed to the frontal lobes. They involve the ability to assess ongoing stimuli for relevance to specific goals, the formation of goals, planning action to achieve goals, ability to evaluate plans for efficacy, and executing plans. According to this description, executive functions involve many processes associated with reasoning and intellectual performance. Indeed, the Digit Symbol subtest of the WAIS-R (discussed in the section on Tests of...

Experimental Allergic Encephalomyelitis

As mentioned earlier, there is no spontaneous animal model that closely resembles MS. EAE is the most widely studied animal model of this disease. EAE is an antigen-specific, T-cell-mediated autoimmune disease that can be induced in many species, although rat and mice models predominate in the literature. Acute EAE is a monophasic illness that more closely resembles ADEM. Chronic-relapsing EAE closely mimics the clinical course of MS with repeated clinical relapses from which the animal makes...

Extracranial Arterial System

HEART, AORTA, COMMON CAROTID, SUBCLAVIAN, INNOMINATE ARTERIES The ascending aorta arises from the left ventricle. The aortic arch gives rise to several important branches. The first branch of the aorta is normally the innominate artery, which is also referred to as the brachiocephalic trunk. Shortly after its origin, the innominate artery divides into the right subclavian and right common carotid arteries. The right vertebral artery arises from the right subclavian artery, courses...

Fabrys Disease

This X-linked lipidosis is characterized biochemically by the accumulation of two glycosphingolipids, globotriaosylceramide and galabiosylceramide. Ihe enzymatic deficiency is alpha-galactosidase A. Ihe molecular structure of the gene encoding the enzyme was first identified as the full-length cDNA clone and is localized to Xq21.33-q22.yi Twenty different mutations have been described for this gene and include deletions or duplications. Ihe majority of the glycosphingolipids are synthesized in...

Facioscapulohumeral Muscular Dystrophy

Facioscapulohumeral muscular dystrophy (FSH MD), or Landouzy-Dejerine muscular dystrophy, is slowly progressive degenerative myopathy that affects particular facial, torso, and extremity muscles. There are at least two loci for FSH MD. Most large families thus far are linked to 4q35, in which no gene has been found. About 15 percent of other clinically indistinguishable families remain unlinked. y Although isolated cases have been identified, generally TABLE 36-6 -- DIFFERENTIAL DIAGNOSES IN...

Familial Spastic Paraplegias

The FSPs, also known as Strumpell-Lorrain syndrome and hereditary spastic paraplegias, are a broad group of TABLE 36-3 -- SELECTED DIFFERENTIAL DIAGNOSIS OF MOTOR NEURON DISEASES OF CHILDREN ACCORDING TO SOME PRESENTING SYMPTOMS Hereditary motor and sensory neuropathies Subacute inflammatory polyradieuloneuropathy Congenital myopathies with distinguishing structural abnormalities genetically and clinically diverse disorders characterized by lower extremity spasticity and weakness. Generally,...

Far Distal Peripheral Lesions

Isolated lesions of either the glossopharyngeal or vagus nerves are unusual. As noted earlier, glossopharyngeal nerve abnormalities may be clinically undetectable unless adjacent structures are also involved. Perhaps the most common vagus nerve lesion is that involving the recurrent laryngeal nerve, resulting in ipsilateral vocal cord paresis and hoarseness of voice. The left nerve has a longer course, with its looped recurrence in the chest rather than in the neck, as on the right. The nerve...

Fatty Acid Oxidation Disorders

Besides the mitochondrial enzyme defects characterized by disordered oxidative phosphorylation, 12 disorders of fatty acid oxidation and ketogenesis are known ( Table, ). 69 Medium-, long-, and short-chain acyl-CoA dehydro- genase deficiencies (MCAD, LCAD, SCAD) are caused by defects of the beta-oxidation spiral the rest, except long- chain l-3 hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency, are due to defects in the carnitine cycle. In these disorders there are three main presentations (1)...

Fetal Alcohol Syndrome

The mechanism by which the abnormalities of the fetal alcohol syndrome are produced is unknown, but it is thought to be due to a direct teratogenic effect. There is no general agreement regarding the limits of vulnerability of the fetus in terms of gestational age. To date, this syndrome has been described only in children of mothers who drank alcohol frequently during their pregnancy. Fetal alcohol syndrome results in low birth weight and small head circumference. Cranial and joint deformities...

Fibrous Dysplasia

Our understanding of the pathogenesis of fibrous dysplasia has advanced greatly in recent years. Several investigators have identified a point mutation in the gene that codes for the alpha subunit of the G-protein, Gsa, in affected bone and other tissues in patients with fibrous dysplasia. The absence of this mutation in non-affected tissues in patients with the disease suggests that a somatic mutation occurs early in embryogenesis to create a genetic mosaic....

Functional Visual Loss

Nonphysiological or functional visual loss can be either subconscious (hysteria) or deliberate and willful (malingering). Commonly encountered neuro-ophthalmic complaints include visual impairment or complete loss of vision, visual field defects such as constricted fields, and monocular diplopia. When confronted with a patient whose complaints and examination do not seem to correlate (subjective objective mismatch) or whose visual deficit is nonphysiological, there are several clinical tools...

Gasserian Ganglion Syndromes

Numerous pathological processes occurring within the middle cranial fossa can result in trigeminal dysfunction by affecting the gasserian ganglion. In children, osteitis of the petrous apex following suppurative otitis media or mastoiditis, which leads to inflammation and infection affecting the trigeminal ganglion, may result in Gradenigo's syndrome. The syndrome is characterized by facial pain, headache, or sensory loss and a sixth cranial nerve palsy, facial palsy (due to seventh nerve...

General Management Goals

Some causes of visual loss, such as optic neuritis, tend to resolve spontaneously. Others due to compressive lesions and pituitary adenomas, for instance, have a good prognosis once the mass is removed surgically. Unfortunately, many of the vascular, hereditary, and degenerative causes of visual dysfunction have a poor prognosis for improvement. Low vision aids may be helpful in some of these cases. In people with poor visual acuity, magnifiers can help them to read newspapers or other printed...

Glomus Jugulare Carotid Body Tumors

Glomus jugulare tumors arise from the paraganglionic tissue surrounding the jugular vein in the area of the middle ear. These tumors most often present late in life, in the sixth or seventh decade, and may have a genetic predisposition. They are locally invasive and highly vascular. Although presenting symptoms include complaints similar to those typical of acoustic neuromas, with tinnitus or hearing loss, the key differentiating features of these tumors are pain and the presence of loud...

Glycogenoses

The glycogenoses or glycogen storage diseases are lysosomal disorders in which glycogen accumulates within a number of tissues hypoglycemia usually accompanies the clinical signs. y These diseases are named for the specific enzyme deficiency that occurs in the glycogen metabolic pathway (i T Me,3.0 .5 ), and their ordering follows the enzymatic steps involved in glycogen synthesis and catabolism. y y y y y y y 43 44 4si y Epidemiology and Risk Factors. Current...

Hemifacial Spasm

Hemifacial spasm (HFS) is characterized by intermittent twitching of the muscles supplied by one facial nerve. It is thought to result from compression of the facial nerve at its junction with the brain stem by an aberrant or ectopic posterior fossa artery. Whereas many cases are idiopathic in origin, a review of 539 cases of HFS for which the cause was specified showed that compression by vascular structures was responsible in 94 percent of cases, tumor in 4 percent, and bony or other...

Hereditary And Degenerative Disorders

Neuronal ceroid lipofuscinosis, especially NCL-2 Leukodystrophies, especially Canavan's disease (neonatal form) and Krabbe's disease Aminoacidopathies, especially maple syrup urine disease, urea cycle disorders, propionie acidemia, methylmalonie acidemia Mitochondrial enzyme defects, especially Leigh's disease, Alpers disease MERFF, MELAS, fatty acid oxidation disorders Conditions associated with generalized seizures, especially tuberous sclerosis and Sturge-Weber syndrome Degenerative motor,...

Hereditary Sensory and Autonomic Neuropathies

The hereditary sensory and autonomic neuropathies (HSANs) are conditions in which primary sensory and autonomic neurons either fail to develop or undergo system atrophy and degeneration. Dyck proposes the comprehensive subdivision seen in T.ab e 36.-10 . These disorders have been called by a large variety of names because their symptoms were described by various investigators. Types I, II, and III are discussed here. Within this classification there are two large divisions HSAN I is a...

Herniation Syndromes

Herniation occurs when the brain is subjected to pressure gradients that cause portions of it to flow from one intracranial compartment to another. Although the brain has substantial elasticity, the arteries and veins responsible for its blood supply are relatively fixed in space, producing a risk that brain shifts will cause the moving portions to lose their blood supply. In the case of lateral herniation, the hernia itself may compress or distort vessels, similarly disrupting blood flow....

HIV1Related Myopathies

Muscle disorders related to HIV-1 infection include HIV-1-associated polymyositis, ZDV toxic myopathy, pyomyositis or infectious myopathy, cardiomyopathy, and the so-called wasting syndrome myopathy. Of these conditions, HIV-1-associated polymyositis and toxic myopathy related to ZDV are the most common. Distinguishing between these two forms of myopathy at times may be difficult. Pathogenesis and Pathophysiology. The pathophysiological mechanisms underlying HIV-related myopathy are uncertain....

Huntingtons Disease

The cognitive impairment in HD, like other subcortical dementias, primarily reflects frontostriatal dysfunction, and there is pathological evidence of both subcortical and cortical pathology. Grossly, the cortical gyri appear normal to slightly atrophic. Coronal sections reveal striking caudate greater than putamen and pallidum atrophy. Neuronal loss and gliosis follow the same regional distribution. The medium-sized spiny type I striatal neurons are...

Hypocapnia

Hyperventilation is defined as breathing in excess of metabolic demands and, therefore, is purely a respiratory disturbance. It produces hypocapnia, respiratory alkalosis, cerebral vasoconstriction (which, in turn, reduces the CBF), a reduction in the availability of O 2 peripherally (through shifts of the O 2 dissociation curve), a reduction in the level of ionized serum Ca, and when sustained, significant hypophosphatemia. y Thus, neurological features are frequent, and patients with...

Idiopathic Hypersomnia

Idiopathic hypersomnia is clinically similar to narcolepsy in that daytime sleepiness occurs despite adequate amounts of apparently normal sleep at night, but cataplexy does not occur and there is no association with specific HLAs. The pathogenesis is unknown. Circulating somnogenic factors or focal lesions that affect systems involved in sleep-wake regulation may play a role in some cases. Idiopathic hypersomnia is less common than narcolepsy by a ratio of about 1 10. Recent viral illness may...

Impulse Dyscontrol and Aggression Syndromes

The impulse dyscontrol and aggression syndrome consists of an inability to resist an impulse to perform a harmful act the impulse is accompanied by a buildup of tension needing to be released, and is followed by a feeling of satisfaction or relief when the act is committed. This in turn is followed by either relief, remorse, or a sense of justification for the act. Impulse dyscontrol and aggression can occur in neurologically normal individuals, but this behavior becomes pathological when...

Inclusion Body Myositis

The specific hallmarks of inclusion body myositis (IBM) are inflammation, vacuolated muscle fibers, intracellular amyloid deposits, and 15 to 18 nm tubulofilamentous inclusions. Although there are familial forms of this disease, either autosomal dominant or recessive, inflammation is only rarely seen in those cases, Wi and, therefore, the familial forms are best referred to as inclusion body myopathies. The inflammatory cells that are present in affected muscle...