Материал: Kaplan USMLE-1 (2013) - Anatomy

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Section IV • Neuroscience

Clinical Correlate

Anterograde Amnesia

Bilateral damage to the medial temporal lobes including the hippocampus results in a profound loss ofthe ability to acquire new information, known as anterograde amnesia.

KorsakoffSyndrome

Anterograde amnesia is also observed in patients with Korsakoff syndrome. Korsakoff syndrome is seen mainly in alcoholics who have a thiamine deficiency and often follows an acute presentation ofWernicke encephalopathy. Wernicke encephalopathy presents with ocular patsies, confusion, and gait ataxia and is also related to a thiamine deficiency. In Wernicke-Korsakoffsyndrome, lesions are always found in the mammillary bodies and the dorsomedial nuclei ofthe thalamus.

In addition to exhibiting an anterograde amnesia, Korsakoffpatients also present with retrograde amnesia. These patients confabulate, making up stories to replace past memories they can no longer retrieve.

Klilver-Bucy Syndrome

KlUver-Bucy syndrome results from bilateral lesions of the amygdala and hippocampus. These lesions result in:

•Placidity-there is marked decrease in aggressive behavior; the subjects become passive, exhibiting little emotional reaction to external stimuli.

•Psychic blindness-objects in the visual field are treated inappropriately.

For example, monkeys may approach a snake or a human with inappropriate docility.

•Hypermetamorphosis-visual stimuli (even old ones) are repeatedly approached as though they were completely new.

•Increased oral exploratory behavior-monkeys put everything in their mouths, eating only appropriate objects.

•Hypersexuality and loss of sexual preference

•Anterograde amnesia

478 MEDICAL

Chapter u • Limbic System

AlzheimerDisease

• . Alzheimer disease accounts for 60% of allcases of dementia. The inci dence increases with age.

•Clinical: insidious onset, progressive memory impairment, mood altera tions, disorientation, aphasia, apraxia, and progression to a bedridden state with eventual death

•Five to 10% of Alzheimer cases are hereditary, early onset, and transmit ted as an autosomal dominant trait.

Table IV-11-1. Genetics ofAlzheimer Disease (AD)

Gene	Location	Notes
Amyloid precursor	Chromosome 21	Virtually all Down syndrome
protein (APP) gene		patients are destined to develop
		AD in their forties. Down patients
		have triple copies of the APP
		gene.

Presenilin-1 gene	Chromosome 14
Presenilin-2 gene	Chromosome 1
Apolipoprotein E	Chromosome 19
gene

Majority of hereditary AD cases early onset

Early onset

Three allelic forms ofthis gene: epsilon 2, epsilon 3, and epsilon 4

The allele epsilon 4 of apolipoprotein E (Apo£) increases the risk for AD, epsilon 2 confers relative protection

Lesions involve the neocortex, hippocampus, and subcortical nuclei, including forebrain cholinergic nuclei (i.e., basal nucleus of Meynert). These areas show atrophy, as well as characteristic microscopic changes. The earliest and most se verely affected areas are the hippocampus and temporal lobe, which are involved in learning and memory.

Table IV-11-2. Pathology of Alzheimer Disease

Intraand extracellular accumulation of abnormal proteins

Senile plaques

AP amyloid: 42-residue peptide from a normal transmembrane protein, the amyloid precursor protein (APP)

Abnormal tau (a microtubule-associated protein)

Core ofAP amyloid surrounded by dystrophic neuritic processes associated with microglia and astrocytes

Neurofibrillary tangles (NFT)

Cerebral amyloid angiopathy (CAA)

Granulovacuolar degeneration (GVD) and Hirano bodies (HBs)

lntraneuronal aggregates of insoluble cytoskeletal elements, mainly composed of abnormally phosphorylated tau forming paired helicalfilaments (PHF)

Accumulation ofAP amyloid within the media of small and medium-sized intracortical and leptomeningeal arteries; associated with intracerebral hemorrhage

GVD and HBs develop in the hippocampus and are less significant diagnostically

MEDICAL 479

A band, skeletal muscle, 48f, 49 Abdomen

anterior wall. SeeAnterior abdominal wall posterior wall. See Posterior abdominal wall radiological images of, 278f-282f

regions and planes of, 232f, 233f surface anatomy of, 232

Abdominal aorta, 255, 255f branchesof,255-258, 258f-259f

Abdominalviscera. See also individual organs arterial supplyto, 255-258, 255f developmentof, 247-249

andrelationship to peritoneum, 245 venousdrainageof, 259, 260f

Abdominopelvic fascia, 234, 235f Abducensnerve (CN VI), 387f, 393

horizontal conjugate gaze and, 406, 408 nucleus of, 393

Absorption, in colon, 102 Accessory duct ofSantorini, 108

Accessory glands, male reproductive system, 132-135 Accessorynucleus, 392 Accommodation-convergence reaction, 438, 440 Acinar cells, 107

Acinus/acini hepatic, 109 pancreatic, 106

Actin thin filaments, 49, 50 Adie pupil, 440 Adipocytes, 28 Aganglionosis, colonic, 250 Agnosia, visual, 468 Agraphia,463

alexia without, 468, 470f Air-bloodbarrier.See Blood-airbarrier Albinism, 150

Alexiawithoutagraphia, 468, 470f Alpha-feto protein (AFP) levels, 335 Alveolar ducts, 83, 83f

Alveolar sacs, 83, 83f Alveolarwall, 84 Alveoli, 83, 83f, 84f

surfactantand, 84 Alzheimerdisease,475, 479

genetics of, 479

intermediate filamentsand, 14 neuron decay in, 418 pathology of, 479

Amino acidchains,in collagen synthesis, 30f, 31

Amnesia, anterograde, 478

Ampulla ofVater, pancreas and, 108 Amyotrophic lateral sclerosis (ALS), 378, 378f

Index

Analcanal, 254

Analtriangle, 272 Anastomoses

lowerlimb, 305-306, 306f portacaval, 262, 262f upperlimb, 293, 294f, 295

Anchoringjunctions, 16 Anencephaly, 337 Angiotensin I/II, 77 Ankle joint, 310, 31Of Annular pancreas, 247, 249

Anterior abdominalwall,232-235 bloodvessels of, 235

fasciaof, 234, 235f

inguinal region andcanal of, 235 innervation of, 235

lymphatics of, 235

superficial structures of, 234, 235f surfaceanatomyof,232

Anterior cerebral artery (ACA),459,460f occlusionof,459

Anterior cruciate ligament (ACL), 309, 309f Anteriormediastinum, 206f, 207

Anterior spinal artery (ASA) occlusion, 378, 378f Anterograde amnesia, 478

Anterograde axonal degeneration, 63, 346, 346f Anterograde axonal transport, 59, 345 Anterolateral (spinothalamic) system, 372, 373f, 390 Antigen-presenting cells, 66-67

Aorta

coarctation of, 210, 210f thoracic, 207

Aortic arch, 209

Aorticopulmonaryseptum formation, 203, 203f Aphasia

conduction,466 expressive,464 receptive,466

Apocrine sweat glands, 151 Appetite, physiology of, 104

Appositional growth, ofcartilage, 35, 37 Apraxia, transcortical, 466, 470f APUD cells

gastric. See Enteroendocrine cells

pulmonary. See Pulmonary neuroendocrine (PNE) cells Arachnoid, spinal meninges and, 177, l76f

Argyll Robertsonpupil,440 Arnold-Chiarimalformation, 337 Asomatognosia, 467 Astereognosis, 371

Astrocytes, 59

Astrocytoma, 348

Athetosis, 433

MEDICAL 481

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