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Alterations in Cognitive Systems: A Comprehensive Guide to Neurologic Dysfunction

This chapter explores the various alterations in cognitive systems, including consciousness, awareness, arousal, and the content of thought. It also discusses the clinical manifestations of these alterations, such as coma, brain death, seizures, and cognitive impairments.

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Alterations in Cognitive Systems: A Comprehensive Guide to Neurologic Dysfunction

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  1. Concepts of Neurologic Dysfunction Chapter 16

  2. Alterations in Cognitive Systems • Consciousness • State of awareness of oneself and the environment • Arousal • State of awakeness • Awareness • Content of thought

  3. Alterations in Arousal • Structural • Supratentorial • Infratentorial • Subdural • Extracerebral • Intracerebral • Metabolic • Psychogenic

  4. Alterations in Arousal • Coma is produced by either: • Bilateral hemisphere damage or suppression • Brain stem lesions or metabolic derangement that damages or suppresses the reticular activating system

  5. Alterations in Arousal • Clinical manifestations • Level of consciousness changes • Pattern of breathing • Posthyperventilation apnea (PHVA) • Cheyne-Stokes respirations (CSR) • Pupillary changes • Oculomotor responses • Motor responses

  6. Clinical Manifestations

  7. Clinical Manifestations

  8. Clinical Manifestations

  9. Clinical Manifestations

  10. Brain Death (Brainstem Death) • Body can no longer maintain internal homeostasis • Brain death criteria • Completion of all appropriate and therapeutic procedures • Unresponsive coma (absence of motor and reflex responses) • No spontaneous respirations (apnea) • No cephalic (ocular or caloric) reflexes • Isoelectric EEG • Persistence for 1 hour and 6 hours after onset

  11. Cerebral Death • Cerebral death (irreversible coma) is death of the cerebral hemispheres exclusive of the brainstem and cerebellum • No behavioral or environmental responses • The brain can continue to maintain normal respiratory and cardiovascular functions, temperature control, and GI function

  12. Cerebral Death • Survivors of cerebral death • Remain in coma • Emerge into a vegetative state (“wakeful unconscious state”) • Progress into a minimal conscious state • Akinetic mutism (AM) • Locked-in syndrome

  13. Seizures • Sudden, transient alteration of brain function caused by an abrupt explosive, disorderly discharge of cerebral neurons • Motor, sensory, autonomic, or psychic • Convulsion • Clonic-tonic (jerky, contract-relax) movements associated with some seizures

  14. Seizures • Generalized seizures • Partial (focal) seizures • Secondary generalization • Status epilepticus • Experience of a second seizure before the person has fully regained consciousness from the preceding seizure or a single seizure lasting more than 30 minutes

  15. Seizures • Postictal state • State that follows the seizure • Epileptogenic focus • Group of neurons that appear to be hypersensitive to paroxysmal depolarization • Tonic phase • Clonic phase

  16. Seizure Syndromes • Epilepsy • “To be seized by a force from without” • Types • Idiopathic • Symptomatic • Cryptogenic

  17. Alterations in Awareness • Selective attention • Ability to select from available, competing environmental and internal stimuli • Sensory inattentiveness • Extinction • Neglect syndrome • Selective attention deficit

  18. Alterations in Awareness • Declarative memory • Nondeclarative memory • Dysmnesia • Retrograde amnesia • Anterograde amnesia • Vigilance, detection, and working memory deficits

  19. Data Processing Deficits • Agnosia • Tactile, visual, auditory, etc. • Aphasia • Dysphasia • Expressive dysphasia • Transcortical dysphasia

  20. Acute Confusional States • Acquired mental disorder characterized by deficits in attention and coherence of thoughts and action • Secondary to drug intoxication, metabolic disorder, or nervous system disease

  21. Dementia • Progressive failure of cerebral functions that is not caused by an impaired level of consciousness • Classifications • Cortical • Alzheimer and Pick diseases • Subcortical • Parkinson and Huntington diseases • Cortical and subcortical • Infectious and Creutzfeldt-Jakob diseases

  22. Alzheimer Disease • Familial, early and late onset • Nonhereditary (sporadic, late onset) • Theories • Mutation for encoding amyloid precursor protein • Alteration in apolipoprotein E • Pathologic activation of N-methyl-D-aspartate (NMDA)

  23. Alzheimer Disease • Neurofibrillary tangles • Senile plaques • Clinical manifestations • Forgetfulness, emotional upset, disorientation, confusion, lack of concentration, decline in abstraction, problem solving, and judgment • Diagnosis is made by ruling out other causes of dementia

  24. Increased Intracranial Pressure • Normal 5 to 15 mm Hg • Caused by an increase in intracranial content • Tumor growth, edema, excessive CSF, or hemorrhage • Stage one • Stage two • Stage three • Stage four

  25. Herniation

  26. Herniation Syndromes • Supratentorial herniation • Uncal • Uncus or hippocampal gyrus (or both) shifts from the middle fossa through the tentorial notch into the posterior fossa • Central • Downward shift of the diencephalon through the tentorial notch • Cingulate • Cingulate gyrus shifts under the falx cerebri • Infratentorial herniation

  27. Cerebral Edema • Increase in the fluid (intracellular or extracellular) within the brain • Types • Vasogenic • Cytotoxic • Ischemic • Interstitial

  28. Hydrocephalus • Variety of conditions • Excess fluid within the cranial vault, subarachnoid space, or both • Caused by interference in CSF flow • Decreased reabsorption • Increased fluid production • Obstruction within the ventricular system

  29. Hydrocephalus • Noncommunicating hydrocephalus • Communicating (extraventricular) hydrocephalus • Hydrocephalus ex vacuo • Normal-pressure hydrocephalus

  30. Alterations in Emotions and Moods • Anger, hostility, envy, fear, and love all guide behavior and are mediated largely by the limbic system • Limbic system dysfunction results in emotion and mood alterations

  31. Alterations in Motor Function • Hypotonia • Hypertonia • Spasticity • Gegenhalten (paratonia) • Rigidity

  32. Alterations in Movement • Paresis and paralysis • Pyramidal motor syndromes • Upper motor neuron syndromes • Hemiparesis or hemiplegia • Diplegia • Paraparesis or paraplegia • Quadriparesis or quadriplegia • Spinal shock

  33. Alterations in Movement

  34. Alterations in Movement

  35. Alterations in Movement • Lower motor neuron syndromes • Flaccid paresis or flaccid paralysis • Hyporeflexia or areflexia • Gamma neuropathies • Fibrillation

  36. Lower Motor Neuron Syndromes

  37. Lower Motor Neuron Syndromes • Amyotrophies • Paralytic poliomyelitis • Nuclear palsies • Progressive spinal muscular atrophy • Progressive bulbar palsy • Bulbar palsy

  38. Alterations in Movement • Hyperkinesia • Excessive movement • Chorea, wandering, tremor at rest, postural tremor, etc. • Paroxysmal dyskinesias • Tardive dyskinesia

  39. Alterations in Movement • Huntington disease • Also known as “chorea” • Autosomal dominant hereditary-degenerative disorder • Severe degeneration of the basal ganglia (caudate and putamen nuclei) and frontal cerebral cortex • Depletion of γ-aminobutyric acid (GABA)

  40. Alterations in Movement • Hypokinesia • Decreased movement • Akinesia • Bradykinesia • Loss of associated movement

  41. Parkinson Disease • Severe degeneration of the basal ganglia (corpus striatum) involving the dopaminergic nigrostriatal pathway • Parkinsonian rigidity • Parkinsonian bradykinesia • Postural abnormalities • Autonomic and neuroendocrine symptoms • Cognitive-affective symptoms

  42. Parkinson Disease

  43. Disorders of Posture (Stance) • Dystonia • Dystonic postures and movements • Decorticate posture • Decerebrate posture • Basal ganglion posture • Senile posture

  44. Disorders of Posture (Stance)

  45. Disorders of Gait • Spastic gait • Scissors gait • Cerebellar gait • Basal ganglion gait • Senile gait

  46. Disorders of Expression • Hypermimesis • Hypomimesis • Dyspraxias and apraxias

  47. Disorders of Expression

  48. Extrapyramidal Motor Syndromes • Basal ganglia motor syndromes • Cerebellar motor syndromes • Rostral vermis • Caudal vermis • Neocerebellar syndrome

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