Transcript Chapter 14
Chapter 14 Level of Consciousness “ the most critical clinical index of nervous system function, with changes indicating either improvement or deterioration of the individual’s condition” Table 14-3 Levels of Altered Consciousness Alterations in Cognitive Networks Full consciousness: awareness of self and the environment Arousal: state of awakeness Mediated by the reticular activating system Content of Thought: all cognitive functions Awareness of self, environment and affective states (moods) Alterations in Arousal Causes Table 14-1 & 14-2 Structural Divided by location above or below tentorial plate Metabolic Psychogenic Alterations in Arousal Pathological processes Infectious, vascular, neoplastic, traumatic, congenital, degenerative, polygenic Metabolic Hypoxia, electrolyte disturbances, hypoglycemia, drugs and toxins Alterations in Arousal “range from slight drowsiness to coma” Coma – produced by either Bilateral cerebral hemisphere damage or suppression Brain stem* lesions or metabolic derangement that damages and suppresses the reticular activating system *midbrain, medulla, pons (Figure 12-5) Alterations in Arousal • Clinical manifestations : critical for evaluation “extent of brain dysfunction” “index for identifying ↑ or ↓ CNS function” 1) Level of consciousness 2) Pattern of breathing - Post hyperventilation apnea (PHVA) - Cheyne–Stokes respiration (CSR) 3) Pupillary changes (size and reactivity) 4) Oculomotor response (position and reflexes) 5) Motor response (skeletal muscle) President Lincoln April 14, 1865 Pathway of the bullet Clinical Manifestations Clinical Manifestations Clinical Manifestations Decorticate & Decerebrate Brain Death “never recover nor maintain internal homeostasis” Total Brain Death – criteria (5): (cerebrum, brain stem & cerebellum) Completion of all appropriate and therapeutic procedures Unresponsive coma (absence of motor and reflex responses) No spontaneous respirations (apnea) Brain death – criteria No ocular responses Isoelectric EEG: 6 to 12 hours without hypothermia/depressant drugs Cerebral Death “death exclusive of brain stem and cerebellum” No behavioral or environmental responses Brain continues to maintain internal homeostasis Survivors Coma Vegetative state (“wakeful unconscious state”) Minimal conscious state Locked-in syndrome Seizures “Sudden, transient alteration of brain function caused by an abrupt explosive disorderly discharge of cerebral neurons” Alteration in brain function (transient) Altered level of arousal Convulsion – seizure with tonic-clonic movement Epilepsy – seizures recur without treatment (5 to 10/1000) Conditions - Seizures Cerebral lesions Biochemical disorders Cerebral trauma Epilepsy Seizures Partial (focal/local) Simple, complex, secondary, generalized Generalized (bilateral/symmetric) Unclassified Seizures Epileptogenic focus Group of neurons that appear to be hypersensitive to sudden depolarization Hyperthermia, hypoxia, hypoglycemia, hyponatremia, sensory stimulation and certain sleep phases Aura – partial seizure precedes generalized Prodroma – early manifestation – hours to days before Seizures Tonic – contraction Excitation spreads to subcortical, thalamic and brain stem areas Loss of consciousness Clonic – relaxation Inhibitory neurons of cortex, anterior thalamus and basal ganglia Alterations in Awareness Memory Retrograde amnesia – past memories Antegrade amnesia – new memories Temporary or permanent (severe head injury or Alzheimer disease) Executive attention deficits Inability to maintain sustained attention Inability to set goals Working memory deficit Table 14-6 Clinical manifestations Memories:amygdala thalamus hippocampus prefrontal cortex Data Processing Deficits Agnosia – failure to recognize the form and nature of an object: CVA Tactile, visual, auditory Dysphasia – inability to arrange words in logical order: CVA (middle cerebral artery-L cerebral hemisphere) Expressive – cannot find words, difficulty writing (Broca’s area) Receptive – language is meaningless (inappropriate words, neologisms) – Wernicke Data Processing Deficits Dementia* Progressive failure of cerebral functions that is not caused by an impaired level of consciousness ↓ orienting, memory language and executive attention networks Table 14-13 Comparison of Delirium & Dementia Dementia Degeneration of neurons Compression-space occupying lesion Atherosclerosis Genes-Alzheimer & Huntington diseases CNS infection –HIV, Creutzfeldt-Jakob “nerve cell damage and brain atrophy” Alzheimer Disease (AD) Familial onset Early-onset-chromo mutations # 21 (very rare) Late onset-90% cases ? Chromo #19* Theories Mutation for encoding amyloid precursor protein Alteration in apolipoprotein E* Loss of neurotransmitter of choline Alzheimer Disease (AD) Neurofibrillary tangles Senile plaques Clinical manifestations Forgetfulness, emotional upset, disorientation, confusion, lack of concentration, decline in abstraction, problem solving and judgment Diagnosis – R/O other causes Burden of Alzheimer’s Disease 5.4 million Americans 16 million by 2050 6th leading cause of death:#prevented, cured, slowed >/= 65y/o average survival: 4-8 yrs, may up to 20yrs Caregivers burden: 60% emotional stress : 30%depressed Cost 2011: $183 billion $1 trillion by 2050 J.Alzheimer’s Assoc. March 2011 Know the Signs Memory loss that disrupts daily life Trouble planning or solving problems Difficulty completing tasks Confusion with time or place Trouble understanding images and spatial relationships New problems with speaking or writing words Misplacing things and inability to retrace steps Decreased or poor judgment Know the Signs Social withdrawal Change in mood or personality Review Table 14-14 Cerebral Hemodynamics CBF – blood flow CPP – perfusion pressure CBV – blood volume Cerebral oxygenation – “ critical factor” Injury States ↓ cerebral perfusion Normal perfusion but ↑ intracranial pressure (ICP) ↑ cerebral blood volume SO: “must maintain CPP and control ICP” Increased Intracranial Pressure (IICP) ↑ intracranial content, edema, excess CSF or hemorrhage Normal 5 to 15 mmHg Stages 1-4 (Figure 14-10) Stage 1 vasoconstriction and external compression of venous system - ↓ ICP (autoregulation) Stage 2 General Autoregulation - blood vessel diameter to maintain a constant blood flow is lost with ↑ ICP ↑ vasoconstriction to elevate BP > ICP a) ↓O2 ↑CO2 → deterioration b) small pupils, neurologic hyperventilation, widened pulse pressure and ↓HR Local vasodilation 2° to ↑ CO2 →↑ BV →↑↑ ICP → approaches SBP - ↓ perfusion with severe hypoxia/acidosis IICP – not evenly distributed throughout the cranial vault Cerebral Edema • Increase in the fluid (intracellular or extracellular) within the brain (↑ volume) • Results: trauma, infection, hemorrhage, tumor, ischemia, infarct or hypoxia 1) Vasogenic: BBB is disrupted - ↑ plasma protein to extracellular space - ↑ ICP 2) Cytotoxic: toxic factors → failure NA-K+ transport system: K+ out, H2O in 3) Ischemic (infarction): vasogenic and cytotoxic → cell necrosis → lysosomes → BBB↑ 4) Interstitial (hydrocephalus): ↑ volume about ventricles Hydrocephalus (Types Table 14-16) Excess fluid within the cranial vault, subarachnoid space or both Caused by interference in CSF flow ↓ reaborption ↑ fluid production Obstruction Infancy through adulthood Spinal Shock “complete cessation of spinal cord function below the lesion” • Complete flaccid paralysis • Absence of reflexes • Marked disturbance of bowel and bladder function • Days to weeks – Return of spinal reflexes → hyperactive → spasticity, rigidity Michael J Fox Parkinson Disease After age 40 – peak onset 58 – 62 years 107 to 187 per 100,000 Severe degeneration of the basal ganglia involving dopaminergic nigrostriatal pathway Dopamine: inhibitory neurotransmitter Acetylcholine: stimulatory neurotransmitter IMBALANCE of” neurotransmitters motor modulation” Ach________________Dopamine Parkinson Disease Parkinson Disease Clinical manifestations Tremor at rest Rigidity (muscle stiffness) Bradykinesia (poverty of movement) Postural disturbance Dysarthria (uttering of words) Dysphagia (difficulty swallowing) Progressive dementia Parkinson Disease