pathophysiology chapter 45
TRANSCRIPT
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CHAPTER 45
CHRONIC DISORDERS OF NEUROLOGIC FUNCTION
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SEIZURE DISORDER• Transient neurologic event of paroxysmal
abnormal or excessive cortical electrical discharges that are manifested by disturbances of skeletal motor function, sensation, autonomic visceral function, behavior, or consciousness• Due to an alteration in membrane potential
that makes certain neurons abnormally hyperactive and hypersensitive to changes in their environment
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BRAIN AND CEREBELLAR DISORDERS
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BRAIN AND CEREBELLAR DISORDERS (CONT.)
• Generalized seizures involve the entire brain from the onset of the seizure• Partial seizures are those in which abnormal
electrical activity is restricted to one brain hemisphere• Status epilepticus is a continuing series of
seizures without a period of recovery between seizure episodes and can be life-threatening
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BRAIN AND CEREBELLAR DISORDERS (CONT.)
Diagnosis and Treatment of Seizures• Electroencephalograms assess the
electrical patterns of brain regions• Laboratory studies identify
metabolic/nutritional deficits, infections, and exposure to toxins• Antiseizure medications prevent or reduce
seizure episodes; seizure precautions prevent injury
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DEMENTIA• A syndrome associated with many
pathologic processes and characterized by progressive deterioration and continuing decline of memory and other cognitive changes• Important to first rule out manageable
causes of dementia; often cause unknown
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DEMENTIA (CONT.)• The dementia of Alzheimer disease is
characterized by degeneration of neurons in temporal and frontal lobes, brain atrophy, amyloid plaques, and neurofibrillary tangles• Cause remains unknown, although genetic
and environmental triggers are suggested• Synthesis of brain acetylcholine is deficient
and treatment is aimed at increasing acetylcholine levels by reducing acetylcholine reuptake
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DEMENTIA (CONT.)
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PARKINSON DISEASE• May be idiopathic or a consequence of the
use of certain drugs• Dopamine deficiency in the basal ganglia is
associated with symptoms of motor impairment• Difficulty initiating and controlling
movements results in akinesia, tremor, and rigidity• Tremor occurs at rest and hand tremors
exhibit pill-rolling movements• Attempts to passively move the extremities
are met with cogwheel rigidity
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PARKINSON DISEASE (CONT.)
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PARKINSON DISEASE (CONT.)• General lack of movement, loss of facial
expression, drooling, propulsive gait, and absent arm swing• Treatment is aimed at restoring brain
dopamine levels or activity by administration of dopamine precursors, dopamine agonists, monoamine oxidase inhibitors, and anticholinergics• Antidepressant therapy may be needed and
surgical procedures may be helpful for motor symptoms
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PARKINSON DISEASE (CONT.)
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CEREBRAL PALSY• Diverse group of crippling syndromes that
appear during childhood and involve permanent, nonprogressive damage to motor control areas of the brain• Classified on the basis of neurologic signs
and symptoms, with the major types involving spasticity, ataxia, dyskinesia, or a mix of one or more of the three
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CEREBRAL PALSY (CONT.)• Etiology may include prenatal infections, or
diseases of the mother; mechanical trauma to the head before, during, or after birth; exposure to nerve-damaging poisons or reduced oxygen supply to the brain• Treatment varies according to the nature
and extent of brain damage• Muscle relaxants, anticonvulsant drugs,
orthopedic surgery, casts, braces, and traction are among the therapies used
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HYDROCEPHALUS• Characterized by abnormal accumulation of
fluid in the cerebroventricular system• Normal pressure hydrocephalus is due to an
increased volume of CSF• Obstructive hydrocephalus is due to an
obstruction to the flow of CSF• Communicating hydrocephalus occurs due
to abnormal absorption of CSF
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HYDROCEPHALUS (CONT.)
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HYDROCEPHALUS (CONT.)• Medical treatment is limited• Obstructions may be corrected surgically• The most effective treatment for
management of hydrocephalus is surgical correction employing a shunt
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HYDROCEPHALUS (CONT.)
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CEREBELLAR DISORDERS• Cerebellum is responsible for coordinated
control of muscle action, excitation and inhibition of postural reflexes, and maintenance of balance• Etiology of cerebellar disorders includes
abscess, hemorrhage, tumors, trauma, viral infection, or chronic alcoholism• Clinical manifestations include ataxia,
hypotonia, intention tremors, and disturbances in gait and balance
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MULTIPLE SCLEROSIS• MS is a demyelinating disease of the CNS
that primarily affects young adults• Risk of contracting MS is greater for persons
living above the 37th parallel• Cause unknown, but immunologic
abnormalities and environmental factors are suspected• Demyelination can occur throughout the
CNS but often affects the optic and oculomotor nerves and spinal nerve tracts
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SPINAL CORD AND PERIPHERAL NERVE
DISORDERS
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MULTIPLE SCLEROSIS• Symptoms are slowly progressive; the
disease is marked by exacerbations and remissions• Symptoms may include double vision,
weakness, poor coordination, and sensory deficits; bowel and bladder control may be lost; memory impairment is common• Management is symptomatic; short-term
steroid therapy may be helpful during acute exacerbations, and immune-modifying drugs may slow progression of symptoms
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MULTIPLE SCLEROSIS (CONT.)
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SPINA BIFIDA• Developmental anomaly characterized by
defective closure of the bony encasement of the spinal cord (neural tube) through which the spinal cord and meninges may or may not protrude
• If anomaly not visible, condition is called spina bifida occulta
• If there is an external protrusion of the saclike structure, the condition is called spina bifida cystica, and further classified according to the extent of neural involvement
• Treatment is based on the severity of the defect and neurologic dysfunction
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AMYOTROPHIC LATERAL SCLEROSIS
• ALS is a progressive disease affecting both the upper and lower motor neurons• Cause remains unknown• Weakness and wasting of the upper
extremities usually occur, followed by impaired speech, swallowing, and respiration• Typically occurs between the ages of 40-60
years and affects men more than women
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AMYOTROPHIC LATERAL SCLEROSIS (CONT.)
• Clinical manifestations include weakness, atrophy, cramps, stiffness, and irregular twitching of muscle fibers• Diagnosis is based on clinical signs and
symptoms, EMG, nerve conduction studies, MRI, and serum laboratory testing• The glutamate inhibitor, riluzole, may be
helpful in managing ALS
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SPINAL CORD INJURY• SCI is usually traumatic, a result of motor
vehicle accidents, falls, penetrating wounds, or sports injuries• The cord may be compressed, transected,
or contused• Further injury may result from hemorrhage,
swelling, and ischemia
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SPINAL CORD INJURY (CONT.)
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SPINAL CORD INJURY (CONT.)• Spinal shock occurs immediately following
SCI and is characterized by temporary loss of reflexes below the level of injury• Muscles are flaccid; skeletal and autonomic
reflexes are lost• Neurogenic shock may occur after SCI due
to peripheral vasodilation• Hypotension and circulatory collapse can occur;
high spinal cord injuries can affect respiratory muscles, leading to ventilatory failure
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SPINAL CORD INJURY (CONT.)
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SPINAL CORD INJURY (CONT.)• Autonomic dysreflexia is an acute reflexive
response to sympathetic activation below the level of injury• Visceral stimulation (full bladder or bowel) and
activation of pain receptors below the injury are common stimuli
• Manifestations include hypertension, bradycardia, flushing above the level of injury, and clammy skin below the level of injury
• Prompt removal of the offending stimulus; aggressive blood pressure management may be needed
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SPINAL CORD INJURY (CONT.)• Treatment includes appropriate stabilization
of spinal vertebrae• May be accomplished surgically with internal
fixation or with external fixation and bracing • High-dose methylprednisolone may be used
to decrease secondary injury• Intensive rehabilitation is required to
maximize function
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GUILLAIN-BARRÉ SYNDROME• Characterized by muscle weakness that
begins in the lower extremities and spreads to the proximal spinal neurons• Cause unknown; postinfectious
immunologic mechanism is suspected• Progressive ascending weakness or
paralysis, may affect respiratory muscles• Treatment is supportive; spontaneous
recovery usually occurs
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BELL PALSY• Bell palsy, or neuropathy of the facial
nerve; paralysis of the muscles on one side of the face• Symptoms include unilateral facial
weakness, facial droop and diminished eye blink, hyperacusis, and decreased lacrimation• Often self-limiting condition with unknown
cause• Treatment is supportive, and spontaneous
recovery usually occurs
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BELL PALSY (CONT.)