Chapter 16
Alterations in Cognitive Systems,
Cerebral Hemodynamics, and Motor
Function
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Alterations in Cognitive Systems
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Consciousness
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
Arousal vs. awareness
• State of wakefulness
• Mediated by the reticular activating system
Awareness
• Cognitive functions that embody awareness of self,
environment, and affective states (i.e., moods)
• Content of thought
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Alterations in Arousal
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Coma is produced by either:


Bilateral hemisphere damage or suppression
Brainstem lesions or metabolic derangement that
damages or suppresses the reticular activating
system
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Alterations in Arousal

Structural
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




Supratentorial
Infratentorial
Subdural
Extracerebral
Intracerebral
Metabolic
Psychogenic
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Alterations in Arousal

Clinical manifestations
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
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
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Level of consciousness changes
Pattern of breathing
• Posthyperventilation apnea (PHVA)
• Cheyne-Stokes respirations (CSR)
Pupillary changes
Oculomotor responses (Doll’s eyes)
Motor responses
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Clinical Manifestations
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Clinical Manifestations
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Clinical Manifestations
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Clinical Manifestations
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Brain Death (Brainstem Death)


Body cannot maintain internal homeostasis
Brain death criteria

Completion of all appropriate, 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
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Cerebral Death



Cerebral death (irreversible coma): 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
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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
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Seizures




Disruption in balance of excitation and
inhibition
Sudden, transient alteration of brain function
caused by an abrupt explosive, disorderly
discharge of cerebral neurons
Motor, sensory, autonomic, or psychic
Convulsion

Tonic-clonic (jerky, contract-relax) movements
associated with some seizures
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Seizures



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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
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Seizures
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

Resting potential instability
Bursts of action potentials
(hypersynchronization)
Epileptogenic focus
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


Group of neurons that appear to be hypersensitive
to paroxysmal depolarization
Tonic phase
Clonic phase
Postictal state

State that follows the seizure
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Seizures: Consequences
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


250% increase in adenosine triphosphate (ATP)
Cerebral oxygen consumption increased by 60%
Cerebral blood flow also increases approximately
250%
Available glucose and oxygen are depleted
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



With severe seizures the brain tissue may require
more ATP than can be produced
Lactate accumulates in the brain tissues
May produce secondary hypoxia, acidosis, and lactate
accumulation
May result in progressive brain tissue injury and
destruction
Cellular exhaustion and destruction
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Seizure Syndromes
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Epilepsy
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


“To be seized by a force from without”
Types
• Idiopathic
• Symptomatic
• Cryptogenic
Aura
Prodroma
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Alterations in Awareness
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Selective attention
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

Ability to select from available competing
environmental and internal stimuli
Sensory inattentiveness
• Extinction
• Neglect syndrome
Selective attention deficit
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Alterations in Awareness



Declarative memory
Nondeclarative memory
Dysmnesia
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

Retrograde amnesia
Anterograde amnesia
Vigilance, detection, and working memory
deficits
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Data Processing Deficits
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Agnosia



Tactile, visual, auditory, etc.
Aphasia
Dysphasia


Expressive dysphasia
Transcortical dysphasia
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Acute Confusional States
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Acquired mental disorder with deficits in attention
and coherence of thoughts and action
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

Secondary to drug intoxication, metabolic disorder, or
nervous system disease
Disruption of reticular activating system of upper
brainstem and its projections to thalamus, basal
ganglion, and specific areas of the cortex and limbic
areas
Abrupt onset
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Dementia


Progressive failure of cerebral functions 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
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Alzheimer Disease
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

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)
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Alzheimer Disease



Neurofibrillary tangles
Senile plaques
Clinical manifestations



Forgetfulness, emotional upset, disorientation,
confusion, lack of concentration, decline in abstraction,
problem solving, and judgment
Insidious onset
Diagnosis made by ruling out other causes of
dementia
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Increased Intracranial Pressure
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
Normal 5 to 15 mmHg
Caused by increased intracranial content





Tumor growth, edema, excessive CSF, or
hemorrhage
Stage one
Stage two
Stage three
Stage four
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Herniation
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Herniation Syndromes

Supratentorial herniation
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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
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Cerebral Edema


Increase in the fluid (intracellular or
extracellular) within the brain
Types

Vasogenic
 Cytotoxic
 Ischemic
 Interstitial
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Hydrocephalus
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

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
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Hydrocephalus


Noncommunicating hydrocephalus
Communicating (extraventricular)
hydrocephalus
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
Hydrocephalus ex vacuo
Normal-pressure hydrocephalus
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Alterations in Motor Function
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Hypotonia
Hypertonia
Spasticity
Gegenhalten (paratonia)
Rigidity
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Alterations in Movement
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Paresis and paralysis
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
Pyramidal motor syndromes
Upper motor neuron syndromes
• Hemiparesis or hemiplegia
• Diplegia
• Paraparesis or paraplegia
• Quadriparesis or quadriplegia
• Spinal shock
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Alterations in Movement
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Alterations in Movement
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Alterations in Movement
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Lower motor neuron syndromes
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
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
Flaccid paresis or flaccid paralysis
Hyporeflexia or areflexia
Gamma neuropathies
Fibrillation
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Lower Motor Neuron Syndromes
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Lower Motor Neuron Syndromes
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Amyotrophies
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
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

Paralytic poliomyelitis
Nuclear palsies
Progressive spinal muscular atrophy
Progressive bulbar palsy
Bulbar palsy
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Alterations in Movement
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Hyperkinesia
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


Excessive movement
Chorea, wandering, tremor at rest, postural
tremor, etc.
Paroxysmal dyskinesias
Tardive dyskinesia
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Alterations in Movement
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Huntington disease
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



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 gamma-aminobutyric acid (GABA)
Choreiform movemets
Disrupted thought processes
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Alterations in Movement
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Hypokinesia
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Decreased movement
Akinesia
Bradykinesia
Loss of associated movement
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Parkinson Disease

Severe degeneration of the basal ganglia
(corpus striatum) involving the dopaminergic
nigrostriatal pathway






Parkinsonian rigidity
Parkinsonian bradykinesia
Parkinsonian tremor
Postural abnormalities
Autonomic and neuroendocrine symptoms
Cognitive-affective symptoms
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Parkinson and Dementia
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

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

50% of persons have depression, an inherent part of the
pathologic state and not a situational response
30% treated on outpatient basis have dementia; 80% of
persons requiring institutional care have dementia
Disorientation, confusion, memory loss, distractibility,
and difficulty with concept formation, abstraction,
calculations, thinking, and judgment
Symptoms fluctuate, but they progressively worsen
Anxiety disorders; impulse-control disorders; and
punding, a disorder of stereotypic motor behavior in
which there is intense fascination with repetitive handling
and examining of mechanical objects
Excessive daytime sleepiness is experienced in more
than 50% of persons
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Disorders of Posture (Stance)
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Dystonia
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Dystonic postures and movements
Decorticate posture
Decerebrate posture
Basal ganglion posture
Senile posture
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Disorders of Posture (Stance)
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Disorders of Gait
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
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

Spastic gait
Scissors gait
Cerebellar gait
Basal ganglion gait
Senile gait
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Disorders of Expression
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

Hypermimesis
Hypomimesis
Dyspraxias and apraxias
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Disorders of Expression
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Extrapyramidal Motor Syndromes
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
Basal ganglia motor syndromes
Cerebellar motor syndromes
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

Rostral vermis
Caudal vermis
Neocerebellar syndrome
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