Ch. 17 Notes

Chapter 17: Alterations in Cognitive Systems, Cerebral Hemodynamics, and Motor Function

Chapter Objectives

  • Relate arousal and awareness to consciousness.

  • Describe three major groups of arousal alterations, including structural, metabolic, and psychogenic categories, along with their sites and causes.

  • Define and describe the terms that articulate various levels of consciousness: confusion, lethargy, obtundation, stupor, and coma.

  • Summarize accompanying clinical manifestations with altered levels of consciousness, focusing on:
      - Pattern of breathing
      - Pupillary changes
      - Oculomotor responses
      - Motor responses

  • Compare and contrast brain death (brainstem death) and cerebral death.

  • Identify common criteria used to determine brain death.

  • Compare clinical features of:
      - Coma
      - Vegetative state
      - Minimally conscious state
      - Akinetic mutism
      - Locked-in syndrome

  • Define cognition and identify areas of brain and theories associated with cognitive disorders.

  • Compare anterograde and retrograde memory.

  • Define and describe data processing disorders: agnosia, dysphasia, aphasia, acute confusional states, and dementias.

  • Describe Alzheimer's disease's etiology, clinical manifestations, and pathophysiology.

  • Characterize cerebral hemodynamics and stages of increased intracranial pressure (ICP).

  • Define and describe herniation syndromes and the pathogenesis of four types of cerebral edema: vasogenic, cytotoxic, ischemic, and interstitial.

  • Describe hydrocephalus, comparing communicating and noncommunicating variants.

  • Compare and contrast upper and lower motor neuron syndromes.

  • Compare paresis and paralysis.

  • Describe terms associated with movement alterations: hemiplegia (hemiparesis), diplegia, paraplegia (paraparesis), quadriplegia (quadriparesis).

  • State effects of spinal shock on sensorimotor, reflex, bowel, and bladder function.

  • Define and describe the damage associated with nuclear palsies.

  • Differentiate among progressive spinal muscular atrophy, progressive bulbar palsy, and bulbar palsy.

  • Categorize and compare basal ganglia motor syndrome and cerebellar motor syndrome.

  • Demonstrate and describe examples of posturing responses: dystonia, decorticate posture, decerebrate posture, basal ganglion posture, and senile posture.

  • Demonstrate and describe gait disorders: spastic, scissors, cerebellar, basal ganglion, and senile gait.

  • Define alterations in motor function: hypotonia, hypertonia, spasticity, gegenhalten (paratonia), and rigidity.

  • Indicate clinical symptoms associated with hyperkinesia syndromes.

  • Differentiate hypokinetic disorders: akinesia, bradykinesia, and loss of associated movement.

  • State possible mechanisms for Parkinson's disease and its manifestations.

  • Describe the pathophysiology and clinical manifestations of Huntington disease.

  • Relate clinical manifestations of amyotrophic lateral sclerosis (ALS) to upper motor neuron and lower motor neuron changes.

  • Explain the impact of demyelination and plaque formation in multiple sclerosis, including initial manifestations and types.

  • Describe pathophysiology and manifestations of Guillain-Barré syndrome and neuromuscular junction changes in myasthenia gravis.

Alterations in Cognitive Systems

  • Functional adequacy: A complex and integrated process involving three major neural systems:
      - Cognitive
      - Sensory
      - Motor
      - Alterations in these systems can cause issues and diseases, ultimately affecting functional adequacy.

  • Consciousness:
      - Full consciousness: State of awareness of oneself and the environment, with responses to it.
      - Arousal: State of being awake, mediated by the reticular-activating system.
      - Awareness: Encompasses all cognitive functions, mediated by attentional, memory, language, and executive systems.

  • Involves three major neural systems:
      - Attentional
      - Memory and language
      - Affective or emotive
      - There are several alterations which may include:
        - Alterations in arousal
        - Alterations in awareness
        - Data-processing deficits
        - Seizure disorders.

Alterations in Arousal

  • Types of alterations:
      - Structural: Defined by the original location of damage:
        - Supratentorial: Above the tentorium cerebelli
        - Infratentorial: Below the tentorium cerebelli
        - Subdural: Below the dura mater
        - Extracerebral: Outside the brain tissue
        - Intracerebral: Inside the brain tissue
      - Metabolic alterations: Affecting energy substrate delivery and neuronal excitability due to drugs or toxins.
      - Psychogenic disorders: Psychiatric in nature affecting arousal.

  • Neurologic functions critical for evaluation:
      - Level of consciousness
      - Pattern of breathing
      - Pupillary reaction
      - Oculomotor responses
      - Motor responses.

Clinical Manifestations of Alterations in Arousal

  • Pattern of breathing:
      - Evaluates the level of brain dysfunction and severity of coma.
      - Examples of abnormal breathing patterns:
        - Posthyperventilation apnea: Regulated by lower brainstem centers.
        - Cheyne-Stokes respirations: Alternating periods of hyperventilation and apnea.
        - Central neurogenic hyperventilation: Sustained hyperventilation from lesions in the central pons.
        - Apneustic respirations: Prolonged inspiratory and expiratory phases due to injury at pons or upper medulla.
        - Cluster respirations: Clusters of rapid breaths associated with trauma or medulla compression.
        - Ataxic respirations: Irregular breaths with periods of apnea due to medulla damage.

  • Pupillary changes:
      - Evaluates brainstem dysfunction:
        - Ischemia/hypoxia leads to dilated, fixed pupils.
        - Fixed pupils may indicate hypothermia.
        - Medications like atropine or scopolamine yield dilated, fixed pupils.
        - Midposition or unequal, fixed pupils may result from sedative-induced coma.
        - Opioids cause pinpoint pupils; barbiturate intoxication results in fixed pupils.

  • Oculomotor responses: Help assess the level of brain dysfunction during coma, e.g., dolls eyes reflex.

  • Motor responses: Evaluate brain dysfunction level and indicate the damaged side. Responses include:
      - Purposeful (indicating intact corticospinal system)
      - Inappropriate/non-purposeful (indicating severe dysfunction)
      - Not present (degrees of unresponsiveness)
      - Vomiting, yawning, and hiccups indicate medulla involvement.

Level of Consciousness Changes

  • A critical index of nervous system function, indicating improvement or deterioration.
  • Normal responses: being alert and oriented.
  • Abnormal responses can range from confusion to coma, which are defined as follows:
      - Confusion: Loss of ability to think clearly and impaired judgment.
      - Disorientation: Initial loss of time awareness, followed by place and, lastly, self-recognition.
      - Lethargy: Limited movements/speech, easily aroused but possibly disoriented.
      - Obtundation: Moderate reduction in arousal; falls asleep unless prompted and responds minimally.
      - Stupor: Deeply unresponsive; arousal requires vigorous stimulation; responses are physical withdrawals.
      - Light coma: Purposeful movements with stimulation.
      - Coma: No responses to stimuli; motor movements can occur with noxious stimuli.
      - Deep coma: Total unresponsiveness to any stimuli.

Possible Patient Outcomes

  • Dependent on brain damage cause, extent, and coma duration:
      - Mortality: Some individuals may not regain consciousness and experience neurologic death.
      - Disability (morbidity): Some may recover consciousness and function, while others may experience permanence of disability.

Brain Death Criteria

  • Brain death: Total irreversible cessation of brain activity, including brainstem.
  • Criteria include:
      - Completion of all therapeutic procedures
      - Unresponsive coma with no reflex movements
      - No spontaneous respirations
      - No brainstem responses
      - Isoelectric EEG for 6-12 hours.

Cerebral Death

  • Defined as an irreversible coma with death of the cerebral hemispheres, while the brainstem remains functional:
      - Maintains respiratory and cardiovascular functions, along with normal temperature and metabolic functioning.
  • Survivors may:
      - Stay in a coma
      - Emerge into a vegetative state or minimally conscious state.
      - Exhibit kinetic mutism with minimal awareness or locked-in syndrome, where individuals cannot move or speak but are conscious.

Alterations in Awareness

  • Awareness includes cognitive functions such as:
      - Self-awareness and awareness of environment and affective states.
      - Involves interconnected brain circuits.
Selective Attention
  • Ability to choose from competing stimuli:
      - Sensory inattentiveness includes conditions such as extinction and unilateral neglect syndrome.
Memory Types
  • Essential functions encompassing recording, retention, and retrieval of knowledge:
      - Declarative memory
      - Nondeclarative memory
      - Cerebellar memory
      - Emotional memory.
Dysmnesia
  • Affects memory, including:
      - Retrograde amnesia: Loss of past memories.
      - Anterograde amnesia: Inability to form new memories.
      - Vigilance, detection, and working memory deficits are mediated by frontal brain areas.
Pathophysiology affecting these functions can include:
  • Direct destruction from ischemia and hypoxia
  • Indirect destruction caused by compression
  • Effects from toxins, chemicals, or metabolic disorders.

Data Processing Deficits

  • Deficits include:
  • Agnosia: Failure to recognize objects (tactile, visual, auditory).
  • Aphasia: Loss in language comprehension (includes both expressive and receptive types).
  • Dysphasia: Classifications include expressive and receptive dysphasia, as well as transcortical dysphasia.
  • Acute confusional states and dementias.

Dementia

  • Defined as progressive failure of cerebral functions leading to impairment:
  • Pathophysiology:
      - Can involve neuron degeneration, compression, atherosclerosis, brain trauma, genetic predisposition, CNS infections, etc.
  • Clinical manifestations:
      - Include impairments in intellectual function, memory, and language, alongside behavioral changes.
  • Treatment is largely supportive as no specific cure exists.
  • Rehabilitation and involving family are essential.

Alzheimer's Disease

  • Leading cause of dementia, irreversible, diagnosed mainly postmortem.
  • Clinical evaluation involves:
      - History, cognitive tests, lab tests, and imaging.
  • Risk Factors: Age, family history; can be familial with early or late onset.
  • Pathophysiology includes neurofibrillary tangles, neuritic plaques, and degeneration of cholinergic neurons affecting acetylcholine levels.
  • Clinical manifestations: Progressively leads to severe cognition loss with symptoms of forgetfulness, confusion, and gradual cognitive decline.
  • Treatment options are limited; cholinesterase inhibitors may improve cholinergic transmission.

Frontotemporal Dementia

  • Previously called Pick disease, rare and severe degenerative disease affecting frontal lobes, facilitating tissue death and dementia, mostly presenting before 60 years of age with familial ties.

Cerebral Hemodynamics

  • Key Features: Include alterations in blood flow, ICP, and oxygen delivery, aiming to balance ICP with jugular vein oxygen saturation.
  • Increased Intracranial Pressure (ICP):
      - Normal range: 5–15 mmHg.
      - Caused by tumors, edema, excessive cerebrospinal fluid, or hemorrhage.
Stages of Increased ICP
  • Stage 1: Vasoconstriction and external compression.
  • Stage 2: Continued expansion of intracranial content.
  • Stage 3: Brain hypoxia and hypercapnia; loss of autoregulation.
  • Stage 4: Brain herniation and potential herniation syndromes.

Brain Herniation Syndromes

  • Shifting brain tissue disrupts blood flow and neurons.
  • Types include:
      - Supratentorial herniation: Involves temporal lobe and hippocampal gyrus.
      - Infratentorial herniation: Involves cerebellar tonsils shifting through foramen magnum.

Cerebral Edema

  • Increased fluid concentrations in the brain categorized by:
      - Vasogenic: Clinically significant.
      - Cytotoxic: Caused by toxic factors.
      - Interstitial: Around ventricles.

Hydrocephalus

  • Conditions resulting in excess fluid accumulation in cerebral ventricles, commonly caused by obstruction, decreased reabsorption, or increased production.
      - Types:
        - Noncommunicating (obstructive)
        - Communicating (nonobstructive)
        - Hydrocephalus ex vacuo
        - Normal-pressure hydrocephalus.

  • Clinical manifestations: May include increased ICP, cognitive decline, unsteady gait, urinary urgency, and inattentiveness.

  • Treatment often involves surgical interventions or shunt placement.

Alterations in Neuromotor Function

  • Movements are controlled by:
      - Cerebral cortex
      - Pyramidal system
      - Extrapyramidal system
      - Muscle motor units.
Dysfunction Symptoms
  • May include:
      - Extrapyramidal motor syndromes
      - Complex motor performance alterations
      - Muscle tone changes
      - Muscle movement alterations.

Upper and Lower Motor Neuron Syndromes

  • Paresis: Weakness; partial paralysis.
  • Paralysis: Loss of motor function.
Upper Motor Neuron Syndromes include:
  • Hemiparesis (one side), hemiplegia (paralysis on one side), diplegia (both limbs),
    paraparesis (lower limbs), quadriparesis (all limbs).
Lower Motor Neuron Syndromes may lead to:
  • Impaired voluntary and involuntary movements, with different degrees of paralysis or paresis.
  • Conditions are contingent upon the specific deficits and their locations within the nervous system.

Extrapyramidal Motor Syndromes

Basal Ganglia Motor Syndrome
  • Involves movement excess or paucity, including rigidity and cogwheel phenomena, altering posture and muscle tone.
Cerebellar Motor Syndrome
  • Primarily presents with ipsilateral effects, muscle tone loss, ataxia, weak muscles, and balance problems.

Disorders of Posture

  • Involves balance disruptions and abnormal motor activity:
      - Dystonia: Sustained muscle contractions leading to abnormal posture.
      - Examples include decorticate, decerebrate, and basal ganglion postures.

Disorders of Gait and Balance

  • Gait disorders can result from upper motor neuron dysfunction:
      - Spastic gait
      - Scissor gait
      - Ataxic gait from cerebellar issues

Disorders of Expression

  • Affects motor aspects of communication:
  • Hypermimesis: Pathologic laughter or crying.
  • Hypomimesis: Loss of voice modulation, i.e., aprosody.
  • Dyspraxias and apraxias involve impaired ability to perform skilled motor tasks.

Alterations in Muscle Tone

  • Hypotonia: Decreased muscle tone.
  • Hypertonia: Increased muscle tone, which includes:
      - Spasticity: Hyperexcitability of stretch reflexes.
      - Paratonia (gegenhalten): Resistance during passive movements.
      - Rigidity: Firm, tense muscle types, including plastic, lead pipe, cogwheel.
Alterations in Muscle Movement
  • Hypokinesia: Decreased movement leads to conditions like akinesia (lack of voluntary motion) and bradykinesia (slow movement).
  • Hyperkinesia: Excessive movement, can manifest as chorea, tremors, and postural dyskinesia.
  • Tardive dyskinesia: Psychotropic-induced slow-onset, rapid stereotypic movements.

Parkinson Disease

  • Severe degeneration of basal ganglia affecting the nigrostriatal pathway leads to loss of dopaminergic neurons in substantia nigra.
  • Symptoms include rigidity, bradykinesia, akinesia, autonomic neuroendocrine dysfunction, cognitive-affective symptoms, and potential dementia.
  • Treatment includes:
      - Levodopa, anticholinergic drugs, surgery, rehabilitation therapies.

Huntington Disease

  • A rare autosomal dominant disorder characterized by striatal and basal ganglia degeneration causing chorea and emotional lability with progressive dementia.
  • Treatment focuses on symptomatic relief with no definitive cure available.

Amyotrophic Lateral Sclerosis (ALS)

  • Neuromuscular disease characterized by the degradation of both upper and lower motor neurons.
  • Clinical manifestations include:
      - Muscle weakness, paralysis, cranial nerve involvement (speech, swallowing difficulties).
      - Treatment includes riluzole (Rilutek), supportive care, and family involvement.

Demyelinating Disorders

  • Damage to the myelin sheath, affecting CNS and peripheral nervous systems.
  • Conditions include multiple sclerosis (CNS) and Guillain-Barré syndrome (PNS).
Multiple Sclerosis (MS)
  • A progressive, chronic autoimmune demyelinating disorder presenting in varied forms:
      - Clinical manifestations can include relapsing-remitting episodes, progressive patterns.
      - Treatments aim to manage symptoms and may include corticosteroids, immunotherapy, Vit D, and potential stem cell therapy.

Guillain-Barré Syndrome

  • Acquired inflammatory autoimmune disease causing demyelination of peripheral nerves.
  • Treatment involves ventilatory support and managing autonomic dysfunction, often requiring aggressive rehabilitation post-remission.

Neuromuscular Junction Disorders

  • Associated with autoimmune processes and mutations affecting motor functions:
      - Include myasthenia gravis and Lambert-Eaton myasthenic syndrome.
Myasthenia Gravis
  • Chronic autoimmune condition resulting in decreased nerve impulse transmission at the neuromuscular junction, primarily due to antibodies against acetylcholine receptors.
  • Clinical manifestations include:
      - Fatigue worsening with activity, ocular issues, dysphagia, myasthenic and cholinergic crises.
  • Treatment focuses on immunosuppressive therapy, supportive measures, or crisis management.