Neurologic Pathophysiology Review

Differentiate between Arousal vs Awareness

• Consciousness: State of awareness of oneself and the environment.
  • Includes the ability to respond to external stimuli with a variety of responses.
  • Two components:
  • Arousal: The state of being awake, mediated by the reticular activating system.
  • Awareness: Cognitive functions that include awareness of self, environment, and affective states (mood); content of thought.

Definition of Coma

• Coma: A state characterized by no verbal response to external stimuli; even noxious stimuli (e.g., deep pain) may yield motor movement.
• Causes of coma:
  • Bilateral hemisphere damage or suppression (e.g., metabolic derangement, hypoxia, hypoglycemia).
  • Brain stem lesions or metabolic derangement affecting the reticular activating system.
• Types of Coma:
  • Light Coma: Associated with purposeful movement on stimulation.
  • Deep Coma: No response to any stimulus.

Alterations in Arousal (Not on Study Guide)

• Clinical manifestations include:
  • Changes in level of consciousness (LOC): crucial index of nervous system function; changes may signal improvement/deterioration.
  • Breathing patterns, pupillary changes, and oculomotor responses.
  • Motor responses can be purposeful, inappropriate, or absent.
  • Includes involuntary actions (e.g., vomiting, yawning) controlled by the medulla.

Differentiate Between Dysphasia Types (Not on Study Guide)

• Wernicke's Dysphasia: Difficulty in understanding language (verbal/reading comprehension).
• Broca's Aphasia: Expressive dysphasia affecting speech and writing, yet comprehension is retained.

Delirium vs. Dementia

• Delirium:
  • Hyperkinetic confusional state, often due to disruptions in the right middle temporal gyrus.
  • Develops over 2-3 days, often resolves suddenly/gradually.
  • Clinical manifestations include difficulty concentrating, restlessness, irritability, insomnia, and poor appetite.
• Dementia:
  • Progressive failure of cerebral functions without altered levels of consciousness.
  • Symptoms: Loss of orientation, memory, language, judgment, decision-making.
  • Patho: Can be due to degeneration, atherosclerosis, or brain trauma.

Comparison of Delirium and Dementia

Alzheimer Disease Pathophysiology and Manifestations

• Types:
  • Familial (early and late onset) and Nonhereditary (sporadic, late onset).
• Causes (exact unknown):
  • Mutations leading to amyloid precursor protein production.
  • Alterations in apolipoprotein E.
  • Loss of neurotransmitter stimulation.
• Characterized by neurofibrillary tangles and senile plaques in the cerebral cortex and hippocampus.
• Clinical manifestations include forgetfulness, emotional disturbances, confusion, decline in problem-solving abilities.
• Diagnosis involves ruling out other causes; definitive diagnosis postmortem.

Seizure Disorders, Types, Pathophysiology, and Manifestations

• Seizure: Sudden, transient alteration of brain function due to explosive, disorderly neuronal discharge.
• Epilepsy: Recurrence of seizures; specific identifiable cause may not exist.
• Convulsion: Tonic-clonic movements associated with some seizures.

Causes of Seizures

• Can include epilepsy, metabolic disorders, infections, withdrawal symptoms, brain trauma, and more.

Types of Seizures

• Generalized: Neurons bilaterally affected (e.g., absences, myoclonic, tonic-clonic).
• Partial (Focal): Neurons unilaterally affected (e.g., simple partial, complex partial).
• Secondary Generalized: Partial seizures progressing to generalized.
• Status Epilepticus: Continuous seizures for more than 5 minutes or recurring seizures without regaining consciousness.

Seizure Sequence and Clinical Manifestations

1. Resting potential instability.
2. Seizure initiation and bursts of action potentials.
3. Tonic Phase: Contraction.
4. Clonic Phase: Relaxation.
5. Post-Ictal State: Follows the seizure.

• Aura: Sensory experiences before seizures.
• Prodromal Symptoms: Early indicators like malaise or headache.

Cerebral Edema Types and Pathophysiology

• Cerebral edema: Increase in brain fluid, harmful due to blood vessel distortion and brain tissue displacement.
• Types include:
  • Vasogenic Edema: Increased capillary permeability; disrupts blood-brain barrier.
  • Cytotoxic Edema: Metabolic toxicity leads to cell swelling without disrupting blood-brain barrier.
  • Interstitial Edema: Seen with non-communicating hydrocephalus; CSF movement into brain tissue.

Hydrocephalus Basics

• Hydrocephalus: Excess fluid in cranial vault/subarachnoid space due to CSF flow interference.
• Types:
  • Communicating Hydrocephalus: Blockage occurs after CSF leaves ventricles; affects absorption.
  • Non-communicating Hydrocephalus: Blockage in ventricles; often congenital.

Clinical Manifestations of Increased ICP

• Cushing's Triad: Hypertension, bradycardia, irregular respirations.

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