NEUROLOGY

Parkinson's Disease (PD): Pathophysiology and Overview

• Definition: Also known as Paralysis Agitans. It is a progressive, degenerative disease of the nervous system commonly observed in older adults.

• Primary (Idiopathic) PD: The cause is unknown (idiopathic), though it is linked to a combination of genetic and environmental factors.

• Secondary PD: Results from identifiable external or underlying factors, such as medications, stroke, vascular disease, head trauma, infections (e.g., encephalitis), or toxins (e.g., carbon monoxide $(CO)$, Manganese).

• Misdiagnosis: Often misdiagnosed as Huntington's disease (HD) in younger populations due to overlapping early symptoms and atypical presentations.

• Neuroanatomical Basis: The basal ganglia (a group of neurons at the base of the cerebrum) is responsible for maintaining voluntary movements.

• Neurotransmitter Balance:   - Dopamine: Produced in the substantia nigra and adrenal glands. It has an INHIBITORY effect.   - Acetylcholine (ACh): Produced and secreted by the basal ganglia and peripheral nerve endings. It has an EXCITATORY effect.   - The Problem: Degeneration of the substantia nigra leads to decreased dopamine (inhibitory effect). Motor function depends on the balance between dopamine's inhibitory and ACh's excitatory functions.

PD Etiology, Incidence, and Risk Factors

• Etiology: Attributed to a multifactorial combination of:   - Environmental Factors: Exposure to chemicals, metals, and well water.   - Age: Typically over $40$ years.   - Heredity: Genetic factors (often seen in Primary PD).   - Biological Factors: Reduced estrogen levels.   - Secondary PD Causes: Often follows a traumatic brain injury (TBI) or a brain tumor/lesion.

• Incidence Stats:   - Approximately $1$ million people are affected in the US; approximately $60,000$ Americans are diagnosed yearly.   - Over $10$ million people worldwide live with PD.   - Roughly $4\%$ are diagnosed before age $50$, with rare cases diagnosed at age $30$.   - Men are $1.5$ times more likely to have PD than women.

PD Assessment and Clinical Manifestations

• Classic Early Motor Symptoms:   - Resting Tremors: Usually unilateral at first.   - Bradykinesia: Slowed movement.   - Muscle Rigidity: Present in all stages.

• Muscle Rigidity Classifications:   1. Cogwheel: Rhythmic interruption of muscle movement.   2. Plastic: Mildly restrictive movement.   3. Lead pipe: Total resistance to movement.

• Late-Stage Findings: Gait disturbance/postural instability.

• Non-Motor Symptoms (Nearly all patients experience at least one; often precede diagnosis): Drooling, forgetfulness, urinary urgency, loss of sense of smell, constipation, dysphagia, gastroparesis, and Irritable Bowel Syndrome (IBS) without diarrhea.

• Facial and Autonomic Manifestations:   - Mask-like face (facial muscle rigidity), difficulty chewing/swallowing leading to poor nutrition.   - Excessive perspiration, orthostatic hypotension, bladder and bowel issues.

• Speech and Cognitive Impact:   - Monotonous, soft, rapid, or halting speech patterns.   - Depression (most common emotional impairment), apathy, anxiety, insecurity, mood changes, insomnia, dementia, and psychosis.

PD Diagnostics, Medications, and Long-Term Management

• Diagnosis: Based on clinical findings and the presence of $2$ of the $4$ classic symptoms (resting tremors, muscle rigidity, bradykinesia, and postural instability). Dopamine levels can be measured in cerebrospinal fluid (CSF).

• Levodopa Trial: A diagnostic test where a patient takes levodopa to see if symptoms reduce. A "positive" result is a $30\%$ or greater improvement in motor scores. Helps differentiate PD from Multiple System Atrophy (MSA) or Progressive Supranuclear Palsy (PSP).

• Gold Standard Treatment: Carbidopa/Levodopa (Sinemet).   - Carbidopa is added to prevent the metabolism of levodopa before it reaches the brain.   - Only $1\%$ of the medication reaches the brain and is available for $1$ hour; requires careful timing of repeated doses.   - GI dysfunction (constipation/delayed emptying) affects bioavailability.

• Long-term Levodopa Effects (After $5-10$ years):   - Dyskinesia: Facial grimacing, rhythmic jerking, head bobbing, chewing/smacking movements.   - On-Off Syndrome: "On" effect (medication effective) alternating with "Off" (near immobility).

• Other Medications:   - COMT Inhibitors (e.g., entacapone): Prolongs levodopa half-life.   - Dopamine Agonists (e.g., ropinirole): Mimics dopamine; reserved for those under $65$ with intact cognition due to side effects (hallucinations, impulse control disorders).   - Anticholinergics (e.g., benztropine): For tremors; use caution in elderly (confusion, urinary retention).   - Muscle Relaxants (baclofen): For spasms.   - Atropine sulfate ($sublingual$): For drooling.   - Pimavanserin: For hallucinations/delusions.

• Managing Toxicity/Tolerance: Includes reducing dosage, changing frequency, or a "Drug Holiday" (no PD drugs for up to $10$ days while monitoring symptoms).

• Surgical Management:   - Deep Brain Stimulation (DBS): Electrodes implanted to stimulate dopamine release or block ACh release.   - MR-Guided High-intensity Focused Ultrasound (MRgFUS): Sound waves create a controlled lesion (ablation) to disrupt abnormal circuits.   - Stereotactic Pallidotomy: 3D imaging used to target and lesion areas causing motor symptoms.

Alzheimer's Disease (AD): Pathophysiology and Diagnosis

• Definition: A subtype of dementia; a progressive, irreversible neurodegenerative disorder characterized by a gradual (insidious) decline in brain function.

• Pathological Changes:   1. Neurofibrillary Tangles: Tangled masses of nonfunctioning neurons (twisted inside cells) disrupting signal transport.   2. Neuritic (Senile) Plaques: Deposits of beta-amyloid protein that disrupt neuronal communication and trigger inflammation.   3. Vascular Degeneration: Decreased cerebral blood flow and microvascular damage leading to hypoxia.   4. Neurotransmitter Loss: Significant decrease in Acetylcholine (ACh), which is critical for memory and learning.

• Brain Physical Changes: Loss of neurons in the hippocampus (memory) and cerebral cortex (reasoning) causes the brain to weigh less and occupy less space.

• Assessment Tools: Mini-Mental State Exam (MMSE), Montreal Cognitive Assessment (MoCA), FACT (Fruits, Animals, Colors, Towns), and the Clock Drawing Test (CDT).

• Definitive Diagnosis: Brain tissue autopsy remains the standard for confirming plaques and tangles; PET scans/CSF/blood tests can detect biomarkers (amyloid protein).

AD Classifications and Stages

• By Age/Cause:   - Early-Onset (EOAD): Before age $65$, often genetic, rapid progression.   - Late-Onset (LOAD): After age $65$, most common, associated with aging.   - Familial (FAD): Rare, inherited autosomal dominant gene mutations.   - Sporadic: Most common, no clear inheritance pattern, multifactorial.

• Clinical Stages:   1. Preclinical: Brain changes begin; asymptomatic.   2. Mild Cognitive Impairment (MCI): Early measurable decline; memory problems start; daily function largely preserved.   3. Dementia Phase:      - Stage 1 (Early/Mild): Forgetfulness of recent events (earliest symptom), mood/personality changes, difficulty with complex tasks.      - Stage 2 (Moderate/Middle): Worsening memory/confusion, language problems, agitation, wandering, Sundowning (increased confusion at night).      - Stage 3 (Severe/Late): Loss of communication, total dependence for ADLs, physical deterioration.

AD Management and Nursing Care

• Behavioral Management:   - Early Stages: Reality orientation is appropriate.   - Late Stages: Validation therapy is more appropriate (avoid confrontation).   - Strategies: Cognitive stimulation (reminiscing), consistent routine, cardiorespiratory fitness (prevents/slows progression).

• Pharmacological Treatment:   - Cholinesterase Inhibitors (e.g., donepezil, rivastigmine): For mild-moderate AD (rivastigmine for severe). Delays ACh destruction.   - NMDA Antagonists (e.g., memantine): Blocks excess glutamate damaging cells; used in moderate-severe AD.   - Monoclonal Antibodies (e.g., Lecanemab): Reduces amyloid plaques in MCI or early-stage AD.   - Note on Antidepressants: SSRIs like sertraline are used; avoid Tricyclics in the elderly due to anticholinergic effects.

Seizures and Epilepsy

• Definitions:   - Seizure: Imbalance in brain's inhibitory (GABA) and excitatory forces leading to abnormal electrical discharges.   - Epilepsy: Chronic disorder with $2$ or more unprovoked seizures.

• Generalized (Grand Mal) Types:   1. Tonic-Clonic: $2-5$ minutes. Tonic (stiffening/loss of consciousness) followed by Clonic (rhythmic jerking). Biting and incontinence common.   2. Tonic: Sudden muscle rigidity ($30$ seconds to minutes), loss of consciousness, autonomic changes.   3. Clonic: Rhythmic jerking of all extremities simultaneously.   4. Myoclonic: Brief ($seconds$), arrhythmic jerking; usually occurs in clusters.   5. Absence: Short (<20 seconds) loss of consciousness without aura; repetitive blinking (automatism) common.   6. Atonic (Akinetic): "Drop attacks"; brief loss of postural tone.

• Partial (Focal) Types:   1. Simple: No loss of consciousness, includes an aura and one-sided movement.   2. Complex: "Blackout" ($1-3$ minutes), includes automatisms and postictal amnesia.

• Seizure Terminology:   - Automatism: Involuntary repetitive movements (lip smacking, picking at clothes).   - Aura: Warning sensation (strange smell, déjà vu, stomach rising).   - Postictal phase: Recovery phase characterized by confusion, drowsiness, and headache.

• Emergency Management:   - Status Epilepticus: Seizure >5 minutes or repeated for $30$ minutes. This is a medical emergency.   - Intervention: Administer Lorazepam IV ($4\,mg$, repeated once to $8\,mg$) or Diazepam. If IV access is unavailable, use Midazolam IM ($10\,mg$) or Diazepam rectal gel.

• Nursing Interventions: Turn patient to the lateral recovery position (airway priority), do not restrain, do not place objects in mouth, use suction for visible secretions only (do not force).

Cerebrovascular Accident (CVA/Stroke)

• Definition: Death of brain tissue due to disrupted blood supply (perfusion). Specialized as a "brain attack."

• Ischemic Stroke (87% of cases):   - Thrombotic: Rupture of plaque in cerebral or carotid artery; gradual onset.   - Embolic: Clot travels (often from the heart, e.g., Atrial Fibrillation); sudden onset.

• Hemorrhagic Stroke:   - Intracerebral (ICH): Bleeding into tissue, often due to hypertension.   - Subarachnoid (SAH): Bleeding into subarachnoid space, often due to Aneurysm or Arteriovenous Malformation (AVM). Signs: "Worst headache of life," N/V, photophobia.

• Assessment:   - Right Hemisphere Stroke: Issues with visual/spatial perception, neglect syndrome, and personality changes.   - Left Hemisphere Stroke: Issues with language (aphasia), math, and analytical thinking.

• BP Management Goals:   - Ischemic (No tPA): Permissive hypertension acceptable up to $220/120\,mmHg$.   - Ischemic (Eligible for tPA): BP must be <185/110\,mmHg before therapy.   - Hemorrhagic: Target SBP between $130$ and $150\,mmHg$ (optimal $140$).

• Fibrinolytic Therapy: Tissue Plasminogen Activator (tPA/alteplase) given within $3-4.5$ hours of onset. Withhold aspirin for $24$ hours post-tPA.

• Hyperperfusion Syndrome: Risk after carotid endarterectomy; sudden restore of flow to vessels that lost autoregulation, causing too much blood to rush into the brain.

Bell's Palsy

• Definition: Idiopathic facial paralysis; acute, unilateral paralysis of the $7^{th}$ Cranial Nerve. Right side is most common.

• Clinical Presentation: Sudden onset (peaking within $48$ hours). Forehead is affected (unlike stroke). Most cases ($80-90\%$) resolve in $6$ weeks to $3$ months.

• Symptoms: Ear pain, taste alteration ($60\%$ of cases), inability to close eye (risk for corneal abrasion).

• Management: Corticosteroids (e.g., prednisone) given within $72$ hours of onset. Eye protection (lubrication, patches) is the highest priority.

Guillain-Barré Syndrome (GBS)

• Pathophysiology: Autoimmune attack on peripheral nervous system (PNS) myelin/axons. Often follows bacterial (Campylobacter) or viral (Flu, CMV) infection.

• Key Feature: Ascending symmetric muscle weakness leading to flaccid paralysis. Progression upward toward respiratory muscles.

• Phases:   1. Acute: $1-4$ weeks.   2. Plateau: $2$ days to $2$ weeks.   3. Recovery: $4-6$ months up to $2$ years. Recovery occurs in descending order (reverse).

• Assessment: Lumbar puncture reveals increased protein in CSF. Forced Vital Capacity (FVC) monitoring is critical; FVC < 20\,mL/kg indicates impending respiratory failure.

• Management: Plasmapheresis (removes antibodies) or IVIG (Intravenous Immunoglobulin). Do not encourage early ambulation during the paralysis phase.

Questions & Discussion

• Q: Which PD patient should the nurse assess first?

• A: The client with difficulty swallowing and coughing during meals (Aspiration/Airway risk).

• Q: Which stroke patient is the priority?

• A: The client with sudden severe headache, vomiting, and decreasing LOC (indicates Hemorrhagic Stroke/Increased ICP).

• Q: What is the priority intervention for Bell's Palsy?

• A: Eye care/protection due to the inability to close the eyelid (risk for permanent vision loss).

• Q: In GBS, what denotes a critical respiratory risk?

• A: A Forced Vital Capacity (FVC) below $20\,mL/kg$.