5.10 Disorders of the Nervous System

Nervous disorders are conditions that affect the structure or function of the brain, spinal cord, or peripheral nerves. The FBISE curriculum classifies them into five major categories.

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Classification of Nervous Disorders (SLO B-12-G-36)

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1. Vascular Disorder — Stroke (Cerebrovascular Accident, CVA)

Causes

• Ischemic stroke (most common): A blood clot blocks an artery supplying the brain, cutting off oxygen.
• Hemorrhagic stroke: A blood vessel ruptures, causing bleeding into brain tissue.
• Risk factors include hypertension, atherosclerosis, diabetes, and smoking.

Symptoms

• Sudden numbness or paralysis on one side of the body (face, arm, leg)
• Slurred speech or difficulty understanding language
• Sudden vision loss
• Severe headache with no known cause
• Loss of balance and coordination

Treatment

• Ischemic: Thrombolytic drugs (e.g., tPA — tissue plasminogen activator) to dissolve clots; must be given within 4.5 hours.
• Hemorrhagic: Surgery to repair the ruptured vessel.
• Rehabilitation therapy (physiotherapy, speech therapy).

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2. Infectious Disorder — Meningitis

Causes

• Inflammation of the meninges (the three protective membranes surrounding the brain and spinal cord).
• Bacterial meningitis: Caused by Neisseria meningitidis or Streptococcus pneumoniae — more severe.
• Viral meningitis: Caused by enteroviruses — usually milder.

Symptoms

• Severe, sudden headache
• High fever
• Stiff neck (nuchal rigidity) — a hallmark sign
• Photophobia (sensitivity to light)
• Nausea and vomiting
• In severe cases: seizures, altered consciousness, and a characteristic non-blanching rash (bacterial).

Treatment

• Bacterial: Immediate intravenous antibiotics (e.g., penicillin, cephalosporins) and corticosteroids.
• Viral: Supportive care (rest, fluids, analgesics).
• Prevention: Meningococcal vaccine.

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3. Structural Disorder — Brain Tumor

Causes

• Abnormal, uncontrolled growth of cells within the brain.
• Primary tumors originate in brain tissue (e.g., gliomas, meningiomas).
• Secondary (metastatic) tumors spread from cancers elsewhere in the body.
• Exact cause often unknown; risk factors include radiation exposure and genetic predisposition.

Symptoms

• Persistent, worsening headaches (especially in the morning)
• Seizures
• Vision, speech, or hearing problems
• Personality and cognitive changes
• Nausea and vomiting due to increased intracranial pressure

Treatment

• Surgery: To remove the tumor if accessible.
• Radiotherapy: High-energy radiation to destroy tumor cells.
• Chemotherapy: Anti-cancer drugs.
• Corticosteroids: To reduce brain swelling.

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4. Functional Disorder — Headache

Headaches are the most common functional nervous disorder. They involve pain in the head or neck region without necessarily having a structural cause.

Types

• Tension headache: Most common; caused by muscle tension, stress, or fatigue.
• Migraine: Severe, throbbing, often one-sided headache; may be accompanied by nausea, vomiting, and sensitivity to light/sound. Caused by abnormal brain activity affecting blood vessels and nerves.
• Cluster headache: Intense pain around one eye, occurring in clusters.

Causes

• Stress, dehydration, lack of sleep, hormonal changes, certain foods.

Symptoms

• Dull aching or throbbing pain in the head
• Nausea, vomiting (in migraines)
• Sensitivity to light and sound

Treatment

• Analgesics (paracetamol, NSAIDs like ibuprofen)
• Triptans for migraines
• Lifestyle modifications (stress management, regular sleep)

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5. Degenerative Disorders

A. Alzheimer's Disease

Category: Degenerative

Causes:

• Progressive destruction of neurons, particularly cholinergic neurons (acetylcholine-producing).
• Accumulation of amyloid plaques (protein deposits between neurons) and neurofibrillary tangles (twisted tau protein inside neurons).
• Genetic factors (e.g., APOE-e4 gene) and aging are major risk factors.

Symptoms:

• Early: Short-term memory loss, difficulty finding words.
• Progressive: Confusion, disorientation, personality changes.
• Late: Inability to recognize family, loss of basic functions.

Treatment:

• No cure; treatment is symptomatic.
• Cholinesterase inhibitors (e.g., donepezil) slow acetylcholine breakdown.
• Supportive care and behavioral therapy.

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B. Parkinson's Disease

Category: Degenerative

Causes:

• Death of dopamine-producing neurons in the substantia nigra of the midbrain.
• Dopamine deficiency disrupts smooth, coordinated movement.
• Cause is largely unknown; genetic and environmental factors play a role.

Symptoms:

• Resting tremors ("pill-rolling" tremor of the hands at rest)
• Rigidity (muscle stiffness)
• Bradykinesia (slowness of movement)
• Shuffling gait and postural instability
• Expressionless face ("masked face")

Treatment:

• Levodopa (L-DOPA): Converted to dopamine in the brain — the most effective drug.
• Dopamine agonists: Mimic dopamine action.
• Deep brain stimulation (DBS) surgery in advanced cases.

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C. Multiple Sclerosis (MS)

Category: Degenerative (Autoimmune)

Causes:

• The immune system mistakenly attacks the myelin sheath of axons in the CNS.
• Demyelination leads to formation of hardened scar tissue called scleroses (plaques).
• These plaques disrupt or block nerve impulse conduction.

Symptoms:

• Muscle weakness and spasms
• Vision problems (optic neuritis)
• Fatigue and numbness
• Loss of coordination and balance
• Bladder and bowel dysfunction

Treatment:

• No cure; disease-modifying therapies (e.g., interferon-beta) slow progression.
• Corticosteroids for acute relapses.
• Physiotherapy and symptomatic management.

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Summary Table