CHAPTER 34 Chronic and Degenerative Neurologic Disorders – Comprehensive Study Notes

Neuron Anatomy and Physiology

  • Fundamental unit: Neuron – specialized cell transmitting electro-chemical signals.

    • Soma (cell body) – contains the nucleus; metabolic center.

    • Dendrites – branched projections receiving incoming stimuli.

    • Axon – single, long projection conducting impulses away from soma.

    • Segmented by Schwann cells that wrap the axon, forming myelin.

    • Node of Ranvier – unmyelinated gap; facilitates saltatory conduction.

    • Axon terminal – synaptic boutons where neurotransmitters are released.

  • Nerve-impulse propagation ("nerve conduction")

    • Resting membrane potential maintained by \text{Na}^+ /\text{K}^+ ATPase.

    • Depolarization: \text{Na}^+ influx → threshold reached → action potential.

    • Repolarization: \text{K}^+ efflux.

    • Myelin ↑ conduction velocity (saltatory jumps from node to node).

    • Demyelination (e.g.

    • MS – CNS demyelination.

    • GBS – PNS demyelination.
      ) slows/blocks signal → clinical weakness, paresthesia.

Neurological Assessment

Subjective Data (History)

  • Past or recent head injury, stroke, seizures, dizziness/vertigo, in-coordination, memory issues.

  • Time course – acute vs chronic.

  • Recent infection, toxin, or medication exposure.

Glasgow Coma Scale (GCS)

  • Rapid, objective measure of level of consciousness (LOC).

  • Eye-opening (E)

    • Spontaneous =4

    • To voice =3

    • To pain =2

    • None =1

  • Verbal response (V)

    • Oriented =5

    • Confused =4 (converses but disoriented)

    • Inappropriate words =3 (random/ expletives)

    • Incomprehensible sounds =2 (moans, groans)

    • None =1

  • Motor response (M)

    • Obeys commands =6

    • Localizes pain =5

    • Withdraws (flexion) =4

    • Abnormal flexion (decorticate) =3

    • Abnormal extension (decerebrate) =2

    • None =1

  • Total \text{GCS}=E+V+M (range 3\rightarrow 15). Score \le 8 denotes coma & need for airway protection.

Orientation (“A&O”)

  • Person – own identity / caretaker.

  • Place – present location.

  • Time – date, day, or season.

  • Situation – reason for encounter.

Diagnostic Imaging: MRI vs. CT

  • MRI (Magnetic Resonance Imaging)

    • Uses strong magnetic fields & radio-frequency pulses → high-contrast images of soft tissue (brain, spinal cord, muscles, ligaments).

    • Advantages: no ionizing radiation; multi-planar; detects demyelination, tumors, ischemia, MS plaques.

    • Limitations: claustrophobia, metal implants, longer scan time, expensive.

  • CT (Computed Tomography)

    • X-ray–based cross-sectional slices.

    • Excellent for bone, acute hemorrhage, fractures, trauma; fast (≤ 5 min) – favored for ED triage.

    • Disadvantages: ionizing radiation; less soft-tissue contrast.

  • Decision making: acute stroke → non-contrast CT first (rule-out bleed), then MRI for ischemic focus; spinal cord compression → MRI; poly-trauma with fractures → CT.

Seizure Disorders

  • Definition: transient, uncontrolled abnormal electrical activity in brain producing changes in motor, sensory, autonomic, or psychic function.

  • Classification

    • Generalized – both hemispheres; LOC lost.

    • Focal (partial) – one cortical area; awareness may be retained (simple) or impaired (complex).

  • Status epilepticus

    • Continuous seizure activity ≥ 30\,\text{min} (or ≥ 5 min per modern criteria) without recovery.

    • Neurological emergency → airway, benzodiazepines, antiepileptics.

Headache Types

  • Primary (no structural cause)

    • Tension – bilateral, band-like; stress linked; NSAIDs, relaxation.

    • Migraine – unilateral throbbing; +/- aura (visual scintillations); trigeminovascular activation; treat with triptans.

    • Cluster – severe unilateral orbital; autonomic features (lacrimation); male > female; oxygen + sumatriptan.

    • New Daily Persistent Headache (NDPH) – sudden onset daily pain lasting > 3 months.

  • Secondary

    • Sinusitis, HTN crisis, TMJ disorders, intracranial bleeding, infection, tumor.

Parkinson’s Disease (PD)

  • Progressive, degenerative loss of dopaminergic neurons in substantia nigra → ↓ dopamine.

  • Four cardinal motor signs: Tremor at rest, Rigidity, Bradykinesia, Postural instability.

  • Multisystem manifestations

    • Motor: small handwriting (micrographia), masked facies, shuffling gait, reduced arm swing, freezing.

    • Autonomic: constipation, orthostatic hypotension, sweating.

    • Ocular/facial: blepharospasm, sialorrhea, hypophonia (soft voice), dysphagia.

    • Neuropsychiatric: depression, anxiety, cognitive decline, sleepiness.

  • Respiratory risk: upper-airway obstruction, impaired ventilatory control → aspiration pneumonia.

Amyotrophic Lateral Sclerosis (ALS)

  • AKA Lou Gehrig’s disease.

  • Pathology: progressive motor neuron degeneration (upper & lower) in brain & spinal cord.

    • Normal neuron → continuous muscle signaling.

    • ALS neuron → lost signaling → atrophy.

  • Clinical picture

    • Limb weakness, fasciculations, spasticity, hyperreflexia, dysarthria, dysphagia.

    • Cognition usually preserved but can have frontotemporal dementia.

  • Prognosis: median survival 3–5 years; death often from respiratory failure.

Multiple Sclerosis (MS)

  • Auto-immune, inflammatory demyelination in CNS with axonal injury.

  • Common in females 20–40 yrs; relapsing-remitting most frequent.

  • Symptoms: optic neuritis, internuclear ophthalmoplegia, sensory loss, ataxia, bladder dysfunction.

  • MRI: periventricular "Dawson’s fingers" plaques.

  • Treatment: disease-modifying agents (interferons, monoclonal antibodies), steroids for relapse.

Huntington’s Disease (HD)

  • Autosomal-dominant CAG trinucleotide repeat expansion of HTT gene.

    • Each child has 50\% risk; siblings risk equally.

  • Onset 30–50 yrs (juvenile form possible).

  • Manifestations

    • Chorea (jerky involuntary movements), dystonia.

    • Cognitive decline, psychiatric (depression, irritability).

  • Genetic counseling & definitive testing essential.

Guillain-Barré Syndrome (GBS)

  • Acute, immune-mediated polyneuropathy, often post-viral (e.g., flu, Campylobacter).

  • Characteristic features

    • Ascending, symmetrical weakness beginning in feet → legs → trunk → cranial nerves.

    • Areflexia or hyporeflexia.

    • Paresthesia, mild sensory loss; neuropathic pain.

    • Possible autonomic instability (BP fluctuation, arrhythmias).

  • CSF : albuminocytologic dissociation (↑ protein, normal WBC).

  • Differentiation from stroke/myopathy

    • Stroke – focal deficit with hyperreflexia/spasticity; imaging shows lesion; acute onset without evolution over days.

    • Myopathy – proximal > distal weakness, normal sensation, reflexes preserved or mild ↓; CK elevated.

  • Management: IVIG or plasmapheresis; monitor respiration (vital capacity < 15 mL/kg → intubate).

Myasthenia Gravis (MG)

  • Auto-antibody against acetylcholine receptor (AChR) or MuSK at neuromuscular junction.

  • Clinical triad: fluctuating skeletal-muscle weakness, fatiguability, improvement with rest.

    • Ocular: ptosis, diplopia.

    • Bulbar: dysphagia, dysarthria.

    • Limb/axial: proximal > distal.

  • Tensilon (edrophonium) test – transient improvement.

  • Crisis: respiratory muscle involvement.

  • Treatments: pyridostigmine, steroids, immunosuppressants, thymectomy.

Case Study – Mr. John Thomas (36 yrs)

  • Presentation: progressive ascending weakness & paresthesia 3 days, preceded by viral infection 2 wks ago; difficulty walking, climbing stairs, breathing, swallowing; slurred speech.

  • Differential points

    • GBS

    • Temporal link to infection; symmetric ascending pattern; both motor & respiratory involvement; areflexia expected.

    • Stroke

    • Usually sudden, unilateral, with upper motor-neuron signs; CT/MRI would show lesion; no ascending pattern.

    • Myopathy (e.g., polymyositis)

    • Typically proximal weakness without sensory loss; slower progression; CK ↑; reflexes intact.

  • Key investigations: neuro exam for reflexes, pulmonary function (FVC), CSF, EMG/NCS.

  • Early ICU admission → IVIG.

Ethical, Practical & Clinical Implications

  • Rapid recognition of degenerative vs acute reversible neurologic conditions directly affects morbidity/mortality (e.g., status epilepticus, GBS respiratory failure).

  • Radiation exposure considerations (MRI preferred in pediatrics, pregnancy unless emergent CT required).

  • Genetic counseling for inherited disorders (HD) – psychological impact, reproductive choices.

  • Palliative care discussions in ALS & advanced PD.

  • Resource allocation – long-term rehab, assistive devices, caregiver burden.