🦠 Poliomyelitis (Polio): Pathophysiology and Physio Management

Poliomyelitis is an acute viral infection caused by the poliovirus, primarily affecting the central nervous system. While eradicated in many parts of the world due to vaccination, understanding its consequences—asymmetrical flaccid paralysis and Post-Polio Syndrome (PPS)—is essential for neuro-physiotherapy students.

1. 📚 Classification and Etiology

A. Types of Poliomyelitis

Type	Clinical Manifestation	Relevance for Physio
1. Abortive Polio	Mild flu-like illness. No neurological symptoms.	None. Complete recovery.
2. Non-Paralytic Polio	Fever, headache, neck stiffness (meningitis-like symptoms). No muscle paralysis.	Limited, focused on pain relief.
3. Paralytic Polio	Muscle weakness and Flaccid Paralysis.	Most Important. Leads to permanent disability and deformities.

B. Etiology and Pathophysiology

• Cause: Poliovirus (an enterovirus).
• Transmission: Fecal-oral route (highly contagious).
• CNS Target: The virus selectively invades and destroys the Anterior Horn Cells (AHCs) in the spinal cord, which are the cell bodies of the Lower Motor Neurons (LMNs).

2. 🔬 Pathophysiology: LMN Lesion and Residual Paralysis

The severity of paralysis depends on the extent of AHC destruction. Polio is a classic example of an LMN lesion.

• LMN Lesion Features: Leads directly to Flaccid Paralysis (loss of tone), Areflexia (loss of reflexes), and subsequent rapid Muscle Atrophy.
• Recovery Stage: Surviving AHCs compensate by sending out collateral sprouts to re-innervate orphaned muscle fibers. This leads to the initial phase of strength return.
• Residual Paralysis: Any muscle weakness remaining after 18 months is considered permanent, resulting in lifelong disability and potential deformities.

3. 🚩 Clinical Features and Common Deformities

A. Paralytic Stage Symptoms (Asymmetrical)

• Onset: Rapid onset of muscle weakness (flaccid paralysis).
• Distribution: Typically Asymmetrical (e.g., one leg worse than the other, or only one limb affected). Lower limbs are most commonly affected (Spinal Polio).
• Sensory: Sensation is usually preserved because the sensory pathways and dorsal root ganglia are not targeted by the virus.
• Bulbar Polio: If cranial nerves are affected (Bulbar Polio), respiratory paralysis and swallowing difficulties can occur ($\rightarrow$ requiring urgent ventilation and suctioning).

B. Common Orthopedic Deformities

Deformities result from muscle imbalance (strong, unaffected muscles pull against paralyzed muscles) and the persistent pull of gravity.

• Foot: Equinus Foot (plantarflexion deformity) and Foot Drop (due to paralyzed ankle dorsiflexors).
• Knee: Genu Recurvatum (back knee or hyperextension) during gait due to weak quadriceps (compensating with gravity/ligaments).
• Spine: Progressive Scoliosis due to asymmetrical trunk muscle weakness.
• Limb Length Discrepancy: Affected limbs grow slower due to lack of muscle use.

4. 📋 Physiotherapy Assessment

Assessment guides acute protection and long-term maximizing of functional strength.

• Muscle Strength: Detailed MMT (Manual Muscle Testing) to accurately grade residual strength and monitor recovery.
• Tone & Reflexes: Confirmation of Hypotonia and Areflexia (LMN signs).
• Deformities: Assessment of fixed contractures and limb length discrepancy.
• Function & Gait: Analysis of compensatory gait patterns and assessment of orthotic needs.

5. 🛠️ Physiotherapy Management: Stage-Specific Approach

A. Acute Stage (Early Weeks - Protection and Rest)

Goal: Prevent further muscle damage and minimize contractures/pain.

• Rest & Positioning: Strict bed rest for affected limbs (2–3 weeks). Use splints/sandbags to maintain muscles in a shortened position to prevent overstretching.
• Movement: Gentle Passive ROM (PROM) only (avoiding pain/vigorous mobilization) to maintain joint integrity.
• Pain: Use Hot Fermentation or heat modalities to relieve muscle pain and spasm.
• Cardinal Rule: ABSOLUTELY AVOID VIGOROUS EXERCISE OR FATIGUE, as this can increase neuronal damage.

B. Recovery Stage (After Paralysis Stabilizes - Reinnervation)

Goal: Regain strength from recovering motor units and prevent overwork weakness.

• Strengthening (Graded): Begin training using gravity-eliminated exercises (MMT grades 1–2). Progress cautiously to anti-gravity (MMT grade 3) and finally to light resistance (MMT grade 4+).
• Avoid Overwork Weakness: Never exercise to the point of fatigue or pain. Rest periods must be generous.
• Functional Focus: Hydrotherapy is excellent as it reduces the effect of gravity, allowing movement with minimal energy cost.
• Stretching: Gentle, sustained stretching of tight antagonists (e.g., Achilles tendon for foot drop).

C. Chronic/Residual Stage (Maximizing Function)

• Orthotic Management: Key for stability and function. AFO for foot drop, KAFO for weak quadriceps, or shoe raises for limb length discrepancy. Orthotics prevent compensatory gait patterns (like Genu Recurvatum).
• Gait Training: Focus on safe and efficient gait with assistive devices. If compensation is necessary (e.g., using a back-knee gait for weak quads), orthoses may be needed to protect the joint structure.
• Functional Training: ADL and transfer training using preserved muscle strength.

6. ⚠️ Long-Term Risk: Post-Polio Syndrome (PPS)

PPS is a neurological disorder that occurs decades (15–40 years) after initial polio recovery.

• Cause: Gradual metabolic fatigue and failure of the initially enlarged, overstretched motor units created during the recovery phase (macro motor units).
• Symptoms: New onset Muscle Weakness (in initially affected or unaffected muscles), overwhelming Fatigue, muscle pain, and breathing difficulties.
• Management Principle: Energy Conservation and Avoidance of Overexertion. Exercise must be very low intensity; the focus shifts to preserving remaining strength, not gaining new strength. Use adaptive equipment (orthotics, wheelchair) liberally.

🎓 Academic Exam Notes / Short Answers

• Pathophysiology of Polio: Destruction of Anterior Horn Cells (LMN cell bodies) by the poliovirus, leading to LMN paralysis.
• LMN Features in Polio: Flaccid paralysis, Hypotonia, Areflexia, Sensation preserved, rapid Atrophy.
• Physiotherapy in Acute Polio: Strict rest, gentle PROM, hot fermentation for pain. Vigorous exercise is CONTRAINDICATED.
• Orthotic Management: AFO for foot drop, KAFO for quadriceps weakness. Used to prevent deformity (e.g., Genu Recurvatum) and maximize function.
• Gait Abnormality: Genu Recurvatum (due to weak quads) and Foot Drop.

7. 🛑 Complications and Prognosis

• Complications: Respiratory failure (Bulbar Polio), long-term Deformities (Scoliosis, Equinus), Osteoporosis, and severe Fatigue (PPS).
• Prognosis: Functional recovery occurs mostly within the first year. Weakness remaining after 18 months is considered permanent residual paralysis.

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❓ Frequently Asked Questions (FAQs)

Q: Why is polio paralysis typically asymmetrical?

A: The poliovirus selectively attacks motor neurons, and this destruction is typically scattered and random rather than uniform across the spinal cord, leading to the characteristic asymmetrical pattern of muscle paralysis and weakness.

Q: In the recovery stage, why must the physio avoid overwork weakness?

A: The muscles rely on large, hyper-functioning "macro motor units" formed by the surviving neurons. Overworking these units can lead to metabolic exhaustion and damage, causing the surviving neurons to die back, thus permanently reducing the potential for functional recovery. This rule is crucial in preventing PPS later in life.

Q: What is the risk of Genu Recurvatum (Back Knee) in a recovering polio patient?

A: Genu recurvatum occurs due to severe quadriceps weakness. During walking, the patient locks the knee joint in hyperextension (often assisted by gravity or plantarflexion force) to stabilize the leg. While functional, it overstretches posterior structures and can damage the knee joint capsule/ligaments over time.

Q: How do muscle fasciculations (twitching) relate to the polio lesion?

A: Fasciculations are a transient sign of the LMN lesion, representing spontaneous firing of the damaged or irritated motor neurons in the anterior horn. They often disappear once the destruction or recovery process stabilizes.

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🎯 10 Practice MCQs for Poliomyelitis Exam

Q1. The primary neurological structure destroyed by the poliovirus is the:

Answer: A). Polio is a classic motor neuron disease causing an LMN lesion.

Q2. Which clinical sign is characteristic of the Paralytic Polio (LMN) lesion?

Answer: C). Flaccidity, areflexia, and asymmetrical weakness are the hallmarks of paralytic polio.

Q3. In the acute stage of polio (early weeks), the MOST critical instruction for physiotherapy management is to:

Answer: B). Neurons are actively under attack; rest is mandatory to prevent increased metabolic demand and further destruction.

Q4. Post-Polio Syndrome (PPS) is caused by:

Answer: B). PPS occurs decades later when the 'macro motor units' fail due to metabolic overload.

Q5. Paralysis in Polio is typically asymmetrical because:

Answer: A). The random nature of the viral attack on AHCs results in the asymmetrical weakness pattern.

Q6. In the recovery stage, a muscle with MMT grade $2/5$ should be exercised:

Answer: B). MMT grade 2 indicates movement only in a gravity-eliminated plane. Progression must be cautious to avoid overwork.

Q7. The common deformity of Genu Recurvatum (back knee) is a compensation for weakness in which muscle group?

Answer: C). Quadriceps weakness forces the patient to lock the knee in hyperextension during stance phase for stability.

Q8. Paralysis is considered permanent residual paralysis if it persists beyond:

Answer: C). Most motor recovery (reinnervation) is complete within 18 months.

Q9. If a polio survivor develops new weakness and overwhelming fatigue decades later, the treatment principle for the physio is:

Answer: B). This describes Post-Polio Syndrome (PPS), where management shifts to preservation and energy pacing.

Q10. Which statement regarding sensation in paralytic polio is correct?

Answer: C). The poliovirus selectively attacks AHCs (motor) and spares the sensory neurons of the dorsal root ganglia.

📚 Important Academic References

• Sharrard, W. J. W. (1978). The management of poliomyelitis. The Journal of Bone and Joint Surgery. British volume, 60-B(4), 540-550. (Orthopedic and LMN principles).
• Silver, J. K., et al. (2014). The prevalence of post-polio syndrome in polio survivors: a systematic review and meta-analysis. Archives of Physical Medicine and Rehabilitation, 95(4), 755-761. (PPS definition and management).
• O’Sullivan, S. B., & Schmitz, T. J. (2019). Physical Rehabilitation (7th ed.). F.A. Davis Company. (For LMN assessment and motor recovery stages).
• Centers for Disease Control and Prevention (CDC). (2023). Polio vaccination. (Prevention and etiology).