Makindo Medical Notes

Related Subjects: |Poliomyelitis |Post Polio Syndrome |Anterior Horn Cell diseases

🧠 About Anterior Horn Cell Diseases

• Anterior Horn Cell Diseases are conditions that damage the lower motor neurons (LMNs) located in the anterior horn of the spinal cord.
• These neurons control voluntary muscle movement, so disease results in LMN signs such as weakness, wasting, fasciculations, and hyporeflexia.
• Some conditions may also involve the brainstem motor nuclei, causing bulbar symptoms 🗣️ like dysphagia and dysarthria.
• Inherited forms include the Spinal Muscular Atrophies (SMA) 🧬, which present across the lifespan with varying severity.

⚠️ Causes

• 🦠 Poliomyelitis: Viral infection that destroys anterior horn cells → acute flaccid paralysis.
• 🧓 Motor Neuron Disease (MND/ALS): Progressive neurodegeneration affecting both UMN and LMN.
• 👶 Werdnig–Hoffman Disease (SMA Type 1): Severe infantile SMA → profound weakness, “floppy baby.”
• 🧑 Kugelberg–Welander Disease (SMA Type 3): Childhood/adolescent SMA with progressive weakness but longer survival.

🩺 Clinical Features

• 💪 Flaccid Weakness: LMN-type weakness with reduced tone.
• 🔽 Hyporeflexia/Areflexia: Absent or reduced tendon reflexes.
• ⚡ Muscle Wasting: Progressive atrophy of affected muscles.
• 👀 Fasciculations: Fine twitching of muscle fibres (LMN hallmark).
• 🗣️ Bulbar Symptoms: Dysphagia, dysarthria, tongue weakness/wasting.
• 🧬 SMA Spectrum:
  • 👶 Infantile SMA (Werdnig–Hoffman): Severe hypotonia, poor prognosis.
  • 🧑 Childhood SMA (Kugelberg–Welander): Progressive weakness with preserved intellect.
  • 👵 Adult-onset SMA: Slowly progressive limb weakness.

🔬 Investigations

• ⚡ Nerve Conduction Studies (NCS): Typically normal → helps distinguish from neuropathies.
• 📉 Electromyography (EMG): Shows denervation + fasciculations.
• 🧬 Genetic Testing: Confirms SMA (SMN1 gene deletions).

💊 Management

• 🤝 Supportive Care:
  • 🏃 Physiotherapy & OT to maintain mobility.
  • 💨 Respiratory support (e.g., NIV in advanced disease).
  • 🍽️ Nutritional support if dysphagia present.
• 🌟 New SMA Therapies:
  • 💉 Nusinersen (Spinraza): Increases SMN protein production.
  • 🧬 Zolgensma: Gene therapy → restores functional SMN1.
  • 💊 Risdiplam: Oral therapy enhancing SMN2 splicing.
• 🧓 MND Care: Riluzole (modest survival benefit), multidisciplinary support, symptom control.

📚 Key Point

Anterior horn cell diseases cause a classic LMN syndrome 🦵 (wasting, fasciculations, flaccid weakness, areflexia). The challenge is distinguishing them from neuropathies ⚡ and myopathies 💪, which require different investigations and management.