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🧠 About
- 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.
