Makindo Medical Notes

⚠️ The physician must carefully balance the risks of persistent hyponatraemia against the dangers of rapid correction. 🎯 High-risk groups: patients with hypoxia, alcoholism, liver disease, or severe malnutrition.

🧠 Central Pontine Myelinolysis (Osmotic Demyelination Syndrome)

• First described in 1956, CPM is characterised by demyelination within the central pons due to rapid electrolyte shifts.
• Most often triggered by overly fast correction of chronic hyponatraemia.
• Despite being non-inflammatory, the syndrome can cause devastating, often irreversible neurological deficits.

⚠️ Aetiology

• Rapid correction of chronic hyponatraemia (especially with hypertonic saline).
• Pathophysiology: as sodium rises quickly, osmotic forces draw water out of swollen CNS cells → dehydration → oligodendrocyte injury and myelin destruction.
• Other causes: severe hypernatraemia correction, liver transplantation, chronic alcoholism, profound malnutrition.

📌 Risk Factors

• Chronic alcohol dependence 🍺
• Malnutrition/cachexia 🍽️
• Liver disease or post–liver transplant 🏥
• Initial sodium <120 mmol/L for >48h ⏳
• Overcorrection: >12 mmol/L in 24h or >18 mmol/L in 48h 🚫

🩺 Clinical Features

• Progressive quadriparesis → quadriplegia.
• Brainstem involvement:
  • Dysarthria (slurred speech)
  • Dysphagia (difficulty swallowing)
  • Ophthalmoplegia with bilateral pinpoint pupils 👁️
• Cognitive/behavioural: delirium, confusion, reduced consciousness.
• Classic exam clue: intact corneal reflexes despite severe deficits.
• Fever may mislead towards infection.

🔍 Differential Diagnosis

• Brainstem stroke 🧠
• Brainstem encephalitis (e.g. Listeria)
• Tetanus or meningitis
• Drug toxicity/overdose
• Seizure-related: post-ictal state, non-convulsive status epilepticus

🧪 Investigations

• Bloods: FBC, U&E, LFTs, clotting; look for chronic liver disease, alcohol misuse, malnutrition.
• CSF: Often non-diagnostic; may show ↑ protein.
• MRI (preferred):
  • T2 hyperintense lesion in central pons → classic "bat-wing" or "trident" sign 🦇
  • May extend into thalamus, midbrain, medulla or cerebellum.

💊 Management

• Prevention is key ✅:
  • Correct sodium slowly: <10–12 mmol/L in 24h, <18 mmol/L in 48h.
  • In very high-risk groups (alcoholic, malnourished): aim even lower (≤8 mmol/L per 24h).
• Close monitoring: Frequent serum sodium checks (every 2–4h during correction).
• Supportive therapy:
  • Neurorehab, physiotherapy 🏃
  • Speech therapy for dysphagia 🗣️
  • Nutritional support and alcohol cessation counselling.
• Outcome: Some recovery possible, especially with rehab, but severe cases may leave permanent disability.

📉 Prognosis

• Mild cases: partial recovery possible with rehab.
• Severe cases: persistent locked-in–like state or death.
• Emphasis: slow correction saves lives.

📚 References

• Verbalis JG, et al. (2013). Hyponatremia treatment guidelines 2013. Am J Med.
• Martin RJ. (2004). Central Pontine and Extrapontine Myelinolysis: The osmotic demyelination syndromes. J Neurol Neurosurg Psychiatry.
• NICE CG174: Hyponatraemia Management, 2020 update.