A 36 year old alcoholic man was admitted to hospital with obtunding, jaundice and cachexia. In addition to deranged LFTs, anaemia and thrombocytopenia, all thought to be related to cirrhosis, he had Creat 194 (eGFR 36), Na 138, K 2.6. He was treated for alcohol withdrawal but was difficult to manage; for a few days he was intubated and ventilated. Lactulose was thought to blame for very profuse diarrhoea, and he developed significant electrolyte disturbance. Serum sodium rose to 158 over 30 hours at one point; then slowly improved with water hydration over several days. Potassium rose to 3.4 then dropped back to 2.4 before slowly returning to normal.
5 days later his conscious level reduced again and he developed spastic quadriplegia. An MRI scan later that day is shown above.
Question: what is the likely caused of this problem? Could anything have been done to prevent it?
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What the experts thought ...
This is osmotic demyelination (old name: Central Pontine Myelinolysis) but it is a very unusual example caused by rapid onset of hypernatraemia. Usually it is attributed to too-rapid correction of very low plasma [Na], but presumably the principle is the same. A few principles.
- The hyponatraemia needs to be of some duration (not acute).
- The delayed onset of symptoms, 2-6d after the peak change in sodium, is typical.
- A ‘safe rate’ for correction of chronic hyponatraemia is said to be less than 8 mmol every 24h (up to 10 mmol quickly for severe acute symptoms). (UpToDate)(UoE login required).
- Risk factors for its occurrence include alcohol abuse, liver disease, malnutrition, pre-existing brain disease. It is also much more likely if starting sodium is <120.
What happened? He is said to have made a good neurological recovery over a week or so. This is not always the case.
- Imaging is very well presented in Radiopaedia on Osmotic demyelination. It’s worth looking quickly through the cases there to see the variations in appearance, and distinguishing from pontine infarction (shown at the foot of that page), in which the abnormality doesn’t cross the midline.
- Wikipedia on Central Pontine Myelinolysis does quite a good job.
- (UpToDate)(UoE login link) is comprehensive.