The most common cause is the rapid correction of low blood sodium levels (hyponatremia).
Some scholars postulate that the real cause might be the lack of a substance that is essential for brain activity and is lacking due to malnutrition.
The fact that this condition is most frequently observed in patients with general ill health (alcoholism, cachexia etc.) is in accordance with this assumption. 
Imaging by MRI demonstrates an area of high signal return on T2 weighted images.
Frequently observed symptoms in this disorder are sudden para or quadraparesis, dysphagia, dysarthria, double vision and loss of consciousness. The patient may experience locked-in syndrome where cognitive function is intact, but all muscles are paralyzed with the exception of eye blinking.
To avoid myelinolysis, the correction of hyponatremia should not exceed 1 mEq/L per hour. 
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^ Kleinschmidt-DeMasters BK, Norenberg MD. Rapid correction of hyponatremia causes demyelination: relation to central pontine myelinolysis. Science. 1981;211(4486):1068-70. PMID 7466381
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