Central pontine myelinolysis is a neurological condition involving severe damage to the myelin sheath of nerve cells in the pons (an area of the brainstem). It is predominately iatrogenic (treatment-induced), and is characterized by acute paralysis,  dysphagia (difficulty swallowing), dysarthria (difficulty speaking), and other neurological symptoms. Central pontine myelinolysis was first described as a disorder in 1959. The original paper described four cases with fatal outcomes, and the findings on autopsy. The disease was described as a disease of alcoholics and malnutrition. Central pontine indicated the site of the lesion and myelinolysis was used to emphasise that myelin was affected. The authors intentionally avoided the term demyelination to describe the condition, in order to differentiate this condition from multiple sclerosis and other neuroinflammatory disorders.Since this original description, demyelination in other areas of the central nervous system associated with osmotic stress has been described outside the pons (extrapontine). Osmotic demyelination syndrome is the term used for both central pontine myelinolysis and extrapontine myelinolysis.Central pontine myelinolysis, and osmotic demyelination syndrome, present most commonly as a complication of treatment of patients with profound hyponatremia (low sodium), which can result from a varied spectrum of conditions, based on different mechanisms. It occurs as a consequence of a rapid rise in serum tonicity following treatment in individuals with chronic, severe hyponatremia who have made intracellular adaptations to the prevailing hypotonicity. Signs and symptoms
Symptoms depend on the regions of the brain involved.
The favourable factors contributing to the good outcome in central pontine myelinolysis without hyponatremia were: concurrent treatment of all electrolyte disturbances, early intensive care unit involvement at the advent of respiratory complications, early introduction of feeding including thiamine supplements with close monitoring of the electrolyte changes and input.Research has led to improved outcomes. Animal studies suggest that inositol reduces the severity of osmotic demyelination syndrome if given before attempting to correct chronic hyponatraemia. Further study is required before using inositol in humans for this purpose. Prognosis
Though traditionally the prognosis is considered poor, a good functional recovery is possible. All patients at risk of developing refeeding syndrome should have their electrolytes closely monitored, including sodium, potassium, magnesium, glucose and phosphate. Recent data indicate that the prognosis of critically ill patients may even be better than what is generally considered, despite severe initial clinical manifestations and a tendency by the intensivists to underestimate a possible favorable evolution. While some patients die, most survive and of the survivors, approximately one-third recover; one-third are disabled but are able to live independently; one-third are severely disabled. Permanent disabilities range from minor tremors and ataxia to signs of severe brain damage, such as spastic quadriparesis and locked-in syndrome. Some improvements may be seen over the course of the first several months after the condition stabilizes.The degree of recovery depends on the extent of the original axonal damage. References
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