Central pontine myelinosis - A case report with short literature review

Central pontine myelinolysis is a rare neurological disease of unknown etiology, characterized by symmetrical demyelinating lesions of the pons and mainly observed in cases of severe electrolytic disorders. Extrapontine demyelination of the thalamus or the cerebellum has been described in a few cases. Severe hyponatremia is considered as the most dangerous predisponding situation and its rapid correction is one of the most frequently reported mechanisms inducing pontine myelinolysis. It has also been reported in cases of diabetic ketoacidosis, disequilibrium syndrome due to terminal renal insufficiency, hypokalaemia in anorexia nervosa, hepatic encephalopathy and severe underlying disorders such as chronic alcoholism, malignancy, malnutrition and AIDS. Osmotic stress is regarded as an important etiopathogenetic factor. However, the exact underlying pathophysiological mechanism remains uncertain.

We report the case of an old patient already treated with diuretics, who presented a state of increasing confusion and disorientation, followed by a generalised epileptic seizures after forced intake of cathartics. This clinical deterioration was attributed to severe hyponatremia. This electrolytic disorder was corrected after admission to the intensive care unit within only 12 hours, at a correction rate of over >2 mmol/I per hour. The patient regained consciousness, but presented severe ataxia, dysarthria and dysphagia. She was unable to sit or stand. She had also great difficulties in swallowing, mostly fluids. In retrospect, this clinical syndrome was attributed to an extended demyelination of the central pons. The extremely rapid correction of the observed hyponatremia was regarded as the cause of osmotic stress leading to this demyelinating lesion, which was documented by means of magnetic resonance imaging (MRI) as a lesion of high signal intensity in T2 and low signal intensity in the T1-weighted images. Absence of a perifocal edema was characteristic of this case. The clinical course and the typical radiographic findings allowed the definite exclusion of order differential diagnostic alternatives, such of a brainstem tumor or an acute ischemic pontine infarction. The diagnosis of central pontine myelinolysis was then set.

This case of obviously iatrogenic central pontine myelinolysis suggests that extreme attention is needed when dealing with patients at risk of electrolytic deficits and especially in cases of hyponatremia. Controlled correction of low sodium levels should succeed very slowly without exceeding a rate of more than 0.5 mmol/I per hour.

A short literature review on pathogenetic, diagnostic and therapeutic issues of central pontine myelinolysis is also presented in this paper.

Key words: Central pontine myelinolysis, hyponatriemia.