Atypical forms of the osmotic demyelination syndrome.

Osmotic demyelination syndrome (ODS) is the damage over the central nervous system caused by several electrolytes, metabolic and toxic disorders. We aimed to describe cases of unusual forms of ODS. In a 9-year period, 25 consecutive patients with ODS (15 men; mean age 42 years) were registered in our referral institution, among them, four (16 %) with atypical neuroimaging findings were abstracted for this communication. None of them presented cardiorespiratory arrest, head trauma, seizures, neuromyelitis optica spectrum or contact with toxic chemicals. Case 1 was a 33-year-old alcoholic man without hypertension or electrolyte imbalance, who presented a classic central pontine myelinolysis (CPM) and a hemorrhage within the pons. Case 2 was a 34-year-old alcoholic man with hypoglycemia and hyponatremia who presented CPM and diffuse bihemispheric extrapontine myelinolysis (EPM) after correction of serum sodium. Case 3 was a 52-year-old woman with mild hypokalemia and hyponatremia (inadequately corrected), who presented a peduncular and cerebellar EPM. Case 4 was a 67-year-old woman who had a suicidal attempt with antidepressants and carbamazepine without impaired consciousness, who complicated with mild hyponatremia associated with a classical CPM and a spinal cord EPM. Case 2 died and the rest remained with variable neurological impairments at last follow-up visit. With modern neuroimaging, the so-called atypical forms of ODS may not be as rare as previously thought; however, they could have a more adverse outcome than the classical ODS.