Demyelinating Disorders of the Nervous System Due to Osmotic Disequilibrium

Introduction: In central nervous system (CNS), oligodendrocytes form myelin. In peripheral nervous
system large proportions of axons are unmyelinated, instead they are ensheathed by non myelinating
schwann cells and arranged in Remak bundles. Osmotic demyelination (ODS) syndrome is a
neurologic disorder that can occur after rapid correction of hyponatremia. Acute hypernatremia results
in sudden shrinkage of brain cells leading to parenchymal or subarachnoid hemorrhages and/or
subdural hematomas mainly in pediatric patients.
Aim: Our aim is to present a case of hypernatremia which has led on to a flaccid quadriparesis due to
brain stem demyelination. Rapid correction of hypernatremia as a cause for pyramidal tract
demyelination is not documented in the literature.
Presentation of Case: A 53 year old male was brought to the emergency services with suspected
stroke. He was treated with intravenous mannitol and oral glycerine from the primary health centre.
We detected hypoglycemia (blood sugarwas 50 mg/dl-Ref range: ≤70 mg%) and dextrose was given
intravenously. Subsequently the patient went into a hypernatremic state with serum sodium 170 milli
equivalents /liter which was corrected rapidly. This was corrected over 48 hours to 140 milli
equalents/litre. The rate of correction exceeded 0.62 millimols/liter/hour (Ideal: 0.5 mmol/L/h). On the
6th day the patient developed acute quadriparesis. Magnetic resonance imaging (MRI) of brain
revealed bilateral symmetric demyelination of the corticospinal tracts. Over six months the
neurological deficit improved with complete resolution of the changes in previous MRI.
Discussion: Osmotic Demyelination Syndrome (ODS) has been a recognized complication of rapid
correction of hyponatremia. Experiments in animals and clinical experience suggest that correction of
chronic hyponatremia should be kept at a slow rate to combat this complication. The characteristic
sites include pons and basal ganglia. Such a complication has not been described due to rapid
correction of hypernatremia. This is probably the first case report in the literature where acute onset of
quadriparesis resulted from demyelination of the pyramidal tract consequent to a rapid correction of
hypernatremia. We had to wait about 6 months for the patient to obtain a complete functional recovery
and the neuro imaging was repeated after 6 months to confirm the disappearance of the initial findings
thus implicating rapid correction of hypernatremia as the cause of his morbidity.
Conclusion: This is the first time extrapontine reversible myelinolysis due to rapid correction of
hypernatremia has been documented. To prevent this potentially fatal complication it will be prudent if
hypernatremia is corrected slowly. Osmotic Demyelination Syndrome (ODS) can occur with rapid
correction of hyponatremia or hypernatremia. The first of its kind our report highlights the importance
of rate of correction of Sodium in the brain which may functionally interfere with the rapidly conducting
fibers rich in oligodendrocytes resulting in transient or permanent neuronal dysfunction.