Central pontine myelinolysis.

Central pontine myelinolysis (CPM), a neurologic disorder caused most frequently by rapid correction of hyponatremia, is characterized by demyelination that affects the central portion of the base of the pons. There are no inflammatory changes, and blood vessels are normal. Clinical features usually reflect damage to the descending motor tracts and include spastic tetraparesis, pseudobulbar paralysis, and the locked-in syndrome. Magnetic resonance imaging of the brain, the imaging procedure of choice, shows an area of prolonged T1 and T2 relaxation in the central pons, which may have a characteristic shape. Recovery varies, ranging from no improvement to substantial improvement. To avoid CPM, correction of serum sodium in patients with hyponatremia should not exceed 12 mEq/24 h. We describe a case of CPM in a hyponatremic patient who presented with a cerebellar syndrome with no pyramidal tract involvement and in whom the rate of correction of serum sodium was within the recommended limits.