Central Pontine Myelinolysis

      Central pontine myelinolysis, also called osmotic demyelination syndrome, is a disorder characterized pathologically by dissolution of the myelin sheaths of fibers within the central aspect of the basis pontis. In extreme cases there may be extension to the pontine tegmentum, midbrain, thalamus, internal capsule, and cerebral cortex. The myelinolysis occurs with relative sparing of the nerve cells and axon cylinders. Many patients are asymptomatic, and at the other extreme are patients whose symptoms are masked by coma. Most clinically diagnosed cases present with spastic quadriparesis, pseudobulbar palsy, and acute changes in mental status, with progression possible to altered levels of consciousness and death. Survival is possible with varying residual neurologic deficits. Although initial reports were largely confined to chronic alcoholics, central pontine myelinolysis has also been seen in patients with electrolyte disturbances, particularly hyponatremia that has been rapidly corrected, and in liver transplant patients being immune-suppressed with cyclosporine. Endnote

      The lesions on MR are seen best as areas of hypointensity on IR images and hyperintensity on T2-weighted images in the central pons with sparing of the pontine tegmentum and ventrolateral pons. Lesions have an oval shape on sagittal images, a bat-wing configuration on coronal images and various shapes on the axial images. Endnote The extrapontine lesions often resolve completely, leaving some residual pontine abnormality. Enhancement is not a feature of this disease, but severe cases may show peripheral enhancement of the pontine lesions. Diffusion techniques usually show increased diffusibility and increased apparent diffusion coefficient (ADC), but restricted diffusion and decreased ADC can be seen acutely during the first week. 

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