Ring-Enhancing Lesion in Central Pontine Myelinolysis

A 4-year-old boy was seen in an emergency department after 3 days of vomiting and watery diarrhea. After his sodium level decreased from 136 to 118 mEq/L, he had a seizure, resulting in respiratory arrest, and required mechanical ventilation. His sodium level increased to 128 mEq/L with rehydration, but he developed “locked-in syndrome.”

His initial magnetic resonance image revealed increased signal lesions in the left pons, right basal ganglia region, and both medial temporal lobes (Figure).

Three weeks later, he was alert and able to move his extremities, although with a right hemiparesis. When he was discharged to rehabilitation, he remained severely dysphagic and required tube feeding.

This child’s clinical presentation and magnetic resonance imaging findings support the diagnosis of central pontine and extrapontine myelinolysis. In 1959, central pontine myelinolysis was first described in alcoholic patients.¹ Although children develop central pontine myelinolysis, they have different risk factors.² During rehydration, the rapid adjustment of sodium levels dehydrates the brain, perhaps because the introduction of potassium and other organic substances into the cells does not occur rapidly.³ Consequently, the myelin sheath is detached from the axon, resulting in oligodendrocyte damage and demyelination of the central pontine area and potentially extrapontine regions.⁴ Extrapontine demyelination has only recently been described in children.⁵ The pons and basal ganglia are preferred areas of demyelination, perhaps because in these regions gray and white matter are in close proximity. Locked-in syndrome occurs in extreme cases.

Magnetic resonance imaging is the most reliable method for confirming central pontine myelinolysis. Changes on the magnetic resonance image may persist after clinical improvement.⁶ In this child’s case, the magnetic resonance image improved after only a week, even in the face of locked-in syndrome. Myelinolysis in other regions, in this case the putamen and medial temporal lobes, also has been described. To our knowledge, a ring-enhancing lesion, on the other hand, has not been previously reported.

Correspondence: Dr Roach, Department of Neurology, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157.

Author Contributions:Study concept and design: Choksi and Roach. Acquisition of data: Roach. Analysis and interpretation of data: Choksi and Roach. Drafting of the manuscript: Choksi and Roach. Critical revision of the manuscript for important intellectual content: Choksi and Roach. Administrative, technical, and material support: Roach. Study supervision: Roach.