A 55-year-old alcoholic man with chronic hyponatremia (serum Na+ 112 mEq/L) is rapidly corrected over 24 hours to 135 mEq/L. Two days later, he develops quadriplegia, pseudobulbar palsy, and locked-in syndrome. MRI shows a central pontine lesion. The characteristic histopathological finding in the affected pons is:

• A Fibrinoid necrosis of arterioles with perivascular hemorrhage
• B Demyelination with relative preservation of axons and myelin-laden macrophages ✓
• C Microglial nodules and neuronophagia
• D Perivenous demyelination with preserved axons

Explanation

Rapid correction of hyponatremia can cause osmotic demyelination syndrome (central pontine myelinolysis). Histology shows myelin loss with relative axonal preservation and macrophages containing myelin debris. Option D describes acute disseminated encephalomyelitis (ADEM). Option C is seen in viral encephalitis. Option A is typical of hypertensive microangiopathy.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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