Hyponatremia can cause which of the following?

• A. Hypernatremia
• B. Seizures and confusion
• C. Polyuria
• D. Hypertension

Answer: (B)

Low serum sodium lowers blood osmolality, so water moves into brain cells and causes cerebral edema. That swelling disrupts neuronal function and leads to neurologic symptoms like confusion and seizures, which is why these are the classic and most concerning manifestations of hyponatremia. The brain is highly sensitive to osmotic changes, so when sodium is diluted, the resulting edema can quickly produce altered mental status and convulsions, especially in acute or severe hyponatremia.

Hypernatremia would produce problems from brain cell dehydration rather than swelling, so it isn’t what hyponatremia causes. Polyuria points to conditions that make you lose water, not dilute brain sodium, and hypertension is not a direct consequence of low sodium.