When sodium levels in the body are low, water tends to enter cells, causing them to swell. When this occurs in the brain, it is referred to as cerebral edema. Cerebral edema is particularly dangerous because the brain is confined in the skull without room for expansion, and the swelling can lead to brain damage as the pressure increases within the skull.
In chronic hyponatremia, in which the blood sodium levels drop gradually over time, symptoms are typically less severe than with acute hyponatremia (a sudden drop in blood sodium level). Symptoms can be very nonspecific and can include:
Confusion or altered mental state.
Decreased consciousness, which can proceed to coma and death.
Other possible symptoms include:
Muscle spasms or cramps.
Weakness and tiredness.
Nausea and vomiting may accompany any of the symptoms.
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