What is a primary symptom of hyponatremia?

Hyponatremia, defined as a serum sodium level below 135 mEq/L, can have significant neurological effects due to the brain's sensitivity to changes in osmolarity. One of the primary symptoms associated with hyponatremia is seizures. This occurs because the low sodium levels can lead to cerebral edema, causing increased intracranial pressure and subsequent neurological dysfunction.

Seizures can arise in this context as the brain becomes increasingly irritated and unstable due to osmotic imbalances affecting neuronal excitability. Other symptoms may present as the condition worsens, such as confusion, lethargy, or decreased consciousness, but seizures represent a severe manifestation that indicates urgent medical attention is required.

In contrast, while severe headache, fatigue, and dehydration may be associated with various medical conditions, including those that result in changes in fluid balance, they are not as directly linked to the acute and serious implications of hyponatremia as seizures are. Seizures are particularly concerning in this context as they can indicate a critical state that requires immediate evaluation and management.