Which statement correctly describes the relationship between electrolyte levels and seizure threshold?

• A. Low potassium and low magnesium lower seizure threshold
• B. High potassium lowers seizure threshold
• C. Sodium is the only important electrolyte for seizures
• D. Magnesium has no effect on seizures

Answer: (A)

Electrolyte balance directly affects how easily brain cells fire. Magnesium acts as a protective brake on neurons by blocking NMDA receptors; when magnesium is low, this blockade is lifted, NMDA channels become more active, calcium enters more freely, and neurons become more excitable, lowering the seizure threshold. Potassium helps set the resting membrane potential: high extracellular potassium depolarizes neurons, making them easier to excite and more prone to seizures. While the strongest, most consistent link is magnesium deficiency lowering the threshold, disturbances in electrolyte levels in general can tilt the balance toward seizures. So recognizing that low magnesium lowers seizure threshold, and that electrolyte abnormalities can increase neuronal excitability, fits best with the idea that electrolyte changes contribute to seizure risk.