- Blood brain barrier is impermeable to sodium
- Astrocytes express aquaporins to maintain water balance
- TRPV1 receptors in hypothalamus detect tonicity changes in blood
- Osmolytes are up- or downregulated depending on tonicity
CNS Symptoms of Hyponatremia
| Time to Hyponatremia | Condition or Behavior Contributing | Symptoms |
| Hours | Psychogenic polydipsia | Headache, vomiting, seizures, increased intracranial pressure |
| 1-2 days | Post-operative SIADH, CSW | |
| >2 days | Alcoholism, cirrhosis, malnutrition, others | Malaise, fatigue, cramps, falls, seizures when Na+ < 110 mEq/L |
Central Pontine Myelinolysis
- Pons most susceptible region of brain
Pons Cranial Nerves
- Pons contains neurons for CN V, VI, VII, and VIII
