Diabetes is a chronic condition in which insulin, the hormone that modulates the metabolism of sugar in the body, is either completely absent or ineffective in its function. Patients with diabetes usually present with abnormally high levels of glucose, or sugar, in their blood stream. With treatment, sugar levels are normalized, but can sometimes drop too low. Both high and low blood sugar can cause seizures in diabetic patients.
Hyperglycemia is the condition in which blood sugar is at abnormally high levels. High blood sugar leads to hyper-excitability of the neurons that make up the central nervous system, including the brain. Neurons need a normal level of glucose, their main source of energy, to function correctly. With the brain's overexcited imbalance, hyperglycemic seizures can be be triggered. In other words, too much sugar makes the neurons work too much, predisposing them to “short circuit,” causing a seizure.
Low blood sugar can also lead to seizures. Hypoglycemic seizures are actually more common than hyperglycemic seizures. The reason seems to be related to the fact the brain depends completely on body’s sugar to work, since it doesn’t produce its own glucose. It is difficult to predict at what level of glucose a patient will have a seizure, as patients with chronic high levels of glucose may have seizures at a higher level than does who have normal blood sugar. Low blood sugar reduces the activity of neurons in the brain. In the absence of this regulated function, the neurons respond by reducing the activity across synapses, the microscopic spaces in between neurons that propagate the brain’s activities and preserve bodily function. This in turn leads to a seizure.
Other electrolyte imbalances
Poorly controlled diabetes can also result in poorly controlled levels of other electrolytes, which can then trigger seizures. For example high serum sodium, or hypernatremia, can cause seizures. This happens because water follows sodium around the body. If the blood has too much sodium, water will try to leave the brain, which usually preserves its quantity of sodium by its own protective mechanisms. The brain responds by increasing its concentration of sodium-like substances to prevent too much water going out. If the blood’s sodium concentration is corrected too quickly, the brain won’t have time to re-adapt to the new state, and water will flood it, resulting in a condition called cerebral edema, which can then lead to seizures.