[GordonS]

AFAIK, when it's mild your brain is not actually starved of glucose at all, and hypoglycemic symptoms (e.g. brain fog) are caused by your endocrine system changing hormone levels (such as cortisol) to "signal" your body that it needs glucose to increase blood sugar levels. If it gets severe enough, then the brain can run out of glucose and the person can die - but AFAIK the body prioritises the brain for fuel above all else, so it really is the last thing to go.

[garganzol]

Glucose can be present in blood but the brain can be still unable to consume it due to diabetes (insulin absence) or some form of a mitochondrial disease (inability to transfer glucose to ATP via oxidation).

In both cases this is a panic situation from brain's point of view which is compensated by a spontaneous "stop" (seizure as OP seems to call it) and by injecting adrenaline with a corresponding response from endocrinal system (more glucose + more insulin).

[wittyreference]

Neuronal glucose uptake is via transporter GLUT1, which is insulin independent. Insulin-dependent glucose uptake is primarily GLUT4. Even in insulin absence, the brain gets its sugar.