Seizure Disorders & Status Epilepticus

Normal brain function depends on a running balance between excitation and inhibition: glutamate is the brain’s main excitatory neurotransmitter, GABA its main inhibitory one. A seizure happens when that balance tips toward excitation. Paroxysmal depolarization shifts trigger synchronous discharges of progressively larger groups of interconnected neurons — many neurons firing at the same time instead of independently — and that abnormal, excessive, synchronized discharge is the clinical seizure.

What the seizure looks like depends on which neurons get recruited: changes in level of consciousness, behavior, movement, memory, or sensation. Most seizures last 30 seconds to 2 minutes and do not cause lasting harm — the danger comes when the discharge does not stop, which is where status epilepticus begins.

The ILAE 2017 framework classifies seizures by onset. In a focal-onset seizure, one area of cortex activates first; activity may stay local or spread. Focal seizures are subdivided by awareness — focal aware (replacing the old “simple partial”) and focal impaired awareness (replacing “complex partial”) — and by motor versus nonmotor onset. A generalized-onset seizure involves diffuse activation of both hemispheres from the start; when onset can’t be determined, it is classified as unknown onset.

The two categories connect: a focal seizure can propagate across both hemispheres and become a focal to bilateral tonic-clonic seizure. That is why an aura matters so much diagnostically — an aura is itself the onset of a focal aware seizure, a sensory warning that is similar each time (déjà vu, a rising epigastric sensation, an offensive smell or abnormal taste, paresthesias, vision or hearing changes, sudden fear). A “generalized” convulsion that begins with an aura actually started focally.

The generalized-onset family produces the classic exam pictures: the tonic-clonic convulsion, the blank-stare absence episode, brief shock-like myoclonic jerks, and the sudden atonic “drop attack” — each detailed in the manifestations below.

Not every seizure means epilepsy. About 25–30% of new-onset seizures are provoked (acute symptomatic) — triggered by an identifiable acute insult such as hypoglycemia, hyponatremia, hypocalcemia, alcohol or benzodiazepine withdrawal, missed antiseizure-medication doses, fever and infection (including meningitis and encephalitis), hypoxic or traumatic brain injury, stroke, tumor, sleep deprivation, or drug toxicity. Fix the cause and the seizures stop — which is why the first-seizure workup hunts metabolic and toxic causes before anyone reaches for a maintenance drug.

Epilepsy is the tendency to seize without provocation: at least two unprovoked seizures more than 24 hours apart, per the ILAE — or, after a single unprovoked seizure, when the probability of further seizures over the next 10 years is at least 60%, similar to the recurrence risk after two. The numbers explain the definition: after one unprovoked seizure, recurrence within 5 years is between one-third and one-half; after a second or third, it rises to about three-quarters.

The scale is worth knowing: roughly 50 million people worldwide have epilepsy — one of the most common neurological diseases — and the cause is unknown in about half of cases globally. Up to 70% could become seizure-free with appropriate antiseizure medicines, yet the WHO notes the stigma is often harder to overcome than the seizures themselves. In children 6 months to 5 years, febrile seizures are their own category: a simple febrile seizure (single, generalized, ≤ 15 minutes) is benign, does not cause long-term neurological problems, and carries only a 1–2% risk of later epilepsy.

Status epilepticus is ≥ 5 minutes of continuous seizure activity, or recurrent seizures without recovery of consciousness between them. The ILAE 2015 Task Force frames it with two operational time points for convulsive seizures: t1 = 5 minutes, the point at which a seizure is unlikely to stop on its own — start treatment; and t2 = 30 minutes, the point past which there is compelling evidence of long-term consequences — neuronal death, neuronal injury, and alteration of neuronal networks. In vitro models show permanent neurological damage can begin after about 30 minutes of status epilepticus.

Status becomes self-sustaining at the receptor level. With ongoing seizure activity, synaptic GABA-A receptors are internalized (endocytosed), so there are fewer of them at the synapse and the response to GABAergic drugs falls — while glutamate receptors are upregulated, tipping the brain further toward a proconvulsant state. Clinically, “seizures beget seizures”: the longer it runs, the harder it is to stop, and underdosed or delayed benzodiazepines increase refractoriness. That is the entire logic of the treatment timeline — hit hard and early, because the drug target is disappearing.

The convulsing patient is also failing systemically: ongoing convulsion threatens hypoxia, aspiration, cardiovascular collapse, and metabolic derangement. And not all status convulses — nonconvulsive status epilepticus is impaired mental status with absent or subtle motor signs and seizure activity on EEG. Suspect it in unexplained persistent altered consciousness; EEG is required to diagnose it. The stakes are real: first-episode generalized convulsive status carries roughly 16–20% mortality, rising to roughly 40% or higher in refractory status.