well let me start by noting that not all body shaking is caused by a seizure. seizures are caused by abnormal brain signals while other types of involuntary body movement such as tremors may be hereditary and of unknown origin. there also are different types of seizures. some of them involve mild to severe convulsions but some of them merely cause a person to sort of stare off into space for awhile as if they can't hear you. seizures rarely (dare i say "never") last up to 20 minutes. most seizures last just a few minutes maybe 3 to 5 minutes or so before they end. if you believe you've had a seizure you should see a doctor for further examination and assessment. it's important to do this because a seizure can be a symptom of another underlying health problem such as in infection. i hope this helps! it is because i am a survivor of one. i have epilepsy from several head injuries and in 2012 minutes after surgery for a lumbar laminectomy i had a documented +30 minute seizure which ended with having a 4 day stay in icu along with scaring a surgeon and a anesthesiologist. even with all the precautions a 6 hour stay ended up with a 4 day camping trip at one of my least favorite places. luckily i don't remember anything except for the usual aura headaches and tiredness after each seizure. what saved my life was communication asking questions and family and doctor support. meds i take: keppra and depakote.
what type of seizure last for about 16 to 20 minutes?