Seizure is usually a sudden and involuntary contraction of a group of muscles. However, a seizure can also be as subtle as marching numbness of a part of body, a brief loss of memory, sparkling of flashes, sniffing an unpleasant odor, a strange epigastric sensation or a sensation of fear. Therefore, it is traditional to classify the seizures as motor, sensory, autonomic, emotional and cognitive.
Many seizures are due to unknown reasons.