A clear warning sign of a seizure is when a person experiences violent convulsions, such as jerking and stiffening of the body. When this happens, the patient often is having a generalized seizure. Generalized seizures are typically caused by abnormal surge of activity in the whole brain, so the patient loses awareness quite quickly. However, not all seizures are obvious. For example, focal seizures, which occur in one part of the brain, can be difficult to diagnose because symptoms can be internal. If someone is having a focal seizure, symptoms can vary. A person could experience changes in feeling or sensation, such as numbness, tingling, feeling hot or cold, or a sudden change in emotions. They may suddenly feel intense fear, confusion, or a feeling that their memory is altered. Symptoms could also include changes in heart rate or a lack of normal body movement.