Here's a video showing what a tonic seizure (not a tonic clonic seizure) might be like. During a tonic seizure a person's muscles will suddenly become stiff. If they are standing up they will usually fall, often backwards and could potentially injure the back of their head. Tonic seizures are generally very brief and will happen without any warning. For more information on tonic seizures read Ben O'Keefe's blog http://bit.ly/1O5v4Yr | Epilepsy Society