Seizures in cats can be generalised, with loss of consciousness and strong movements, but they can also be more subtle and affect only part of the body or the cat's behaviour. After a seizure the cat may be disorientated, hungry, restless or unusually tired.
The vet first tries to establish whether the episode really was an epileptic seizure and then whether the cause is structural, reactive or without an identifiable underlying disease. Blood tests are often part of the first investigation, and depending on age and findings, more advanced neurological diagnostics may be considered.
Make the surroundings safe and leave your cat alone during the seizure. Do not try to open its mouth or hold its body. Time it, and film it if you can do so safely. Seek emergency care if the seizure goes on for a long time, if several seizures come close together or if your cat does not recover normally between episodes.