If your seizures could cause you to fall off a horse, you may be able to ride, but should be closely supervised by someone walking alongside the horse. You should always wear a riding hat. It would be a good idea to discuss horse riding with your own doctor if you have uncontrolled seizures.
Some riding schools offer specialised riding saddles with a stay safe harness which attaches you to the horse to prevent falls, these saddles are usually used for individuals with disabilities such as cerebral palsey, however, upon request these saddles are usually made available to those with epilepsy at times when not in prior use, and we would recommend phoning ahead to pre-book your usage of it if you require it.
Always ensure your riding instructor is aware of your epilepsy, and seizure type/s so that they may make extra arrangements if necessary such as providing a 1-2-1 tutor, supervisor, or first aider to walk alongside your horse. This is for your safety!