Mutated Na+ channels result in the development of epilepsy. This makes it easier for these channels to open, increasing their excitability, allowing the epileptiform activity to occur.
Head injuries and brain tumours are also able to lead to a tendency to have seizures and epileptiform brain activity. This is due to the pressure experienced by the brain tissue.
Ion channels are the main causing agent however, due to their involvement in the formation of action potentials. They are, therefore, the main target of antiepileptic drugs.