The more severe the injury, the more likely are seizures to happen. The longer coma lasts, the more severe is the injury and the greater the risk of seizures. The seizures can occur weeks or months or even years after the injury and can be few, or many and permanent. Such seizures are often associated just with the electric currents of injury and are temporary - they usually do not recurr. Early seizures can result in later epilepsy, though this is not frequent.
Similar findings hold good with seizures after stroke.
Early seizures do not also mean late seizures in most patients. Infections of the brain. In the so-called underdeveloped lands the commonest causes of epilepsy are brain injury or parasites such as cysticercosis, hydatid disease among many others. Any major disturbance of the chemistry of the body can result in seizures. Some chemical imbalances also affect other drugs which the patient may be taking causing additional problems.