This is epilepsy: Atonic seizures, also known as drop seizures, cause a loss of muscle control. Since this most often affects the legs, it often causes you to suddenly collapse or fall down. Clonic seizures. These are associated with repeated or rhythmic, jerking muscle movements. When epilepsy is diagnosed in older adults, it's sometimes from another neurological issue, like a stroke or a brain tumor. Other causes can be related to genetic abnormalities, prior brain infection, prenatal injuries