I read your question carefully and I am sorry about the you sister in law's troubles.
Seizures are not usually related to back issues. They can have many diverse causes like infections, stroke, brain tumor, metabolic alterations of blood and tissue components (electrolytes) etc. So many exams are often needed to find the cause the cause like head CT or MRI, EEG, blood tests,
cerebrospinal fluid tests and according to their results the cause is treated.
Of course seizure treatment can be started rightaway without waiting for the results of all the tests, there are many drugs available (
valproic acid,
carbamazepine,
levetiracetam, phenytoin, etc) which I am sure the
neurologist knows, but while they're important to control the current situation, to make a prediction about what to expect in the future depends on what the cause is which must be evaluated with the above mentioned tests.
Hope things work out for the best. Don't hesitate to come back for further questions.