I believe your father will not have convulsion but it may be a tremor or shocking of hand or legs due to stiffness or spasticity. I suggest to visit a neuro physician and check what it is. Because for common man both looks same. Only one thing you can differentiate if along with this so called convulsion episode as per you he also have loss of consciousness. Then it can be convulsion or else it can be only a tremor. But in both cases you need to visit the neuro physician and have a check. And also keep checking his blood pressure regularly mainly daily in morning and if that is also fine then don t worry much. Just take a visit of doctor as well start doing some more physio therapy for further functional improvement. Take care