Blacking out after having a fall(Related to Hereditary Cerebellar Ataxia?)

Hi,
My father is 57 years old and suffers from Hereditary Cerebellar Ataxia.He cannot write anymore,has slurry speech and has problems maintaining his balance while walking.

Yesterday, it so happened that he fell down while climbing the stairs.Now,for the next 5 mins he was all right.But after that,he sort of blacked out.He fainted and was not in his senses.After about 10 seconds,he regained consciousness but his body was cold and he was sweating.After a while,he was normal.We got an ECG done,his BP checked but all reports turned out O.K.Similar thing had happened earlier on two prior occasions.Not sure why this keeps happening every time he falls or experiences some sort of anxiety/trauma.

Any help/opinion/insight on why this happens would be greatly appreciated.