This a great question. You have several different types of ataxia and some of these have specific findings on oculomotor testing. Spinocerebellar Ataxia type 3, for instance, you have square wave jerks and deficient gain in the video head impulse test. However, in SCA 3 you will rarely have spontaneous or positional nystagmus. On the other hand, with SCA 6, you do have positional downbeat almost in all patients. Lastly, SCA type 1, 2 and 17 are characterised by having slow saccades. Each of these disorders demonstrate specific findings on ocular motor testing making a VNG exam important in the differential diagnosis.