“Pinball” intrusions in spinocerebellar ataxia type 3

Saccadic intrusions are involuntary saccades that interrupt fixation and are usually conjugate between eyes.1 Although saccadic intrusions may be seen in healthy individuals, they also accompany certain neurologic disorders (usually manifesting higher frequency or amplitude) including cerebellar disease.2 We present a patient with spinocerebellar ataxia type 3 (SCA3) with an uncommon monocular/disconjugate alternating type of saccadic intrusion.