 Brun's nystagmus are localizing the stagmus. What we'll observe is that the patient will gaze to the right and we'll see fast frequency, low amplitude nystagmus beating in the direction of gaze. These are peripheral vestibular nystagmus. In left gaze, what we see are slower frequency, higher amplitude nystagmus, again beating in the direction of gaze. These are gaze parietic nystagmus. This combination of vestibular nystagmus to one side and gaze parietic nystagmus to the other side characterize Brun's nystagmus. When seen, they should suggest an extrinsic lesion in the cerebellum-pontine angle.