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Seen here are two patients with alternating hypertropias. The first is a 70-year-old woman with a diagnosis of cerebellar ataxia, neuropathy, vestibular areflexia syndrome (CANVAS). In the video, both spontaneous downbeat nystagmus (DBN) and gaze-evoked nystagmus (GEN) are apparent, in addition to a right hypertropia in right gaze and a left hypertropia in left gaze, also referred to as an alternating skew deviation or an abducting hypertropia. The combination of these three findings (DBN, GEN, alternating skew) is highly suggestive of cerebellar flocculus/paraflocculus disease.1 ; The second patient is a 40-year-old woman who also has an alternating hypertropia, although in her case this is an adducting hypertropia due to bilateral 4th nerve palsies. In her case, there is a right hypertropia in left gaze and a left hypertropia in right gaze.
