Spontaneous veical nystagmus is seen in the lesion of

Veical downbeat nystagmus indicates lesion at craniocervical region such as Arnold-Chiari malformation or degenerative lesion of the cerebellum. Veical upbeat nystagmus is seen in lesions at the junction of pons and medulla or pons and midbrain. Ref: Dhingra 7e pg 43.