In a review of 27 cases of down-beat nystagmus, unsteadiness of gait and oscillopsia were common associated symptoms. Eight of the 27 patients were proved to have platybasia or the Arnold-Chiari malformation. The others had a variety of etiologic diagnoses, but most had suggestive lesions in the caudal end of the brain stem or upper cervical regions.
Cogan DG. Down-Beat Nystagmus. Arch Ophthalmol. 1968;80(6):757-768. doi:10.1001/archopht.1968.00980050759015