1. Upbeat nystagmus-nystagmus in which the fast component is upward and usually most marked when the gaze is directed upward; usually due to a lesion in the posterior fossa
A. Brainstem lesion, such as that of the vestibular nuclei
B. Cerebellar disease-acute or chronic, especially in the vermis
C. Cerebellar degeneration
D. Drugs-barbiturates and Dilantin (phenytoin)
F. Labyrinth disease-rare; has no lateralizing value
G. Multiple sclerosis
2. Downbeat nystagmus-nystagmus in which the fast component is downward and usually most marked when the gaze is directed downward; probably due to a lesion in the lower end of the brain stem or cerebellum
A. Alcoholic cerebellar disease
B. Aneurysm of the supraclinoid part of left carotid siphon
medulla through foramen magnum
D. Cerebellar atrophy/degeneration
F. Deformities of cervical spine
G. Diabetes mellitus
I. Ependymoma of posterior part of the fourth ventricle
K. Insufficiency of basilar artery
L. Klippel-Feil anomaly-upward displacement of odontoid process into foramen magnum
M. Meningioma extending into pontine cistern
N. Morphine poisoning
O. Multiple sclerosis (disseminated sclerosis)
P. Neurogenic muscular atrophy
Q. Platybasia (cerebellomedullary malformation syndrome)
Burde RM, Henkind P. Downbeat nystagmus. Surv Ophthalmol 1981; 25:263.
Chrousos GA. Downbeat nystagmus and oscillopsia associated with carbamazepine. Am J Ophthalmol 1957; 103: 221-224.
Holmes GL, et al. Primary position upbeat nystagmus following meningitis. Ann Ophthalmol 1981; 13:935.
Monteiro ML, Sampaio CM. Lithium-induced downbeat nystagmus in a patient with Arnold-Chiari malformation. Am J Ophthal 1993; 116:648-649.