SEP 23, 2016
Three main types of nystagmus are commonly seen in primary gaze with motion in the vertical direction. The first two are jerk nystagmus: upbeat nystagmus (UBN) and downbeat nystagmus (DBN). The third is acquired pendular nystagmus (APN). UBN consists of slow drifts of the eyes downward with corrective fast movements upwards. It is, by definition, present in primary gaze and is typically more prominent in upgaze. UBN is much less common than DBN and APN and is most typically seen in multiple sclerosis and Wernicke encephalopathy.
Paraneoplastic syndromes cause cancer-related, immunemediated, acute to subacute decline in nervous system function remote from a cancer site. They are most commonly associated with small-cell cancers such as lung cancer, but are also often seen with ovarian and breast carcinoma and testicular germ cell tumors. Typical paraneoplastic syndromes that involve vision include optic neuropathy, retinopathy, cerebellar degeneration with downbeat nystagmus, and opsoclonus. The cancer is often occult and undiagnosed at onset of visual or neurological symptoms, and exhaustive search for an underlying malignancy is critical.