Timothy C. Hain, MD Page last modified: December 15, 2016
Video of upbeating nystagmus due to Wernicke's encephalopathy.
Upbeating nystagmus describes an eye condition in which the eyes drift downward and make upward corrective movements (beats). Here we are mainly discussing upbeating nystagmus that occurs in persons who are sitting upright, and that have their eyes in the center (primary position).
For those who like to get to the meat quickly, there is usually not very much to learn from weak upbeating nystagmus, but strong upbeating nystagmus is usually caused by brainstem damage.
|Upbeating nystagmus is shown on the bottom panel of the figure to the left.|
UBN is uncommon. At Chicago Dizziness and Hearing, we have only 20 patients with UBN out of a total of about 15,000 "dizzy" patients. This suggests that UBN is uncommon, even when patients are observed with very sensitive methods. Of these 20 patients, 13/20 were women, and the average age was 46. Most of these patients were diagnosed with migraine.
Upbeat nystagmus is also found in smokers as a side effect of nicotine, in persons with alcohol intoxication (Fetter et al, 1999) and as a side effect of medications. For example, some of the SSRI type antidepressents seem to be associated with upbeating nystagmus. This is commonly seen with venlafaxine as well.
Migraine can, of course, cause nearly any nystagmus. This type of UBN is generally suppressed by fixation. These benign associations are far more common than serious brainstem disease.
Common causes of UBN, usually suppressed by fixation, and usually of no significance:
Uncommon causes of UBN, which may be visible with fixation
While cancer is a very rare cause of UBN, and we have encountered it once in the last 10 years. It should not be your first thought.
Upbeating Nystagmus in a patient with a renal mass. Recorded using an Micromedical Technology IR tracking system at Chicago Dizziness and Hearing. Image courtesy of Dr. Marcello Cherchi.
Strong primary position upbeat nystagmus has been described in lesions of the medulla, the ventral tegmentum, the anterior vermis of the cerebellum, and the adjacent brachium conjunctivum and midbrain. We have occasionally seen UBN in individuals with the Chiari malformation as well as in spinal cord lesions. These are rare occurences however.
UBN has been reported in association in specific disorders such as Wernicke's encephalopathy, multiple sclerosis, brainstem infarction and other lesions.
In the author's experience with a Wernicke's patient (only one of the 20 described above), the nystagmus has a peculiar increase on downgaze (one would expect the opposite). Presumably this would implicate the neural integrator which controls gaze holding.
Supplemental material Video of upbeating nystagmus due to Wernicke's encephalopathy.
While UBN is generally caused by midline lesions, cases have been reported in unilateral medial midbrain lesions. Hirose and others (1998) have proposed that in this instance, UBN may be caused by a lesion in the nucleus intercalatus of Staderini, one of the three subnuclei of the perihypoglossal nucleus (others include the nucleus of Roller, the nucleus prepositus hypoglossi which performs neural integration for the horizontal oculomotor system).
Ranalli and Sharpe (1988) suggested that some forms of UBN were explained by disruption of the ventral tegmental pathway for the upward VOR (vestibulo-ocular reflex), causing imbalance in the vertical VOR.
Upbeat nystagmus can be modulated by convergence, changing into downbeat, when it occurs congenitally as well as when associated with Wernicke's. This has been reported by Cox and others (1981).