Upbeat nystagmus recorded in center gaze position from a subject with vestibular migraine during an episode of acute vertigo.
(vv)BaranyUpbeatnystagmus.mp4(tt)
From: Committee for the International Classification of Vestibular Disorders of the Barany Society.2.1.2.2.2.Upbeat Nystagmus. Retrieved from http://www.jvr-web.org/images/2.1.2.2.2.-Upbeat-nystagmus.m4v
Upbeat nystagmus (UBN) is jerk nystagmus induced by slow downward drifts of the eyes followed by resetting upward fast phases. In keeping with Alexander's law, nystagmus amplitude and frequency often increase with upgaze2.
UBN is rarer than DBN and is also a fixation nystagmus, which occurs in primary position.
UBN is usually increased by convergence or lateral gaze. Convergence may change an upbeat nystagmus to a downbeat nystagmus (eg, in Wernicke’s encephalopathy3).
UBN may not follow Alexander's law, but may instead increase in downgaze and have linear-, increasing-, or decreasing-velocity waveforms. Like downbeat nystagmus, it may be influenced by head position but generally not by visual fixation3.
Unlike downbeat, UBN does not normally increase in lateral gaze.
Pathogenesis
Vertical and often upbeat nystagmus from the medulla are due to involvement of the inferior part of the 4th ventricle, including the inferior cerebellum (flocculus, tonsil, nodulus and uvula) and the medulla4, in which case, there is involvement of the perihypoglossal nuclei, paramedian tract cell groups, or selective disruption of ascending vestibular pathways for upward (versus downward) eye movements. The gaze-evoked and upbeat nystagmus of Wernicke’s encephalopathy suggest involvement of the NPH–MVN complex.
Causes
In most cases, paramedian lesions in the medulla oblongata or the midbrain (pontomesencephalic junction, close to the superior cerebellar peduncles5) are found, for example, in patients with multiple sclerosis, brainstem ischemia or tumors, or Wernicke’s encephalopathy.
UBN may also be seen with paraneoplastic syndromes, associated with anti-Ma2 antibodies.
(vv)POSTFM.mp4(tt)
From: Kronenbuerger M, Olivi A, Zee DS. Pearls & Oysters: Positional vertigo and vertical nystagmus in medulloblastoma: A picture is worth a thousand words. Neurology. 2018;90(4):e352-e354. doi:10.1212/WNL.0000000000004866
Patient had medullary lesion likely affecting the nucleus propositus hypoglossi (NPH) and medial vestibular nuclei with damage to the velocity storage mechanism of the vestibular system.
(vv)UBNWray.mp4(tt)
From: Wray S. Upbeat Nystagmus. Neuro-Ophthalmology Virtual Education Library.
Retrieved from: https://collections.lib.utah.edu/ark:/87278/s6kd4vg2