Is it possible to have a spontaneous nystagmus without a unilateral weakness?
Absolutely. Spontaneous nystagmus can result from an abnormality of either the peripheral system and/or the central system. I will assume that you are familiar with how spontaneous nystagmus is generated by a peripheral vestibular imbalance. In cases of some central disorders the abnormality may cause an imbalance of canal connection causing a spontaneous nystagmus. The central disorder can also increase or decrease the VOR gain or alter the VOR time constant, again resulting in spontaneous nystagmus. The hallmark of spontaneous nystagmus resulting from a peripheral abnormality is that the nystagmus is suppressed with vision. In central cases, the spontaneous nystagmus is unaffected by vision. Henry P. Trahan, Au.D., is Assistant Professor of Audiology at the Arizona School of Health Sciences.
