Voluntary saccadic oscillations resembling opsoclonus (saccadomania)

Abstract

Saccadic oscillations are instabilities of visual fixation which may take several forms. These are generally involuntary in nature and often pathological with localising value as part of the neurological examination [1]. Saccadic oscillations are often categorised according to whether or not there is an intersaccadic interval, present in square wave jerks and macrosquare wave jerks but absent in ocular flutter and opsoclonus (saccadomania). Such movements may be a consequence of structural, inflammatory, or paraneoplastic disease affecting the brainstem and/or cerebellum, hence require investigation. Sometimes saccadic oscillations may be under voluntary control in the absence of brainstem or other pathology. For example, “voluntary nystagmus” describes brief (few seconds) bursts of high frequency (ca. 25Hz) low amplitude (ca. 1 degree) conjugate horizontal oscillations of back-to-back saccades, often induced by a vergence effort (i.e. these are saccades, not nystagmus, as there is no slow phase). Voluntary nystagmus, also known as voluntary flutter or psychogenic flutter, may in fact be a common, but easily overlooked, phenomenon [2,3]. In contrast, only occasional reports of voluntary saccadic oscillations resembling opsoclonus have appeared.