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M. L. Rosenberg; The Clinical Spectrum of Involuntary Horizontal "End-on-End" Saccades. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2829.
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Voluntary nystagmus is a well known entity most commonly encountered in the setting of a patient seeking secondary gain. At times however voluntary nystagmus can be indistinguishable from ocular flutter either by clinical exam or by eye movement recordings. The situation can be made more complex as there are patients reported who admit to spells of voluntary nystagmus but also note episodes that are said not to be under their control. To try and better understand this condition patients with end on end saccades from any condition were collected retrospectively from cases seen by the author.
Patient records available for computer searching were evaluated for cases noted on clinical examination to have end on end saccades. Other clinical findings, the final diagnosis and radiological findings were gathered from the clinical and the hospital records. Patients who admitted to voluntary nystagmus or who had evidence of secondary gain or other psychological difficulties were excluded. Patients with micro-flutter were also not included in this study. 66 patients were included in this study.
Of the 66 patients 13 were found to have involuntary flutter-like movements on exam but were diagnosed as being normal. 48 were found to have a specific neurological disagnosis while 5 had neurological problems of unclear etiology. The most common diagnosis was multiple sclerosis. The abnormal saccades were noted at times to be induced by convergence (26), saccades (6), or pursuit movements (6), while at other times were spontaneous (46).
Not all patients with what appears to be ocular flutter have an underlying neurological problem, although most do. Similarly not all those with what appears to be voluntary nystagmus are free of underlying neurological disease. All patients with spontaneous flutter or flutter induced by pursuits or saccades, who did not have similar movements inducible by convergence, had neurological disease. All subjects with flutter-like movements induced by saccades were also found to have underlying neurological disease. Ocular flutter, with or without an association with convergence, was rarely the only sign on initial exam of neurological disease. Although clinically difficult at times, it is critically important to distinguish voluntary nystagmus from ocular flutter. Although psychological disorders are not always clinically obvious, the absence of a clear secondary gain should be an important clue to look for a possible organic process.
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