there are 45 sub-divisions of nystagmus , each divided into groups apparently - 'oscillatory' appears compatible with Judiths' suggestion of 'small swinging'

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Note added at 3 hrs (2009-09-04 23:05:15 GMT)
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..but there may be additional entries in the text that clarify the exact sub-division

The terms "fine" and "coarse" are used to describe the amplitude of ocular jerking movements in nystagmus, just at they are used to describe amplitude of tremor.

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Note added at 20 hrs (2009-09-05 15:36:56 GMT)
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From "Энциклопедический словарь медицинских терминов"; издательство "Советская энциклопедия", 1983, том II стр. 239: Н. МЕЛКОРАЗМАШИСТЫЙ - Н., отличающияся малой амплитудной колибаний глазных яблок; характерен для патологических процессов в лаборинте вутреннего уха.

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Note added at 20 hrs (2009-09-05 15:54:12 GMT)
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In the context of the complete phrase in which "мелкоразмашистый нистагм" is cited above, it appears to represent the variant of nystagmus seen in distubances involving the eighth cranial nerve, the vestibulocochlear nerve. The crux of the matter is what is implied by "мелкоразмашистый", which I believe emphasizes the amplitude of oscillatory movements. It is an adjective that can be applied in other contexts, such as a small-amplitude (fine, as opposed to coarse) tremor.

http://gradusnik.ru/rus/students/istbol/hnevrol/w-nevrol1

VIII пара - предверноулитковые нервы: острота слуха снижена, больше справа. Речь различает. Временами отмечает головокружения. Мелкоразмашистый горизонтальный нистагм справа.

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Note added at 1 day5 hrs (2009-09-06 00:55:39 GMT) Post-grading
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So, I would suggest this translation for the complete phrase:

Спонтанный, горизонтальный, мелкоразмашистый нистагм в обе стороны.

Spontaneous, horizontal, bidirectional, fine (small-amplitude) nystagmus

Note references in "Color Atlas of Neurology"; Reinhard Rohkamm, 2004; to "amplitude (fine, medium, coarse)" under a the description of the examination of a patient with nystagmus.

http://books.google.com/books?id=EK08J953yzgC&pg=PA88&lpg=PA...