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A. A. Kumar, C. S. Constantinescu, F. A. Proudlock, M. G. Thomas, R. J. McLean, I. Gottlob; Analysis of Eye Movement Recordings in Multiple Sclerosis. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2542.
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There are few studies investigating nystagmus in patients with multiple sclerosis (MS) using eye movement recordings. Our aim was to characterise nystagmus in multiple sclerosis using eye movement recordings, including the various nystagmus-like oculomotor abnormalities. We also analysed the extent of oculomotor abnormality in relation to disease severity (EDSS score) and MS type (relapsing-remitting, secondary-progressive and primary progressive).
Eye movements were recorded (EyeLink, 250Hz) in 50 subjects diagnosed to have MS and referred to specialist neuro-ophthalmological clinic for management of nystagmus. Amplitude and frequency of pendular nystagmus was measured in primary position and 15° to the right and left, and classified as either dysconjugate or conjugate. Other abnormalities recorded included gaze evoked nystagmus (GEN), monocular abducting nystagmus secondary to INO, square wave jerks (SWJ) and oscillations. EDDS were scored by the Neurologist and the initial EDDS score on referral was recorded.
Pendular nystagmus was observed 66.7% of patients with a mean amplitude and frequency (±SD) of 1.57° (±1.48°) and 4.06Hz (±1.14Hz), respectively. 94% of pendular nystagmus was dysconjugate mainly due to a difference in amplitude between the two eyes (absolute mean difference 37.0% ±35.0%) rather than frequency (absolute mean difference 3.6% ±6.8%). There was no clear change in pendular nystagmus amplitude or frequency with MS severity or type (p>0.05). Most patients showed a coexistence of a number of oculomotor deficits including pendular nystagmus, GEN, INO and SWJ although the occurrence of these was not related to MS severity or type (p>0.05). The combination of some types of oculomotor deficits mimicked other nystagmus forms, e.g. INO with SWJ resembled clinically horizontal jerk nystagmus. EDDS score (mean 5.5) did not correlate to the number of oculomotor abnormalities.
The pendular nystagmus seen in patients with MS was mainly dysconjugate and the dysconjugacy related to the amplitude and not the frequency of nystagmus. The (co)existence of various other oculomotor abnormalities is observed in most MS patients although their presence is not related to the MS severity or stage. Eye movement recordings can assist in differentiating various oculomotor abnormalities which is difficult to characterise on clinical examination and to plan the pharmacological treatment according to the abnormality seen.
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