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Show Unusual Monocular Pendular Nystagmus in Multiple Sclerosis Laurence Jasse, Alain Vighetto, MD, Sandra Vukusic, MD, PhD, Denis Pelisson, PhD, Caroline Tilikete, MD, PhD Abstract: Two unusual cases of monocular pendular nystagmus in patients with multiple sclerosis are re-ported. One patient showed regular horizontal oscillations of the right eye in abduction, associated with right ab-duction paresis. The second patient had a similar abnor-mal eye movement of the left eye in adduction, with partial left internuclear ophthalmoplegia. Such eye posi-tion- dependent monocular pendular nystagmus provides new insights into pathogenic mechanism for acquired pendular nystagmus. Different mechanisms are discussed such as the combination of paresis and commonly ac-cepted hypothesis of dysfunction of visual and/or motor feedback loops in the ocular motor neural network. Journal of Neuro-Ophthalmology 2011;31:38-41 doi: 10.1097/WNO.0b013e3181f8dc23 2011 by North American Neuro-Ophthalmology Society The most frequently reported eye movement disorders in multiple sclerosis (MS) are internuclear oph-thalmoplegia, isolated ocular motor palsy, gaze-evoked nystagmus, and pendular nystagmus (1). Pendular nystag-mus is characterized by quasi-sinusoidal oscillations of the eyes along a horizontal, vertical, or torsional direction. Pendular nystagmus in MS may be asymmetrical and in this case, most frequently of greater amplitude in the eye with poorer vision (2). Strictly, monocular forms of pendular nystagmus in MS have been reported, either associated with chronic visual deficit following optic neuropathy (2,3) or observed during convergence (4). We report 2 patients with MS with monocular horizontal pendular nystagmus, which was specifically triggered in eccentric gaze. CASE REPORTS Case 1 A 40-year-old woman was evaluated with a 5-year history of relapsing-remitting MS. The first manifestation of the de-myelinating disease was a right sixth nerve paresis, and since then, she complained of diplopia in right gaze. Due to recurrent episodes of left lower limb paresthesis, she was treated with azathioprine. She was referred to the neuro-ophthalmology unit for daily episodes of paroxysmal os-cillopsia in her right eye. Her expanded disability status scale (EDSS) score was 2 (minimal disability). Visual acuity was 20/20 in each eye, with no relative afferent pupillary defect and normal fundi. Automated perimetry, static contrast sensitivity values, and scores for the Farnsworth-Munsell D-15 Hue test and Ishi-hara color plates for each eye were normal. Visual evoked potentials were normal bilaterally. Ocular motor examination showed right esotropia with abduction paresis of the right eye. Horizontal pendular nystagmus of the right eye was observed during right gaze. The nystagmus persisted as long as the eccentric gaze was maintained and ceased when the patient directed her eyes to primary position or left gaze. Pendular nystagmus was dampened at near fixation, convergence, and with a 4-diopter base-out prism placed in front of the right eye. Gabapentin (up to 900 mg/d for 2 months), carbama-zepine (up to 600 mg/d for 2 months), or clonazepam (up to 1 mg/d for 2 months) yielded no benefit. Case 2 A 42-year-old woman with a 5-year history of relapsing-remitting MS was referred to the neuro-ophthalmology unit INSERM UMR-S 864, Espace et Action, Universite´ Lyon I (LJ, AV, DP, CT), BRON Cedex, France; Universite´ Lyon 1 (AV, CT), Hospices Civils de Lyon, hoˆpital neurologique, service de neurologie D et unite´ de neuro-ophtalmologie, BRON Cedex, France; and Universite´ Lyon 1 (SV), Hospices Civils de Lyon, hoˆpital neurologique, Service de Neurologie A, BRON Cedex, France. Supported by ‘‘Projet de Recherche Clinique des Hospices Civils de Lyon'' Grant n HCL/P/2006.432/25. Conflict of interest: None. Address correspondence to Laurence Jasse, INSERM UMR-S 864, Espace et Action, Universite´ Lyon I, 16 avenue du Doyen Le´pine, 69676 BRON Cedex, France; E-mail: laurence.jasse@inserm.fr 38 Jasse et al: J Neuro-Ophthalmol 2011; 31: 38-41 Original Contribution Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. for monocular oscillopsia. This occurred due to the de-velopment of pendular nystagmus in the left eye during adduction of that eye. There was no improvement following a course of systemic steroids. Two months later, the patient complained of decreased vision. Visual acuity was found to be 20/50 in each eye, and visual field testing disclosed centrocecal scotoma in the right eye and central scotoma in her left eye. Felt to have bilateral optic neuritis, a course of steroids was prescribed and interferon therapy was started. Her most recent EDSS score was 1 (no disability). Visual acuity was 20/25, right eye, and 20/32, left eye. Static central visual field (Metrovision , Pe´renchies, France) disclosed decreased macular threshold of the right eye and a mild global defect on the left. Static contrast sensitivity was subnormal for the left eye with 2 of the 6 tested spatial frequencies. Scores of Farnsworth-Munsell D-15 Hue test and Ishihara color plates test showed numerous errors for her left eye. Visual evoked potentials showed bilateral in-crease of latency with P100 value at 168 millisecond, right eye, and 176 millisecond, left eye. Ocular motor exami-nation disclosed bilateral horizontal gaze-evoked nystag-mus. In far right gaze, a monocular horizontal pendular nystagmus of her left adducting eye was observed, persisting as long as the adduction was maintained. Left adducting saccadic velocity was diminished, consistent with left in-ternuclear ophthalmoplegia. Eye Movement Recording Eye movements were recorded using infrared video-ocu-lography (monocular 25 Hz frequency or binocular 100 Hz frequency; Synapsys, Marseille, France). In both cases, the pendular nystagmus was observed only in eccentric gaze. For Case 1, this was in the abducting right eye (Fig. 1) and for Case 2, in the adducting left eye (Fig. 2). The amplitude of nystagmus was approximately 2 , and its frequency was 3-4 Hz. In Case 2, gaze-evoked nystagmus was recorded and convergence also elicited binocular horizontal pendular nystagmus, with a mean frequency of 3.5 Hz and a mean amplitude of 1 for both eyes (Fig. 2). Measurement of saccades disclosed slight hypometria and decreased velocity of abducting saccades performed by the right eye in Case 1 and of adducting saccades made by the left eye for Case 2 (Table 1). In Case 1, there was limitation of rightward saccades in the right eye consistent with abduction paresis. For Case 2, adducting saccades of the left eye showed decreased amplitude and velocity due to left internuclear ophthalmoplegia. Smooth pursuit, vesti-bulo- ocular reflex gain, and its inhibition by fixation (ocular fixation index) were subnormal for both patients. DISCUSSION We describe 2 patients with MS complaining of chronic monocular oscillopsia brought about by an unusual form of monocular pendular nystagmus. Both patients presented some clinical features consistent with the common forms of pendular nystagmus observed in MS in terms of frequency (4-5 Hz), small amplitude (5), and for Case 2, in association with optic neuropathy (2-4,6). It may also be seen in the setting of normal optic nerve function (7,8) as in our Case 1. Our 2 cases are unusual in that their monocular pendular nystagmus was observed only in eccentric horizontal gaze. While monocular nystagmus of the abducting eye is ob-served with internuclear ophthalmoplegia in MS, it is of jerk and not pendular form. Monocular adduction pendular nystagmus can be observed in MS but has only been re-ported with convergence (4). Explanations for pendular nystagmus in patients with MS involve abnormal delays in feedback loops that control eye stability. First, a role of a persistent delay of visual FIG. 1. Case 1. Horizontal eye position recording in primary and eccentric right gaze. A monocular pendular nystagmus of the abducting right eye is triggered in right gaze, beyond 10 of abduction. The nystagmus has a frequency of 4 Hz frequency and mean amplitude of 2 to 3 . Positive values: gaze right; negative values: gaze left. Jasse et al: J Neuro-Ophthalmol 2011; 31: 38-41 39 Original Contribution Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. FIG. 2. Case 2. Horizontal eye position recording in primary gaze, eccentric right gaze, and during convergence. A monocular pendular nystagmus of the adducting left eye occurs in right gaze, and a binocular pendular nystagmus is triggered with convergence. The nystagmus is of 3.5 Hz frequency and 2 mean amplitude. Binocular gaze-evoked nystagmus is also seen on right gaze. Positive values: gaze right; negative values: gaze left. 40 Jasse et al: J Neuro-Ophthalmol 2011; 31: 38-41 Original Contribution Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. feedback secondary to demyelination of the optic nerve has been proposed (2). This hypothesis is supported by the previous reports of large oscillations occurring in an eye having a severe optic neuropathy (2,4). This could explain the monocular nystagmus in our Case 2 but does not ac-count for the nystagmus being triggered by eccentric gaze. Moreover, this proposal has been challenged by experi-mental data in patients showing persistence of the nystag-mus in darkness (9), and in patients with MS, there is no change in the nystagmus even with prolongation in latency of visually guided eye movements (10). A second hypothesis involves a role of abnormal delay in the ocular motor feedback loops secondary to demyelination of central neurons. Instability in motor feedback could involve the ocular motor neural integrator, as suggested by transient suppression of the nystagmus following saccades (8). Our data did not allow us to evaluate the effect of saccades on pendular nystagmus. However, the theory of an unstable neural in-tegrator could lead to triggering of nystagmus with eccentric gaze. The onset of nystagmus during convergence, such as observed in our Case 2, also supports the concept of instability in motor feedback loops involving the vergence system (4). Finally, there may be a role for ocular motor paresis in precipitating monocular pendular nystagmus. In Case 1, demyelination involved the sixth nerve fascicle and in Case 2, the left medial longitudinal fasciculus. It is well known that peripheral motor paresis can trigger central adaptive changes (9). This consists of detecting visual errors due to ocular motor paresis and increasing the innervation to the paretic eye through central feedback loops (11). In our 2 patients, these adaptive changes took place in a neural network affected by demyelination, and instability in these feedback loops might have triggered monocular eye posi-tion- dependent pendular nystagmus. REFERENCES 1. Frohman EM, Frohman TC, Zee DS, McColl R, Galetta S. The neuro-ophthalmology of multiple sclerosis. Lancet Neurol. 2005;4:111-121. 2. Barton JJ, Cox TA. Acquired pendular nystagmus in multiple sclerosis: clinical observations and the role of optic neuropathy. J Neurol Neurosurg Psychiatry. 1993;56: 262-267. 3. Larmande P, Cassarini JF, Maillot F. [Monocular circumduction nystagmus. Are the central oculomotor pathways partly monocular?]. Rev Neurol (Paris). 1995; 151:338-340. 4. Barton JJ, Cox TA, Digre KB. Acquired convergence-evoked pendular nystagmus in multiple sclerosis. J Neuroophthalmol. 1999;19:34-38. 5. Leigh RJ. Clinical features and pathogenesis of acquired forms of nystagmus. Baillieres Clin Neurol. 1992;1: 393-416. 6. Strubel D, Eber AM, Monjour A, Rohmer F, Collard M. [Circumduction nystagmus. 4 cases (author's transl)]. Rev Otoneuroophtalmol. 1980;52:433-438. 7. Castaigne P, Chain F, Pierrot-Deseilligny C, Larmande P. [Monocular circumduction nystagmus (author's transl)]. Rev Neurol (Paris). 1979;135:51-57. 8. Das VE, Oruganti P, Kramer PD, Leigh RJ. Experimental tests of a neural-network model for ocular oscillations caused by disease of central myelin. Exp Brain Res. 2000; 133:189-197. 9. Leigh RJ, Zee DS. The neurology of eye movements. Contemporary neurology series 70. 4th edition. Oxford, United Kingdom: Oxford University Press, 2006:763. 10. Averbuch-Heller L, Zivotofsky AZ, Das VE, Discenna AO, Leigh RJ. Investigations of the pathogenesis of acquired pendular nystagmus. Brain. 1995;118(pt 2):369-378. 11. Optican LM, Zee DS, Chu FC. Adaptive response to ocular muscle weakness in human pursuit and saccadic eye movements. J Neurophysiol. 1985;54:110-122. TABLE 1. Summary of eye movement recording for our 2 patients Amplitude Case 1 Case 2 Normal Left Eye Right Eye Left Eye Right Eye Limits Right saccades Accuracy % (SD) 15 97.6 (7.2) 87.6 (7) 63.5 (6) 95.1 (9.4) 86-113 30 95.8 (3.7) 85 (3.7) 50 (5.1) 74.1 (9) 93-107 Velocity /s (SD) 15 369.2 (22) 327.6 (15.5) 204.8 (36.6) 331.5 (29) 310-490 30 471.5 (41.3) 431.7 (58.5) 220 (30) 389.5 (51) 380-610 Left saccades Accuracy % (SD) 15 96.1 (11.3) 97.5 (13.1) 86.3 (5.1) 91 (1.7) 86-113 30 94 (2.2) 99 (4.1) 78.6 (7.2) 81.3 (9.4) 93-107 Velocity /s (SD) 15 334.8 (51) 335.6 (63.5) 363.3 (16.1) 352.6 (6) 310-490 30 439.6 (35.9) 446.8 (41.5) 411.2 (22.9) 392.3 (31.5) 380-610 Smooth pursuit Left Right Left Right Horizontal gain 15 0.65 0.77 0.82 0.77 0.6-1.0 30 0.86 0.83 0.85 0.76 Down Up Down Up Vertical gain 20 0.56 0.46 0.63 0.63 VOR 0.25 Hz (gain) 0.35 0.40 0.2-0.8 OFI 0.25 Hz (gain) 0.12 0.12 ,0.10 OFI, ocular fixation index; VOR, vestibulo-ocular reflex. Jasse et al: J Neuro-Ophthalmol 2011; 31: 38-41 41 Original Contribution Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. |
