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Show ORIGINAL CONTRIBUTION Oscillopsia Without Nystagmus Caused by Head Titubation in a Patient with Multiple Sclerosis Frank A. Proudlock, PhD, Irene Gottlob, MD, and Cris S. Constantinescu, MD, PhD Oscillopsia in patients who have brain stem disorders but not nystagmus is attributed to a failure of the vestibular-ocular reflex ( VOR) to compensate for head movements. We report a patient who had marked head titubation and oscillopsia in aggressive multiple sclerosis but no nystagmus. Her severe head titubation precluded our ability to measure a VOR accurately. Because oscillopsia has also been described after rapid voluntary head oscillations in normal subjects, we queried whether the oscillopsia in our patient could be ascribed to the head movement alone. Six normal control subjects did not experience oscillopsia while shaking their heads at the same frequency as the patient's titubation. We conclude that the oscillopsia in our patient was probably the result of an impaired VOR or an alternative compensatory mechanism. ( JNeuro- Ophthalmol 2002; 22: 88- 91) n multiple sclerosis ( MS), acquired nystagmus, reflecting demyelination in the brainstem and cerebellum, may lead to disabling oscillopsia, an illusion of movement of the visual environment ( 1- 4). In fact, the term oscillopsia was first introduced in the literature by Brickner ( 5) in relation to multiple sclerosis. Head tremor is also a well- recognized feature of MS. It typically presents as titubation of the head and is caused by cerebellar and brainstem involvement with MS plaques. Although peripheral vestibular dysfunction frequently results in nystagmus and oscillopsia, head tremor alone does not necessarily result in oscillopsia, because the vestibulo- ocular reflex ( VOR) or other compensatory mechanisms stabilize the retinal images ( 6). Rarely, oscillopsia occurs in the absence of nystagmus when head tremor coexists with vestibular dysfunction ( 7,8). Oscillopsia with reduction of visual acuity ( jumbling) also occurs Leicester- Warwick Medical School, University of Leicester, Leicester Royal Infirmary, Department of Ophthalmology, Leicester, UK ( FAP, IG), and the Division of Neurology, School of Medical and Surgical Sciences, University of Nottingham, Queen's Medical Center, Nottingham, UK ( CSC). Address correspondence to Cris S. Constantinescu, MD, PhD, Division of Clinical Neurology, University Hospital, Queen's Medical Center, B Floor, Medical School Building, Nottingham NG7 2UH, UK This work was supported in part by the Ulverscroft Foundation. without nystagmus in the presence of high frequency and high amplitude head shaking, a phenomenon that can be seen in normal individuals ( 9). In MS, most patients who have brainstem and cerebellar involvement sufficiently severe to cause VOR abnormalities also have associated nystagmus, which is the typical cause of oscillopsia. We describe here a patient with MS who had significant head titubation and presented with disabling oscillopsia. There was no nystagmus on clinical examination or eye movement recordings. VOR could not be reliably measured because of the head tremor. We investigated whether oscillopsia would occur in normal subjects with the degree of head shaking shown by the patient. The normal subjects did not report oscillopsia. Therefore, oscillopsia in our patient was likely caused by the head tremor combined with a deficit in the VOR or other compensatory mechanism. METHODS Head and eye movement recordings of the patient and normal subjects were performed using a high- resolution infrared video pupil tracker ( EyeLink Eye Tracker; Senso- Motoric Instruments, Freiburg, Germany), which was used to sample OD and OS position at a rate of 250 Hz. The eye data were calibrated using a series of nine fixation points repeated until satisfactory values were achieved. The head position was derived from the same system using a series of four infrared markers placed around the screen, tracked with an infrared camera mounted on the forehead above the eyes. The quality of the head data was verified by pointing the head to a series of targets using a laser pen mounted on the head. Pupil and head tracking cameras were mounted on a head clamp. The whole system weighs less than 500 g and is balanced around the head horizontal rotational axis. The subject was instructed to look at a dot projected onto a screen every second. The stimulus was created by a VisualLab stimulus generator ( SensoMotoric Instruments) and projected onto a rear projection screen using a XGA video projector ( Hitachi CPX- 958). The subject sat in a chair 1.2 m from the screen. Eye tracker recordings were converted into Spike2 neurophysiological software ( Cambridge Electronic Design, UK). n 8 8 . DDI: 1O. 1O97/ O1. WNO1QQO, Q018224.83526„ 715. J . Neuro- Ophthalmol. Vol. 22, No. 2,. 2Q02 , Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction oftnis article is prohibited. PROUDLOCK ET AL. JNeuro- Ophthalmol, Vol. 22, No. 2, 2002 FIG. 1. Magnetic resonance imaging of the brain showing multiple T2 hyperintense lesions characteristic of multiple sclerosis in the ( A) hemispheric white matter, ( B) brainstem, and ( C) cerebellum. In addition, a triaxial accelerometer ( Model EGCS-A- 2, sensitivity 2378 mV/ g; Entran, Herts, UK) of 50 g weight was mounted on the head of the control subjects to confirm the measurements of the eye and head tracker system. A 12- bit analog to digital converter ( Model 1401 Micro; Cambridge Electronic Design, UK) was used to sample the head acceleration data at 1 kHz. The accelerometer was mounted independently from the eye and head tracker to test for artefacts resulting from slippage of the head clamp. To obtain recordings with the head immobilized for the patient with head tremor, the patient's head was firmly held manually by her husband. Head movements were recorded for normal control subjects who generated voluntary head oscillations at 4 to 5 Hz while reading the Moorfields bar reading book ( Clement Clark Ltd, London, UK). RESULTS Patient Our 41 - year- old patient was well until 9 years prior to our evaluation, when she developed the first symptoms of MS. These included paresthesiae in the hands and legs and ataxia. She subsequently had an aggressive course marked by relapsing neurologic events. The diagnosis of MS was confirmed by magnetic resonance imaging scan, which showed multiple hyperintense lesions in the periventricular white matter of both hemispheres, in the corpus callosum, and throughout the brainstem and cerebellum ( Fig. 1). The course of her MS became secondarily progressive, and she developed a spastic paraparesis, bilateral hand intention tremor, head titubation, and significant oscillopsia in the absence of nystagmus. On our initial evaluation, she reported decreased vision and oscillopsia, which she described as the illusion of seeing the environment oscillating. A 4 to 5 Hz head titubation was observed. Bilateral optic disc pallor was present. Examination of the eye movements with the head immobilized by the patient's husband failed to reveal significant nystagmus. Without head immobilization, she could not read the 6- meter visual acuity chart. With the head firmly immobilized manually by her husband, visual acuity improved to 6/ 36 in both eyes. Hearing was intact. The remainder of her neurologic examination was notable for appendicular and gait ataxia and a spastic paraparesis. Head movement recordings showed 4 to 5 Hz head tremor ( Fig. 2). When the head was immobilized, no nystagmus was seen. The patient reported no oscillopsia. Precise measurements of VOR gain were not possible due to technical difficulties with calibration caused by her head tremor. Also because of the head tremor, caloric testing was not practicable. Saccadic velocities were symmetrical between the two eyes and reasonably accurate ( Fig. 3). Treatment with gabapentin ( 4) in escalating doses up to 2700 mg daily moderately dampened the tremor and the oscillopsia, and her visual acuity increased to 6/ 60 without the head being stabilized. Control Subjects Six control subjects ( two men, four women, mean age 35 years, SD 13 years, range 23- 58 years) with no neurologic or ophthalmologic abnormalities ( other than corrected refraction in three subjects) were investigated for the occurrence of oscillopsia during voluntary head oscillations. The 89 Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited JNeuro- Ophthalmol, Vol. 22, No. 2, 2002 OSCILLOPSIA WITHOUT NYSTAGMUS CAUSED BY HEAD TITUBATION Head Free- Head Stabilized- Right Eye Position ( cleg) Left Eye Position ( cleg) 10 degrees FIG. 2. Simultaneous eye and head movement recordings show oscillations of the head ( clinically corresponding to tremor, titubation) with simultaneous oscillations of the eyes, which do not represent nystagmus. With the head stabilized manually, there is no evidence of nystagmus. Upward deflections of the recordings indicate movement to the right; downward deflections indicate movement to the left. mean and standard deviations of the voluntary head oscillations generated by the control subjects were 4.8 Hz and 0.43 Hz, respectively, similar to the mean frequency of the head titubation of the patient ( 4.5 Hz). The amplitude range was wide, with maximal values up to four times greater than that generated by the patient. The six normal subjects did not report oscillopsia. Five subjects could read page N5 of the Moorfields bar chart ( equal to visual acuity 6/ 5) during voluntary head shaking. In one control subject ( 3 diopter myopia in either eye), visual acuity decreased from N5 to N8 during high amplitude head movement ( exceeding the patient's tremor amplitude). DISCUSSION In normal subjects, head movement does not typically result in oscillopsia because an efficient VOR and possibly other compensatory mechanisms maintain visual fixation. Oscillopsia does develop in patients who have an impaired VOR in addition to head tremor ( 7,8). In our patient, as we presume in many patients with MS, the rapid titubation precluded our ability to accurately measure the VOR. Rapid, high amplitude head shaking may also lead to oscillopsia even in normal people ( 9). However, the control subjects in this study did not report oscillopsia at a degree of head shaking equivalent to our patient's. We are left with the presumption that in our patient, the oscillopsia and the resultant reduced visual acuity were caused by a deficit in the VOR or another compensatory mechanism that we could not measure. This case demonstrates that oscillopsia in MS can, in rare cases, be caused by head tremor in the absence of nystagmus. Fig. 3. Eye movement recordings show similar velocities and amplitudes of sac-cades of the OD and OS. Upward deflections of the recordings indicate movement to the right; downward deflections indicate movement to the left. Right Eye Velocity ( deg/ s) Left Eye Velocity ( deg/ s) Right Eye Position ( deg) Left Eye Position ( deg) Target Position ( deg) 20 degrees U „ 90 . „ „ . , „ . . © 2002 Lippincott Williams & WUkins , Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. PROUDLOCK ET AL. JNeuro- Ophthalmol, Vol. 22, No. 2, 2002 REFERENCES • McDonald WI, Barnes D. The ocular manifestations of multiple sclerosis, 1: abnormalities of the afferent visual system. J Neurol Neurosurg Psychiatry 1992; 55: 747- 52. 2. Barnes D, McDonald WI. The ocular manifestations of multiple sclerosis, 2: abnormalities of eye movements. J Neurol Neurosurg Psychiatry 1992; 55: 863- 8. 3. Aschoff JC, Conrad B, Kornhuber HH. Acquired pendular nystagmus with oscillopsia in multiple sclerosis: a sign of cerebellar nuclei disease. J Neurol Neurosurg Psychiatry 1974; 37: 570- 7. 4. Averbuch- Heller L. Acquired nystagmus. Curr Treat Options Neurol 1999; 1: 68- 73. 5. Brickner RM. Oscillopsia: new symptom commonly occurring in multiple sclerosis. Arch Neurol Psychiatr 1936; 36: 586- 9. 6. Cohen B. The vestibulo- ocular reflex arc. In Handbook of Sensory Physiology: The Vestibular System. Vol VI/ I. Berlin: Springer, 1974: 477- 540. 7. Bronstein AM, Gresty MA, Mossman SS. Pendular pseudonystag-mus arising as a combination of head tremor and vestibular failure. Neurology 1992; 42: 1527- 31. 8. Yen MT, Herdman SJ, Tusa RJ. Oscillopsia and pseudonystagmus in kidney transplant patients. Am J Ophthalmol 1999; 128: 768- 70. 9. Kamei T, Takahashi S. Meyer zumGottesberge's head- shaking test for the evaluation of jumbling. Acta Otolaryngol Suppl 1991 ; 481: 470- 3. Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. |