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WEMINO (wall eyed monocular internuclear ophthalmoplegia) syndrome is a rare neurological impairment involving disconjugate ocular movements.1 Neuroradiological findings of the lesion responsible for WEMINO syndrome have not been reported to date. We report a case of the syndrome in which cerebral magnetic resonance imaging (MRI) clearly showed a tiny isolated lesion causing this impairment.
The patient was a 61 year old Japanese man who had been admitted to hospital for surgery for mitral regurgitation. He had a two year history of mitral incompetence, and mitral valve plasty was completed successfully on 21 September 2000. There were no postoperative problems.
On the afternoon of 27 September, one week after the operation, he suddenly experienced double vision, and was found to have left exotropia without blepharoptosis. On neurological examination, adduction of left eye was disturbed and it could not move beyond the midline of orbit, although full abduction was possible. Bilateral upward nystagmus was noted on forward gaze. Right ocular movement was not disturbed in any direction, but horizontal nystagmus appeared on rightward gaze. There was deficiency of left convergence. No ptosis occurred at any time. His pupils showed isocoria and responded promptly to light. Vertical ocular movement was not disturbed in either eye (fig 1A). Other neurological findings were completely normal. His ocular symptoms were summarised as comprising a left internuclear ophthalmoplegia with ipsilateral exotropia; these findings have been termed WEMINO syndrome.1
Cerebral computed tomography, undertaken immediately after onset, did not show any abnormalities.
We considered that he might have had a cerebral embolus caused by microthromboembolism following the heart surgery, but echocardiography did not show any obvious thrombus. We speculated that the responsible lesion was isolated in the area that included the medial longitudinal fasciculus because his impairments were limited to the ocular symptoms described above. He had been given warfarin potassium since 25 September, but the anticoagulant effect was insufficient on the day of symptom onset. Thus heparin sodium was begun intravenously in a dose of 10 000 units/day, and the dose of warfarin was gradually increased.
MRI performed 20 hours after onset showed a tiny isolated lesion at the left paramedian pontine tegmentum just adjacent to the fourth ventricle on both fluid attenuated inversion recovery (FLAIR) imaging and diffusion weighted MRI (fig 1B). This corresponds to the anatomical area of the medial longitudinal fasciculus. The tiny lesion showed high signal intensity on FLAIR imaging and diffusion weighted MRI, and low signal intensity on T1 weighted MRI. These MRI findings are typical of an acute lesion resulting from cerebral infarction. Other parts of the brain showed no abnormalities. Cerebral magnetic resonance angiography showed neither stenosis nor occlusion of any of the major vessels.
The ocular impairment began to improve by the third day after onset. On the seventh day, the left exotropia on forward gaze had disappeared, and the left internuclear ophthalmoplegia had begun to improve. By the 13th day, eye position and ocular movement were completely normal, and on the 14th day the high signal intensity on FLAIR MRI had diminished.
There are various syndromes that involve disconjugate ocular movement and eye position simultaneously. WEMINO syndrome consists of symptoms similar to internuclear ophthalmoplegia with ipsilateral exotropia.1 There are two other syndromes supposedly involving a combination of injury to the medial longitudinal fasciculus and exotropia; these are paralytic pontine exotropia (PPE),2,3 and non-paralytic pontine exotropia (NPPE).4,5 However, WEMINO syndrome can be discriminated from both PPE and NPPE, because the latter show exotropia on the side contralateral to the injured medial longitudinal fasciculus. There have been few reports describing WEMINO syndrome, and up to now no lesions in the central nervous system have been identified as a cause of the syndrome. Johnston and Sharpe reported that the neuropathological findings in one case of WEMINO syndrome were confined to a lesion of the pontine tegmentum, sparing the oculomotor nucleus.1 As the exotropia in our WEMINO patient disappeared within a short space of time, the symptom could be regarded as an acute phase phenomenon accompanying injury to the medial longitudinal fasciculus. Thus exotropia in patients with WEMINO syndrome might not be confirmed at an appropriate stage, as in PPE and NPPE patients.2,5
Cerebral MRI in our patient showed a tiny isolated lesion corresponding to the medial longitudinal fasciculus in the pontine tegmentum. This report is the first in which MRI has shown that WEMINO syndrome can arise from damage confined to the area of the medial longitudinal fasciculus.
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