[A case of bilateral horizontal gaze ophthalmoplegia: The 1+1 syndrome].

Introduction: Oculomotor deficiencies in multiple sclerosis (MS) are frequently characterized by internuclear ophthalmpoplegia or isolated abduction or adduction palsies. Complete unilateral conjugate gaze paralysis and the "one and a half" syndrome are rare. Complete bilateral horizontal gaze paralysis has been exceptionally reported.
Observation: Here, we describe an unusual oculomotor paralysis as a suspected first event of MS. A 24-year-old woman with an uneventful medical history presented for sudden onset of binocular diplopia. On examination, abduction and adduction saccades were impossible, whereas vertical eye saccades and convergence were normal. Oculocephalic reflex failed to improve horizontal eye movement. No nystagmus and no other sign of brainstem dysfunction were observed. Visual acuity was 4/10 in the right eye and 6/10 in the left eye. A sign of Marcus Gunn was noted in the right eye. Blood samples and cerebrospinal fluid were normal, no oligoclonal bands were detected. Visual evoked potentials were significantly impaired in both eyes and argued for bilateral optic neuritis. Brain MRI scans showed white matter T2-hypersignal abnormalities, which fulfill Barkhof criteria for MS. A small symmetric lesion was noted in the posterior part of the medial pontine tegmentum. As a first episode of MS was suspected, treatment with methylprednisolone 1000 mg/d for 3 days was started, and was followed by complete recovery of eye movements and visual acuity after 3 weeks.
Discussion: To our knowledge, only two cases of complete horizontal bilateral ophthalmoplegia have been reported in the literature. Both were associated with peripheral facial nerve palsy as a first event in MS. In our case report, we describe for the first time a complete bilateral horizontal ophthalmoplegia with no other brainstem dysfunction. By analogy with the "one and a half" syndrome, such complete horizontal gaze paralysis could be named a "one and one" syndrome and seems to be specifically related to a first event of MS.
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