A Case Report of WEBINO Syndrome with Convergence Impairment

A 73-year-old man suddenly presented with alternating exotropia, bilateral medial longitudinal fasciculus (MLF) syndrome, and impaired convergence. This symptom has been known as wall-eyed bilateral internuclear ophthalmoplegia (WEBINO syndrome). Diffusion-weighted images on magnetic resonance imaging showed a smalllocalized lesion in his pontine tegmentum. Based on he had some ischemic risk factors; he was diagnosed as having an ischemic stroke and started an antiplatelet therapy. His convergence impairment was improved, but abduction impairment of the right eye remained even 3 months later. The causing lesion of WEBINO syndrome has been reported to be either midbrain or pons mainly due to ischemic strokes or demyelinating diseases. In some cases, this syndrome was accompanied by convergence impairment; however, the pathophysiologic mechanism has not yet been elucidated. The neural circuit of vergence is discharges to the medial rectus subnucleus located in the abducens nerve nucleus. The mesencephalic reticular formation and nucleus reticularis tegmenti pontis (NRTP) are important regions in making signals of the supranuclear pathway, and NRTP impairment can induce the slow and fast vergence impairment. Thus, an involvement of near region of NRTP might be associated with WEBINO syndrome with convergence impairment.