What are the signs and symptoms of one-and-a-half syndrome in vertebrobasilar stroke?

Updated: Aug 09, 2021
  • Author: Vladimir Kaye, MD; Chief Editor: Stephen Kishner, MD, MHA  more...
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This syndrome is caused by a lesion affecting the PPRF and MLF simultaneously, resulting in ipsilateral conjugate gaze palsy and INO [17] A patient with this syndrome is completely unable to move the ipsilateral eye, and is able only to abduct the contralateral eye, with resulting nystagmus; the ‘one’ in the syndrome name refers to the former, and the ‘half’ to the latter.

The patient with a lesion in the ipsilateral PPRF or abducens nucleus and MLF connecting to the contralateral CN VI exhibits horizontal gaze palsy when looking toward the side of the lesion and exhibits INO when looking away from the side of the lesion. Associated features may include vertical nystagmus, exotropia of the contralateral eye, and skew deviation. Vertical gaze and convergence generally are preserved.

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