Objective
To describe a second type of the one-and-a-half syndrome in which adduction rather than abduction of one eye is the preserved horizontal movement.
Design and Patient Setting
A patient experiencing mucormycosis of the cavernous sinus suffered a sixth-nerve palsy and simultaneous carotid artery occlusion with infarction and a contralateral horizontal gaze palsy.
Results
The patient experienced an eye movement syndrome with complete paralysis of horizontal eye movement in the ipsilateral eye and paralysis of horizontal eye movement in one direction, in this case abduction due to the gaze palsy, in the contralateral eye. Adduction of the contralateral eye was the only remaining horizontal eye movement.
Conclusion
A lesion in the cavernous sinus producing occlusion of the internal carotid artery and a sixth-nerve palsy may produce a second type of one-and-a-half syndrome. Adduction rather than abduction of one eye is the preserved horizontal eye movement. This combination of eye movement deficits is unlikely to be produced by a lesion in any other location. Mucormycosis, with its propensity to produce vascular occlusion, is a likely, although not specific, cause.
