[4 cases of one and a half syndrome' observed following surgery of primary pontine hemmorhage].

In 1967, Fisher named the "one and a half syndrome" for a particular ocular movement which is observed in the lesion of pontine tegmentum, when horizontal movement of one eye is totally disabled and the abducence of another eye is only preserved associating mono-ocular nystagmus in the same eye. Vertical movement and convergence are preserved. We experienced this syndrome in four cases of small localized hematoma of the pontine tegmentum which were all removed under operative microscope. All patients are alive more than 10 months under consciousness and with improved neurological sign. Three of them were probably due to hypertensive hemorrhage and the rest was due to arterio-venous malformation of the pontine tegmentum. Three of them showed this syndrome before operation and observed even after operation. One patient was operated on one and a half hours after the apoplectic attack under semicomatous condition and he improved with this syndrome postoperatively. In most previous reports, this syndrome was noted in severe cases of pontine hematoma or basilar artery thrombosis and they expired soon thereafter. All our cases survived in satisfactory condition and ocular movement could be followed up for a long time. The mechanism of this syndrome was also discussed.