[A study of eight patients with non-paralytic pontine exotropia]

We reported 8 patients with non-paralytic pontine exotropia (NPPE): 7 men and 1 woman aged from 56 to 79 years (mean: 67.8 years). From 1991 to 1994, 402 patients with acute infratentrial cerebrovascular diseases other than subarachnoid hemorrhage were admitted to our hospital within 7 days after the ouset of their stroke. NPPE was observed in 2% of these patients. NPPE was noted on admission in 6 of them, while it developed during the hospital stay in 2 others with paralytic pontine exotropia and bilateral median longitudinal fasciculus (MLF) syndrome, respectively. Abnormal convergence and alternating exotropia were noted in 6 and 2 patients respectively. The duration of NPPE was 0.5 to 4 days (mean; 2 days), and the ocular movement disorder was transient in all patients. When MRI was performed to detect the causative lesion, a small infarct was found in the upper, middle, and lower pons in 1, 3, and 4 patients, respectively. NPPE is generally considered to develop when the MLF and the paramedian pontine reticular formation (PPRF) are completely and incompletely destroyed respectively. In the present study, however, the pathophysiological features of the NPPE patients with alternating exotropia could not be explained by this mechanism, and severe MLF damage was considered to be a contributory factor.