Introduction:

The aim of the study was to investigate the clinical characteristics of isolated oculomotor paralysis (OP) cases caused by pure midbrain infarction (MI) with pupil sparing.

Material and methods:

Patients with pure MI and pontine infarction (PI) at our hospital were included in this study. We compared the blood pressure and lipid levels between the two groups. And the clinical data and imaging features were summarized.

Results:

In total, 33 and 35 patients were included in the MI and PI groups, respectively. There was no significant difference in the distribution of age (64.9 ±10.0 vs. 65.1 ±10.8 years, p = 0.927) and males (84.8% vs. 74.3%, p = 0.282) between the MI and PI groups, respectively. The pure MI group had a comparable level of serum lipoprotein and cardiovascular risk factors compared with the PI group except for a lower proportion of hypertension (57.6% vs. 85.7%, p = 0.010). The majority (72.7%) of culprit lesions in the pure MI group was located in the paramedian area of the midbrain, and the ocular muscle palsies mostly involved the medial rectus (75.8%).

Conclusions:

The Chinese patients with OP caused by pure MI were mainly characterized with rapidly progressive symptoms, multiple cerebrovascular risk factors, and typical MRI signs. Further efforts should be made in the differential diagnosis of this atypical midbrain syndrome.