Isolated unilateral oculomotor paresis in pure midbrain stroke
Yu Amano1, Yosuke Kudo1, Hideyuki Kikyo1
1Department of Neurology, Yokohama Brain and Spine Center, Yokohama, Japan.
Background And Purpose:
Pure midbrain stroke can cause isolated unilateral oculomotor paresis. We attempted to determine whether there is a difference in the oculomotor paresis pattern between pure midbrain infarction and midbrain hemorrhage.
Methods:
Pure midbrain stroke patients who presented with isolated unilateral oculomotor paresis were identified from a group of 2447 consecutive patients hospitalized for acute cerebral infarction or hemorrhage during the period May 2008 through April 2014. Detailed oculomotor findings were evaluated in the identified patients per the cause of the stroke.
Results:
Five patients with infarct and 1 with hemorrhage became our study subjects. Lesions were located in the paramedian area of the midbrain involving the oculomotor fascicles. The pupillary sphincter and inferior rectus muscles were selectively spared in the infarct patients, whereas these muscles were selectively affected in the hemorrhage patient.
Conclusion:
Fibers in the oculomotor fascicle that innervate the levator palpebrae, superior rectus, and inferior oblique muscles appear to be more susceptible to ischemic damage than those that innervate the pupillary sphincter and inferior rectus muscles. Isolated impairment of the pupillary sphincter and inferior rectus muscles may be suggestive of a non-ischemic process.
Insights
Midbrain stroke can cause oculomotor nerve issues. This study found that ischemic damage in the midbrain selectively affects certain eye muscles, unlike hemorrhage, suggesting different causes for isolated oculomotor paresis.
Area of Science:
- Neuroscience
- Neurology
- Ophthalmology
Background:
- Pure midbrain stroke can lead to isolated unilateral oculomotor nerve palsy.
- Oculomotor nerve palsy affects eye movement and eyelid control.
Purpose of the Study:
- To differentiate oculomotor paresis patterns between midbrain infarction and midbrain hemorrhage.
- To identify specific fascicle involvement based on stroke type.
Main Methods:
- Retrospective analysis of 2447 patients with acute cerebral infarction or hemorrhage.
- Identification of patients with isolated unilateral oculomotor paresis.
- Detailed evaluation of oculomotor findings correlated with stroke etiology.
Main Results:
- Six patients (5 infarct, 1 hemorrhage) with pure midbrain stroke and oculomotor paresis were identified.
- Infarct patients showed selective sparing of pupillary sphincter and inferior rectus muscles.
- Hemorrhage patient selectively affected pupillary sphincter and inferior rectus muscles.
Conclusions:
- Fibers innervating levator palpebrae, superior rectus, and inferior oblique muscles are more vulnerable to ischemic damage.
- Isolated impairment of pupillary sphincter and inferior rectus muscles may indicate a non-ischemic origin.
- Distinguishing between infarct and hemorrhage is crucial for understanding oculomotor nerve damage patterns.
