Magnetic Resonance Imaging Findings in Patients With Duane Retraction Syndrome

Area of Science:

• Ophthalmology
• Neurology
• Radiology

Background:

• Duane retraction syndrome (DRS) involves abnormal innervation of the lateral rectus (LR) muscle by the oculomotor nerve (CN III) due to abducens nucleus absence.
• MRI is utilized to investigate the morphological characteristics of cranial nerves (CN III, CN VI) and extraocular muscles in DRS patients.

Purpose of the Study:

• To investigate morphological characteristics of CN III, CN VI, and extraocular muscles in DRS patients using MRI.
• To assess the association between ocular motility, horizontal rectus muscle volumes, and CN III/VI in DRS.

Main Methods:

• MRI scans (3D T1/2) of the brainstem and orbit were obtained for 42 DRS patients (48 eyes) and 20 controls (40 eyes).
• Patients were classified into DRS Type I, II, and III.
• Cranial nerves (CN III, CN VI) and extraocular muscles (LR, MR) were visualized and their volumes assessed.

Main Results:

• Abducens nerves (CN VI) were absent in 100% of Type I and 88% of Type III DRS eyes, but present in 100% of Type II.
• Oculomotor nerves (CN III) were thicker on the affected side in Type I and III DRS.
• Abducens nerve presence correlated with better abduction; horizontal rectus muscle volumes correlated with CN III diameter.

Conclusions:

• Different DRS types exhibit distinct CN VI and CN III appearances on MRI.
• Horizontal rectus muscles show adaptive morphological changes in response to aberrant innervation.
• Neuroimaging findings offer potential new diagnostic criteria for DRS classification and understanding its pathophysiology.