MRI in isolated sixth nerve palsies.

Area of Science:

• Neuro-ophthalmology
• Neuroradiology
• Neurology

Background:

• The etiology of isolated sixth nerve palsy is often unclear, with vascular disease frequently presumed.
• Previous studies lacked clarity on the diagnostic yield of neuroimaging for acute sixth nerve palsy.
• A standardized approach to Magnetic Resonance Imaging (MRI) in these cases was needed.

Purpose of the Study:

• To determine the frequency of causative lesions identified by MRI in acute unilateral sixth nerve palsy.
• To compare MRI findings in patients with and without a history of vasculopathy.
• To evaluate the necessity of follow-up MRI in specific patient subgroups.

Main Methods:

• Prospective study of 43 patients with acute unilateral sixth nerve palsy.
• Standardized Magnetic Resonance Imaging (MRI) protocol was employed.
• Correlation of MRI findings with clinical history, particularly vasculopathy, and follow-up imaging.

Main Results:

• A causative lesion was identified on initial MRI in 63% of patients.
• Tumors or tumor-like lesions accounted for 49% of identified causes; presumed vasculopathy was 15%.
• Patients with initially normal MRI were more likely to have a history of vasculopathy (62%) compared to those with visible lesions (15%).

Conclusions:

• Routine MRI is recommended for all patients with acute sixth nerve palsy, irrespective of suspected etiology.
• MRI can identify significant lesions, including tumors, that might otherwise be missed.
• Follow-up MRI is unnecessary for patients with normal initial scans, spontaneous symptom regression, and a history of vasculopathy.