Neuroimaging and acute ocular motor mononeuropathies: a prospective study

Area of Science:

• Neurology
• Ophthalmology
• Radiology

Background:

• Acute, isolated ocular motor mononeuropathies, such as cranial nerve III, IV, or VI palsies, can cause new-onset diplopia.
• The necessity of neuroimaging, specifically magnetic resonance imaging (MRI), in evaluating these conditions in adults over 50 remains a clinical question.

Purpose of the Study:

• To evaluate the diagnostic yield and cost-effectiveness of gadolinium-enhanced MRI in patients older than 50 years presenting with acute, isolated cranial nerve III, IV, or VI palsies.

Main Methods:

• A prospective case series included 93 patients over 50 with new-onset diplopia and isolated cranial neuropathies without other neurologic deficits.
• All participants underwent gadolinium-enhanced MRI.
• Cost analysis utilized Current Procedural Terminology codes and Medicare costs from 2010, with cost utility estimated using published data.

Main Results:

• Only 1 out of 93 patients had an MRI-identified lesion directly related to the cranial mononeuropathy.
• The total modeled cost for imaging was $131,688 to identify an underlying cause in this single patient, with no change in management.
• The estimated cost utility for the patient with a causative lesion was $90.19 for diagnosis alone.

Conclusions:

• Routine MRI scanning may not be medically necessary for all adults over 50 experiencing isolated cranial nerve III, IV, or VI palsies.
• Physicians should judiciously consider patient history and clinical findings to determine the need for initial neuroimaging in this population.