What is the recommended imaging modality for diagnosing Morton neuroma?

Recommended Imaging for Morton Neuroma

MRI and ultrasound are the preferred imaging modalities for diagnosing Morton neuroma, with MRI showing 93% sensitivity and ultrasound showing 90% sensitivity. 1, 2, 3

First-Line Imaging Approach

• Radiographs are insensitive for diagnosing Morton neuroma but should be performed initially to exclude other causes of forefoot pain such as osteoarthritis, Freiberg's infraction, and stress fractures 3
• After negative or equivocal radiographs, either MRI without IV contrast or ultrasound is recommended for diagnosing Morton neuroma 4, 1

Advantages of Each Modality

MRI

• Provides excellent visualization of Morton neuroma with 93% sensitivity 2
• Better for differential diagnosis and detecting other potential causes of metatarsalgia 3
• Most effective when performed with the patient in prone position with foot plantar flexed 5
• T1-weighted axial and coronal images with an axial FSE T2-weighted sequence may detect neuromas more consistently than enhanced T1 fat-suppressed sequences 6

Ultrasound

• High sensitivity (90%) for detecting Morton neuroma 2
• Allows dynamic examination and direct clinical correlation during the procedure 1, 3
• More cost-effective and widely available than MRI 7
• Enables ultrasound-guided interventions such as corticosteroid injections 7

Clinical Considerations

• Clinical assessment remains highly sensitive and specific for diagnosing Morton neuroma, with some studies suggesting it may be superior to imaging alone 8
• The American College of Radiology recommends both MRI and ultrasound as appropriate imaging modalities for Morton neuroma 4, 2
• Power Doppler ultrasound has proven useful in identifying increased blood supply in the setting of metatarsalgia, including Morton neuroma 4

Common Pitfalls

• Small neuromas (<6mm) may be missed on ultrasound but can still cause significant symptoms 8
• Ultrasound accuracy is operator-dependent and subject to variability based on technique and experience 7
• Reliance on a single imaging modality may lead to inaccurate diagnosis in some cases 8
• Other conditions such as intermetatarsal bursitis can mimic Morton neuroma on imaging 5

Algorithmic Approach

1. Begin with plain radiographs to exclude other osseous causes of forefoot pain 3
2. If radiographs are negative or equivocal:
   • Use ultrasound if dynamic assessment and direct clinical correlation are desired 3
   • Use MRI if better soft tissue characterization or evaluation of other potential causes is needed 3
3. Consider clinical correlation regardless of imaging findings, as small neuromas may cause symptoms despite being difficult to visualize 8