Preliminary Diagnosis: Morton's Neuroma
I. What imaging technique is first-line for this diagnosis?
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Magnetic resonance imaging (MRI) of the forefoot The use of IV contrast may be useful for differential diagnosis in select cases.
II. Describe the advantages and disadvantages of this technique for diagnosis of Morton's neuroma.
Advantages
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Often diagnostic for Morton’s neuroma (MN), seen as a teardrop-shaped mass at the plantar aspect of the interdigital space
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Useful in evaluating for other causes of forefoot pain
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If surgery is considered, MR imaging can confirm the diagnosis and reveal the number and exact location of neuromas.
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Does not include exposure to ionizing radiation
Disadvantages
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Expensive
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Time consuming
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Requires patient cooperation and the images are susceptible to motion artifact. Uncooperative patients may need sedation.
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Closed-bore magnets may be uncomfortable for claustrophobic and obese patients.
III. What are the contraindications for the first-line imaging technique?
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Patients with non–MR-compatible hardware
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Relatively contraindicated in pregnant women within the first trimester because of the lack of studies regarding the effect of the magnetic field on the embryo
IV. What alternative imaging techniques are available?
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Ultrasound (gray scale)
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Plain radiographs
V. Describe the advantages and disadvantages of the alternative techniques for diagnosis of Morton's neuroma.
Ultrasound
Advantages
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May be diagnostic for MN
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Safe, cost-effective, fast, readily available method
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In experienced hands, the accuracy of US is similar to MRI for larger neuromas.
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The cause of the patient’s pain can be accessed by applying direct pressure by the probe.
Disadvantages
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Less accurate for detection of small lesions (which are often asymptomatic)
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Operator-dependent imaging technique.
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Limited evaluation of other possible causes of forefoot pain, especially osseous abnormalities
Plain Radiographs
Advantages
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Readily available, fast, low-cost imaging technique
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Plain radiographs may show splaying of metatarsal heads in patients with MN
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Radiographs are useful for differential diagnosis and evaluation of osseous causes of forefoot pain, such as Freiberg’s infraction, stress fractures and arthritis
Disadvantages
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Exposure to ionizing radiation
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Limited for soft tissue evaluation, offering poor anatomic detail
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Plain film findings are often indirect signs and not specific
VI. What are the contraindications for the alternative imaging techniques?
Ultrasound
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No significant contraindications
Plain Radiographs
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No significant contraindication. Some instutitions may require consent in pregnant patients.
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