From the Guidelines
Morton's neuroma is best diagnosed through a combination of clinical evaluation and imaging studies, with MRI being the most sensitive and reliable method, having a sensitivity of 87%, specificity of 100%, accuracy of 89%, PPV of 100%, and NPV of 60% in surgically treated patients 1. The diagnosis begins with a thorough medical history and physical examination, where the doctor will press on the affected area to reproduce pain and feel for a mass or click between the toes. Patients typically describe burning pain, numbness, or tingling between the third and fourth toes that worsens with walking and improves with rest. Some key points to consider in the diagnosis of Morton's neuroma include:
- The doctor may perform Mulder's test by squeezing the forefoot while simultaneously pressing between the metatarsal heads, which may produce a painful clicking sensation.
- Imaging studies such as ultrasound or MRI can confirm the diagnosis by visualizing the enlarged nerve, though these are not always necessary if clinical findings are clear.
- X-rays may be ordered to rule out other conditions like stress fractures or arthritis.
- Nerve conduction studies are occasionally used to exclude other neurological conditions.
- The diagnosis is based on the characteristic location of pain, the pattern of symptoms that worsen with tight footwear or walking, and physical examination findings.
- Early diagnosis allows for more conservative treatment options before surgical intervention becomes necessary. It's worth noting that while ultrasound can also be used to diagnose Morton's neuroma, MRI is generally considered more sensitive and reliable, with a pooled sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio of 93%, 68%, 1.89, and 0.19, respectively 1. Additionally, high-resolution US can approach the sensitivity of MRI in detecting Morton’s neuromas, with sensitivities ranging from 83%-96% and no significant differences between the two modalities found in a meta-analysis 1.
From the Research
Diagnosis of Morton's Neuroma
- Morton's neuroma is a painful lesion of the interdigital nerve, usually at the third intermetatarsal space, associated with fibrotic changes in the nerve, microvascular degeneration, and deregulation of sympathetic innervation 2.
- The diagnosis of Morton's neuroma is usually made from evaluation of a patient's subjective complaints, clinical findings, and exclusion of other differential diagnoses 3.
- Occasionally, when other neurological conditions exist or when the clinical findings are atypical, various imaging techniques may be helpful in the diagnosis of interdigital neuromas 3.
- Ultrasonography is a highly accurate diagnostic tool for Morton's neuroma, but it is subject to interoperator variability due to differences in technique and level of experience 4.
Clinical Presentation
- Patients with Morton's neuroma usually present with burning or sharp metatarsalgia at the dorsal or plantar aspect of the foot 2.
- Symptoms include burning or shooting pain in the webspace that extends to the toes, or the sensation of walking on a pebble 5.
- These symptoms impact on weight-bearing activities and quality of life 5.
Imaging Techniques
- Ultrasound aids in the accurate diagnosis of Morton's neuroma and guides treatment, such as infiltration of the area with a corticosteroid and local anesthetic, chemical neurolysis with alcohol or radiofrequency thermal neurolysis 2.
- Magnetic resonance imaging (MRI) can also be used to confirm the diagnosis of Morton's neuroma 5.
- The anatomy of the common plantar digital nerves and surrounding structures in the forefoot is relevant to the understanding of Morton's neuroma, especially from a sonographic point of view 4.