From the Guidelines
Morton's neuroma is diagnosed through a combination of clinical evaluation and imaging studies, with ultrasound being the first choice for its non-invasive nature and ability to visualize the neuroma, as supported by recent studies 1. The diagnosis begins with a thorough medical history and physical examination, where the doctor will press on the affected area to reproduce the pain and listen for a clicking sensation called Mulder's sign. Patients typically describe burning pain, numbness, or tingling between the toes, most commonly in the space between the third and fourth toes. The pain often worsens with walking or when wearing tight shoes. Some key points to consider in the diagnosis of Morton's neuroma include:
- Clinical evaluation: A thorough medical history and physical examination are essential in diagnosing Morton's neuroma.
- Imaging studies: Ultrasound and MRI are commonly used imaging techniques in the diagnosis of Morton's neuroma, with ultrasound being the first choice due to its non-invasive nature and ability to visualize the neuroma 1.
- Diagnostic criteria: The diagnosis of Morton's neuroma is based on a combination of clinical evaluation and imaging studies, with a focus on reproducing the patient's symptoms and visualizing the neuroma.
- Ruling out other conditions: Imaging tests such as X-rays may be used to exclude other causes of foot pain like stress fractures or arthritis, as they are insensitive to diagnose Morton's neuroma but useful to exclude other causes of webspace pain 1. The use of ultrasound in the diagnosis of Morton's neuroma is supported by a meta-analysis that found high sensitivities for ultrasound and MRI, with no significant differences between the two modalities 1. In uncertain cases, MRI may be used as it provides detailed images of soft tissues, and has been shown to be a sensitive and reliable method to evaluate patients with metatarsalgia and Morton's neuroma, with a sensitivity of 87%, specificity of 100%, accuracy of 89%, PPV of 100%, and NPV of 60% in surgically treated patients 1.
From the Research
Diagnostic Criteria for Morton's Neuroma
The diagnostic criteria for Morton's neuroma include:
- 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
- Symptoms such as dull or sharp pain, numbness and/or tingling in the third and fourth digits, burning sensation, cramping, and a feeling of "walking on a stone" around the metatarsal heads 3
- Clinical tests such as thumb index finger squeeze, and Mulder's click and foot squeeze tests can be used for diagnosis 3
- Imaging modalities such as ultrasound and magnetic resonance imaging (MRI) can be used for confirmation, especially for differential diagnosis, exact localization, and number of neuromas 3, 4
Imaging Modalities
- Ultrasonography has a slightly higher sensitivity in the diagnosis of Morton's neuroma, particularly of neuromas smaller than 5 mm, and should be the preferred imaging modality in suspected cases 4
- MRI should be reserved for cases with equivocal diagnosis 4
- Ultrasound is a highly accurate diagnostic tool for Morton's neuroma, but is subject to interoperator variability due to differences in technique and level of experience 5
Clinical Findings
- Morton's neuroma is a common pathology affecting the forefoot, caused by pressure or repetitive irritation leading to thickness of the digital nerve, located in the third or second intermetatarsal space 6
- The diagnosis of Morton's neuroma is mainly based on characteristic symptoms and clinical findings, but may be confirmed by ultrasonography 5