Do I have Morton’s neuroma?
History suggestive of Morton’s neuroma:
Here are a few helpful symptoms that may suggest Morton’s neuroma.
- Feeling of moderate to severe pain (burning or stabbing in character) when the area between the third and fourth toe is exposed to manual pressure.
- Feeling of pinching pain in the lower foot after periods of prolonged standing or walking
- A subjective feeling of standing on a pebble or stone.
- The sensations are significantly reduced due to thickening of nerves. The healthcare provider should squeeze the foot with gentle application of pressure to ascertain the sensitivity to sensation and pressure.
- Nerve enlargement is seen in some cases; however, the nerve swelling is often too small to be noticeable by the naked eye.
It is highly recommended to see your provider for a complete evaluation and diagnosis of Morton’s neuroma. This is mainly because, other musculoskeletal conditions (such as arthritis, nerve damage, traumatic injury etc.) presents with similar signs and symptoms.
Clinical tests that are used in the diagnosis of Morton’s neuroma:
- Tinel’s sign: Detection of inflamed or irritated nerves by lightly tapping on it is referred to as Tinel’s sign. It is performed by gentle tapping of the space between the third and fourth toe (or other metatarsal spaces). A positive Tinel’s sign is marked by feelings of pin and prick like sensations, tingling and numbness in the fore-foot after gentle tapping.
- Mulder’s sign: This test is ideally performed when you are is lying on your back. The practitioner then gently squeezes your foot between your metatarsal heads while at the same time pressing the ball of the foot in the area of the neuroma. A positive Mulder’s sign is when this squeezing is painful. Sometimes an audible ‘click’ is also heard (Mulder’s click). A positive Mulder’s sign helps in localizing the exact site of the Morton’s neuroma.
It should be noted that a negative Tinel’s sign or Mulder’s sign does not rule out a Morton’s neuroma.
Radiological tests to confirm Morton’s neuroma:
Radiological investigation may be used to confirm the exact site, location and size of the neuroma. Most frequently employed tests are:
X-ray: X-rays can rule out any fracture (especially stress fractures that are fairly common in young girls or athletes). Additionally, X-rays also helps in excluding other injuries or lesion of metatarsals.
MRI: MRI (magnetic resonance imaging) can be performed to diagnose a Morton’s neuroma. In addition, MRI also helps in excluding other potential causes of pain and discomfort; such as tumor growth or mass, present between the third and fourth toe. However a negative MRI does not exclude the presence of a Morton’s neuroma.
Ultrasound: Ultrasound is a cost-effective radiological modality that is used for identification of exact site and size of Morton’s neuroma. Many practitioners use ultrasound to guide their procedures such as diagnostic injections, cryosurgery, radio frequency ablation and neurolytic injections. According to a study reported in the peer reviewed journal Clinical Radiology(1), the sensitivity of Ultrasound in the diagnosis of Morton’s Neuroma is 90% which is about the same as MRI yet investigators believe that ultrasound is the preferred option over MRI if neuroma is under 5mm in dimensions(2). A negative Ultrasound does not exclude the presence of a Morton’s neuroma.
Diagnostic injection is a tool which is frequently used for accurate diagnosis of painful Morton’s neuromas. As part of the procedure, a local anesthetic agent such as lidocaine is injected into the suspected neuroma, preferably under ultrasound guidance. If the pain significantly decreases after introducing the anesthetic agent in the web-space, a diagnosis of Morton’s neuroma is generally made. A diagnostic injection is often considered the gold standard for diagnosis.
Clinical diagnosis is key
Morton’s neuroma is above all a clinical diagnosis. A positive MRI or Ultrasound does not necessarily confirm the diagnosis of Morton’s neuroma. You can have a clear Morton’s neuroma on MRI or ultrasound but the cause of your pain may not be that Morton’s neuroma. It is estimated that up to 60% of the population have Morton’s neuromas on MRI or ultrasound but have no symptoms.
Similarly, a negative MRI or ultrasound does not exclude the diagnosis of Morton’s neuroma. Some Morton’s neuromas are very small and very hard, even impossible to detect with MRI or Ultrasound but may be extremely painful.
It is critical that you see a practitioner well experienced with Morton’s neuroma. For more information on the diagnosis of Morton’s neuroma, see here.