How is the diagnosis of a neuroma made?

The diagnosis of neuroma is made through a combination of getting a description of the symptoms from the patient, clinical examination, diagnostic ultrasound, x-rays, MRI, and occasionally the response to treatments.

Patient history

The first step in making a diagnosis of a neuroma is to interview the patient. There are common descriptions that we hear often from patients with neuroma pain. These include symptoms as follows:

 

  • Numbness or tingling in two adjacent toes
  • Pain between two adjacent toes
  • Pain in the ball of the foot
  • Burning sensation in the foot or toes
  • Feeling a pebble in the sock
  • A ball or bunched-up piece of fabric in the sock
  • Shooting or electrical shock in the foot or toes

Physical examination

After obtaining a thorough history from our patients, we perform a physical examination of the foot. As always, we evaluate the vascular, neurological, dermatological, and orthopedic presentation.

 

Specifically, we target the area where the patient indicates the pain is. Most often, it is between the third and fourth toes at the ball of the foot. The second most common area is between the second and third toes at the ball of the foot.

 

We start with palpating (pressing on) the area in question. Most often, pain is elicited by pressing up on the ball of the foot between the third and fourth metatarsal heads. We will also squeeze the forefoot from the first to the fifth metatarsals to put pressure on the nerve from the sides.

 

Mulder's sign

 

We also do a combination of these two examinations by pressing from the side and the bottom at the same time. Often, patients will experience neuroma type pain when we perform the combination of the two tests described above, called the Mulder sign. It is named after a Dutch orthopedic surgeon, Jacob D Mulder.

 

In addition, we test for sensory deficit on the inside of the toes. The anatomy is such that after the common metatarsal nerve splits, the two small nerves innervate the bottom of the adjacent third and fourth toes. When one has neuromas, it is common to have sensory deficit, or numbness in these areas.

 

Another mechanical test for neuroma involves grasping the third metatarsal head and the fourth metatarsal head, and pressing them together while moving them in opposite directions, up and down. This simulates the metatarsal heads compressing the nerve and can result in neuroma type pain.

X-Rays

Nerves and neuromas do not show up on x-ray. Therefore, it is not possible to see a neuroma when taking foot x-rays. However, x-rays are beneficial in ruling out other pathologies that have similar symptoms to neuromas. These include: Metatarsal fractures, stress fractures, joint dislocations, and arthritic changes in the metatarsal phalangeal joints.

Diagnostic ultrasound

We perform diagnostic ultrasound daily in our office when we are trying to diagnose neuromas. In general, diagnostic ultrasound allows us to see different densities of tissues. With fluid, or inflammation of the foot, the sound waves pass right through the fluid without bouncing off, and creating a signal. Therefore, areas of increased fluid, including inflammation, will appear more black on ultrasound. It is common to see a black halo around an inflamed nerve.

 

The nerve itself does bounce sound waves back causing it to appear hyperechoic, or have increased signal. This allows us to see an enlarged nerve and measure it. We also put pressure on the ultrasound probe to see if the tissue is compressible. Localized fat between the metatarsals will compress whereas the neuroma will not.

 

Additionally, diagnostic ultrasound is helpful in discovering other causes of pain in the area including bursitis, tendinitis, ganglion and other common soft tissue masses

MRI

The best imaging test to visualize neuromas as an MRI. The nerve anatomy can be easily seen, with an MRI. Therefore, enlargement of the normal nerve size is often obvious. Additionally, an MRI is able to visualize the inflammation around the nerve and between the metatarsals.

 

Additionally, MRI is excellent diagnosing other pathologies that may be causing pain in the area including tendinitis, bursitis, stress fracture, ligamentous injury, ganglion, and other common soft tissue masses.

Diagnostic injections

On rare occasions, we have performed diagnostic local anesthesia blocks of the common metatarsal nerve to diagnose neuromas. Using a short acting local anesthesia, an injection was placed around the common metatarsal nerve. When this nerve is made to be numb, the neuroma pain will go away.

Treatment, as a diagnostic tool

On rare occasions, we are unable to make the diagnosis of a neuroma through all the above examinations and tests. When we have ruled out all other diagnoses, and still suspect neuroma, we will start initiating neuroma treatments. If the neuroma pain goes away with these treatments, we retrospectively can make the diagnosis of a neuroma.

Differential diagnosis of neuroma

There are many things that can mimic the symptoms and pain of neuromas in the foot. The anatomy of the ball of the foot includes the bones, ligaments, cartilage, nerves, tendons and tendon sheaths. There can also be soft tissue masses present including both benign and cancerous neoplasms. The following is a list of other possible diagnoses that may mimic the symptoms of neuroma:

 

  • Sprain, torn ligament
  • Plantar plate injury (thickened bottom ligaments of the metatarsophalangeal joint)
  • Dislocation of metatarsophalangeal joint
  • Arthritis of the metatarsophalangeal joint
  • Metatarsal fracture
  • Metatarsal stress fracture
  • Freiberg’s infarction (collapse of metatarsal head)
  • Tendinitis
  • Torn tendon
  • Ganglion
  • Joint effusion
  • Osteochondritis (cartilage injury)
  • Bursitis

 

As I am sure you can imagine, is very important to rule out these many diagnoses that can be present with neuroma type pain. Treatments will differ depending on the proper diagnosis.