Morton’s Neuroma

Clinical Presentation:

Patients with Morton’s neuroma present with pain in the forefoot, particularly over the sole of the forefoot.  However, not all pain in the forefoot is a Morton’s neuroma.  In fact, most chronic pain in the forefoot is NOT the result of a Morton’s neuroma, but rather is from metatarsalgia – inflammation (synovitis) of the “toe/foot” joints. The symptoms from Morton’s neuroma are due to irritation to the small digital nerves as they pass across the sole of the foot and into the toes (Figure 1). Therefore, with true Morton’s neuroma, it is not uncommon to have nerve-type symptoms either numbness in the toes or a burning sensation extending into the toes. Different nerves innervates different parts of the toes. Therefore, it is most common to have symptoms involving part of the 2nd and 3rd toes, or parts of the 3rd and 4th toes. However, it is uncommon to have symptoms in multiple spots on the foot.

Figure 1: Location of Nerve (between the base of the 2nd and 3rd toes)

Nerve of Foot

 

Irritation to the nerve is usually directly or indirectly related to localized loading to the front of the foot as the patient walks. The nerve will get repetitively loaded due to the location of the metatarsal heads or the strong ligament that runs between the metatarsal heads (Figure #2). This causes localized injury to the nerve with resulting scarring and fibrosis of the nerve. This leads to symptoms in the distribution of the nerve. The pain is usually worse when wearing enclosed shoes that are constrictive.

Figure 2: Location of nerve right under the skin (between base of 3rd and 4th toes)

Nerve of Foot

 

Physical Examination:

Patients with classic Morton’s neuroma symptoms will have pain with pressure at the base of the involved toes (either between the 2nd and 3rd toes, or between the 3rd and 4th toes) (Figure 3).  In addition, squeezing the front of the foot together can exacerbate symptoms. As well, they may have numbness on the sides of one toe and the adjacent toe as this corresponds with the distribution of the involved nerve (Figure 4).

Figure 3: Typical Pain locations

Typical Pain of Foot

Figure 4: Distribution of involved nerve

Involved Nerve of Foot

 

Imaging Studies

Plain x-rays of the foot may demonstrate that one or more of the metatarsals are long (Figure #5). Not uncommonly, the second and/or third metatarsal maybe long relative to the third or fourth. This can create a situation where excessive load is occurring in and around the vicinity of the digital nerve.

Non-Operative Treatment:

Most non-operative treatment is usually successful, although it can take a while to figure out what combination of non-operative treatment works best for each individual patient.  Non-operative treatment may include:

  1. The use of comfort shoe wear.
  2. The use of a metatarsal pad to decrease the load through the involved area of the plantar forefoot.
  3. A period of activity modification to decrease or eliminate activities, which maybe exacerbating the patient’s symptoms.  For example, avoiding long periods of standing or other activities that result in significant repetitive loading to the forefoot can be very helpful.  Wearing high heels should be avoided.
  4. Local corticosteroid injections can help decrease inflammation associated with the nerve. However, this does not necessarily address the underlying loading forces that maybe causing the injury to the nerve in the first place.

It has been proposed that an alcohol injection in and around the nerve will cause a controlled death to the nerve and subsequently eliminate symptoms from the nerve. In theory, this may be helpful. In practice, adequate prospective studies have not demonstrated the benefit of this procedure above and beyond the other standard non-operative treatments available.  In addition there is the concern that the alcohol will cause excessive scarring and death of other important structures in the area.

Operative Treatment:

Operative treatment of Morton’s neuroma should be entertained only after failure of nonoperative management. Standard operative treatment involves identifying the nerve and cutting (resecting) it proximal to the point where it is irritate/injured. This is usually done through an incision on the top (dorsal) aspect of the foot, although in rare instances, an incision on the sole (plantar) aspect of the foot maybe used. An incision on the sole of the foot works very well, unless an excessive scar forms in which case it can be problematic.

Some physicians will attempt to treat Morton’s neuroma by releasing the intermetatarsal ligament and freeing the nerve of local scar tissue. This may also be beneficial.

The ultimate success of a Morton’s neuroma treated surgically is somewhat unclear.  This is likely due to the idea that in most instances a “Morton’s neuroma” is actually more than just an isolated nerve problem but rather consitutes a metatarsalgia where other structures (such a as the MTP joints) are also problematic, not just the nerve. Therefore, addressing the nerve as well as the other components of a metatarsalgia may offer a better chance of surgical success. However, like many conditions in foot and ankle, it is ideal if this condition can be managed without surgery.

Potential Surgical Complications:

Potential operative complications include:

  1. Infection.
  2. Wound healing problems. Wound healing problems can be particularly problematic if the incision is on the plantar surface of the foot as scars in this area can be quite troublesome.
  3. Deep Vein Thrombosis (DVT).
  4. Pulmonary embolism (PE).
  5. Continued pain. This is not uncommon as the nerve maybe only a part of the pain generating complex.
  6. Reflex sympathetic dystrophy or complex regional pain syndrome – (CRPS). In some instances, an aggravation of the nerve such as what may occur at the time of the surgery can lead to the development of a complex regional pain syndrome, which can be quite troublesome. Fortunately, this complication is relatively uncommon.

Edited August 17th, 2009