MRI vs EMG for Baxter's nerve

by Bessie
(Florida)

After xray and 8 weeks PT my podiatrist ordered an MRI for entrapped Baxter nerve diagnosis. PT said to have my neurologist do nerve test. He ordered an EMG for tarsal tunnel syndrome diagnosis. My podiatrist says the MRI is all I need.

I am scared of surgery and husband said we will get different docs diagnosis until someone says no surgery.

Having MRI next week and insurance won't cover EMG but will have it if it is needed eventually when I can afford it.

Is this something I should discuss with both my doctors?

Thank you

Bessie

RESPONSE

Hi Bessie,

Let me start off by saying that certainly you should discuss your treatment options with your any doctor involved in this particular problem as they are the most familiar with your situation.

Having said that I do have a few concerns based on your narrative and I would like to address them.

According to you, it seems like all you had so far was an x-ray and some physical therapy; hardly what I would call any real treatment for a possible Baxter's nerve.

Baxter's nerve is an irritation of one of the branches coming off the medial plantar nerve. (the red arrow is pointing to Baxter's nerve on the bottom of the heel).

It is a diagnosis that is generally not too difficult to make just by examination. In most cases there will be pain when the doctor presses on the inside of the heel, even though your actual pain may be on the bottom of the heel when you walk. This same pain is usually not evident on pressing in the same spot on the other foot.

Additionally, there may be some degree of numbness on the bottom of the affected heel compared to the other heel. This can be identified by using a dull pin and pressing against the bottom of each heel, the affected heel will be duller than the other heel.

In most cases of a heel neuroma (Baxter's nerve) the heel will become more painful, the more you walk. This is in contrast to plantarfasciitis which is most painful on initial ambulation and then eases up as you walk.

The reason a heel neuroma will worsen as you walk is because the pounding of the heel during ambulation will aggravate the nerve and make it worse.

In my mind at least making the diagnosis of Baxter's nerve is not that difficult. I have found it rare in my practice that people just have Baxter's nerve issues; I tend to find that they run concurrent with plantarfasciitis.

Plantarfasciitis tends to be easier to treat and when patients end up having prolonged pain that does not respond to the usual therapies for plantarfasciitis, it is usually due to a heel neuroma or even a heel bursitis.

Moving along, one of the problems with a heel neuroma is that it may actually be a tarsal tunnel (the foot equivalent of carpal tunnel seen in the hand), where the nerve further up the foot at the level of the ankle becomes entrapped and can give symptoms such as heel pain as well as more diffuse pain in the foot.

Now, you podiatrist wants to do an MRI and states that is all you need. The problem with an MRI is that I have found them to be poor prognosticators of neuromas.

In theory they should be able to identify enlarged nerves but in my experience they tend to give too many false negatives, meaning they do not find neuromas when one actually exists.

I can tell you of multiple instances over my career where I have had an MRI that came back negative for a Morton's neuroma, which is a neuroma in the forefoot, only to go in surgically and actually remove a neuroma.

In theory, an MRI should be able to reveal nerve entrapment found in tarsal tunnel, but an EMG, at least in my opinion would be the better test.

Having said all that, if you were my patient, at this point I would not be ordering any tests without actually have given you some specific treatment, besides physical therapy.

One of my favorite treatments for heel neuromas is the use of 4% percent denatured alcohol injections given weekly for upwards of seven weeks. What this injection does is sclerose or deaden the nerve and in doing so, reduces or eliminates the heel pain of a heel neuroma.

There are additional treatments that are mildly invasive that can be done for your heel pain such as injected CO2 which essentially freezes the nerve to keep it from hurting.

The amount of fat that you have on the bottom of your heel may also be a factor is heel neuroma. I do not know how old you are but as we age the one area where we lose fat is on the bottom of the foot. Some younger individuals also exhibit very little heel fat.

The problem here is that without much fat to cushion the area, Baxter's nerve is constantly being irritated by walking. Thus, in many instances adding a heel cushion to deaden the impact of heel strike when walking may go a long way in reducing symptoms.

At this point in time I do not think you are a candidate for surgery, certainly not without having tried some less invasive therapies. It may turn out that even after some of these treatments, if you are still in enough pain, then a surgical procedure may be indicated.

In closing, discuss all this with your doctor(s). You should always be part of the decision making process since it is your foot. If you find that you end up being at odds with what your doctor recommends, then seek out a second opinion with a doctor in your area.

Marc Mitnick DPM
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