What Are The Best Injections For Morton’s Neuroma?

One of the mainstay treatments of Morton's neuromas involves injections. There are three common injections and other combinations of medications in injection form.

First of all, there is the diagnostic injection of local anesthesia to see if injecting the nerve provides complete pain relief. It sometimes proves that the nerve the doctor thought was the problem really is not the problem. One would give these local anesthetic injections with medications (commonly bupivacaine) that last around five hours so the patient can be 100 percent sure of the amount of relief attained. I am a big believer in this method of identifying the right nerve or if it is a nerve at all causing the pain, since you only inject the nerve and not the tendons, ligaments, joints, etc. Sometimes, even though you are giving an injection that should last five hours, since you are blocking the pain cycle, the relief can last much, much longer. Many doctors will give these injections once or twice a week until the severe pain cycle completely breaks down, greatly minimizing the symptoms.

The second most common type of injection involves cortisone, which acts to reduce swelling. The amount of injection varies from person to person and body part to body part, but I have lived by the rule of providing no more than five cortisone shots per year for a patient. I can count on one hand how many patients have needed more than three cortisone shots per year so four or five shots is unusual, but sometimes necessary. Each one of my cortisone shots is 10 mg of a long-acting steroid. As the crystal dissolves, there is slowly less cortisone working on a daily basis. I find no use for short-acting cortisone.

I once had a patient come in for surgical consultation after she failed to improve with 10 cortisone injections over a six-month period. Her doctor had recommended surgery and it was a simple appointment to verify that this was appropriate. When we found out what the doctor had used in each injection, I was dumbfounded. He was using long-acting cortisone but in a homeopathic dose of 0.1 mg per shot. If you do the math, you would realize that it would have taken him 100 shots to equal the dosage of one of my shots.

Why am I discussing dosage? The five-dose recommendation per year is based on actually getting 50 mg of long-acting cortisone in one area. One smart patient with one smart doctor helped me understand that a local cortisone shot can affect the entire body since the body can absorb small amounts. I call this Dorothy's Rule after one of my patients. This rule is essentially that a patient should not get more than one shot of long-acting cortisone per month for the entire body. This applies to patients who are getting cortisone shots for their foot and at the same time for their knee, shoulder, etc.

When giving cortisone shots, the doctor should stay away from the skin, making the injection as deep as possible and avoiding tendons if possible. Cortisone near a tendon can weaken the tendon and cause tearing as it can thin the skin. The skin usually gets healthy gradually but it can take nine months or longer, and the skin cannot tolerate further shots at this time. Normally, one would mix cortisone with the long-acting local anesthetics to get five hours of post-shot pain relief. If the patient does not feel any relief after the shot, the shot missed the painful spot.

After cortisone injection, tell patients not to run or jump for two weeks (another reason athletes hate cortisone shots). Tell patients to check pain relief in the first five hours, at one week and at the two-week follow-up. If 10 mg is not enough (with the goal being 80 percent reduction in pain), give a second shot and the two-week follow-up period starts over again.

During this series of cortisone shots, I do not have patients go to physical therapy but they can cross-train with non-jumping and running activities. With many activities like cycling, patients have to assess if it has a negative impact on them. Tell the patients to ice the affected area three times daily. At each two-week interval, if patients seem to be at the 80 percent level, they gradually return to activity. Hopefully, the doctor and patient have learned what to avoid, what to wear in the shoes, how to tape, etc., to minimize the re-irritation during the return to activity program. Any cortisone shot after the first shot in the nine-month window of time is considered a booster shot.

The third most common type of shot is to desensitize the nerve with alcohol. We use to teach that the alcohol would kill the nerve but only 40% alcohol will do that. Most podiatrists do not feel that an injection of more than 20% alcohol is safe for the foot so many podiatrists never risk injury by staying at 10% max. You definitely do not want to damage other structures in your attempt to desensitize the nerve. We are not sure how long this desensitization lasts but typically it lasts for years. The jury is still out on this.  

I mix a long-acting local anesthetic with 100% concentrated denatured alcohol to achieve a 6% alcohol solution. Then I inject 1 mL of this solution at the most proximal aspect of the nerve in a bolus pattern. You attempt to hit the thinnest part of the nerve before it thickens to adhere to the neuroma. Use topical cold spray to anesthetize the skin, depositing 100 percent of the medicine along the nerve. Give these injections in a series of five, each one seven to 10 days apart. Fifty percent of patients get excellent results, 20 percent have good results (some improvement) and 30 percent get no relief.

After each series, I recommend one month to rest the soft tissue. If the patient noted no response from the first series, I do not normally recommend a second series. Of the patients alcohol helps, 20 percent or so need only one series of five injections to feel 80 percent better, 70 percent need two series, and 10 percent need three series in my experience. The bigger the neuroma on magnetic resonance imaging (MRI), the less likely it is that the alcohol shots will work but the art of all this is deciding who has a chance.

If it were my foot, I would go through the alcohol injection series to achieve the 80 percent relief. If relief did not happen, I would get sporadic cortisone shots, get great orthotic devices that take pressure off the area and ice my foot two to three times daily. You can also give the cortisone shots while doing the alcohol injections if there is an unexpected flare-up.

Editor’s note: This blog originally appeared at https://www.drblakeshealingsole.com/2010/08/mortons-neuromas-which-shots-to-get.html . It is reprinted with permission from the author.