What is a Morton’s Neuroma
When we walk, we land on the heel of our foot and then transfer the weight to the ball and toes of the foot before we take off again. There is some slight rotation and pressure in the bones of the midfoot and toes as we make this step.
There is a space between the long bones in the middle of the foot which can rub together during this movement and over time, irritate the nerves which travel there. These nerves are called the interdigital nerves; they are the nerves that travel in between the different toes to supply them. This nerve is the interdigital nerve, which winds in between the toes to supply them.
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A Morton’s neuroma is a compressive injury of the interdigital nerve in the forefoot due to compression and constant irritation. It is not a true neuroma, which is a swelling of nerve tissue which can get in the way, as the condition is degenerative rather than by virtue of a growth itself.
What are the symptoms of a Morton’s Neuroma?
The symptoms include a burning, tingling or sharp pain between the toes both when walking but also sometimes at rest. This condition is also referred to as Morton metatarsalgia, interdigital neuritis, Morton entrapment, interdigital neuralgia, interdigital neuroma, interdigital nerve compression syndrome, and intermetatarsal neuroma.
How is a Morton’s Neuroma diagnosed?
The diagnosis of a Morton’s neuralgia is based on history and clinical examination. Pressing on the area of concern and a gentle squeeze of the forefoot to simulate the rubbing of that nerve will often reproduce the symptoms and give a diagnosis. In some cases, you can even feel a clicking or crunching sensation, called the ‘Mulder’s click’ which also suggests this diagnosis. Sometimes, an ultrasound or MRI is necessary to finalise the diagnosis; if there is suspicion that this may be an atypical lesion, an old fracture, ganglion or some other diagnosis, imaging is helpful.
How is a Morton’s neuroma treated?
Physiotherapy is the first step in treating this problem. Strengthening the lower back, buttocks, hips, abdomen and quadriceps (knee muscle) will help reduce the load being transferred to the midfoot. Some cases will clear up with this treatment alone.
If the pain continues and the diagnosis is clear, a steroid injection might be useful. A steroid injection involves a needle being used to enter the space of the affected nerve and deliver hydrocortisone or similar steroid. These steroids reduce inflammation significantly and are used for reducing the swelling of disc disease, cartilage in the knee or shoulder to name a few.
What does the procedure involve?
The doctor will clean the area, put out a sterile gown and then wear gloves to feel the area of the pain. An injection of a numbing medication, called lidocaine, will be done to see if that settles the nerve pain. If the pain settles, the position is right and a steroid injection into the area can take place.
This procedure is uncomfortable with a bit of pain. It is minimally invasive and the chance of hitting another structure such as an artery or the nerve itself is possible, but usually uncommon. There is a rare chance of bleeding, infection and also it should be noted that everybody is different and the steroid injection does not solve the pain for everybody.
Are there alternatives to the injection?
If pain is bad enough and not getting better with physiotherapy, a steroid injection would almost certainly be the next step. The options after this include surgery to remove any enlarged nerve or pieces of bone compressing the structure.
REFERENCES
Munir U, Tafti D, Morgan S. Morton Neuroma. [Updated 2021 Jun 2]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-.
Ruiz Santiago F, Prados Olleta N, Tomás Muñoz P, Guzmán Álvarez L, Martínez Martínez A. Short term comparison between blind and ultrasound guided injection in morton neuroma. Eur Radiol. 2019;29(2):620-627. doi:10.1007/s00330-018-5670-1
