Morton's neuroma
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| ICD-10 | G57.6 |
|---|---|
| ICD-9 | 355.6 |
Morton's neuroma (also known as Morton's metatarsalgia, Morton's neuralgia, plantar neuroma and intermetatarsal neuroma) is a benign neuroma of the interdigital plantar nerve.
This problem is characterised by numbness and pain, relieved by removing footwear.
Although it is labeled a "neuroma", many sources do not consider it a true tumor, but rather a thickening of existing tissue.
[edit] Symptoms and signs
Symptoms include: pain on weight bearing, frequently after only a short time; the pain is felt as a shooting pain affecting the contiguous halves of two toes. Burning, numbness and parasthesia may also be experienced. Classically the 3rd digital space between the 3rd and 4th toes is affected, but the condition can occasionally occur in the 2nd and 3rd interdigital space. The pain is caused by pressure on the enlarged section of nerve where it passes between the metatarsal heads, and is squeezed between them. The first toe is usually not involved. Neuroma in the 4th/5th interdigital space is described, but is extremely rare.
Negative signs include no obvious deformities, erythema, signs of inflammation or limitation of movement. Direct pressure between the metatarsal heads will replicate the symptoms, as will compression of the forefoot between the finger and thumb so as to compress the transverse arch of the foot
There are other causes of pain in the forefoot. Too often all forefoot pain is categorized as neuroma. Other conditions to consider are capsulitis, which is an inflammation of ligaments that surrounds two bones, at the level of the joint. In this case it would the ligaments that attach the toe bone to the metatarsal bone. Inflammation from this condition will put pressure on an otherwise healthy nerve and give neuroma type symptoms. Additionally, an intermetatarsal bursitis between the third and fourth metatarsal bones will also give neuroma type symptoms because it too puts pressure on the nerve.
Since a neuroma is a soft tissue condition an MRI should be helpful in diagnosis, however, often an MRI will be inconclusive for neuroma even though a neuroma exists.
