Morton's neuroma
Encyclopedia
Morton's neuroma is a benign
neuroma
of an intermetatarsal plantar nerve
, most commonly of the third and fourth intermetatarsal spaces.
This problem is characterised by pain
and/or numbness, sometimes relieved by removing footwear
.
Despite the name, the condition was first correctly described by a chiropodist named Durlacher, and although it is labeled a "neuroma", many sources do not consider it a true tumor
, but rather a perineural fibroma (fibrous tissue formation around nerve tissue).
, frequently after only a short time. The nature of the pain varies widely among individuals. Some people experience shooting pain affecting the contiguous halves of two toes. Others describe a feeling like having a pebble in your shoe. Burning, numbness, and paresthesia
may also be experienced.
Morton's neuroma lesions have been found using MRI in patients without symptoms.
, 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. This is referred to as Mulder’s Sign.
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 be the ligaments that attach the phalanx (bone of the toe) 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. Freiberg's disease, which is an osteochondritis
of the metatarsal head, causes pain on weight bearing or compression.
and corticosteroid
injections are widely used conservative treatments for Morton’s neuroma. In addition to traditional orthotic arch supports, a small foam or fabric pad may be positioned under the space between the two affected metatarsals, immediately behind the bone ends. This pad helps to splay the metatarsal bones and create more space for the nerve so as to relieve pressure and irritation. It may however also elicit mild uncomfortable sensations of its own, such as the feeling of having an awkward object under one's foot. Corticosteroid injections can relieve inflammation in some patients and help to end the symptoms. For some patients, however, the inflammation and pain recur after some weeks or months, and corticosteroids can only be used a limited number of times because they cause progressive degeneraton of ligamentous and tendinous tissues.
Sclerosing alcohol injections are an increasingly available treatment alternative if the above management approaches fail. Dilute alcohol (4%) is injected directly into the area of the neuroma, causing toxicity to the fibrous nerve tissue. Frequently, treatment must be performed 2-7 times, with 1-2 weeks between interventions. An 82-90% success rate has been achieved in clinical studies, equal to or exceeding the success rate for surgical neurectomy with fewer risks and less significant recovery.
If such interventions fail, patients are commonly offered surgery known as neurectomy
, which involves removing the affected piece of nerve tissue. Postoperative scar tissue formation (known as stump neuroma) can occur in approximately 20% of cases, causing a return of neuroma symptoms. Neurectomy can be performed using one of two general methods. Making the incision from the dorsal side (the top of the foot) is the original, traditional method but requires cutting the transverse ligament that connects the 3rd and 4th metatarsals in order to access the nerve beneath it. This results in exaggerated postoperative splaying of the 3rd and 4th digits (toes) due to the loss of the supporting ligamentous structure. This has aesthetic concerns for some patients and possible though unquantified long-term implications for foot structure and health. Alternatively, making the incision from the ventral side (the sole of the foot) allows more direct access to the affected nerve without cutting other structures. However, this approach requires a greater post-operative recovery time where the patient must avoid weight bearing on the affected foot because the ventral aspect of the foot is more highly ennervated and impacted by pressure when standing.
Cryogenic neuroablation is a lesser known alternative to neurectomy surgery. Cryogenic neuroablation (also known as cryo injection therapy or cryosurgery) is a term that is used to describe the destruction of axons to prevent them from carrying painful impulses. This is accomplished by applying extremely low temperatures of between −50C to −70C to the nerve-neuroma.
This results in degeneration of the intracellular elements, axons, and myelin
sheath (which houses the neuroma) with wallerian degeneration
. The epineurium
and perineurium
remain intact, thus preventing the formation of stump neuroma. The preservation of these structures differentiates cryogenic neuroablation from surgical excision and neurolytic agents such as alcohol. An initial study showed that cryo neuroablation is initially equal in effectivenesss to surgery but does not have the risk of stump neuroma formation. Longer term, cryogenic neuroablation has a higher recurrence rate of the original neuroma symptoms than surgery.
Benign
A benign tumor is a tumor that lacks the ability to metastasize. Common examples of benign tumors include moles and uterine fibroids.The term "benign" implies a mild and nonprogressive disease. Indeed, many kinds of benign tumors are harmless to human health...
neuroma
Neuroma
A neuroma is a growth or tumor of nerve tissue. Just as the Latin word for swelling is now restricted to neoplasias, the equivalent Greek suffix -oma has shared in that fate. Thus, the typical modern usage of neuroma is for nerve tumors...
of an intermetatarsal plantar nerve
Plantar nerve
The plantar nerves are a pair of nerves innervating the sole of the foot. They arise from the posterior branch of the tibial nerve.-Medial plantar nerve :...
, most commonly of the third and fourth intermetatarsal spaces.
This problem is characterised by pain
Pain
Pain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...
and/or numbness, sometimes relieved by removing footwear
Footwear
Footwear consists of garments worn on the feet, for fashion, protection against the environment, and adornment. Being barefoot is commonly associated with poverty, but some cultures chose not to wear footwear at least in some situations....
.
Despite the name, the condition was first correctly described by a chiropodist named Durlacher, and although it is labeled a "neuroma", many sources do not consider it a true tumor
Tumor
A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...
, but rather a perineural fibroma (fibrous tissue formation around nerve tissue).
Symptoms and signs
Symptoms include: pain on weight bearingWeight bearing
In orthopedics, weight-bearing is the amount of weight a patient puts on the leg on which surgery has been performed. In general, it is described as a percentage of the body weight, because each leg of a healthy person carries the full body weight when walking, in an alternating fashion.After...
, frequently after only a short time. The nature of the pain varies widely among individuals. Some people experience shooting pain affecting the contiguous halves of two toes. Others describe a feeling like having a pebble in your shoe. Burning, numbness, and paresthesia
Paresthesia
Paresthesia , spelled "paraesthesia" in British English, is a sensation of tingling, burning, pricking, or numbness of a person's skin with no apparent long-term physical effect. It is more generally known as the feeling of "pins and needles" or of a limb "falling asleep"...
may also be experienced.
Morton's neuroma lesions have been found using MRI in patients without symptoms.
Diagnosis/differential diagnosis
Negative signs include no obvious deformities, erythemaErythema
Erythema is redness of the skin, caused by hyperemia of the capillaries in the lower layers of the skin. It occurs with any skin injury, infection, or inflammation...
, signs of inflammation
Inflammation
Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...
, 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. This is referred to as Mulder’s Sign.
There are other causes of pain in the forefoot. Too often all forefoot pain is categorized as neuroma. Other conditions to consider are capsulitis
Capsulitis
Capsulitis refers to inflammation of a capsule.Types include:* Adhesive capsulitis of shoulder* Plica syndrome, which is an inflammation of the articular capsule of the knee joint...
, which is an inflammation of ligaments that surrounds two bones, at the level of the joint. In this case, it would be the ligaments that attach the phalanx (bone of the toe) to the metatarsal
Metatarsus
The metatarsus or metatarsal bones are a group of five long bones in the foot located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the medial side : the first, second, third, fourth, and fifth...
bone. Inflammation from this condition will put pressure on an otherwise healthy nerve and give neuroma-type symptoms.
Additionally, an intermetatarsal bursitis
Bursitis
Bursitis is the inflammation of one or more bursae of synovial fluid in the body. The bursae rest at the points where internal functionaries, such as muscles and tendons, slide across bone. Healthy bursae create a smooth, almost frictionless functional gliding surface making normal movement painless...
between the third and fourth metatarsal bones will also give neuroma-type symptoms because it too puts pressure on the nerve. Freiberg's disease, which is an osteochondritis
Osteochondritis
Osteochondritis is a painful type of osteochondrosis where the cartilage or bone in a joint is inflamed.It often refers to osteochondritis dissecans...
of the metatarsal head, causes pain on weight bearing or compression.
Histopathology
Microscopically, the affected nerve is markedly distorted, with extensive concentric perineural fibrosis. The arterioles are thickened and occlusion by thrombi are occasionally present.Imaging
Though a neuroma is a hard tissue abnormality and won’t be visualized on standard radiographs, the first step in the assessment of forefoot pain is an X-ray in order to evaluate for the presence of arthritis and exclude stress fractures/reactions and focal bone lesions, which may mimic the symptoms of a neuroma. Ultrasound (sonography) accurately demonstrates thickening of the interdigital nerve within the web space of greater than 3mm, diagnostic of a Morton’s neuroma. This typically occurs at the level of the intermetatarsal ligament. Frequently, intermetatarsal bursitis coexists with the diagnosis. Other conditions that may also be visualized with ultrasound and can be clinically confused with a neuroma include synovitis/capsulitis from the adjacent metatarsophalangeal joint, stress fractures/reaction, and plantar plate disruption. MRI can similarly demonstrate the above conditions; however, in the setting where more than one abnormality coexists, ultrasound has the added advantage of determining which may be the source of the patient’s pain by applying direct pressure with the probe. Further to this, ultrasound can be used to guide treatment such as cortisone injections into the webspace, as well as alcohol ablation of the nerve.Treatment
OrthoticsOrthotics
Orthotics is a specialty within the medical field concerned with the design, manufacture and application of orthoses. An orthosis is an orthopedic device that supports or corrects the function of a limb or the torso...
and corticosteroid
Corticosteroid
Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex. Corticosteroids are involved in a wide range of physiologic systems such as stress response, immune response and regulation of inflammation, carbohydrate metabolism, protein catabolism, blood electrolyte...
injections are widely used conservative treatments for Morton’s neuroma. In addition to traditional orthotic arch supports, a small foam or fabric pad may be positioned under the space between the two affected metatarsals, immediately behind the bone ends. This pad helps to splay the metatarsal bones and create more space for the nerve so as to relieve pressure and irritation. It may however also elicit mild uncomfortable sensations of its own, such as the feeling of having an awkward object under one's foot. Corticosteroid injections can relieve inflammation in some patients and help to end the symptoms. For some patients, however, the inflammation and pain recur after some weeks or months, and corticosteroids can only be used a limited number of times because they cause progressive degeneraton of ligamentous and tendinous tissues.
Sclerosing alcohol injections are an increasingly available treatment alternative if the above management approaches fail. Dilute alcohol (4%) is injected directly into the area of the neuroma, causing toxicity to the fibrous nerve tissue. Frequently, treatment must be performed 2-7 times, with 1-2 weeks between interventions. An 82-90% success rate has been achieved in clinical studies, equal to or exceeding the success rate for surgical neurectomy with fewer risks and less significant recovery.
If such interventions fail, patients are commonly offered surgery known as neurectomy
Neurectomy
Neurectomy is the surgical removal of a nerve or a section of a nerve. This procedure may be performed, for example, in cases of chronic pain where other treatments have failed. However the removal of the nerve can also cause negative effects, such as permanent numbness...
, which involves removing the affected piece of nerve tissue. Postoperative scar tissue formation (known as stump neuroma) can occur in approximately 20% of cases, causing a return of neuroma symptoms. Neurectomy can be performed using one of two general methods. Making the incision from the dorsal side (the top of the foot) is the original, traditional method but requires cutting the transverse ligament that connects the 3rd and 4th metatarsals in order to access the nerve beneath it. This results in exaggerated postoperative splaying of the 3rd and 4th digits (toes) due to the loss of the supporting ligamentous structure. This has aesthetic concerns for some patients and possible though unquantified long-term implications for foot structure and health. Alternatively, making the incision from the ventral side (the sole of the foot) allows more direct access to the affected nerve without cutting other structures. However, this approach requires a greater post-operative recovery time where the patient must avoid weight bearing on the affected foot because the ventral aspect of the foot is more highly ennervated and impacted by pressure when standing.
Cryogenic neuroablation is a lesser known alternative to neurectomy surgery. Cryogenic neuroablation (also known as cryo injection therapy or cryosurgery) is a term that is used to describe the destruction of axons to prevent them from carrying painful impulses. This is accomplished by applying extremely low temperatures of between −50C to −70C to the nerve-neuroma.
This results in degeneration of the intracellular elements, axons, and myelin
Myelin
Myelin is a dielectric material that forms a layer, the myelin sheath, usually around only the axon of a neuron. It is essential for the proper functioning of the nervous system. Myelin is an outgrowth of a type of glial cell. The production of the myelin sheath is called myelination...
sheath (which houses the neuroma) with wallerian degeneration
Wallerian degeneration
Wallerian degeneration is a process that results when a nerve fiber is cut or crushed, in which the part of the axon separated from the neuron's cell body degenerates distal to the injury. This is also known as anterograde degeneration, or orthograde degeneration...
. The epineurium
Epineurium
The epineurium is the outermost layer of connective tissue surrounding a peripheral nerve. It is made of dense irregular connective tissue and usually contains multiple nerve fascicles as well as blood vessels which supply the nerve...
and perineurium
Perineurium
In the peripheral nervous system, nerve fibers are each wrapped in a protective sheath known as the endoneurium. These are bundled together into groups known as fascicles, each surrounded by a protective sheath known as the perineurium. Several fascicles may be in turn bundled together with a blood...
remain intact, thus preventing the formation of stump neuroma. The preservation of these structures differentiates cryogenic neuroablation from surgical excision and neurolytic agents such as alcohol. An initial study showed that cryo neuroablation is initially equal in effectivenesss to surgery but does not have the risk of stump neuroma formation. Longer term, cryogenic neuroablation has a higher recurrence rate of the original neuroma symptoms than surgery.
Morton's neuroma in popular culture
Dorothy Zbornak, a character in the NBC television show "The Golden Girls," was diagnosed with a Morton's Neuroma in the episode titled "The Operation."External links
- Overview at Mayo ClinicMayo ClinicMayo Clinic is a not-for-profit medical practice and medical research group specializing in treating difficult patients . Patients are referred to Mayo Clinic from across the U.S. and the world, and it is known for innovative and effective treatments. Mayo Clinic is known for being at the top of...
- Podiatry Channel
- American Orthopaedic Foot and Ankle Society
- American Academy of Podiatric Sports Medicine
- Morton's Neuroma . Net
- Morton's Neuroma.co.uk
- Morton's Neuroma Blog
- Image gallery of MRI & Ultrasound evaluation of forefoot pain
- What is Morton's Neuroma - www.SimonMoyes.co.uk