Morton's Neuroma
   HOME

TheInfoList



OR:

Morton's neuroma is a benign neuroma of an intermetatarsal plantar nerve, most commonly of the second and third intermetatarsal spaces (between the second/third and third/fourth metatarsal heads; the first is of the big toe), which results in the entrapment of the affected nerve. The main symptoms are pain and/or numbness, sometimes relieved by ceasing to wear footwear with tight
toe box The toe box is the section of footwear that surrounds the toes on closed-toe shoes. Toe boxes that are too tight can cause injuries and foot deformity, foot deformities, whereas wider toe boxes may be used to treat or prevent common foot condition ...
es and
high heels High-heeled shoes, also known as high heels (colloquially shortened to heels), are a type of shoe with an upward-angled sole. The heel in such shoes is raised above the ball of the foot. High heels cause the legs to appear longer, make the we ...
(which have been linked to the condition). The condition is named after Thomas George Morton, though it was first correctly described by a chiropodist named Durlacher. Some sources claim that entrapment of the plantar nerve resulting from compression between the metatarsal heads, as originally proposed by Morton, is highly unlikely, because the plantar nerve is on the plantar side of the
transverse metatarsal ligament The transverse metatarsal ligament is a narrow band which runs across and connects together the heads of all the metatarsal bones. It is blended anteriorly with the plantar (glenoid) ligaments of the metatarsophalangeal articulations. Its plantar ...
and thus does not come into contact with the metatarsal heads. It is more likely that the transverse metatarsal ligament is the cause of the entrapment. Though the condition is labeled as a neuroma, many sources do not consider it a true
tumor A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...
, but rather a perineural
fibroma Fibromas are benign tumors that are composed of fibrous or connective tissue. They can grow in all organs, arising from mesenchyme tissue. The term "fibroblastic" or "fibromatous" is used to describe tumors of the fibrous connective tissue. Wh ...
(fibrous tissue formation around nerve tissue).


Signs and symptoms

Symptoms include pain on
weight bearing In orthopedics, weight-bearing is the amount of weight a patient puts on an injured body part. Generally, it refers to a leg, ankle or foot that has been fractured or upon which surgery Surgery is a medical specialty that uses manual and ins ...
, 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 akin to having a pebble in the shoe or walking on razor blades. Burning, numbness, and
paresthesia Paresthesia is a sensation of the skin that may feel like numbness (''hypoesthesia''), tingling, pricking, chilling, or burning. It can be temporary or Chronic condition, chronic and has many possible underlying causes. Paresthesia is usually p ...
may also be experienced. The symptoms progress over time, often beginning as a tingling sensation in the ball of the foot. Morton's neuroma lesions have been found using
MRI Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to generate pictures of the anatomy and the physiological processes inside the body. MRI scanners use strong magnetic fields, magnetic field gradients, and rad ...
in patients without symptoms.


Diagnosis

Negative signs include a lack of obvious deformities,
erythema Erythema (, ) is redness of the skin or mucous membranes, caused by hyperemia (increased blood flow) in superficial capillaries. It occurs with any skin injury, infection, or inflammation. Examples of erythema not associated with pathology inc ...
, signs of
inflammation Inflammation (from ) is part of the biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. The five cardinal signs are heat, pain, redness, swelling, and loss of function (Latin ''calor'', '' ...
, 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 that often lead to miscategorization as neuroma, such as capsulitis, which is an inflammation of ligaments that surround two bones at the level of the joint. If the ligaments that attach the
phalanx The phalanx (: phalanxes or phalanges) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar polearms tightly packed together. The term is particularly used t ...
(bone of the toe) to the
metatarsal bone The metatarsal bones or metatarsus (: metatarsi) are a group of five long bones in the midfoot, located between the tarsal bones (which form the heel and the ankle) and the phalanges ( toes). Lacking individual names, the metatarsal bones are ...
are impacted, the resulting inflammation may put pressure on an otherwise healthy nerve and produce neuroma-type symptoms. Additionally, an intermetatarsal
bursitis Bursitis is the inflammation of one or more bursae (synovial sacs) of synovial fluid in the body. They are lined with a synovial membrane that secretes a lubricating synovial fluid. There are more than 150 bursae in the human body. The bursae (bu ...
between the third and fourth metatarsal bones will also give neuroma-type symptoms because it too puts pressure on the nerve. Freiberg disease, which is an
osteochondritis Osteochondritis is a painful type of osteochondrosis where the cartilage or bone in a joint is inflamed. It often refers to osteochondritis dissecans (OCD). The term ''dissecans'' refers to the "creation of a flap of cartilage that further dissect ...
of the metatarsal head, causes pain on weight-bearing or compression. Other conditions that could be clinically confused with a neuroma include
stress fracture A stress fracture is a fatigue-induced bone fracture caused by repeated stress over time. Instead of resulting from a single severe impact, stress fractures are the result of accumulated injury from repeated submaximal loading, such as running ...
s/reactions and
plantar plate In the human foot, the plantar or volar plates (also called plantar or volar ligaments) are fibrocartilaginous structures found in the metatarsophalangeal (MTP) and interphalangeal (IP) joints. The anatomy and composition of the plantar plates ar ...
disruption.


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 soft-tissue abnormality and will not be visualized by standard radiographs, the first step in the assessment of forefoot pain is an X-ray to detect the presence of arthritis and exclude stress fractures/reactions and focal bone lesions, which may mimic the symptoms of a neuroma.
Ultrasound Ultrasound is sound with frequency, frequencies greater than 20 Hertz, kilohertz. This frequency is the approximate upper audible hearing range, limit of human hearing in healthy young adults. The physical principles of acoustic waves apply ...
(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. MRI can distinguish conditions that mimic the symptoms of Morton's neuroma, but when more than one abnormality exists, ultrasound has the added advantage of determining the precise source of the patient's pain by applying direct pressure with the probe. Ultrasound may also be used to guide treatment such as
cortisone Cortisone is a pregnene (21-carbon) steroid hormone. It is a naturally-occurring corticosteroid metabolite that is also used as a pharmaceutical prodrug. Cortisol is converted by the action of the enzyme corticosteroid 11-beta-dehydrogenase ...
injections into the webspace, as well as alcohol
ablation Ablation ( – removal) is the removal or destruction of something from an object by vaporization, chipping, erosion, erosive processes, or by other means. Examples of ablative materials are described below, including spacecraft material for as ...
of the nerve.


Treatment


Conservative

Orthotics Orthotics () is a medical specialty that focuses on the design and application of orthoses, sometimes known as braces, calipers, or splints. An is "an externally applied device used to influence the structural and functional characteristics of ...
and improved footwear are the first-line 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. However, it may also elicit mild uncomfortable sensations of its own, such as the feeling of having an awkward object under one's foot. Footwear and orthotics are most effective in neuromas that have existed less than four and a half months and are smaller than . To prevent or treat Morton's neuroma, comfortable shoes that are sufficiently long and have a wide
toe box The toe box is the section of footwear that surrounds the toes on closed-toe shoes. Toe boxes that are too tight can cause injuries and foot deformity, foot deformities, whereas wider toe boxes may be used to treat or prevent common foot condition ...
, flat heel, and thick sole are recommended.
Corticosteroid Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex of vertebrates, as well as the synthetic analogues of these hormones. Two main classes of corticosteroids, glucocorticoids and mineralocorticoids, are invo ...
injections can relieve inflammation in some patients and help end the symptoms. For some patients, however, the inflammation and pain recur after some weeks or months, and corticosteroids may only be used a limited number of times because they cause progressive degeneration of ligamentous and tendinous tissues. About 30% of people who receive steroid injections go on to have surgery. According to a 2021 review, it is most effective in neuromas smaller than . Sclerosing alcohol injections are an increasingly available treatment alternative if other 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 two to four times, with one to three weeks between interventions. A 60–80% 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 done with more concentrated alcohol under ultrasound guidance, the success rate is considerably higher and fewer repeat procedures are needed.
Radiofrequency ablation Radiofrequency ablation (RFA), also called fulguration, is a medical procedure in which part of the electrical conduction system of the heart, tumor, sensory nerves or a dysfunctional tissue is ablated using the heat generated from medium fre ...
is also used in the treatment of Morton's neuroma. The outcomes appear to be similar to, or even more reliable than, alcohol injections, especially if the procedure is performed under ultrasound guidance. A 2019 systematic review of randomised controlled trials found that corticosteroid injections or manipulation/mobilisation reduced pain more than control, extracorporeal shockwave therapy or varus/valgus foot wedges (which did not reduce pain more than control or comparison treatment, and pain reduction was not reported in any wider foot/metatarsal padding studies). The review also found no randomised controlled trials for sclerosing alcohol injections, radiofrequency ablation, cryoneurolysis or
botulinum toxin Botulinum toxin, or botulinum neurotoxin (commonly called botox), is a neurotoxic protein produced by the bacterium ''Clostridium botulinum'' and related species. It prevents the release of the neurotransmitter acetylcholine from axon en ...
injections; these were only assessed with pre-test/post-test case series, which do not measure the benefit of treatment beyond placebo or spontaneous improvement over time.


Surgery

If non-surgical interventions fail, patients are commonly offered
neurectomy A neurectomy, or nerve resection is a neurosurgical procedure in which a peripheral nerve is cut or removed to alleviate neuropathic pain or permanently disable some function of a nerve. The nerve is not intended to grow back. For chronic pain it ...
, a surgery that involves removing the affected piece of nerve tissue. Postoperative scar tissue formation (known as stump neuroma) can occur in approximately 20–30% of cases, causing a return of neuroma symptoms. Neurectomy may be performed using one of two general methods. Making the incision from the dorsal side (the top of the foot) is the more common method but requires cutting the deep transverse metatarsal ligament that connects the third and fourth metatarsals in order to access the nerve beneath it. This results in exaggerated postoperative splaying of the third and fourth digits (toes) resulting from 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 in which the patient must avoid weight-bearing on the affected foot, because the ventral aspect of the foot is more highly enervated and impacted by pressure when standing. It also carries an increased risk of scar-tissue formation in a location that causes ongoing pain. When a patient has multiple neuromas in the same foot, the most common surgical approach is to remove them all using a single incision.
Cryogenic In physics, cryogenics is the production and behaviour of materials at very low temperatures. The 13th International Institute of Refrigeration's (IIR) International Congress of Refrigeration (held in Washington, DC in 1971) endorsed a univers ...
neuroablation (also known as cryoinjection therapy, cryoneurolysis, cryosurgery or cryoablation) is a lesser-known alternative to neurectomy surgery. It involves the destruction of
axons An axon (from Greek ἄξων ''áxōn'', axis) or nerve fiber (or nerve fibre: see spelling differences) is a long, slender projection of a nerve cell, or neuron, in vertebrates, that typically conducts electrical impulses known as action pot ...
to prevent them from carrying painful impulses. This is accomplished by making a small incision (~3 mm) and inserting a cryoneedle that applies extremely low temperatures of between −50 °C to −70 °C to the nerve/neuroma,Cryosurgery Or Sclerosing Injections: Which Is Better For Neuromas?
/ref> resulting in degeneration of the intracellular elements,
axons An axon (from Greek ἄξων ''áxōn'', axis) or nerve fiber (or nerve fibre: see spelling differences) is a long, slender projection of a nerve cell, or neuron, in vertebrates, that typically conducts electrical impulses known as action pot ...
and
myelin Myelin Sheath ( ) is a lipid-rich material that in most vertebrates surrounds the axons of neurons to insulate them and increase the rate at which electrical impulses (called action potentials) pass along the axon. The myelinated axon can be lik ...
sheath (which houses the neuroma) with wallerian degeneration. The
epineurium The epineurium is the outermost layer of dense irregular connective tissue surrounding a peripheral nerve. It usually surrounds multiple nerve fascicles as well as blood vessels which supply the nerve. Smaller branches of these blood vessels penet ...
and
perineurium The perineurium is a protective sheath that surrounds a nerve fascicle. This bundles together axons targeting the same anatomical location. The perineurium is composed from fibroblasts. In the peripheral nervous system, the myelin sheath of each ...
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 cryoneuroablation is initially equal in effectiveness to surgery but does not have the risk of stump neuroma formation. An increasing range of procedures are being performed at specialist centers to treat Morton's neuroma under ultrasound guidance. Studies have examined the treatment of the condition with ultrasound-guided sclerosing alcohol injections, radiofrequency ablation and cryoablation.


References


External links

{{DEFAULTSORT:Morton's Neuroma Anatomical pathology Foot diseases