Morton's neuroma overview

# Overview
Morton's neuroma is a benign neuroma of the interdigital plantar nerve. Although it is labeled a "neuroma", many sources do not consider it a true tumor, but rather a thickening of existing tissue or a swollen, inflamed nerve located between the bones at the ball of the foot. The most common location of a Morton's neuroma is in either the second or the third spacing from the base of the big toe. It is characterised by numbness & pain, and relieved by removing footwear.

# Historical Perspective
The term neuroma originates from two Greek words, neuro- from the Greek word for nerve (), and -oma (-) from the Greek word for swelling. In 1876, neuroma was first described by Thomas Morton and Morton's neuroma was first correctly described by a chiropodist named Durlacher. In 2000, a small studyreviewed the medical records of 85 people who had their feet imaged with MRI, and it was found out that 33% of the patients had morton's neuroma without any pain.

# Pathophysiology
Morton's neuroma is associated with symptomatic collapse of the transverse arch by perineural fibrosis around a plantar digital nerve of the foot due to chronictraction and increased pressure/compression on the interdigital nerve. It is located at the third intermetatarsal space most commonly (between third and fourth metatarsals), and sometimes second or fourth interspaces or bifurcation of the fourth plantar digital nerve. Gross pathological features of morton's neuroma include adherent fibrofatty tissue, small, firm, oval, yellowish-white, slowly growing, palpable nodule on skin (no discoloration of skin on the top of nodule) and </=2cm in size. Histopathological analysis is characterized by extensive fibrosis around and within the nerve, digital artery, thrombosis, epineural and endoneural arterialthickening/vascular hyalinization, and degenerated/demyelinated axons. Possible tissue pathologies associated with interdigital pain of morton's neuroma include perineural fibrosis, endoneural edema, neurofibromata, angioneurofibromata, local demyelination, and local vascular degeneration.

# Causes
The exact cause is unknown. However, morton's neuroma is believed to be associated with wearing tight shoes with tapered toe box or high heels, overpronation, abnormal positioning of toes, flat feet, forefoot problems such as bunions and hammer toes, and high foot arches.

# Differentiating Morton's Neuroma from other diseases
Morton's neuroma must be differentiated from other causes of pain in the forefoot such as metatarsophalangeal joint capsulitis, intermetatarsal bursitis, calluses, stress fractures, Freiberg's disease, osteomyelitis, localized vasculitis, ischemia of plantar digital artery, tarsal tunnel syndrome, rheumatoid arthritis, peripheral neuritis, synovitis, tendonitis, and avascular necrosis.

# Epidemiology and Demographics
Morton's neuroma is more common in women than men.

# Risk Factors
Risk factors for morton's neuroma include improper footwear/tight shoes with tapered toe box, abnormal positioning of toes, flat feet, forefoot problems such as bunions and hammer toes, high foot arches, high heels, overpronation, gait abnormalities, and high-impact sports such as rock-climbing, ballet dancing, jogging, running, snow skiing, racquet and court sports.

# Natural History, Complications and Prognosis
Symptoms of morton's neuroma begin gradually and initially occur only occasionally while wearing the narrow-toed shoes and performing certain aggravating activities. Symptoms may go away temporarily by removing the shoe, massaging the foot and avoiding the aggravating shoes/activities. Symptoms become even more intense & start to worsen progressively with time and may persist for several days or weeks. Ultimately, the temporary changes in the nerve become permanent if left untreated for prolonged periods of time. Common complications of morton's neuroma include difficult walking, trouble performing activities that putpressure on the foot (pressing the gas pedal of an automobile), and feet hurt with wearing certain types of shoes especially high-heels. Postoperative complicationsinclude permanent non-painful numbness, small risk of infection around toes after surgery, incisional soreness, scarring, & recurring stump neuromas. Non-surgicaltreatment is successful in 80% of the cases but does not always improve symptoms and surgery to remove the thickened tissue is successful in about 85% of cases.

# History and Symptoms
Morton's neuroma is most commonly located at the third intermetatarsal space, with other sites being involved including second or fourth interspaces, at the bifurcation of the fourth plantar digital nerve and fifth interspace rarely. Patient complaints of feeling like ''walking on a marble''. Most common symptom of morton's neuroma includes persistent pain on weight bearing affecting the contiguous halves of two toes, with the nature of pain being shooting, burning, stabbing, raw, gnawing or sickening sensations. Other symptoms may include numbness, parasthesia, dysesthesia, functional impairment and psychological distress associatedwith severe decrease in the quality of life.

# Physical Examination
Patients may have antalgic posture. Physical examination may be remarkable for tenderness to palpation, limitation of range of motion, dysesthetic pain and Mulder's sign which includes replication of symptoms or clicking sensations upon direct pressure between the metatarsal heads or compression of transverse arch in forefoot between the finger and thumb. Negative signs include no obvious deformities, erythema or signs of inflammation.

# Laboratory Findings
Blood tests are done to check for inflammation-related conditions, including certain forms of arthritis.

# X-Ray
A foot x-ray may be done to rule out bone pathologies such as arthritis or any stress fractures.

# MRI
MRI can successfully diagnose and assess the location, size, and soft tissue abnormalities associated with Morton's neuroma. As there's a 26% chance of morton's neuroma recurrence after surgery, hence, post-operative MR imaging can help rule out any recurrence. Morton's neuroma-like abnormalities are seen in asymptomatic and symptomatic intermetatarsal spaces on MRI after the resection of morton's neuroma. There's a significant difference in the appearance of morton's neuroma on MRI done in different positions such as prone, supine, or weight-bearing, with the morton's neuroma being best visible in the prone position.

# Other Imaging Findings
Imaging findings on high-resolution ultrasound may help to find out or differentiate any soft tissue abnormalities from morton's neuroma. In 2000, a study was conducted in which ultrasound done on patients with morton's neuroma demonstrated to have 100% sensitivity, 83.3% specificity and 96.7% accuracy in detectingthe location of morton's neuroma. Symptomatic morton's neuroma is at least 5 mm in diameter on sonogram. A presumed plantar digital nerve identified in continuity with the mass on ultrasound leads to an improved diagnostic confidence of morton's neuroma.

# Other Diagnostic Tests
Nerve testing such as electromyography cannot definitely diagnose Morton's neuroma, but may be used to rule out conditions that cause similar symptoms.

# Medical Therapy
Non-surgical treatment is instituted first for the treatment of morton's neuroma. Firstly, the conservative measures are used for the pain relief such as decreasing the pressure on metatarsal heads by using metatarsal support, bars, padded shoe insert just proximal to the metatarsal head, tapping the toe area, orthotics, specialized orthopedic shoes, shoes with wider toe boxes allowing spread of metatarsal heads, low heels, good arch support & stiff soles, determining proper shoewidth, physical therapy, massaging ball of the foot, strength exercises for intrinsic foot muscles, stretching exercises for foot tendons & ligaments, resting the foot, applying ice packs to the sore foot areas and weight loss in overweight patients. When conservative measures fail, medical therapy is used which includes tricyclic antidepressants, anticonvulsants, serotonin-norepinephrine reuptake inhibitors, prolotherapy via Hackett-Hemwall technique which includes ultrasound-guidedinterdigital injection of nerve blocking agents such as steroids, local anaesthetics, dextrose, anti-inflammatory drugs or 4% alcohol sclerosing injections via dorsalapproach into the site of tenderness, oral or injectable anti-inflammatory drugs and painkillers.

# Surgery
Surgery is the last resort in the treatment of morton's neuroma. In some cases, surgery may be needed to remove the thickened tissue/affected nerve in order to help release the pressure on the affected nerve, relieve the pain and improve foot function. Few complications after surgery are possible and include permanent nonpainful numbness if a portion of the affected nerve is removed, risk of postoperative infection around the toes, incisional soreness, scarring, and recurring stump neuromas. Morton's neuroma can be removed surgically either via dorsal or plantar approach, with each approach having its own merits and demerits. Dependingupon each individual case, different surgical procedures that can be used for the treatment of morton's neuroma include neurectomy, cryogenicsurgery/neuroablation, and decompression surgery.

# Primary prevention
Primary preventive measures for morton's neuroma include avoiding ill-fitting shoes, high heels, narrow-toed shoes, overpronation, high-impact sports such as rock-climbing, ballet dancing, jogging, running, snow skiing, wearing comfortable shoes with wide toe box, low heels & good arch support and wearing athletic shoes (with enough padding in the soles) while running or playing sports.