Morton's neuroma overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Sara Mohsin, M.D.[2]Faizan Sheraz, M.D. [3]
Overview
Morton's neuroma is a benign neuroma of the interdigital plantar nerve. It 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.
Historical Perspective
The term neuroma originates from two Greek words, neuro- from the Greek word for nerve (νεῦρον), and -oma (-ωμα) 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.
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 chronic traction 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 arterial thickening/vascular hyalinization, and degenerated/demyelinated axons.
Causes
The exact cause is unknown. However, morton's neuroma is believed to be associated with wearing tight shoes and 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.
Epidemiology and Demographics
Morton neuroma is more common in women than in men.
Risk Factors
Risk factors for morton's neuroma include improper footwear/tight shoes, abnormal positioning of toes, flat feet, forefoot problems such as bunions and hammer toes, high foot arches, high heels, high-impact sports e.g., rock-climbing, & ballet dancing, and overpronation.
Natural History, Complications and Prognosis
Morton's neuroma can make walking difficult. Nonsurgical treatment does not always improve symptoms.
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. Most common symptom of morton's neuroma includes 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 associated with 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.
Other Diagnostic tests
Nerve testing (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, determining proper shoe width, physical therapy, ice massage, strength exercises for intrinsic foot muscles and resting. When conservative measures fail, medical therapy is used which includes tricyclic antidepressants, anticonvulsants, serotonin-norepinephrine reuptake inhibitors, ultrasound-guided interdigital injection of nerve blocking agents such as steroids or local anaesthetics via dorsal approach into the site of tendernes, oral or injectable anti-inflammatory drugs and painkillers.
Surgery
Sugery 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. Permanent nonpainful numbness occurs after surgery if a portion of the affected nerve is removed.
Primary prevention
Primary preventive measures for morton's neuroma include avoiding ill-fitting shoes, high heels, overpronation, high-impact sports such as rock-climbing, ballet dancing and wearing comfortable shoes with wide toe box, low heels and good arch support.