History
Obtaining an accurate history is important to making the diagnosis of Morton's neuroma. Possible reported findings provided by the patient with Morton's neuroma include the following:
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The most common presenting complaints include pain and dysesthesias in the forefoot and corresponding toes adjacent to the neuroma.
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Pain is described as sharp and burning, and it may be associated with cramping.
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Numbness often is observed in the toes adjacent to the neuroma and seems to occur along with episodes of pain.
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Pain typically is intermittent, as episodes often occur for minutes to hours at a time and have long intervals (ie, weeks to months) between a single or small group of multiple attacks.
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Some patients describe the sensation as "walking on a marble."
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Massage of the affected area offers significant relief.
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Narrow, tight high-heeled shoes aggravate the symptoms.
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Night pain is reported but is rare.
Physical
Many sources acknowledge that the examination of patients with Morton's neuroma frequently is negative. However, studies have shown that a clinical history and examination may be more sensitive than ultrasonography or magnetic resonance imaging (MRI). [6, 12] Most often, sensation is wholly intact and maneuvers are unsuccessful in reproducing the characteristic pain. Palpation of the actual neuroma seldom is successful. Most clinicians focus on the history and on the lack of additional findings that might suggest other disorders.
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Firm squeezing of the metatarsal heads with one hand while applying direct pressure to the dorsal and plantar interspace with the other hand may elicit radiating neuropathic pain. Pain localized only to the plantar aspect of the webspace also may be consistent with Morton's neuroma.
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The squeeze test may also result in a "click" (Mulder click) as the neuroma moves between the metatarsals in the dorsal direction. [13]
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Passive and active toe dorsiflexion may aggravate symptoms.
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Sensory abnormalities may be observed, although motor deficits are not consistent with an interdigital neuroma because these are sensory nerves exclusively. Weakness would raise concerns for another diagnosis.
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Careful palpation of the metatarsal heads and shafts may help to differentiate stress fractures or metatarsal head osteonecrosis from Morton's neuroma.
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Palpation of the tarsometatarsal joint and metatarsophalangeal (MTP) joints may reveal tenderness, indicating midfoot arthritis or metatarsalgia (eg, when the tenderness is primarily on the plantar surface only) or MTP synovitis (eg, when the joint is tender with palpation).
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Pain from MTP synovitis is aggravated with forced toe flexion. Subtle joint swelling also may coexist with MTP synovitis. Tenderness localized to the second MTP joint, along with swelling and warmth, may be, in rare cases, an early presentation of Freiburg osteochondrosis.
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Inspection of the foot and evaluation of foot and ankle mechanics should be performed as part of the physical examination, looking for callus formation, hallux valgus, first-ray flexibility, hyperpronation, integrity of the medial arch, and gastrocnemius-soleus flexibility.
Causes
Various factors have been implicated in the precipitation of Morton's neuroma.
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Morton's neuroma is known to develop as a result of chronic nerve stress and irritation, particularly with excessive toe dorsiflexion.
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Poorly fitting and constricting shoes (ie, small toe box) or shoes with heel lifts often contribute to Morton's neuroma. Women who wear high-heeled shoes for a number of years or men who are required to wear constrictive shoe gear are at risk.
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A biomechanical theory of causation involves the mechanics of the foot and ankle. For instance, individuals with tight gastrocnemius-soleus muscles or who excessively pronate the foot may compensate by dorsiflexion of the metatarsals subsequently irritating of the interdigital nerve.
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Certain activities carry increased risk of excessive toe dorsiflexion, such as prolonged walking, running, squatting, and demi-pointe position in ballet. [13]
See the History and Pathophysiology sections.
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Plantar view showing the relationships between the metatarsal heads, the intermetatarsal ligament, and the neuroma.
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Neurectomy: typical incision location.
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Neurectomy: superficial exposure.
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Neurectomy: deeper dissection.
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Neuroma and adherent fibrofatty tissue.
