AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

INTRODUCTION

Section 2 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Background

Morton neuroma (interdigital neuroma), first described in 1876, is a perineural fibrosis and nerve degeneration of the common digital nerve. Morton neuroma is not a true neuroma, although it results in neuropathic pain in the distribution of the interdigital nerve secondary to repetitive irritation of the nerve. The most frequent location is between the third and fourth metatarsals (third web space). Other less common locations are between the second and third metatarsals (second web space) and, rarely, between the first and second (first web space) or fourth and fifth (fourth web space) metatarsals.

Episodes of pain are intermittent. Patients may experience 2 attacks in a week then none for a year. Recurrences are variable and tend to become more frequent. Between attacks, no symptoms or physical signs occur. Two neuromas rarely coexist on the same foot. Other diagnoses should be considered when 2 or more areas of tenderness are present.

Pathophysiology

Interdigital nerves are composed of communicating branches from the lateral and medial plantar nerves. At the level of the metatarsal heads, the interdigital nerve traverses inferior to the intermetatarsal ligament. At this site, the nerve may be compressed or stretched from repetitive toe flexion and extension. Studies have shown perineural fibrosis and demyelination.

Frequency

United States

Morton neuroma is a common disease entity of the foot.

International

Incidence is presumed to be the same internationally as in United States.

Sex

The female-to-male ratio is 5:1.

Age

Highest prevalence of Morton's neuroma is found in patients aged 15-50 years, but the condition may occur in any ambulatory patient.

CLINICAL

Section 3 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

History

Obtaining an accurate history is important to making the diagnosis of Morton neuroma. Possible reported findings provided by the patient with Morton neuroma include the following:

• The most common presenting complaints include pain and dysesthesias in the forefoot and corresponding toes adjacent to the neuroma.
• Pain is described as sharp and burning, and it may be associated with cramping.
• Numbness often is observed in the toes adjacent to the neuroma and seems to occur along with episodes of pain.
• 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.
• Some patients describe the sensation as "walking on a marble."
• Massage of the affected area offers significant relief.
• Narrow tight high-heeled shoes aggravate the symptoms.
• Night pain is reported but is rare.

Physical

Many sources acknowledge that the examination of patients with Morton neuroma frequently is negative. 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 both on the history and on the lack of additional findings that might suggest other disorders.

• 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 web space also may be consistent with Morton neuroma.
• The squeeze test may also result in a "click" (Mulder click) as the neuroma moves between the metatarsals in the dorsal direction (O'Connor, 2001).
• Passive and active toe dorsiflexion may aggravate symptoms.
• 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.
• Careful palpation of the metatarsal heads and shafts may help to differentiate stress fractures or metatarsal head osteonecrosis from Morton neuroma.
• 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).
• 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.
• 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 to precipitate this condition.

• Morton neuroma is known to develop as a result of chronic nerve stress and irritation, particularly with excessive toe dorsiflexion.
• Poorly fitting and constricting shoes (ie, small toe box) or shoes with heel lifts often contribute to Morton 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.
• 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.
• Certain activities carry increased risk of excessive toe dorsiflexion, such as prolonged walking, running, squatting, and demi-pointe position in ballet (O'Connor, 2001).

See the History and Pathophysiology sections.

DIFFERENTIALS

Section 4 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Other Problems to be Considered

Stress fracture of the neck of the metatarsal
Rheumatoid arthritis and other systemic arthritis conditions
Hammer toe
Metatarsalgia (plantar tenderness over the metatarsal head)
Neoplasms
Metatarsal head osteonecrosis
Freiburg osteochondrosis
Ganglion cysts
Intermetatarsal bursal fluid collections
True neuromas

WORKUP

Section 5 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Lab Studies

• No laboratory studies are indicated for diagnosis of Morton neuroma.

Imaging Studies

• Results of plain films are normal in Morton neuroma.
• Ultrasound, though not often used, may detect Morton neuroma but has questionable reliability.
• Computed tomography (CT) scan has been used but may not be as sensitive as magnetic resonance imaging (MRI).
• • MRI, while not needed in most cases for establishing diagnosis of Morton neuroma, has been studied widely.
  • Sensitivity of 87% and specificity as high as 100% have been reported. Asymptomatic neuromas may occur and confound accurate diagnosis.
• Indications exist that Morton neuromas smaller than 5 mm in diameter may not be significant clinically and that other diagnoses may be excluded carefully before diagnosis of a symptomatic Morton neuroma is made with such a small lesion. Imaging with T1 weighting in a coronal plane is recommended for best visualization. In addition, on T2 imaging, the low signal of a Morton neuroma may help differentiate it from a true neuroma, ganglion cyst, or intermetatarsal bursal fluid collection.
• Contrast enhancement usually is demonstrated with Morton neuromas.

Other Tests

• Electromyography and nerve conduction study (EMG/NCS) of Morton neuroma is not used often because of the technical difficulty in performing the test, requiring needle stimulation of the common digital nerve and pickup on the adjacent toe or toes, which may be of short distance. Surface stimulation results most often in volume conduction through the skin to the pickups because of the short distance involved and the large amount of stimulation needed to penetrate the deep tissue separating the nerve from the skin surface.

Histologic Findings

Tissue biopsy is neither needed nor recommended for Morton neuroma.

TREATMENT

Section 6 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Rehabilitation Program

Physical Therapy

Treatment strategies for Morton neuroma range from conservative to surgical management. The conservative approach to treating Morton neuroma may benefit from the involvement of a physical therapist. The physical therapist can assist the physician in decisions regarding the modification of footwear, which is the first step to treatment. Recommend soft-soled shoes with a wide toe box and low heel (eg, an athletic shoe). High-heeled narrow nonpadded shoes should not be worn, as they aggravate the condition.

The next step in conservative management is to alter alignment of the metatarsal heads. One recommended action is to elevate the metatarsal head medial and adjacent to the neuroma, thereby preventing compression and irritation of the digital nerve. A plantar pad is used most often for elevation. Have the patient insert a felt or gel pad into the shoe to achieve the desired elevation of the above metatarsal head.

Other possible physical therapy treatment ideas for patients with Morton neuroma include cryotherapy, ultrasound, deep tissue massage, and stretching exercises. Ice is beneficial to decrease the associated inflammation. Phonophoresis also can be used, rather than just ultrasound, to decrease pain and inflammation further.

Surgical Intervention

Surgical excision of the area of fibrosis in the common digital nerve may be curative when conservative measures are unsuccessful. Common adverse outcomes include dysesthesias radiating from a painful nerve stump after surgical excision of the Morton neuroma. Dysesthesias may be treated as any other dysesthetic pain. (See the Medication section.)

Consultations

If surgical intervention is needed, consultation with an orthopedic surgeon specializing in foot and ankle surgery is recommended.

Other Treatment

A more aggressive approach involves injection of the Morton neuroma. Perform injection into the dorsal aspect of the foot, 1-2 cm proximal to the web space, in line with the MTP joints. Advance the needle through the mid web space into the plantar aspect of the foot until the needle gently tents the skin. Then withdraw it about 1 cm to where the tip of the neuroma is located. Inject a corticosteroid/anesthetic mix. A reasonable volume is 1 mL of corticosteroid and 2 mL of anesthetic. The anesthetic used should not contain epinephrine, as necrosis may result. Care also should be taken not to inject into the plantar pad. Adverse outcomes include plantar fat pad necrosis. Transient numbness of the toes also may occur. Although many practitioners use multiple injections, the likelihood of benefit from subsequent injections, after failure to achieve relief from the initial injection, is negligible.

MEDICATION

Section 7 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Dysesthesias may be treated as any other dysesthetic pain. Tricyclic antidepressants, such as amitriptyline at 10-25 mg PO qhs, may be tried. If this approach is unsuccessful, anticonvulsants (eg, gabapentin, carbamazepine) often are effective.

Drug Category: Tricyclic antidepressants

A complex group of drugs that have central and peripheral anticholinergic effects, as well as sedative effects. They have central effects on pain transmission, and they block the active re-uptake of norepinephrine and serotonin.

Drug Category: Anticonvulsants

Use of certain antiepileptic drugs (AEDs), such as the GABA analogue Neurontin (gabapentin), has proven helpful in some cases of neuropathic pain. Thus, although unstudied, a trial of such an agent might conceivably provide analgesia for symptomatic neuropathy. Used for dysesthesias not controlled with definitive treatment plus tricyclic antidepressants (or in patients unable to take tricyclic antidepressants).

Drug Category: Serotonin-norepinephrine reuptake inhibitors

These agents inhibit neuronal serotonin and norepinephrine reuptake.

FOLLOW-UP

Section 8 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Deterrence/Prevention:

• General prevention includes ensuring that shoes fit properly. Recommend wearing of well-padded low-heeled shoes with wide toe box. No other preventative techniques are recommended.

Complications:

• Chronic pain may develop when treatment is unsuccessful for patients with Morton neuroma. Postoperative complications, such as dysesthesias, are possible when surgery is performed to remove the neuroma. Possible complications following corticosteroid injections may include plantar fat pad necrosis and transient numbness of the toes.

Prognosis:

• Prognosis for recovery is good with conservative treatment; however, patients still may require surgical intervention. Some patients who undergo surgery report as high as 50% recurrence rate.

Patient Education:

• Patients should be well informed about proper footwear.

MISCELLANEOUS

Section 9 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical/Legal Pitfalls

• The most common condition misdiagnosed as Morton neuroma is metatarsophalangeal (MTP) joint synovitis. When pain occurs in the third interspace, the clinician may misdiagnose the condition as Morton neuroma instead of MTP synovitis, which may manifest very much like Morton neuroma. MTP synovitis is distinguished from Morton neuroma by subtle swelling around the joint, pain localized mainly within the joint, and pain with forced toe flexion. Palpation of the MTP joint is performed best with a pinching maneuver from the dorsal and plantar aspects of the joint to elicit tenderness of the joint. Other conditions often misdiagnosed as Morton neuroma include the following:
• • Stress fracture of the neck of the metatarsal
  • Rheumatoid arthritis and other systemic arthritis conditions
  • Hammer toe
  • Metatarsalgia (ie, plantar tenderness over the metatarsal head)
• Less common conditions that have overlapping symptoms with Morton neuroma include the following:
• • Neoplasms
  • Metatarsal head osteonecrosis
  • Freiburg osteochondrosis
  • Ganglion cysts
  • Intermetatarsal bursal fluid collections
  • True neuromas

REFERENCES

Section 10 of 10

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

• Betts LO. Morton's Metatarsalgia. Med J Aust. 1940;1:514.
• Clanton TO, Butler JE, Eggert A. Injuries to the metatarsophalangeal joints in athletes. Foot Ankle. Dec 1986;7(3):162-76. [Medline].
• Cyriax J. Diagnosis of soft tissue lesions.In: Textbook of Orthopaedic Medicine. 8th ed. Philadelphia, Pa:. The Curtis Center;1982.
• Guiloff RJ. Carbamazepine in Morton''s neuralgia. Br Med J. Oct 13 1979;2(6195):904. [Medline].
• Jahss MH, Kummer F. Non-inflammatory synovitis of the second metatarsophalangeal joint and its surgical management. Paper read at: 16th Annual Meeting of American Orthopaedic Foot Ankle Society. February 1986;New Orleans, La.
• Logan PM, Janzen DL, O''Connell JX, et al. Magnetic resonance imaging and histopathologic appearances of benign soft-tissue masses of the foot. Can Assoc Radiol J. Feb 1996;47(1):36-43. [Medline].
• Mizel MS, Miller RA, Scioli MW. Orthopaedic knowledge update. In: Foot and Ankle. Rosemont, Ill:. American Academy of Orthopaedic Surgeons;1998.
• Morton TG. Peculiar painful affection of fourth metatarsophalangeal articulation. Am J Med Sci. 1876;71:37.
• O'Connor FG, Wilder RP, Nirschl R. Foot Injuries in the Runner. In:Textbook of Running Medicine. New York: McGraw-Hill; 2001;258-260.
• Snyder RK. In: Essentials of Musculoskeletal Care. Rosemont, Ill:. American Academy of Orthopedic Surgeons;1997.
• Terk MR, Kwong PK, Suthar M, et al. Morton neuroma: evaluation with MR imaging performed with contrast enhancement and fat suppression. Radiology. Oct 1993;189(1):239-41. [Medline].
• Vazquez-Abad D, Tian L, Monteon V, et al. CRI-EM is a human idiotype highly specific for scleroderma. Ann N Y Acad Sci. Apr 5 1997;815:512-5. [Medline].
• Wu KK. Morton neuroma and metatarsalgia. Curr Opin Rheumatol. Mar 2000;12(2):131-42. [Medline].
• Yocum LA. In: Clinics in Sports Medicine. Vol 7. Philadelphia, Pa:. WB Saunders Co;1988.
• Zanetti M, Weishaupt D. MR imaging of the forefoot: Morton neuroma and differential diagnoses. Semin Musculoskelet Radiol. Sep 2005;9(3):175-86.

Article Last Updated: Jun 7, 2006