Morton’s neuroma

From Symptoms to Solutions: A Guide to Understanding Neuromas

Morton’s neuroma is a common condition affecting the forefoot, particularly the third intermetatarsal space. Despite its name, it is not a true neuroma but rather a thickening and fibrosis of the digital nerve due to chronic pressure or repetitive irritation. This leads to nerve inflammation and structural changes such as neural edema, axonal injury, demyelination, and perineural fibrosis. These degenerative changes contribute to localized pain and discomfort, particularly during weight-bearing activities.

Morton’s neuroma is classified as one of the most prevalent nerve entrapment syndromes, commonly resulting from compression under the transverse metatarsal ligament, chronic traction damage, intermetatarsal bursitis, repetitive microtrauma, and ischemic changes.

Symptoms:

Patients with Morton’s neuroma typically experience forefoot pain, numbness, and a burning sensation in the affected area, often described as a feeling of having a “pebble in the shoe.” Symptoms are more frequent in females and are exacerbated by activities such as walking, running, or wearing tight and heeled shoes.

Approximately 17% of cases are linked to prior foot trauma. Pain is usually burning in nature and worsens with prolonged standing or physical activity. More than half of the affected individuals report altered sensations, and about 25% may experience night pain or discomfort even at rest, particularly in chronic cases. Removing shoes or resting often provides relief in the early stages.

Diagnosis:

Special Tests

Clinical assessment is key to diagnosing Morton’s neuroma. The most sensitive tests include:

Thumb-Index Finger Squeeze Test – Applying pressure around the affected area to reproduce symptoms.
Foot Squeeze Test – Assessing pain response when squeezing the metatarsal heads together.
Mulder’s Click Test – It is performed by squeezing the forefoot while applying direct pressure between the metatarsal heads, often between the third and fourth toes. A positive test is indicated by a palpable or audible click, accompanied by pain or tingling, suggesting the presence of a Morton's Neuroma.

Imaging

Imaging studies aid in confirming the diagnosis and ruling out other causes of forefoot pain:

Weight-Bearing X-ray: Helps evaluate bone structure and exclude fractures or arthritis.
Ultrasound (USS) and MRI: Both are effective in detecting Morton’s neuroma, but MRI is considered the gold standard. The neuroma is best visualized on a T1-weighted axial MRI slice. A transverse diameter of 5 mm or more is considered significant when correlated with clinical findings.

Treatment Approaches:

MRI scan showing Morton’s Neuroma (bold arrow).

Conservative Management

Patient Education: Wearing wide-toe box shoes is often the simplest and most effective way to alleviate symptoms.
Orthotics: A metatarsal bar insole can help redistribute pressure across the forefoot, reducing strain on the neuroma. However, the effectiveness of inversion or eversion insoles is not well-supported by research.

Physiotherapy Intervention

The initial approach to conservative treatment includes rest, massage, footwear adjustment, and modifying activities.

Manual therapy, particularly techniques targeting the muscles and arch of the foot, can help relieve pain and improve foot biomechanics. By releasing muscle tension, enhancing joint mobility. and supporting the foot's natural arch, manual therapy may reduce excessive pressure on the effected nerve. Additionally, it is thought to modify pain perception by altering input, addressing sensorimotor imbalances, and activating descending pain-inhibitory pathways.

Injection Therapy

Corticosteroid Injections: These are commonly used to reduce inflammation around the neuroma, leading to symptomatic relief for up to 12 months.
Ethanol/Alcohol Injections: Studies indicate potential benefits in reducing neuroma size and improving symptoms, but they are associated with complications such as prolonged burning pain. Additionally, alcohol injections may lead to increased fibrosis, making subsequent surgery more challenging.
Radiofrequency Ablation: This procedure involves applying heat (85–90°C) via a probe inserted into the neuroma. Although some small studies have reported good short-term outcomes, the National Institute for Health and Care Excellence (NICE) does not recommend it as a routine treatment due to limited long-term evidence.

Surgical Excision

When conservative measures fail, surgical removal of the neuroma may be considered. Two surgical approaches exist:

Dorsal Approach: Allows immediate weight-bearing post-surgery.
Plantar Approach: Poses a higher risk of wound complications and scar sensitivity.

Post-surgical complications may include persistent pain due to incomplete resection, complex regional pain syndrome, or recurrence (stump neuroma). Recurrent neuromas may form due to adhesion development, accessory nerve branches, or excessive fibrosis. Corticosteroid injections are often used to manage pain following surgery.

References

[1] National Library of Medicine, "Morton's Neuroma," PMC, 2020. Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC7211826/
[2] National Library of Medicine, "Diagnosis and Treatment of Morton's Neuroma," PMC, 2022. Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC9437675/

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