What is Morton's Neuroma
Morton's neuroma is not a true tumor but rather benign perineural fibrosis of the common plantar digital nerve, most commonly occurring in the third intermetatarsal space (between the third and fourth toes), caused by chronic pressure or repetitive irritation. 1, 2
Pathophysiology
The condition involves fibrotic changes in the nerve, microvascular degeneration, and deregulation of sympathetic innervation, rather than actual nerve tumor formation. 3
The second intermetatarsal space is the second most common location, where lateral and medial plantar nerves often join. 4
Histological examination consistently reveals inflammatory tissue and perineural fibrosis, not neoplastic tissue despite the misleading "neuroma" terminology. 5
Clinical Presentation
Patients typically experience burning or sharp metatarsalgia at the dorsal or plantar aspect of the forefoot. 3
Specific symptoms include dull or sharp pain, numbness and/or tingling in the third and fourth digits, burning sensation, cramping, and the characteristic feeling of "walking on a stone" around the metatarsal heads. 4
The condition predominantly affects middle-aged women. 5
Diagnostic Approach
Initial imaging should begin with radiographs to exclude other causes of webspace pain such as osteoarthritis, Freiberg's infraction, and stress fractures, though radiographs are insensitive for diagnosing Morton's neuroma itself. 6, 7
Advanced Imaging After Negative Radiographs
Both ultrasound (90% sensitivity) and MRI (93% sensitivity) are highly accurate and recommended by the American College of Radiology, with no statistically significant difference between the two modalities. 8, 6, 7
Ultrasound offers the advantage of real-time clinical correlation, dynamic assessment during examination to reproduce symptoms, and the ability to guide therapeutic injections. 8, 6
MRI provides superior capability for differentiating Morton's neuroma from other forefoot pathologies and is less operator-dependent than ultrasound. 8
MRI does not require intravenous contrast administration for diagnosis. 8
Important Caveat
- Ultrasound diagnostic performance varies significantly with operator skill and technique, requiring experienced sonographers for optimal sensitivity. 8
Treatment Algorithm
First-Line Conservative Measures
- Conservative management includes orthotics, shoe-wear modifications, and anti-inflammatory medication, though these typically have limited efficacy. 3, 5
Second-Line Minimally Invasive Procedures
When conservative treatment fails, ultrasound-guided procedures should be employed before considering surgery, including corticosteroid injections with local anesthetic placed beside the neuroma using small volumes of triamcinolone acetonide. 8, 3
Chemical neurolysis with alcohol or radiofrequency thermal neurolysis are additional minimally invasive options. 3
These procedures can achieve significant and potentially long-lasting pain reduction, and can be repeated if initial treatment fails, usually leading to complete symptom remission. 3
Current evidence demonstrates that minimally invasive ultrasound-guided treatments significantly reduce the need for subsequent surgery in patients with persistent Morton's neuroma unresponsive to conservative measures. 3