What is a Neuroma?
A neuroma is an abnormal growth of nerve tissue that develops as the inevitable biological response of a nerve after it has been injured or divided, representing the nerve's attempt at repair when regenerating axons are impeded from reconnecting with their distal target. 1, 2
Pathophysiology
- Neuromas form as part of the normal reparative process following peripheral nerve injury, occurring when nerve ends attempt to reconnect with their end organs but fascicular escape and scarring lead to disorganized axonal regeneration 1, 3
- After sharp trauma to a peripheral nerve, regenerating axons become impeded from re-entering the distal nerve stump, resulting in neuroma formation 2
- Painful neuromas can develop even with blunt trauma or nerve retraction when the nerve is not actually divided 2
- The molecular mechanisms involve neurotrophic factors, neuroinflammatory peptides, cytokines, and various ion channels that contribute to both neuroma formation and associated neuropathic pain 1
Clinical Presentation
- Painful neuromas are a substantial cause of morbidity and reduction in quality of life, inducing intense pain that results in immense suffering and disability 1, 4
- While many neuromas are asymptomatic, symptomatic ones present as painful masses that can prevent patients from continuing normal daily activities 4, 2
- The pain is neuropathic in nature and can be debilitating, often accompanied by disruption in motor and sensory function from the underlying nerve injury 1
- Certain nerves, such as the superficial radial nerve, are more prone to developing painful neuromas 2
Diagnostic Approach
- MRI aids in diagnosis, but ultrasound imaging allows cost-effective accurate diagnosis and localization of neuromas by demonstrating their direct contiguity with the nerve of origin 4
- For Morton's neuroma specifically (a common foot neuroma), MRI demonstrates high sensitivity (87-93%) and specificity (68-100%) for detection 5
- Ultrasound has comparable sensitivity (83-96%) to MRI (82-96%) for Morton's neuroma detection, with the advantage of allowing clinical correlation during examination 5
Common Pitfalls
- Unknown factors make certain patients more susceptible to neuroma formation, and no single treatment option has been successful in completely resolving symptoms 1, 2
- The exact pathophysiology remains poorly understood, and the molecular mechanisms driving neuroma formation and resulting neuropathic pain are incompletely understood 1, 2
- Treatment must be tailored individually as neuromas can occur in various locations (hand, upper extremity, foot, amputation stumps) with varying presentations 4, 2, 6