A neuroma is a benign, disorganized growth of nerve tissue that forms after a nerve has been damaged or severed. This non-cancerous mass develops as the body attempts to repair the injury, leading to a tangled bundle of nerve fibers, Schwann cells, and connective tissue. While neuromas can occur anywhere in the peripheral nervous system, they are frequently encountered in the hand and upper extremity due to the high density of nerves and common trauma in this area. The presence of a neuroma often results in significant, chronic pain, which can severely limit the use and function of the affected hand.
What Leads to Neuroma Formation
The formation of a neuroma is the body’s attempt at nerve regeneration gone wrong, primarily triggered by physical injury. When a peripheral nerve is cut or damaged, the nerve’s axons attempt to regrow toward their target. If they cannot find the path to the distal nerve stump, they regenerate in a chaotic, non-functional manner, resulting in a bulbous, tangled mass known as a traumatic neuroma.
Traumatic neuromas develop following accidental injuries such as lacerations, crush injuries, or blunt force trauma to the hand. If a nerve is completely severed and the ends are not surgically reconnected, the proximal nerve stump tries to extend its axons, forming a painful, hyper-sensitive mass at the injury site. Even if the nerve remains structurally continuous but is severely crushed or stretched, internal nerve fibers can be damaged, leading to a neuroma-in-continuity within the nerve’s sheath.
The second category is the stump or amputation neuroma, which forms specifically after surgical procedures like finger or hand amputations. The surgically cut nerve end, unable to find a pathway for proper regeneration, forms a bulbous mass at the end of the nerve stump. This response is essentially unavoidable after nerve division and results from axonal sprouts being blocked by surrounding scar tissue.
The Physiology of Neuroma Pain
The intense pain associated with a neuroma stems from profound physiological changes within the nerve tissue, causing the neuroma to spontaneously generate pain signals. The abnormal nerve endings develop ectopic firing, meaning the nerve fires electrical impulses without external stimulus, sending a constant barrage of messages to the brain.
This hyperexcitability is caused by the abnormal upregulation of voltage-gated sodium channels, particularly the Nav1.7 and Nav1.8 subtypes, at the neuroma site. These channels, which initiate electrical signals in nerve cells, become overexpressed on the injured nerve membrane. Nav1.7 channels amplify small electrical signals, lowering the threshold required to trigger an impulse.
Nav1.8 channels contribute to the nerve’s ability to fire repeatedly and spontaneously, maintaining the persistent pain signal. This increased density of sodium channels makes the nerve segment excessively excitable, translating minor stimuli into a full pain signal. The concentration of these sensitive channels transforms the mass into a generator of chronic neuropathic pain.
In some cases, the sympathetic nervous system contributes through sympathetic-sensory coupling. Following injury, sensory nerve fibers in the neuroma develop an increased number of adrenergic receptors. This makes the sensory nerves sensitive to circulating catecholamines, such as norepinephrine, released during stress. Sympathetic activity can then directly activate the sensory nerve endings, leading to pain exacerbated by non-painful stimuli like temperature changes or emotional stress.
Identifying a Neuroma in the Hand
The diagnosis of a neuroma relies heavily on the patient’s symptoms and a targeted physical examination. A hallmark symptom is lancinating pain, often described as a sudden, sharp, electric shock sensation that shoots up the limb. This distinct pain is frequently accompanied by hyperesthesia, an extreme sensitivity to light touch or pressure over the affected area.
During examination, a physician will palpate the injury area, sometimes feeling a small, firm, and mobile mass beneath the skin. The most indicative diagnostic maneuver is the Tinel’s sign, where the examiner gently taps directly over the suspected neuroma site. A positive result reproduces the characteristic electric shock or tingling sensation that radiates along the injured nerve.
To confirm the diagnosis, high-resolution ultrasound is commonly used to visualize the neuroma mass and assess its relationship to surrounding structures. A definitive diagnostic step is the targeted nerve block, where local anesthetic is injected precisely into the neuroma under ultrasound guidance. Immediate and complete relief confirms the neuroma as the source of chronic pain.
Options for Managing Neuroma Pain
Initial management for neuroma pain often begins with non-surgical strategies aimed at reducing nerve irritation and quieting abnormal signals. Physical therapy includes desensitization techniques, which involve gradually exposing the sensitive area to different textures and pressures to retrain the nervous system’s response. Targeted injections are a frequent approach, including corticosteroids, which are potent anti-inflammatory agents injected near the nerve to reduce swelling.
Another minimally invasive injection technique is alcohol neurolysis, involving injecting a solution of ethyl alcohol directly into the neuroma to chemically destroy the abnormal nerve tissue. This process intentionally damages the nerve to stop the spontaneous firing, often requiring a series of treatments.
For pervasive neuropathic pain, medical management focuses on stabilizing nerve membranes to reduce excitability. Medications often prescribed include anticonvulsant drugs, such as gabapentin or pregabalin, which modulate nerve activity and calm abnormal pain signals. Certain antidepressant medications, like duloxetine, are also used because they affect chemical messengers involved in processing chronic pain.
If conservative and medical treatments fail, surgical options are considered to permanently address the source of the pain. The two main surgical strategies involve either removing the neuroma or relocating the nerve end to a less sensitive environment.
Surgical Strategies
Neurectomy involves surgically excising the neuroma, but the cut nerve end must then be treated to prevent recurrence. This is accomplished through nerve repair or relocation, where the nerve end is implanted into adjacent muscle tissue or bone. This process, called targeted muscle reinnervation or burying the nerve, provides a protected bed that discourages chaotic regeneration.