Neuromas are considered “tumors” of neural structures. For purposes of this chapter, we refer to non-neoplastic neuromas. Neuromas typically form following surgical transection, trauma, or entrapment. Neuromas are considered to be discrete enlargements. If superficial, they may be palpable. If deeper, they may be visualized with noninvasive imaging tools (MRI, ultrasound).
Like trigger points, a neuroma can be stimulated with normal palpation (allodynia). Painful stimuli over a neuroma may lead to an excessive or prolonged pain response, ie, hyperalgesia and hyperpathia. Due to dysfunction of this neural tissue, there may be impairment in conduction. Motor function and sensory processing may be dysfunctional. Autonomous and maladaptive reflexes may be present.
Infiltration with a local anesthetic and steroid may be therapeutic. Perineural infiltration is preferred, since intraneural injections may lead to permanent nerve damage and paradoxically, a deafferentation pain syndrome.
Neuroma injections (NIs) are commonly used as a treatment option in patients with acute and chronic pain. Pain can be present at rest or with movement. Neuroma pain may be exacerbated with constriction, eg, stump and the Morton neuromas.
Trigger points are commonly present in patients who have undergone surgery. This is especially true when the surgical scar injured a peripheral nerve, eg, limb amputation or rib resection or retraction.
Neuromas may be found in the surgical bed:
Neuromas may be confused with tender points, as is usually found in patients with fibromyalgia. Unlike fibromyalgia, neuromas are typically isolated and develop secondary to a specific event.
Physical examination findings include:
A palpable and tender swelling that is painful with light touch (allodynia).
Deeper pressure leads to a more protracted (hyperpathic) and heightened (hyperalgesic) pain response.
The scar should be healed.
Poorly healing scars or ulcers should be addressed, before considering neuroma injections.
Some healed surgical scars may demonstrate dystrophic or color changes.
There may be a significant amount of allodynia, distributed around the scar.
In this situation, there may be a heightened sympathetic response in addition to the presence of neuromas.
Passive stretching of the scar or focal neuroma compression should elicit pain.
This pain should be eliminated following a neuroma injection.
Arguably, a pressure algometer, as described in the trigger point injection chapter, may be useful: “an increase in the pressure pain threshold by 2 to 3 kg, immediately after the NI will indicate an effective injection.”
GOAL OF NEUROMA INJECTIONS
The primary goal of the neuroma injections is to inactivate the neuromas by anesthetizing the primary area of pain through needling and infiltration with an injectable solution.