Atlas of Pain Medicine Procedures 1st Edition

SECTION V

MUSCULOSKELETAL INJECTIONS

CHAPTER 53

Neuroma Injections

Rinoo V. Shah and Ricardo A. Nieves

INTRODUCTION

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.

INDICATIONS

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:

• In areas exposed to repetitive trauma
• Or, in areas exposed to overuse

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

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.

EQUIPMENT AND SUPPLIES

• Sterile gloves
• Betadine and/or alcohol solution or other antiseptic solution, eg, chlorhexidine
• Ethyl chloride spray
• 1% lidocaine (usual anesthetic of choice) and/or 0.25% or 0.5% marcaine, +/– steroid (40 mg depo-medrol, 3 to 6 mg betamethasone, and 2 to 4 mg dexamethasone).
• 10-cc syringe
• 25-gauge 1.5-in needle for superficial neuromas and 22- to 25-gauge 3.5-in needle for deeper neuromas
• Image guidance (fluoroscopy, ultrasound)

PATIENT POSITIONING

• Patient is positioned in the supine, prone, or side lying position depending on the location of neuroma.
• Assurance of comfortable breathing and body positioning by using a head rest, pillows under the chest or abdomen and pillow under the legs.
• In the neck and upper back, the sitting position can be used but prone position preferably due to potential vasovagal reaction.

PROCEDURAL STEPS

• Identify and mark with sterile marker the neuroma locations.
• Area to be injected is cleaned with an antiseptic solution of choice.
• Spray the area to be injected (the taut band) with ethyl chloride to slight frost point.
• Utilizing a 25-gauge 1.5-in needle or 22- to 25-gauge 3.5-in needle for deeper neuromas, insert the needle into the skin.
• One should feel the needle advancing through skin, subcutaneous tissue, normal muscle, and contacting the neuroma or fibrotic tissue.
• Pain should be elicited.
• The needle trajectory should be at a 45-degree angle to the skin. This is especially important near the chest wall.
• After negative aspiration of blood, fluid or air inject a total of 1 to 5 mL of solution per neuroma location.
• Following the injection ethyl chloride stretch and spray can be of help, also acupuncture needle placement and left to disperse for 10 to 15 minutes or gentle massage in the area injected.

POSTINJECTION INSTRUCTIONS

• No heavy activity or exercise except for gentle stretching on the day of the procedure.
• Apply heat to the injection site for 15 minutes 2 to 3 times a day for 3 days with a barrier between skin and heat.
• Postinjection stretching and stabilization program and instructions should be provided along with education on proper posture, spine mechanics, and extremities ergonomics.

POTENTIAL COMPLICATIONS

• Infection
• Bleeding
• Reaction to the medications used (keep total lidocaine used to no more than 20 mL)
• Vasovagal reaction
• Injection site pain (temporary flare up) or more
• Serious complications such as pneumothorax if injected in thoracic area
• If using steroid be aware of potential skin depigmentation changes and possible skin atrophy particularly on thin patients and with superficial muscles.