Treatment of neuopathic pain secondary to neuroma

A neuroma is the result of failed regeneration of a nerve that has been partially or completely severed, which forms a small cluster of cells at the proximal end of the traumatic injury.

The consequence of this process is motor or sensory deficits, or both, in the territory innervated by the particular nerve.

From 20 to 30% of patients develop painful neuroma, but it occurs only in those containing sensory fibers.

What types of neuromas are there?

There are different types of neuromas, which were classified by Sunderland in three types:

1. Neuromas in continuity: those in which the nerve was not completely severed. These are further divided into: Neuroma in continuity in which the perineurium is intact and Neuroma in lateral continuity in which the perineurium is damaged.
2. Neuromas secondary to failed nerve repair.
3. Post-amputation neuromas.

Why are neuromas painful?

Painful neuromas are sensitive to most mechanical stimuli and to any movement.

There are three main mechanisms by which the painful stimulus is produced:

1. Through nerve fibers
2. Through the nerves adjacent to the neuroma by means of epaptic conduction or also called cross-talk.
3. Through afferent sympathetic fibers via the release of norepinephrine which secondarily releases chemical pain mediators.

How is a neuroma diagnosed?

The diagnosis of painful neuroma is usually easy to know due to surgical or traumatic history. Palpation of an increase in volume that is painful on compression and sensitive to mechanical stimuli is common.

Tinel’s sign produces paresthesias that may be painful in the territory innervated by the nerve.

Treatment of neuromas

The treatment of painful neuroma secondary to traumatic injury of the forearm and hand or in any location is difficult. There are multiple recommendations to prevent its formation or medical/surgical treatment of those already present.

It is important to make an adequate multidisciplinary treatment that combines medical and surgical treatment.

The medical treatment includes

1. Physical therapies: percussion, massage, ultrasonography.
2. Vibration: stimulates A-B fibers and blocks activity of type C pain fibers.
3. Steroid injections (mostly lower extremity): In lower extremity neuromas, in a 2014 paper, a reduction in pain was obtained after ultrasound-guided corticosteroid infiltration in 7 cases out of 14 patients.
4. Anesthetic/corticoid injection: Important diagnostic role (suppression test). Important therapeutic role.
5. Pharmacological treatment:

• Tricyclic antidepressants: effective in 1/3 patients for pain relief.
• Serotonin reuptake inhibitors (Venlafaxine, Duloxetine)
• Gabapentin and Pregabalin
• Opioids (oxycodone and tramadol)
• Antiepileptics (Carbamazepine)
• Topical agents (Lidocaine and capsaicin)

When medical treatment fails, surgery may be indicated. The procedures and expectations for our patients’ recovery must be well explained.

It is important that the surgeon has microsurgical experience and knowledge of pathophysiology and surgical procedures to avoid worsening the initial situation. The expectations of results and possible complications are important to be transmitted to the patients.

What does the surgical treatment consist of?

The indication for surgical technique depends on the integrity of the nerve ends as described by Mackinnon:

• If there is the distal end of the nerve and intact sensory receptors, direct neurorrhaphy or nerve grafting is indicated in order to control the regeneration of nerve fibers from the proximal end.

Another way is to use a nerve allograft (Axogen).

• If there is no distal end of the nerve and the affected area is important for function, a transfer of innervated free tissue is indicated, as in the case of loss of sensation in the thumb. In these cases a vascularized transfer of the first or second toe can be performed.

• If the function of the affected area is not critical for function, there is no distal end of the nerve, the area is not suitable for graft transfer or some of the above mentioned techniques have failed, resection of the neuroma is indicated and the proximal end of the nerve should be transposed to an area where there is less mechanical stimulation.

In the case of digital amputation, 50% of the patients have pain and in 10% the pain is incapacitating; in this case, the nerve can be translocated inside the bone, buried in muscle or buried proximally in an area where there is less risk of stimulation.

In our experience, burying the proximal end of the injured nerve to bone is a technique that has been shown to have a good success rate (57 to 99%). Boldrey was the first to describe the introduction of the neuroma into the spinal canal.

Another possibility is excision of the neuroma and transposition to soft tissues without scar. There are authors like Tupper who have 78% of good results. We have good experience, when there is a good muscle belly and good soft tissue coverage.

We present some recommendations based on Mackinnon’s school to improve the technique:

1. Perform adequate mobilization of the nerve.
2. Do not leave too much tension on the nerve.
3. Avoid leaving the nerve with too much angulation at the entrance of the bone.
4. Do not implant the nerve close to the joint.

The forms of treatment currently described offer 65 to 90% long-term satisfaction. Neuropathic pain is one of the leading causes of disability and depression in many pain patients.

It is important to carry out an adequate multidisciplinary medical-surgical treatment, with professionals who have a proven knowledge of peripheral nerve pathology and its sequelae.

The problems have a solution, the important thing is to adapt the treatment to each patient.