Background

When a nerve gets injured, it tries to repair itself. If the circumstances aren't right, it creates a “nerve scar” which is designated as neuroma.

Causes

Any injury, such as a sharp transection,, crush injury, radiation, thermal injury/burn, frost bite, cancer, stretching can lead to neuroma formation. Even inadvertent and excessive retraction during surgery can lead to nerve injury.

Symptoms

Pain, numbness, tingling and possibly weakness can result if the nerve has a motor component that powers a muscle or an entire muscle group. The type of pain caused by a nerve injury is often called “neuropathic pain”.

Diagnosis

The history and physical examination are the most important steps in making a diagnosis. Additional modalities such as MRI neurography and ultrasound can be helpful in diagnosing a nerve injury. Indirect methods include Electromyography (EMG) and Nerve Conduction Studies (NCS).

Treatment

The management of a neuroma depends on a number of factors. Conservative management such as desensitization, various laser modalities, mediations and occupational or physical therapy can help. However, if a critical nerve is involved (especially a motor nerve or mixed nerve), depending on the examination findings, mechanism of injury, and data from nerve studies and imaging studies, surgical management may be recommended.

Complex cases are presented by Dr. Dowlatshahi at regular meetings with a peripheral nerve surgery team at BIDMC which includes expert radiologists and neurologists. Often, decision making can be more complex than often assumed.

Modern surgical neuroma management includes many different modalities. A few examples are:

• Neurolysis.
• Nerve repair.
• Nerve reconstruction with graft (cadaveric or autologous).
• Nerve reconstruction with vascularized nerve graft (autologous).
• Nerve transfer.
• ”Graft to nowhere”.
• Proximal crush and distal end ligation and bury.
• Nerve cap.
• Targeted Muscle Reinnervation (TMR)
• Regenerative Peripheral Nerve Interface (RPNI)

These are most of the currently utilized techniques, but there are others as well. Dr. Dowlatshahi routinely uses these techniques, oftentimes in combination, to treat painful neuromas of peripheral nerves from head to toe.

The following sections give examples of these techniques.

Neurolysis for neuroma in continuity

Neurolysis which essentially means dissecting out a nerve under the microscope can be helpful in certain circumstances. This is particularly helpful in cases where the nerve is encased in scar which creates a constriction around the nerve in question. Also, the nerve can be adherent to the surrounding structures which can lead to symptoms which we call “traction neuritis”. Although this technique should be used in a very targeted/selective manner it can be helpful as an isolated procedure. If the nerve is grossly injured or severed this is not a good option. More definitive measures should be undertaken in those circumstances, such as resection and reconstruction or TMR/RPNI.

This is the case of a teenager that sustained a knee dislocation with dense numbness in the Common Peroneal Nerve (CPN) distribution and foot drop. An initial exploration was performed at the time of a knee surgery. We then took him back to the operating room in conjunction with our peripheral nerve surgery team including an experienced neurophysiologist.

The CPN was dissected extensively, decompressed along its entire length. The neuroma in continuity just proximal the the knee joint was dissected out (intraneural neurolysis) under continuous nerve monitoring. Considering the findings of the EMG during the operation, we decided not to excise and graft the nerve, and to stop after the neurolysis.

Neuroma Excision and Nerve Repair

Neuroma excision and nerve repair or reconstruction can be the simplest way to address a neuroma.

This is a microsurgical procedure that requires specialized instrumentation, skills, as well as a high-powered operating microscope. For mixed or motor nerves, a nerve stimulator is critical. If particularly complex, the intraoperative nerve monitoring team is asked to join which includes two EMG technicians as well as a neurologist with expertise in neurophysiology.

Here is a simple example of a digital nerve (in a finger) with a very small neuroma in continuity that was created iatrogenically from aspirating a ganglion cyst. The patient had a tremendous amount of pain. The nerve was explored revealing a tiny neuroma within the nerve.

The neuroma was exccised and the nerve was repaired with a nerve conduit. The patient recovered well and over the course of 6 months, all the discomfort had gone away, and the patient made a full recovery.

Regenerative Peripheral Nerve Interface (RPNI)

RPNI is a very useful technique to manage neuromas or prevent their formation. This technique involves wrapping a cuff of denervated muscle around a nerve end. The nerve will then innervate the muscle and since the nerve axons have “something to do and somewhere to go”, they are less likely to create a painful neuroma.

In Dr. Dowlatshahi’s practice, RPNI is often used in combination with Targeted Muscle Reinnervation (TMR).

Here is an example of RPNI in a patient that underwent thumb reattachment surgery (replantation). As a carpenter, he had a lot of hypersensitivity and a painful neuroma of his thumb digital nerve. We performed RPNI using a free graft of muscle from his forearm via a separate, short incision. At 12 months, his hypersensitivity had resolved, and he was able to resume work as a carpenter.

Targeted Muscle Reinnervation (TMR)

This is a very useful technique described by Dr. Dumanian from Northwestern University. This technique entails rerouting a cut nerve into a nerve in nearby muscle hereby allowing the cut nerve to grow into this nearby motor nerve and hereby not create a neuroma which can lead to significant pain and impairment.

Dr. Dowlatshahi uses this technique routinely in amputees but also in cases of trauma or cancer removals where nerves are frequently disrupted and can lead to painful neuromas.

Here are several examples of this technique.

In this patient, due to cancer, an above elbow amputation was performed.

Here, several of the TMR nerve transfers are seen (arrows).

In this patient with chronic knee and lower leg pain after a crush injury, we performed denervation of the saphenous nerve in the medial thigh and TMR into a motor nerve of the vastus medialis muscle.

Vascularized Nerve Grafts

Nerve grafts can be taken from cadavers (called allograft), but also from the patient themself (called autograft). Numerous nerves can be used/harvested. Sensory nerves, redundant motor nerves are available to be used if return of function of the part to be reconstructed is critical.

Most often, the nerve grafts are taken out and transferred to the part to be reconstructed as non-vascularized grafts. This means that the nerve needs to then pick up a blood supply over time from the wound bed to which it gets transplanted.

Depending on the nerve to be reconstructed, Dr. Dowlatshahi can transfer the nerve with its blood supply and reattach the small blood vessels that are in the order of 500 microns or less. This is called super-microsurgery which essentially represents working on vessels that are even smaller than those utilized in conventional microsurgery. Supermicrosurgery requires a specialized skillset as well as dedicated super microsurgical instrumentation and suture. A specialized microscope is also required to allow for visualization of very small structures and exceeds the specifications of most conventional operating microscopes.

The advantage of transferring a nerve with its blood vessels and reattaching the blood vessels once the nerve is transferred is that the nerve is alive and this can potentially improve the chances of recovery, especially for critical nerves, or in the case of a scarred wound bed.

In the following, we demonstrate two examples of vascularized nerve transfer.

This is the case of a young adult in their 20’s with a high ulnar nerve injury after sustaining an open humerus fracture in a motor vehicle accident. At the time of the humerus fracture repair, the ulnar nerve was tagged and the patient was transferred to Dr. Dowlatshahi’s care for repair. A nerve reconstruction was performed with autologous, vascularized sural nerve graft, as well as Guyon’s canal release, and anterior interosseous nerve (AIN) to ulnar motor nerve end-to-side transfer. The following photographs show the steps of the operation.

This is the case of a young laborer with a large-gap injury to the critical index finger radial digital nerve. The patient was explored, and when the large gap was identified, the patient was closed up and transferred to Dr. Dowlatshahi for further care. A sural nerve vascularized graft was utilized. The patient regained normal sensation and a normal 2 point discrimination. His sensation and range of motion are demonstrated in the last three photographs. Some degree of cold intolerance has persisted at 3 years postoperatively which is not uncommon in these types of injuries.