What is a mononeuropathy?
Mono = “one” Neuropathy = “nerve injury”
A mononeuropathy is an isolated nerve injury typically caused by frequent compression or a traumatic injury to the nerve.
There are many, many nerves running throughout the body and each one of those have a specific “region” it provides sensation and movement to. Therefore, mononeuropathies present themselves in a specific manor, allowing the diagnosing physician to narrow down what nerve may be involved.
Why does this happen?
As mentioned above, often a mononeuropathy is caused by chronic pressure on the nerve or as a result of direct trauma to the nerve. We will go through examples of each of these.
In compression injuries, also described as ‘entrapment neuropathies’, a nerve is being constantly pressed on by internal structures surrounding the nerve (bone, ligaments and tendons) or even from external factors (frequent leaning on the elbow or crossing the legs).
The most common compression mononeuropathy we see at the clinic is known as Carpal Tunnel Syndrome. This occurs when the median nerve passes through the carpal tunnel that may be too small to fit all structures passing through the same tunnel, causing the median nerve to be compressed by a thick ligament enclosing the carpal tunnel. Other common compression sites include the elbow or the fibular head along the outside of the knee.
A traumatic injury may also be the cause of a mononeuropathy. An example of this could be from breaking a bone, a crush or stretch injury to a limb and even lacerations or cuts to the nerve.
What are the symptoms?
As individual nerves cover specific territories in the body, symptom distribution will vary according to the injured nerve. For simplicity sake, general symptoms include:
· Numbness, tingling or burning of specific areas (i.e. the ring and pinky finger)
· Weakness in the affected nerve segment
· Pain along the compression site (i.e. the wrist or elbow)
· The sensation of swelling or burning
The most important step to coming to a diagnosis is a detailed history from the patient. Understanding the symptoms that the patient is experiencing, along with a list of medical problems, medications and lifestyle choices, allows the clinician to form an idea of what may be causing the problem at hand. Additionally, a physical examination to look for focal sensory loss or weakness adds pieces to the puzzle. Finally, completing nerve and muscle testing called nerve conduction studies (NCS) and/or electromyography (EMG) is beneficial to further localize where the nerve injury is stemming from. All of these steps allow the clinician to quantify the nerve injury, as well as, formulate a treatment plan that best suits the patient. The physician may also order additional investigations if needed (i.e. imaging, bloodwork, etc.).
Treatment & Management
As mentioned above, proper treatment for any nerve injury varies depending on the patient, the severity of the injury and the symptoms. Your clinician will advise treatment options accordingly. In general, for compression mononeuropathies and some traumatic injuries, we typically treat with conservative management before advising injections or surgery. Conservative management includes avoiding movements or habits that are causing the compression. Examples include:
· Splinting of a joint to keep it straight (i.e. the wrist or elbow – typically at night)
· Avoiding leaning or putting pressure on a joint or body area (i.e. leaning on the elbow or crossing the legs)
· Modifying work station or areas where compression is common
If conservative management fails, injection therapy is an option to treat the symptoms the nerve is causing. There are many types of injectates available which your clinician will discuss with you. Finally, for many traumatic nerve injuries and severe compression mononeuropathies, surgery may be the best option in order for the nerve to fully recover. These surgeries include decompression at the affected segment (i.e. carpal tunnel decompression/release) or nerve transfers for traumatic injuries.