Nerve entrapment

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Synonyms

Nerve compression syndrome, compression neuropathy, nerve entrapment, or a "pinched" peripheral nerve.

Definition

A nerve entrapment is caused when a peripheral nerve losses mobility, flexibility, or becomes compressed by surrounding tissues. A nerve entrapment can cause neuropathic / neurogenic pain that can be either acute or chronic in nature.

Nerve entrapment syndromes (meaning a common group of signs and symptoms), occurs in individuals as a result of swelling of the surrounding tissues, or anatomical abnormalities.[1]

Entrapment neuropathies occur within peripheral nerves and is typically characterized by pain and/or loss of function (motor and/or sensory) of the nerves as a result of chronic compression. To adequately diagnose a nerve entrapment, it is important to know the neural pathways and areas of responsibility of the peripheral nerves.

The most common types of nerve entrapments include (but are not limited to):

Of note, chronic mild irritation of a nerve can result in an increase in neural tension. This could be the primary cause of a person's symptoms, or contribute towards their consulting symptoms.[1]

Lastly, it is important to keep in mind that damage or compression of the neural structures often accompany joint or muscle injuries.[2][3] A thorough evaluation of the area is needed for an accurate diagnosis.

Etiology

Nerve entrapment syndromes can result from a chronic injury to a nerve as it travels through an osseoligamentous tunnel; the compression is typically between the ligamentous canal and adjacent bony surfaces.

In cases of nerve entrapment, at least one portion of the compressive surface is mobile. This results in either a repetitive "slapping" insult or a "rubbing/sliding" compression against sharp or tight edges, with motion at the adjacent joint, resulting in a chronic injury. Immobilization of the nerve with a splint or lifestyle adjustments may therefore resolve the symptoms. Entrapment neuropathies can also be caused by systemic disorders, such as rheumatoid arthritis, pregnancy, acromegaly, or hypothyroidism

Pathophysiology

A nerve entrapment can be both ischemic or mechanical in nature.[4]

Repetitive injury and trauma to a nerve may result in microvascular (ischemic) changes, edema, injury to the outside layers of the nerve (myelin sheath) that aid with the transmission of the nerve’s messages, and structural alterations in membranes at the organelle levels in both the myelin sheath and the nerve axon. Focal segmental demyelination at the area of compression is a common feature of compression syndromes. Complete recovery of function after surgical decompression reflects remyelination of the injured nerve. Incomplete recovery in more chronic and severe cases of entrapment is due to Wallerian degeneration of the axons and permanent fibrotic changes in the neuromuscular junction that may prevent full reinnervation and restoration of function.

Risk Factors

Some factors put individuals more at risk for developing a nerve compression or entrapment. These factors include:

  • Prior fracture or dislocations to the local area;
  • Scar tissue and / or myofascial tension;
  • Bone spurs/ arthritis;
  • Swelling or edema;
  • Cysts;
  • Repetitive or prolonged activities that require repetitive movements;
  • Systemic conditions, such as diabetes.[5] 

Because nerve entrapments are so varied in signs, symptoms, causes and locations, it is vital for the clinician to perform a detailed medical history and physical examination to rule out more serious conditions.

Symptoms

Again, the presentation of a nerve entrapment will differ from person to person and will present with localized or referred symptoms along the entrapped nerve. The most common symptoms include:

  • Localized or referred pain (check local peripheral nerve territories);
  • Numbness, tingling, or "eletric shock" feeling;
  • Paresthesia;
  • Burning sensation;
  • Impaired movement of affected body part;
  • Muscle weakness;
  • Muscle wasting;
  • Dry thin skin - chronic cases of motor and sensory nerve entrapment.

Differential Diagnosis

Neurological pain can be difficult to accurately diagnose. It is important to correctly perform your neurological exams and to determine if the symptoms are arrising from the central nervous system (CNS), the spinal cord or nerve root compression, or the peripheral nervous system. It can also be a "Crush", or "Double-Crush syndrome" of several neurological structures.

For a refresher on the neurological exam, click here, for an outline of myotomes, dermatomes and deep tendon reflexes.

See below for a reminder of the cervical and lumbar scans that can be performed in a clinical.

Cervical Scan:

Lumbar Scan:

Examination

Physical Evaluation

Visual Inspection:

Visual inspection and palpation of the entire upper / lower extremity and the cervical or lumbar spine is mandatory. Please refer to your cervical and lumbar scans for a more detailed outline of the mandatory tests.

Inspection should focus on limb asymmetry, muscular atrophy, or abnormal posture (both spinal and peripheral). Limbs should also be compared for temperature and pulse quality changes in provocative positions.[6]

Palpation:

During the medical examination, the clinician will attempt to produce the consulting signs or symptoms by scratching or pushing the area in which the nerve is entrapped. This should produce the consulting pain pattern of the patient.

Upper Extremity

Detailed sensorimotor testing and provocative maneuvers such as Spurling's sign,[7] Tinel's sign,[8], Median Nerve Compression test,[8] Phalen's test,[8] and the Elbow Flexion test[8] can be helpful in diagnosing cervical radiculopathy or specific nerve entrapment syndromes.[6]

Lower Extremity

This should also include detailed sensorimotor testing for the lower back and lower extremity peripheral nerve network. See below for the common nerve tension tests which can be performed in a clinic.

Nerve Tension Tests

Nerve tension tests can be performed by clinicians to produce systematic increases in neural tension by successive additions of movement, which increase neural tension. The tests can provoke the consulting symptoms, or alternatively, symptoms such as pins and needles or numbness.[1]

Common tests include:

  • The straight leg raise (SLR);
  • Slump test;
  • Neural Thomas test;
  • Upper limb tension tests (ULTT - median, radial, and ulnar nerves).

Anesthetics and Electrodiagnostic Testing

  • A physician may also be able to help with the diagnosis of a nerve entrapment syndrome. By administering a couple of millilitres of local anaesthetic in the area of the symptoms, symptoms should subside or disappear all together, if it is purely a nerve entrapment syndrome (which often times is accompanied by other underlying issues or injuries).
  • Electrodiagnostic testing (EDS) may confirm the diagnosis of nerve entrapment as well, however there is no concensus as to a "Gold Standard" for the best diagnostic imagery for a nerve entrapment. Some professionals believe that there is no examination imagery (x-ray, ultrasound, MRI, scintigraphy) that can detect a nerve entrapment.
  • It is also important to note that normal EDS does not rule out symptomatic compressive neuropathy, especially early on in the course of the disease.[9]
  • A clinician can also explore the possibilities of a nerve conduction test. These tests can determine how well the nerve is working and help identify where, and if, it is being compressed or irritated.

Treatment

The treatment of a nerve entrapment syndrome requires the clinician to consider multiple variables specific to the individual. The degree of the entrapment syndrome, the location of the entrapment, and the present level of healing (acute, sub-acute or chronic) all must be considered.[6]

Since the condition is generally non-life threatening, continuing to move is important. The Physiotherapist or health care provider can guide you with the appropriate exercises and which movements to avoid, to prevent further aggravation. The clinician can also consider non-surgical treatments as well as surgical interventions, if conservative approaches are not effective.

Nonsurgical Treatment

  • Postural and biomechanical corrections are also vital to addressing the underlying mechanisms that are causing the neural irritation. The clinician should also be aware of repetitive movement patterns which may be causing the nerve to rub or be pinched by surrounding tissues.
  • A clinician may consider non-steroidal anti-inflammatory medicines, such as ibuprofen aspirin or naproxen, to help reduce swelling around the nerve. Although steroids, such as cortisone, are very effective anti-inflammatory medicines, steroid injections are generally not used because there is a risk of damage to the nerve.
  • Bracing or splinting can also be considered to help encourage rest for the nerve. This is an excellent opportunity for an Occupational Therapy consult.  
  • You can also consider nerve gliding exercises, if the nerve is in the appropriate phase of healing. Nerve gliding exercises are not generally encouraged during the acute healing phase.

Surgical Treatment

Surgery should be considered as the last option for a nerve entrapment syndrome, as it can entail a lengthy recovery for the patient. Again, because of the variability that exists with this type of pathology, it is best to consult a Physician or a Neurosurgeon for the best options for the patient. This could include a more simple procedure, such as a local arthroscopic debridement, or may involved a more involved surgery such as a neural decompression or an open spinal or local surgery.

Looking for more?

  • Click here for more information on a nerve entrapment syndrome.

References

Nerve Compression Syndromes: Diagnosis and Treatment, Robert M. Szabo, 5 August 2008

  1. 1.0 1.1 1.2 Brukner, P., & Khan, K. (2010). Chapter 3: Pain: Where is it coming from? In Clinical Sports Medicine. Rev 3rd Ed. McGraw-Hill Australia. North Ryde.
  2. Greening, J., & Lynn, B. (1998). Minor peripheral nerve injuries: an underestimated source of pain? Man Ther. 3 (4): 187-94.
  3. Pahor, S., & Toppenberg, R. An investigation of neural tissue involvement in ankle inversion sprains. Man Ther. 1 (4): 192-7.
  4. Mackinnon, S.E. (2002). Pathophysiology of nerve compression. Hand Clin. 18(2): 231-41.
  5. Tapadia, M., Mozaffar, T., & Gupta, R. (2010). Compression neuropathies of the upper extremity: update on pathophysiology, classification, and elecrodiagnostic findings. J Hand Surg Am. 35(4): 668-77.
  6. 6.0 6.1 6.2 Wilson, R.J., Watson, J.T., & Lee, D.H. (2014). Nerve entrapment syndromes in musicians. Clinical Anatomy. Vol 27. 861-865.
  7. Ghasemi M, Golabchi K, Mousavi SA, Asadi B, Rezvani M, Shaygannejad V, Mehri S. (2013). The value of provocative tests in diagnosis of cervical radiculopathy. J Res Med Sci 18:S35–S38.
  8. 8.0 8.1 8.2 8.3 Valdes, K., & LaStayo, P. (2013). The value of provocative tests for the wrist and elbow: A literature review. J Hand Ther. 26:32–43.
  9. Hoppman, R.A. (1997). Ulnar nerve entrapment in a French horn player. J Clin Rheumatol 3:290–293.