Common Compression Neuropathies

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Title: Common Compression Neuropathies

Authors:  Asia Filatov, M.D. ¹; Svetlana Faktorovich M.D.¹

Institutional Affiliations:

1. The Marcus Neuroscience Institute, Boca Raton Regional Hospital; Boca Raton, Florida
2. The Florida Atlantic University, Charles E. Schmidt College of Medicine; Boca Raton, Florida

Funding & Conflict of Interest: None

Corresponding Author: Asia Filatov, M.D. [email protected]

Common Compression Mononeuropathies

Entrapment neuropathies, also known as compression neuropathies are common causes neurologic disability, resulting in pain, numbness or weakness in the distribution of the affected nerve. These conditions occur as a result of mechanical injury, such as from direct compression or stretch, as the nerve travels through a distinct anatomical space such as a narrow fibrous or osseous tissue.  This form of injury impairs signal transmission initially by damaging the myelin sheath and eventually, if untreated resulting in long term axonal damage.  Diagnosis can be made by physical examination, electrodiagnostic testing (EMG/NCS) and neuromuscular ultrasound.  Mononeuropathies are rarely reported in children, accounting for less than 10% of the pediatric referrals for EMG/NCS In adults on the other hand, entrapment neuropathies are a very common reason for referral⁴. This chapter explores the cases of common compression mononeuropathies and their clinical presentation.

Compression Mononeuropathies

1. Median Neuropathy at the Carpal Tunnel

                Carpal tunnel syndrome (CTS) is known to be the most common form of focal peripheral neuropathy. This condition arises as a result of the entrapment of the median nerve as it crosses under the flexor retinaculum, also known as the transverse carpal ligament, a fibrous band at the base of the palm.  Along with the adjacent carpal bones, this fibrous tissue forms the border of the carpal tunnel.  This is illustrated in Fig. 1 below.

Fig. 1.    Compression of the Median Nerve. From Gardner BT, Dale AM,                Buckner-petty S, et al. Functional measures developed for clinical          populations identified impairment among active workers with upper          extremity disorders. J Occup Rehabil. 2016;26(1):84-94.

CTS is most often a slowly progressive condition. Initially it is characterized by intermittent symptoms provoked by hyperflexion or hyperextension of the wrist. Activities such as holding phone, typing on a computer and steering wheel are the common triggers of CTS. Often, CTS is bilateral although is often more noticeable in the dominant hand⁸. Symptoms often include paresthesias, pain, and weakness experienced in the median nerve distribution of the hand. Common signs include apb weakness, atrophy, thenar sensory sparing. Also, sensory loss can sometimes extends proximal to the wrist. Electro diagnostic studies are effective in confirming the diagnosis of this condition in a patient with mild to moderate cases⁹.

1. Ulnar Neuropathy at the Elbow

                Ulnar neuropathy is a condition which is commonly experienced, both acutely after an elbow trauma and in the event of a chronic compression neuropathy¹⁰. Stringent clinical evaluation alongside the discerning evaluation of electrodiagnostic studies is effective in ascertaining the prognosis of a patient’s recovery with the operative and non-operative management techniques. Patients diagnosed with the ulnar nerve compressive neuropathy complain of tingling and numbness of the ulnar-sided sections of the hand¹⁰. Specifically, the tingling sensation and the numbness are experienced in the ring finger’s ulnar region and in the small finger. Generally, the symptoms of the condition are experienced intermittently and subsequently worsen during the night, especially if a person flexes the elbow while asleep¹⁰.

During the day, paresthesias may be experienced often as the condition progresses. The symptoms experienced are mainly due to the elbow’s position. The cadaveric studies have shown that the ulnar nerve present at the elbow is a zone predisposed to traction and compression experienced when flexing the elbow¹¹. The Osborne ligament’s prominent bands available at the flexor carpi ulnaris muscles leading edge aggravate the ulnar nerve’s symptoms with activities such as gripping experienced when a person is driving. For laborers and athletes involved in throwing activities, the symptoms associated with the ulnar neuropathy may be prompted by the extended and the intense periods of the increased activity¹². The athletes and the laborers with ulnar neuropathy may also present symptoms of concurrent bonny and soft tissue disease experienced at the elbow such as ligamentous instability, medial epicondylitis, and stress fractures among others¹³. Ganglion cysts and elbow fractures can also trigger the ulnar neuropathy. Fig. 2 below provides an outlook of the ulnar neuropathy.

Fig. 2: Ulnar Neuropathy. From Zeng W, Shiek AI, Pappas E. Detecting the            presence of anterior cruciate ligament injury based on gait dynamics                 disparity and neural networks. The Artificial Intelligence Review. 2019:1-         24. 

                People who apply extended pressure on the hypothenar eminence such as cyclists and laborers from drilling activities are at a greater risk for compression of the ulnar nerve located at the Guyon’s canal⁴.The deep motor branch compromise of the ulnar nerve within the Guyon canal results in the weakness of the adductor pollicis muscle. A clinical assessment of this condition can be achieved by asking the patient to grip a sheet of paper simultaneously at the opposite ends. A Froment sign can be exhibited in this case reflected by a thumb IP joint hyperflexion to recompense for incapacity to adduct the thumb. Ulnar nerve entrapment takes place when the ulnar nerve is compressed, specifically at the wrist or at the elbow. Compression experienced at the elbow is referred to as cubital tunnel syndrome while that at the risk is referred to as the Guyon’s canal syndrome⁴.

A detailed clinical history is necessary to help determine the etiology and location of an entrapment neuropathy, including repetitive activities performed, provocative factors, limb positioning as well as the duration of the presenting symptoms. A detailed neurological exam should be performed to determine the sensory distribution involved as well as muscle pattern involvement.  In the events when a person reports motor muscle weakness without any indication of sensory deficit, a special attention should be provided to the patient. Only in rare case scenarios will an upper motor neuron disease and compressive mass be experienced concurrently¹⁴. A detailed history and neurological exam is useful to distinguish a compression neuropathy from another mimicker.  Additional testing such as electrodiagnostic testing and ultrasound are very helpful in confirming the diagnosis and determining the prognosis ¹⁵. 

• Radial Nerve Injury at the Spiral Groove

                Radial nerve entrapment is less commonly seen than median and ulnar neuropathies and therefore less frequently studied.  However it can present with entrapment at various locations along its course, including the main trunk of the nerve in the proximal arm or isolated branches of the nerve distally.  The most common site of entrapment is at the site of the spiral groove in the upper arm, where the nerve lies along the humerus, making it susceptible to compression. The radial nerve injury is reported majorly due to the compression experienced between the edge of the nerve present at humerus’ operating table’s edge, patient screen compression, or arterial pressure cuffs¹⁶. A radial nerve injury arises due to infection, physical trauma or exposure to toxins¹⁶. The injury, also referred to as radial nerve palsy, results to a burning pain, tingling, or numbness. In this case, the muscles affected are the Brachioradialis, anconeus, extensor carpi, radialis longus, triceps, and the extensor carpi radialis brevis. This injury is also referred to as the Saturday night palsy¹⁶. Saturday night palsy obtains its name from the episodes associated with events of unintentional extended radial nerve compression experienced with the prolonged period of arm draped over a chair. The clinical symptoms of the radial nerve injury include the weaknesses of the motor nerves with sensory disturbances which share similarities to stroke or herniated cervical disk or other neuropathies which are common differential diagnoses of the condition¹⁶.  However, completing physical and examination and history is important towards distinguishing the conditions from Radial Nerve Injury to the spinal groove. Fig. 3 below provides an illustration of the radial nerve injury in different sections including the radial groove and the axilla.

Fig. 3: Radial Nerve Neuropathy. From Chandra P, Kumar R, Mittal N. Recent      developments in human gait research: Parameters, approaches,                 applications, machine learning techniques, datasets and challenges. The                 Artificial Intelligence Review. 2018;49(1):1-40.

                A radial nerve injury which is experienced above the elbow, such as in the case of Saturday night palsy, may be associated with a weakness of the wrist, elbow or finger further accompanied by a disturbance of the sensory nerves along the posterior interosseous nerve (PIN) and the superficial radial nerve (SRN)¹⁷. Some patients diagnosed with Saturday night palsy experienced finger and wrist drop which was accompanied by a reduced sensation in the posterolateral hand. Others complained of weakness in the finger extensors, preserved wrist extension and weak thumb. Having knowledge of the radial nerve’s usual entrapment area with its associated motor function is fundamental in localizing the lesion¹⁷. To diagnose the radial nerve injury noted at the spinal groove, the radial nerve should be examined through the sensory nerve stimulation techniques such as light touch testing activities and pinpricking of the forearm and the posterior arm¹⁷. Additionally, the sensory examination should also be completed on the posterior thumb and the lateral hand through an intact sensation passed over the posterior forearm and posterior arm, which is consistent with the nerve lesion present at the spiral groove¹⁷. The site where the injury is located can be established through a physiologic testing and evaluations of the neurons.

                Radial nerve injury can also exist at the axilla. The compression experienced at this point is mainly as a result of prolonged use of crutches. Immediately after the brachial plexus, the radial nerve travels under the arm close to the axilla. The radial nerve has a responsibility of controlling the triceps muscles present at the back of the arm. Therefore, any damage to the nerve present at the axilla results to the arm’s weakness mainly experienced when pushing objects away. Patients with such injuries can also find it impossible or difficult to bend their wrists backwards in a wrist drop. The finger extensors will also appear weak, thus making it difficult to open the hand fully¹⁷. Isolated injury to the posterior interosseous Nerve (PIN) or those experienced to the branches without an extra damage to the superficial radial nerve is known to be rare. However, they are mainly caused by the penetrating injuries. For instance, the superficial radial nerve injury can be as a result of tight handcuffs. Common differential diagnoses include stroke and peripheral nerve syndromes of the upper extremities.

1. Peroneal Nerve Injury at the Fibular Head

                Fibular neuropathy at the fibular head, also referred to as peroneal neuropathy, is the most common entrapment mononeuropathy in the lower limb ¹⁸. The fibular nerve generates from the roots of the L4-S1 nerves and further travels through the sciatic nerve’s fibular division over the posterior thigh¹⁸. The common fibular nerve is wrapped around the fibular head which is connected at the periosteum as shown in the Fig. 4 below.

Fig. 4. Peroneal Nerve Distribution. From Arnold CM, Dal Bello-Haas V.P.M.,       Farthing JP, et al. Falls and wrist fracture: Relationship to women's                functional status after age 50. Canadian Journal on Aging.                 2016;35(3):361-371.

                From a clinical perspective, the peroneal nerve compression experienced at the fibular head is often presented by a foot drop or change in the sensory ability of the limb. In most case, this involves the deep superficial peroneal branches. Completing a neurological exam will outline the dorsiflexion weakness as well a toe extension, supplied by the deep branch as well as eversion, supplied by the superficial branch.  Additionally, a patient suffering from peroneal neuropathy will complain of loss of sensation noted at the cutaneous distribution of the deep as well as the superficial peroneal nerves. However, it is evident that the chief complaint reported by the patient in this case would be that the affected foot drags on the ground when walking¹⁹.  Presentation is often painless. Nonetheless, in the setting of traumatic nerve injury, pain can be present due to soft tissue swelling and inflammation¹⁹. On the contrary, a chronic compression experienced due to the habitual leg-crossing is often painless. Tapping the nerve at the fibular head may result to tingling and electrical type pain within the sensory distribution at the peroneal nerve ¹⁹.  Differential diagnosis includes sciatic nerve lesions, L5 radiculopathy, and lumbosacral plexopathy.

1. Sciatic Compression Neuropathy

Sciatic neuropathies arise from injury and nerve compression present in the gluteal part or within the thighs. Sciatic neuropathy experienced within the gluteal area arises from trauma. In this case, the nerve can be directly injured in the event of an intramuscular injection to the buttocks. Since the nerve and the hip joint have a close anatomical relationship, the nerve injuries can come about as a result of the hip dislocation at the posterior region, accidental injury experienced during the process of elective hip arthroplasty, and accidental injury. The sciatic neuropathy can also come about as a result of an extensive external nerve compression or endometriosis among others¹⁸. The Fig. 5 below shows the relationship existing between the piriformis muscles and the sciatic nerve.

Fig. 5:  The relationship existing between the piriformis muscles and the sciatic nerve From Arnold CM, Dal Bello-Haas V.P.M.,        Farthing JP, et al. Falls and wrist fracture: Relationship to women's functional status after age 50. Canadian Journal on Aging. 2016;35(3):361-371.

Sciatic neuropathy can look a lot like a peroneal neuropathy and EMG/NCS is necessary to distinguish the two. However, it is evident that sciatic neuropathies are not common in EMG labs and when experienced the patients will present similar findings to peroneal neuropathy. As a result, the electromyographer has the role of making the differentiation. The Table 1 Below can be considered to understand the clinically differentiating factors between the two. The table is also effective in differentiating between the lumbar radic specifically L5 which look like peroneal neuropathy.

Table 1: Differentiating Factors in the cases of Suspected Sciatic Neuropathy From Naeem J, Nur AH, Islam MA, Amelia WA, Bijak M. Mechanomyography-based muscle fatigue detection   during electrically elicited cycling in patients with spinal cord injury. Medical and         Biological Engineering and Computing. 2019;57(6):1199-1211.

Differential diagnosis includes lumbosacral plexopathy and peroneal nerve injury.

Diagnostic workup for Mononeuropathies

                To evaluate mononeuropathies, conducting a nerve conduction study of the motor and sensory nerves is necessary. Additionally, late responses (H reflex and F response) and needle electromyography (EMG) testing are carried out²⁰. EMG is a diagnostic test which is carried out to provide a measure of the electrical activities of the muscles and the peripheral nerves. EMG alongside nerve conduction studies are effective in providing a diagnosis of the motor neuron diseases, peripheral neuropathies, spinal root diseases, primary muscle diseases, and single nerve damage²¹.

                The compression neuropathy workup includes the routine study of the ulnar nerve entrapment which is ordered with an aim of ruling out cases of diabetes mellitus, anemia, and hypothyroidism through studies outlined hereby. The CBC count, fasting blood glucose and urinalysis ²¹. Based on the clinical situation, more tests can be considered such as antinuclear antibody, Hemoglobin A_1C, Renal function tests, renal function tests, and paraproteinemia workup including serim protein electrophoresis alongside immunofixation. Other tests include Lyme serology, Folate level, HIV serology, Vitamins B-12, B-1, and B-6, Gliadin antibody, and Methylmalonic acid. Moreover, Thyroid function tests, Gliadin antibody, Tissue transglutaminase antibody, and Methylmalonic acid ²¹.

Predisposing Conditions

                Cases of mononeuropathies are common in adults and are associated with entrapment or compression. It is evident that mononeuropathies are associated with sensory concerns as well as muscle weaknesses²². Different predisposing conditions for entrapment neuropathies can be experienced in different cases. For instance, pregnant women, people diagnosed with systemic conditions such as diabetes, obesity, alcoholism, thyroid disease and rheumatoid arthritis are highly likely to develop CTS and well as other compressions²².

Management Options

For all entrapment neuropathies, neuropathic pain medication can be used to treat neuropathic pain and paresthesias. Neuropathic pain medications can be used for any entrapment neuropathy, those include but are not limited to NSIADS anti-epileptic agents, antidepressants, topical agents.  Also PT/OT can be helpful to build strength in affected muscles especially in the setting of intrinsic hand weakness. Moreover, it is recommended that for all the neuropathies which result to muscle weakness, occupational and physical therapy is considered as an effective technique of management.

Median Neuropathy Management

In cases of mild to moderate median neuropathy, activity modification to avoid further compression and splinting are the initial treatments of choice.

                Through the guidelines presented by the American Academy of Orthopedic Surgeons, if the symptoms of a patient fail to resolve within a period of 2-7 weeks after the use of a particular form of treatment, then the clinician should resort to an alternative means of therapy²³.  A wrist splint is a lightweight device worn on the hand to restrict range of motion at the wrist. The patient is advised to wear the wrist splint every night on a regular basis and if tolerated, at times during the day when engaging activities that may exacerbate the symptoms²⁴. However, precautions should be taken to avoid prolonged immobilization.

                Activity modification, carried alongside splinting, is also crucial for patients with mild to moderate CTS, including avoiding activities that involve hyperflexion or hyperextension of the affected wrist. When more conservative measures fail, median neuropathy can also be treated through the use of a local steroid injection. The injection option is mainly effective for patients with intermittent symptoms and moderate to severe CTS. If one records mild symptoms, conservative therapy is considered as the most effective remedy. The local injection can have a prognostic and diagnostic role as response predictor to surgical release²⁵. However, effective care should be taken to ensure that the carpal tunnel, tendons or the nerve are not injected in the process. Moreover, more than three injections are not recommended as this poses a risk to the patient’s flexor tendons²⁵. Alternative therapies such as yoga-based programs involving stretching, and relaxation should be avoided since they include wrists hyperextension, and hence likely to worsen the patient’s condition.

                Surgery can also be considered for treating median neuropathy that is mild. The choice of proceeding to the carpal tunnel release (CPR) surgery is founded on the patient’s preference²⁵. Evidently, CTS patients treated through the use of medical techniques eventually required CPR surgery with a low risk of reoperation²³. Classic open CTR surgery can be administered. In this case, a longitudinal incision of about 6 cm is made from the distal wrist crease to the palm section. For the endoscopic surgery, a single or dual portal technique is carried out to limit the patient’s symptoms²³.

Ulnar Neuropathy Management

                Depending on the severity, ulnar neuropathy at the elbow can be managed conservatively ¹¹. Patient education is also a management strategy for ulnar neuropathy. The clinician should educate the patient that this neuropathy is position dependent, and recommend activity modification to minimize stretch or compression on the ulnar nerve¹¹.  For example, avoiding hyperflexion of the elbow or leaning the elbow against a hard surface. Additionally, patients can also consider the use of a protective soft padding, such as a towel, wrapped over the elbow at night ¹². This is usually tolerated well than a rigid splint.

For an ulnar neuropathy at the wrist, at the level of the Guyon’s canal, specialized wrist splints are available. If conservative therapy fails, surgical options are available.

                Furthermore, surgical alternatives can be considered by patients diagnosed with ulnar neuropathy at the elbow. However, controversy exists regarding the best surgical. The surgical strategies can be categorized as in situ decompression or anterior transposition. In situ decompression, which involves endoscopic, mini-incision and open surgery, are common surgical alternatives considered by surgeons located in the USA¹¹. However, the potential for the condition recurrence is significantly high. Anterior transposition includes surgical processes which are achieved through medical epicondylectomy, transmuscular transposition, subcutaneous transposition, or submuscular transposition¹³.

Radial Nerve Injury Management

                Radial nerve palsies can be categorized into primary and secondary radial nerve palsy, or partial and complete radial nerve palsy ¹⁶. In primary nerve palsy, loss of function is experienced during the time of the injury and is related with closed fractures. In secondary nerve palsy, the function loss is experienced during the time of the treatment. Partial or complete nerve palsy is determined by the rate at which the patient has lost the hand or wrist movement. If entrapment at the spiral groove is suspected, imaging should be done to look for source of compression, such as a tumor, cyst or humeral fracture.  Initial treatment of the radial nerve injury at the spinal groove is often treated with rest, immobilization, and nonsteroidal anti-inflammatory medicines (NSAIDS)¹⁶. Maintaining a full passive range of motion is fundamental during the therapy¹⁶. In the case of nerve transection or failure of conservative therapy, surgery is indicated.  Nerve reconstruction is necessary in the case of transection. Neuropathic agents can also be used to treat pain and pareshtesias,

Peroneal Nerve Injury Management

                Peroneal neuropathy at the fibular head can also be managed through the use of conservative treatment and surgical techniques. Medications such as capsaicin, topical lidocaine, and antiepileptic can be considered to remedy the pain experienced by patients diagnosed with peroneal neuropathy¹⁹. However, the choice of treatment should be individualized based on the patient’s medication needs. A patient who complains of weakness only in the toe extensors should consider putting on sturdy footwear which is effective in gait optimization¹⁶. Moreover an AFO brace can be recommended to assist in ambulation in the events of a foot drop. A rocker-bottom shoe can also be considered to reduce the amount of energy which a person must implement to ensure ambulation.

                The clinician should counsel the patient on avoiding putting pressure on the peroneal nerve at the fibular head, including avoiding crossing their legs when sitting and placing a pillow on the affected side when sleeping.  Daily stretching is also recommended for patients with peroneal neuropathy as it aids in preventing contracture¹⁸. Rarely a compressive lesion can be found, such as a ganglion cyst, in which case removal should be considered. In the case of an open injury causing peroneal nerve palsy,  an immediate surgical procedure is indicated¹⁶. In the event a patient’s symptoms do not vanish after conservative treatment, surgical compression can be considered ¹⁸.

Conclusion

                Entrapment neuropathies are common conditions seen by clinicians in a wide range of specialties.  These injuries are often due to external compression or stretch of the affected nerve, therefore activity and position modification is the mainstay of treatment.  Patient education is critical. In majority of cases, conservative management is preferred.  However when conservative management fails or in the cases of open injuries or significant associated weakness, surgical options are available and effective.