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Sciatica

Sciatica or sciatic radicular syndrome, is a pathology that causes pain and weakness of the legs and lower back. It is a common disorder in middle-aged people with a sedentary lifestyle.

“The sciatic nerve is often affected in diseases of the pelvis or lower limbs, as well as by lesions that originate within the nerve itself. Its course is long, which predisposes it to various types of compression. MRN is an important tool for the evaluation of peripheral nerve diseases and should be widely used for the study of the sciatic nerve whenever possible. Detailed knowledge of its anatomy and of the imaging aspects of the main diseases affecting it is fundamental to optimizing imaging studies of the sciatic nerve.”1

The vertebral column is formed by a set of vertebrae, small bones joined to each other by gelatinous tissue (intervertebral discs). The nerve roots coming from the spinal cord pass through the spaces between these vertebrae and form the different nerves that reach the muscles, glands or other places of the body. The nerve roots that make up the sciatic nerve are the largest and longest nerve in the body. It is responsible for the innervation of almost the entire leg. In some cases, the roots that form the sciatic nerve (L4, L5 and S1) are compressed, producing what is known as sciatica.

The compression of the roots can be due to different causes. One of the main ones are herniated discs. It may also be due to tumors around the spine, osteoarthritis of the vertebrae or malformations.

 

Origin and Course of the Sciatic Nerve and the Main Sites of Damage
Fig. 1. Origin and Course of the Sciatic Nerve and the Main Sites of Damage. Panel A shows the normal anatomy surrounding the sciatic nerve. Panels B through I show the main types of damage. Reprinted from “Sciatica.” New England Journal of Medicine, 372(13), 1240-1248. By Ropper, A. H., & Zafonte, R. D. (2015).

 

Symptoms

The compression of the sciatic nerve produces pain in the lumbar area (lumbago) and give rise to symptoms such as:

  • Difficulty to move the leg. Depending on the root that is affected, some movements will be altered since each root controls a certain group of muscles.
  • Alteration of the sensitivity in the leg, which also depends on which nerve root is compressed.
  • Affectation of reflexes, which are automatic responses to a stimulus. If they are affected, they will be diminished or absent. The reflexes that are altered because of sciatic radicular syndrome are the patellar or ankle.

Presentation

“Sciatic neuropathy often presents with foot drop. Patients often experience abrupt pain radiating down the posterolateral limb, with weakness and numbness evolving more gradually. In sciatic neuropathy, the clinical findings are often more consistent with injury to the common fibular division rather than tibial division, sometimes mimicking a common fibular neuropathy at the knee. This finding is particularly true of more distal lesions, as they may not affect the flexors of the knee, or of less severe sciatic nerve injury. Because the common fibular division has fewer and larger fascicles and less supportive tissue compared with the tibial division, it is thought to be more vulnerable to compression. Also, the common fibular division is more taut, and secured at the sciatic notch and fibular neck, resulting in greater potential for stretch injury.

In milder cases at the hip or thigh, the following features are typically noted:

  • Foot drop that may mimic a common fibular neuropathy at the knee
  • Weakness in knee flexion, ankle plantar flexion, ankle inversion
  • Normal or decreased ankle jerk
  • Pain and sensory loss in the foot and possibly the lateral shin

In severe lesions, these signs and symptoms are common

  • Weakness in ankle dorsiflexion and plantar flexion and toe extension and flexion
  • Hamstring weakness
  • Decreased ankle jerk
  • Dysesthesic pain and numbness in the sole and dorsum of the foot and lateral lower leg.”2

How is sciatica diagnosed?

“Sciatica is mainly diagnosed by history taking and physical examination. By definition patients mention radiating pain in the leg. They may be asked to report the distribution of the pain and whether it radiates below the knee and drawings may be used to evaluate the distribution. Sciatica is characterized by radiating pain that follows a dermatomal pattern. Patients may also report sensory symptoms. Physical examination largely depends on neurological testing. The most applied investigation is the straight leg raising test or Lasègue’s sign. Patients with sciatica may also have low back pain but this is usually less severe than the leg pain. The diagnostic value of history and physical examination has not been well studied. No history items or physical examination tests have both high sensitivity and high specificity. The pooled sensitivity of the straight leg raising test is estimated to be 91%, with a corresponding pooled specificity of 26%. The only test with a high specificity is the crossed straight leg raising test, with a pooled specificity of 88% but sensitivity of only 29%. Overall, if a patient reports the typical radiating pain in one leg combined with a positive result on one or more neurological tests indicating nerve root tension or neurological deficit the diagnosis of sciatica seems justified.”3

 

Straight-Leg-Raising Test
Fig. 2. Straight-Leg-Raising Test. Panel A shows the straight-leg-raising test, with assessment for the presence or absence of Lasègue’s sign, and Panel B shows the spinal nerve roots under traction during the test. Reprinted from “Sciatica.” New England Journal of Medicine, 372(13), 1240-1248. By Ropper, A. H., & Zafonte, R. D. (2015).

Recovery process

To recover from a radicular syndrome, the first thing to do is to treat what compresses the nerve root. Depending on the evolution of recovery, rehabilitation may be needed to strengthen the muscles.

When sciatica is caused by a herniated disc the treatment can be conservative, since the symptoms remit after a few days. The non-surgical approach to sciatica can be done in different ways. Treatment usually involves oral analgesics (such as ibuprofen) and application of heat and cold in the lower back to reduce inflammation and relieve pain. If the pain is very intense or does not respond to analgesics, it may be useful to apply corticoids, a more powerful anti-inflammatory drug. They are commonly injected into the painful area. However, you should not abuse of these injections, so they should be reserved for times when pain is very intense.

“Sciatica resolves without treatment in the majority of cases. Numerous systematic analyses have compared various forms of therapy for sciatica, but the validity of their constituent studies is limited. Many conflate treatment for back pain with that for sciatica. Although it is difficult to derive clinically useful information from these compilations, they do provide some perspective on the relative value of treatments.

The most common initial treatment is pain control by means of medication and physical therapy. Activity is usually self-limited in proportion to the degree of discomfort, and although rest is often recommended, it is not better than movement in patients who are able to remain active. Nonsteroidal anti-inflammatory medications may provide short-term relief for low back and sciatic pain; however, it is difficult to determine their effect on sciatica, and many patients report little relief. Orally or systemically administered glucocorticoids have been used to ameliorate sciatica, but it is difficult to interpret their effect. Many guidelines recommend restrictions on the use of opioids. Antiepileptic drugs, gabapentin, pregabalin, antidepressant agents (e.g., tricyclic agents), muscle relaxants, and pain medications have been used but with little supporting data.

Any intervention that temporarily reduces pain and increases participation in exercises, even if it is associated with no long-term benefit, could play a role in care. The benefits of physical therapy and various exercise regimens are difficult to determine, and the superiority of any one program has not been established, although most appear to be safe. Programs include directional preference exercises (back-movement exercises in a direction that causes the locus of pain to move proximally, toward the mid-back, where it is better tolerated), motor-control exercises (also known as specific stabilization exercises) that focus on enhancing control of the transversus abdominis and multifidus muscles, which stabilize the spine, strengthening of other core muscles, stretching, general fitness exercises, and yoga. One conventional approach involves slowly increasing mobilization of the lumbar spinal segments by means of stretching and exercise, improving posture, and strengthening the muscles that stabilize the spinal column and pelvis. It has been difficult to show that this approach accelerates recovery or prevents future injury, but some trials suggest that it is superior to rest in the acute phase of sciatica.”4

On the other hand, when there is severe compression, surgical intervention may be necessary. This option is recommended in approximately one out of every ten patients with a herniated disc.

Rehabilitation and physiotherapy are essential to recover from sciatica with greater speed. It consists of exercising the lumbar muscles to strengthen the area. Aerobic exercise is also recommended to improve general health, endurance and circulation.

“The natural course of sciatica is favorable in most patients and the primary management challenge is adequate pain control. However, some patients do not improve even in the long term. If a disc herniation is found to be the cause of the sciatic syndrome then patients may become surgical candidates. In any case, patients with poor long-term outcome or eventual lumbo-sacral discectomy may be regarded as patients with an unfavorable outcome of the relatively benign sciatic syndrome. The question arises as to whether an eventual unfavorable outcome may be predicted at an early stage.”5

References:

(1) Agnollitto, P. M., Chu, M. W. K., Simão, M. N., & Nogueira-Barbosa, M. H. (2017). Sciatic neuropathy: findings on magnetic resonance neurography. Radiologia brasileira, 50(3), 190-196. Available online at http://www.scielo.br/pdf/rb/v50n3/0100-3984-rb-50-03-0190.pdf

(2) Ropper, A. H., & Zafonte, R. D. (2015). Sciatica. New England Journal of Medicine, 372(13), 1240-1248. Available online at https://mfprac.com/web2018/07literature/literature/Orthopedics/Sciatica_Ropper.pdf

(3) Koes, B. W., Van Tulder, M. W., & Peul, W. C. (2007). Diagnosis and treatment of sciatica. Bmj, 334(7607), 1313-1317. Available online at https://www.lumc.nl/sub/5038/att/812180307081046/905080238511046.pdf

(4) Distad, B. J., & Weiss, M. D. (2013). Clinical and electrodiagnostic features of sciatic neuropathies. Physical Medicine and Rehabilitation Clinics, 24(1), 107-120. Available online at https://depts.washington.edu/neurolog/images/emg-resources/Sciatic_Neuropathies.pdf

(5) Vroomen, P. C., De Krom, M. C. T. F. M., & Knottnerus, J. A. (2002). Predicting the outcome of sciatica at short-term follow-up. Br J Gen Pract, 52(475), 119-123. Available online at https://pdfs.semanticscholar.org/b8ab/cb7a91496e3b639da42e597bdb43b0daf96f.pdf

Robert Velasquez
13 October, 2018

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Hello everyone, my name is Robert Velazquez. I am a content marketer currently focused on the medical supply industry. I studied Medicine for 5 years. I have interacted with many patients and learned a lot...read more:

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