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Dr. Brian Abelson DC

Sciatica Part 2: Non-Disc Causes & Diagnosis

Updated: Aug 17


Image of a Person Suffering From Gluteal Pain

In our first segment, we explored how disc herniations can lead to sciatica, focusing on disc protrusions, extrusions, and sequestrations and why conservative therapy is often the best approach when there are no urgent complications. Now, let's dive deeper. In this part of our series, we'll uncover some lesser-known culprits behind sciatica:


  • Non-discogenic causes of sciatica, including the tethering of the sciatic nerve.

  • Direct compression of the sciatic nerve, beyond disc-related issues.

  • The methods and criteria for accurately diagnosing sciatica.


This exploration will provide a broader understanding of sciatica and how to approach it from a diagnostic and treatment standpoint.


Article Index:


 

Man Holding His Leg

Non-Discogenic Sciatic Nerve Pain

Disc issues don't always cause sciatica. Many non-discogenic conditions can lead to sciatic-like pain, often due to restricted movement or direct compression of the sciatic nerve.


One such condition is Deep Gluteal Syndrome (DGS), where the sciatic nerve gets trapped in the deep gluteal space, causing pain, numbness, and muscle weakness in the buttocks and legs.


Key contributors to DGS include:


  • Piriformis Syndrome: The piriformis muscle tightens or swells, compressing the sciatic nerve and nearby blood vessels.

  • Muscle and Skeletal Compression: Surrounding muscles, bones, or tissues press against the sciatic nerve.

  • Vascular Entrapment: Reduced blood flow and oxygenation in the deep gluteal area due to vascular compression.

  • Trauma: Injuries from falls or car accidents impacting the deep gluteal tissues.


The hallmark of DGS is the presence of fibrous bands that restrict the sciatic nerve's ability to glide smoothly along its path, causing pain and neuropathy. Usually, the sciatic nerve stretches and moves with the body, adapting to daily activities. However, in DGS, these bands limit the nerve's movement, leading to ischemic neuropathy. These bands are usually located either to the side or along the nerve’s path, disrupting its natural motion.


 

Fibrous Bands

Fibrous Band Image

The accompanying image provides two perspectives of the sciatic nerve: a transverse view on the left and a longitudinal section on the right. Remarkably, the sciatic nerve's widest point is nearly as thick as a human thumb!


Recent studies have identified three primary types of fibrous bands that can entrap the sciatic nerve:


  • Fibrous Tissue Bands: Composed entirely of fibrous tissue.

  • Mixed Fibrous and Vascular Bands: A combination of fibrous tissue and blood vessels.

  • Vascular Bands: Predominantly made up of blood vessels.


Endoscopic research, which involves using a scope to explore the body’s internal spaces, has frequently detected these fibrous bands in patients experiencing sciatic nerve compression. These bands can trap the sciatic nerve at various locations along its path, leading to pain and discomfort.

Sciatic Nerve Image

Sciatic Nerve Entrapment


The sciatic nerve can become trapped at several key anatomical sites, which may contribute to your sciatica symptoms:


  • Greater Sciatic Notch and Ischial Tuberosity: Bony structures in your pelvis. If the nerve is compressed in this area, it can cause pain that radiates from the lower back into the buttocks and down the leg.

  • Quadratus Femoris Muscle in the Ischial Tunnel: This muscle, located in the deep buttock region, can press on the sciatic nerve if it becomes tight or inflamed, leading to pain and discomfort.

  • Upper Attachment Points of the Hamstrings: The hamstrings are the muscles at the back of your thigh. Compression of the nerve at these points, especially if you've had a previous injury, can cause pain that extends down the back of the leg.

  • Piriformis Muscle and Obturator Internus-Gemelli Complex: These muscles are also deep in the buttock. If they tighten or spasm, they can pinch the sciatic nerve, leading to buttock and leg pain.


Understanding these sites is crucial for those with sciatica because knowing where the nerve might be compressed can lead to more effective treatment. If you’re experiencing ongoing pain, numbness, or weakness, identifying these areas can help guide therapies that target the specific location of the problem, potentially leading to faster relief.

Signs of Deep Gluteal Syndrome (DGS), which involves nerve entrapment in these areas, include:


  • Severe buttock pain

  • Numbness or tingling in the buttocks or legs

  • Weakness in the legs

  • Limited hip movement

  • Pain that worsens with sitting or certain activities

  • Discomfort in the groin


Recognizing these symptoms can help diagnose and treat DGS, offering a clearer path to relief and improved mobility.


 

Direct Compression Of The Sciatic Nerve


This topic is particularly intriguing because some MSK (musculoskeletal) educators have emphasized direct compression of the sciatic nerve as a significant cause of sciatica. However, as we'll see, this isn't as common as it's sometimes portrayed.


Direct compression of the sciatic nerve can occur in several ways, such as entrapment by the piriformis muscle, the Gemelli-Obturator Internus muscle, or the Quadratus Femoris muscle during ischiofemoral impingement. Additionally, entrapment can also happen with the hamstring muscles. These scenarios may occur alongside or independently of entrapments caused by fibrous bands.

Piriformis Syndrome: Unpacking the Misconceptions

Piriformis Muscle Image

Piriformis Syndrome, often linked to back and buttock pain is frequently misunderstood. Surprisingly, direct anatomical compression by the piriformis muscle accounts for only about 15% of cases. The real culprits are often environmental factors like micro-traumas from repetitive movements or post-surgical changes. Tension in the piriformis fascia can also mimic sciatic nerve compression, leading to easily confused symptoms.


Variations in the piriformis muscle aren’t reliable indicators of this condition despite common beliefs. While biomechanics, genetics, and the higher prevalence in women contribute, these factors don’t tell the whole story. It’s crucial to approach Piriformis Syndrome cautiously to avoid overdiagnosis, especially when the real issue might be disc-related. Understanding the true source of pain is key to effective treatment.



 

Gemelli-Obturator Internus Entrapment

Gemelli-Obturator Internus Muscles Image

The gemelli and obturator internus muscles are part of the hip's lateral rotator group, a set of six small muscles that rotate the femur outward. In cases of entrapment syndrome, the sciatic nerve can become compressed between the piriformis muscle and the superior gemelli/obturator internus.


These muscles are enveloped by the obturator fascia, which connects to the iliac fascia.

While anatomists often categorize these muscles individually, they function as a cohesive group. Their fascial connections are vital for their integrated movement, highlighting the importance of viewing them as a collective unit in understanding this condition.


Image from  Functional Atlas of the Human Fascial System

The Myth of Isolation: Wishful Thinking in Muscle Anatomy

Working in the dissection lab, I realized that the deep lateral rotator muscles of the hip are intricately connected through fascial tissue. Treating these muscles in isolation or considering them as functioning separately is unrealistic. The "Deep Six" muscles are so interconnected that they influence each other's movement through their shared fascial ties.


Anyone who suggests these muscles act independently needs to revisit the dissection lab and see these connections firsthand—because these muscles don't operate in a vacuum; they work as a unified team.

Photo: I highly recommend Carla Stecco's book Functional Atlas of the Human Fascial System. The photo is sourced from page 313 of this essential resource, published by Elsevier Health Sciences.



 

Quadratus Femoris - Ischiofemoral Entrapment

Quadratus Femoris Muscle Image

Ischiofemoral impingement occurs when the quadratus femoris muscle, which stretches from the ischial tuberosity to the femur, exerts pressure on the nearby sciatic nerve. This condition can create significant discomfort, especially during activities like sitting or taking long strides.


The underlying cause of this impingement often involves a narrowed space between the femur and ischial tuberosity. While the exact reasons remain uncertain, factors like abnormal hip dynamics, muscle imbalances, or structural variations in the femur or pelvis are likely contributors.


The interconnectedness of the fascial web also plays a role, as the fascia that envelops and connects these structures can influence pain and movement restrictions.


Common symptoms of ischiofemoral impingement include:

  • Pain in the hip, groin, or thigh

  • Numbness or tingling in the hip or thigh

  • Muscle weakness in the hip or thigh

  • Limited hip movement

  • Pain that worsens with sitting or specific movements


Understanding this syndrome within the broader context of the fascial web highlights the importance of addressing not just the isolated muscle, but the entire interconnected system for effective treatment.



 

Hamstring Related Entrapment's

Bruised Hamstring Image

Hamstring injuries can directly affect the sciatic nerve, with swelling initially irritating the nerve and, over time, leading to scarring (fibrosis) that may trap the nerve during hip movements.


The interconnectedness of the fascial web plays a significant role here. Tension in the hamstrings can influence surrounding muscles and areas like the lower back, exacerbating sciatic nerve compression. It’s also crucial to consider the antagonistic muscles, such as the quadriceps and hip flexors, as imbalances here can worsen the issue.


Key contributing factors include:

  • Repetitive activities like running or cycling

  • Direct impact injuries from falls or accidents

  • Anatomical variations that reduce space for the sciatic nerve


Symptoms to watch for:

  • Intense buttock pain

  • Numbness or tingling in the buttocks or legs

  • Leg weakness

  • Pain worsening with sitting or certain movements

  • Reduced hip flexibility

  • Groin discomfort


Understanding these connections and addressing the injury and the broader muscular balance is critical to effective treatment.



 

Physical Examination

Patients presenting with sciatica-like symptoms need a thorough evaluation, which includes reviewing their medical history, conducting physical observations, and performing orthopedic and neurological tests. This approach helps determine whether the issue is mechanical or signals a more serious underlying condition.


Low Back Examination

Watch the video to see a demonstration of standard orthopedic tests used in a clinical examination of the low back. These tests are essential for diagnosing conditions that may cause sciatica-like symptoms, helping to differentiate between musculoskeletal issues and other potential causes of lower back pain.



 

Neurological/Vascular Testing

A thorough neurological exam is crucial in diagnosing sciatica and related musculoskeletal issues. This exam includes assessing sensory changes through dermatomal patterns, even though these patterns can vary between individuals and aren't universally agreed upon.


The exam also evaluates deep tendon reflexes, which indicate the integrity of the peripheral or central nervous system, using a 0 to 4 scale at key reflex points. Motor function is tested through myotomes, with muscle strength rated from 0 (no contraction) to 5 (full motion against resistance) at specific muscle sites, helping to pinpoint the source of sciatic nerve irritation.


Lower Limb Neuro Examination

The Lower Limb Neurological Examination is crucial for diagnosing sciatica. This exam assesses the sensory and motor neurons that supply the lower limbs, helping identify any nervous system dysfunction. It is an important screening and investigative tool to determine the extent of sciatic nerve involvement and guide effective treatment strategies.


Peripheral Vascular Examination

A Peripheral Vascular Examination is essential when evaluating sciatica to rule out vascular-related pathologies that might mimic or exacerbate nerve-related symptoms. This examination helps prevent cardiovascular and cerebrovascular complications by identifying underlying vascular issues. The video demonstrates some of the most commonly used procedures in daily clinical practice, ensuring a comprehensive approach to diagnosing and managing sciatica.



 

Imaging Techniques for Diagnosing Sciatica

MRI Image of the Lumbar Spine

Imaging plays a vital role in diagnosing sciatica by pinpointing the exact cause of nerve root compression. Here’s how different imaging modalities contribute:


  • X-ray: Primarily used to rule out fractures or tumors, X-rays are limited in diagnosing sciatica since they can't visualize soft tissues or nerves.

  • MRI: The gold standard for sciatica, MRI provides detailed images of the spinal cord, nerve roots, and surrounding tissues, effectively detecting herniated discs, spinal stenosis, and other compressive abnormalities.

  • Ultrasound: Ultrasound offers real-time images of the sciatic nerve and nearby structures, making it useful for diagnosing conditions like piriformis syndrome.


Together, these imaging techniques provide a comprehensive view for accurately diagnosing and treating sciatica.


 

Conclusion Sciatica Part 2

Practitioner On Virtual Call With Patient

Understanding the complexity of sciatica goes beyond just recognizing disc-related causes. This part of our series has highlighted the importance of identifying non-discogenic sources, such as Deep Gluteal Syndrome (DGS) and direct sciatic nerve compression. These insights emphasize that sciatica is not always straightforward, and effective treatment requires a comprehensive approach that considers various anatomical and environmental factors.


In the next part of this series, "Sciatica Part 3—Treatment Logic & Recommendations," we will explore conservative treatment options for sciatica, including spinal manipulation/mobilization and myofascial release procedures. These treatments can provide significant relief for many patients, offering a noninvasive approach to managing sciatica and improving overall function.



 

References Part - 2


  1. Lewis AM, Layzer R, Engstrom JW, Barbaro NM, Chin CT. Magnetic resonance neurography in extraspinal sciatica. Arch Neurol. 2006;63(10):1469–72.

  2. Martin HD, Kivlan BR, Palmer IJ, Martin RL. Diagnostic accuracy of clinical tests for sciatic nerve entrapment in the gluteal region. Knee Surg Sports Traumatol Arthrosc. 2014;22(4):882–8.

  3. Hernando MF, Cerezal L, Pérez-Carro L, Abascal F, Canga A. Deep gluteal syndrome: anatomy, imaging, and management of sciatic nerve entrapments in the subgluteal space. Skeletal Radiol. 2015;44(7):919–34.

  4. Martin HD, Shears SA, Johnson JC, Smathers AM, Palmer IJ. The endoscopic treatment of sciatic nerve entrapment/deep gluteal syndrome. Arthroscopy. 2011;27(2):172–81. [PubMed]

  5. 12. Spinner RJ, Tiel RL. Sciatic nerve compression and piriformis syndrome. In: Midha R, Zager EL, editors. Surgery of Peripheral Nerves : A Case-Based Approach. New York: Thieme; 2008. pp. 186–191.

  6. Adams JA. The pyriformis syndrome -- report of four cases and review of the literature. S Afr J Surg. 1980;18:13–18.

  7. Lohrer H, Nauck T, Konerding MA. Nerve entrapment after hamstring injury. Clin J Sport Med. 2012 Sep;22(5):443-5.

  8. Luis Perez Carro, Moises Fernandez Hernando, Luis Cerezal, Ivan Saenz Navarro, Ana Alfonso Fernandez, and Alexander Ortiz Castillo1 Deep gluteal space problems: piriformis syndrome, ischiofemoral impingement and sciatic nerve release Muscles Ligaments Tendons J. 2016 Jul-Sep; 6(3): 384–396.

  9. Klein MJ. Piriformis syndrome. eMedicine Specialities: Physical Medicine and Rehabilitation: Lower limb Musculoskeletal conditions 2010 fckLR http://emedicine.medscape.com/article/308798-overview

  10. Lori A, Boyajian-O’ Neill, et al. Diagnosis and management of piriformis syndrome:an osteopathic approach. J Am Osteopath Assoc Nov 2008;108(11):657-664

  11. Tonley JC, Yun SM, et al. Treatment of an individual with piriformis syndrome focusing on hip muscle strengthening and movement reeducation: a case report. J Orthop Sports Phys Ther 2010;40(2):103-111.

  12. Lori A, Boyajian-O’ Neill, et al. Diagnosis and management of piriformis syndrome:an osteopathic approach. J Am Osteopath Assoc Nov 2008;108(11):657-664.

  13. Filler AG, Gilmer-Hill H. Piriformis syndrome, obturator internus syndrome, pudendal nerve entrapment, and other pelvic entrapments. In: Winn HR, editor. Youmans neurological surgery. 6th ed. Philadelphia: Saunders; 2009. pp. 2447–55.

  14. Taneja AK, Bredella MA, Torriani M. Ischiofemoral impingement. Magn Reson Imaging Clin N Am. 2013;21(1):65–73.

  15. Torriani M, Souto SC, Thomas BJ, Ouellette H, Bredella MA. Ischiofemoral impingement syndrome: an entity with hip pain and abnormalities of the quadratus femoris muscle. AJR Am J Roentgenol. 2009;193(1):186–90.

  16. Bucknor MD, Steinbach LS, Saloner D, Chin CT. Magnetic resonance neurography evaluation of chronic extraspinal sciatica after remote proximal hamstring injury: a preliminary retrospective analy-sis. J Neurosurg. 2014;121(2):408–14. [PubMed]

  17. Stecco, Carla; Stecco, Carla. Functional Atlas of the Human Fascial System. Elsevier Health Sciences.

  18. Dr. Shawn Thistle - RRS Education - Chiropractic Care for Disc Patients April 28th 2019


 
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DR. BRIAN ABELSON, DC. - The Author


Photo of Dr. Brian Abelson

With over 30 years of clinical practice and experience in treating over 25,000 patients, Dr. Abelson created the powerful and effective Motion Specific Release (MSR) Treatment Systems.


As an internationally best-selling author, he aims to educate and share techniques to benefit the broader healthcare community.


A perpetual student himself, Dr. Abelson continually integrates leading-edge techniques into the MSR programs, with a strong emphasis on multidisciplinary care. His work constantly emphasizes patient-centred care and advancing treatment methods. His practice, Kinetic Health, is located in Calgary, Alberta, Canada.



 


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