Cervical Thecal Sac Indentation at C5–C6

The thecal sac is a fluid-filled membrane that encapsulates the spinal cord and the cauda equina (a bundle of nerve roots at the end of the spinal cord). It provides a protective environment for these delicate structures.

Cervical thecal sac indentation at C5–C6 refers to a pressing-in or deformation of the dura mater “tube” (thecal sac) that surrounds and protects the spinal cord and nerve roots, specifically between the fifth (C5) and sixth (C6) cervical vertebrae in the neck. This indentation often results from structures such as displaced discs, bony outgrowths (osteophytes), or thickened ligaments pushing into the front (ventral) side of thecal sac, which can narrow the space around the spinal cord and cerebrospinal fluid (CSF) RadiopaediaWikipedia.

Anatomy of the Thecal Sac at C5–C6

The thecal sac, also called the dural sac, is a one‐layered sheath of dura mater that extends from the base of the skull (foramen magnum) down to the level of the second sacral vertebra (S2). It encloses the spinal cord above and the cauda equina below, and is separated from the inner vertebral canal by the epidural space Wikipedia.

• Structure & Location: At C5–C6, the thecal sac sits within the spinal canal formed by the vertebral bodies (C5 and C6) and arches, lying just behind the intervertebral disc and facet joints Spine-health.

• Origin & Insertion: Unlike muscles, the thecal sac doesn’t “insert” on bones—it adheres at the foramen magnum above and tapers around the filum terminale at S2 below, with lateral projections that follow each spinal nerve root out of the canal Wikipedia.

• Blood Supply: Segmental radicular arteries (branches of vertebral, ascending cervical, and deep cervical arteries) supply the spinal dura; the cranial dura’s vessels (e.g., meningeal arteries) do not extend into the spinal thecal sac. Venous drainage occurs via epidural venous plexuses Wikipedia.

• Nerve Supply: Small meningeal branches from the upper cervical spinal nerves and the vagus nerve provide sensory innervation to the spinal dura Wikipedia.

• Key Functions:

  1. Protection: Houses and shields the spinal cord and nerve roots from trauma Wikipedia.

  2. CSF Containment: Holds cerebrospinal fluid, which cushions the cord and nerve roots and serves as a shock absorber Wikipedia.

  3. Nutrient & Waste Exchange: CSF circulation within the sac transports nutrients and removes metabolic waste from spinal tissues Wikipedia.

  4. Pressure Regulation: Helps maintain stable intracanal pressure, aiding blood flow within the spinal cord Wikipedia.

  5. Site for Procedures: Provides access for lumbar puncture (spinal tap) and epidural anesthesia Wikipedia.

  6. Nerve Root Sheathing: Forms extensions (dural root sleeves) around exiting nerve roots, protecting them as they leave the canal Wikipedia.

Types of Cervical Thecal Sac Indentation at C5–C6

Indentation can arise from various sources pressing into the sac:

1. Disc Bulge: A mild, uniform bulging of the C5–C6 disc pressing thecal sac gently forward Radiopaedia.

2. Disc Protrusion or Herniation: Focal disc material pushing into the canal, often more pronounced than a bulge Radiopaedia.

3. Disc Extrusion/Migration: Fragmented disc tissue extruding through the annulus into the canal, sometimes migrating above or below C5–C6 Radiopaedia.

4. Osteophytic Complex: Bone spurs from degenerative changes indenting the front of thecal sac Radiopaedia.

5. Facet Joint Hypertrophy: Enlarged facet joints narrowing the canal space Radiopaedia.

6. Ligamentum Flavum Thickening: Overgrown ligament at the back of the canal pushing inward Radiopaedia.

7. Intraspinal Masses: Tumors or cysts inside the canal deforming the sac Radiopaedia.

8. Intraspinal Masses: Tumors or cysts inside the canal deforming the sac Radiopaedia.

9. Epidural Hematoma: Blood collection from trauma or anticoagulation compressing thecal sac

Radiologists often describe the degree and location of thecal sac indentation using a grading system adapted from spinal canal stenosis scales:

• Mild indentation (Grade 1b): Dural deformation without contact against the spinal cord. Radiopaedia

• Moderate indentation (Grade 2): Thecal sac deformation with some CSF still visible around the cord. Radiopaedia

• Severe indentation (Grade 3): Posterior indentation abolishing visible CSF around the cord. Radiopaedia

Indentations can also be classified by location:

• Central: Straight back pressure on thecal sac.

• Paracentral: Slightly off-center, affecting one side more.

• Foraminal: Into the nerve-exiting passage, often causing nerve root compression.

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Common Causes

1. C5–C6 intervertebral disc bulge (age-related degeneration)

2. Disc herniation at C5–C6

3. Osteoarthritis (bone spur formation)

4. Facet joint hypertrophy

5. Ligamentum flavum thickening

6. Congenital spinal canal narrowing

7. Whiplash or trauma to the neck

8. Spondylolisthesis (vertebral slip)

9. Rheumatoid arthritis

10. Ankylosing spondylitis

11. Ossification of the posterior longitudinal ligament

12. Paget’s disease of bone

13. Spinal tumors (meningioma, metastasis)

14. Epidural abscess or infection

15. Epidural hematoma

16. Inflammatory disorders (e.g., sarcoidosis)

17. Diffuse idiopathic skeletal hyperostosis (DISH)

18. Excessive epidural fat (lipomatosis)

19. Post-surgical scarring (fibrosis)

20. Spinal canal cysts (synovial cysts)

Sources: WebMD, NIH NIAMSMerck Manuals

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Possible Symptoms

1. Neck pain or stiffness

2. Radiating arm pain (C6 distribution)

3. Numbness or tingling in thumb/index finger

4. Muscle weakness in biceps or wrist extensors

5. Reduced grip strength

6. Headaches at the base of skull

7. Shoulder blade discomfort

8. Loss of fine motor skills (buttoning shirts)

9. Gait instability or difficulty walking

10. Balance problems

11. Exaggerated deep tendon reflexes

12. Spasticity in arms or legs

13. Lhermitte’s sign (electric shock-like sensations)

14. Bladder or bowel dysfunction

15. Sensory changes in arms/torso

16. Muscle spasms

17. Clumsiness or dropping objects

18. Neck muscle fatigue

19. Choking sensation with neck movement

20. Sleep disturbance due to pain

Sources: Verywell Health, Spine-Health Verywell HealthSpine-health

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Diagnostic Tests

1. MRI of the cervical spine (gold standard)

2. CT scan (bony detail)

3. Plain X-rays (alignment, degeneration)

4. CT myelography (when MRI contraindicated)

5. Electromyography (EMG)

6. Nerve conduction studies

7. Somatosensory evoked potentials

8. Motor evoked potentials

9. Dynamic (flexion-extension) X-rays

10. Bone scan (infection, tumor)

11. Discography (provocative test)

12. Ultrasound (soft-tissue assessment)

13. Laboratory tests (CBC, ESR, CRP for infection)

14. CT angiography (vascular compression)

15. Spinal tap (CSF analysis)

16. Facet joint injection (diagnostic)

17. Selective nerve root block (diagnostic)

18. Kinematic MRI

19. Diffusion tensor imaging (DTI)

20. Virtual reality 3D reconstruction

Sources: Wikipedia, StatPearls WikipediaNCBI

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Non-Pharmacological Treatments

1. Physical therapy (strengthening, stretching)

2. Cervical traction

3. Heat therapy

4. Cold therapy

5. Transcutaneous electrical nerve stimulation (TENS)

6. Ultrasound therapy

7. Manual therapy (mobilization)

8. Soft tissue massage

9. Posture correction exercises

10. Ergonomic workstation adjustments

11. Custom cervical pillow

12. Activity modification

13. Aquatic therapy

14. Yoga

15. Pilates

16. Tai Chi

17. Mindfulness meditation

18. Biofeedback

19. Acupuncture

20. Chiropractic adjustments

21. Cognitive behavioral therapy (CBT)

22. Occupational therapy

23. Weight management program

24. Smoking cessation support

25. Nutritional counseling

26. Home exercise program

27. Walking program

28. Neck stabilization exercises

29. Breathing exercises

30. Education on spine health

Sources: Wikipedia, Verywell Health WikipediaVerywell Health

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Drugs Commonly Used

1. Ibuprofen (NSAID)

2. Naproxen (NSAID)

3. Aspirin (NSAID)

4. Acetaminophen

5. Oral corticosteroids (e.g., prednisone)

6. Epidural steroid injections

7. Cyclobenzaprine (muscle relaxant)

8. Baclofen (muscle relaxant)

9. Tizanidine (muscle relaxant)

10. Gabapentin (anticonvulsant)

11. Pregabalin (anticonvulsant)

12. Amitriptyline (tricyclic antidepressant)

13. Duloxetine (SNRI)

14. Tramadol (opioid)

15. Codeine (opioid)

16. Topical lidocaine patch

17. Capsaicin cream

18. Clonidine patch

19. Diclofenac gel (topical NSAID)

20. Methocarbamol (muscle relaxant)

Sources: Wikipedia, Cleveland Clinic WikipediaCleveland Clinic

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Surgical Options

1. Anterior cervical discectomy and fusion (ACDF)

2. Artificial disc replacement

3. Posterior cervical laminectomy

4. Laminoplasty

5. Anterior corpectomy

6. Posterior cervical foraminotomy

7. Minimally invasive microdiscectomy

8. Posterior cervical instrumentation and fusion

9. Endoscopic cervical decompression

10. Spinal cord stimulation implant

Sources: Wikipedia, StatPearls WikipediaNCBI

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Preventive Measures

1. Maintain good posture while sitting and standing

2. Use an ergonomic workstation

3. Perform regular neck stretches

4. Strengthen core and neck muscles

5. Keep a healthy weight

6. Quit smoking to preserve disc health

7. Use proper lifting techniques

8. Sleep on a supportive pillow

9. Take frequent breaks when working at a desk

10. Stay active with low-impact exercises

Based on general spine health guidelines

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When to See a Doctor

Seek medical evaluation if you experience:

• Severe or worsening neck pain unrelieved by rest

• Radiating arm pain with numbness or weakness

• Loss of bladder or bowel control

• Difficulty walking or balance issues

• Spasticity or hyperreflexia

• New onset of Lhermitte’s sign

• Fever and neck stiffness (suggesting infection)

Source: WebMD WebMD

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Frequently Asked Questions (FAQs)

1. What exactly is thecal sac indentation?
   It’s when something presses into the membrane around your spinal cord, seen as a dent on MRI Spine Info.

2. Is it the same as spinal stenosis?
   Indentation refers to membrane deformation, while stenosis means overall canal narrowing. They often occur together Wikipedia.

3. Can mild indentation worsen?
   Yes—without treatment, mild cases can progress to moderate or severe indentation.

4. Will physical therapy help?
   Yes, targeted exercises and manual therapies can reduce pressure and improve function Wikipedia.

5. When is surgery necessary?
   Surgery is considered if conservative treatments fail or if you have neurological deficits like weakness or bladder issues NCBI.

6. Can indentation cause permanent damage?
   If severe and untreated, it can lead to lasting spinal cord injury.

7. How long is recovery after ACDF?
   Most people take 6–12 weeks to return to normal activities, with complete fusion in 3–6 months NCBI.

8. Are there non-drug pain relief options?
   Yes—heat/cold packs, TENS, acupuncture, and massage can all help.

9. Can diet affect my spine health?
   A balanced diet rich in calcium, vitamin D, and anti-inflammatory foods supports disc and bone integrity.

10. Is it safe to exercise?
    Low-impact activities like walking, swimming, and yoga are generally safe with guidance.

11. Do I need a collar?
    A soft collar may relieve pain short-term but is not recommended for long-term use due to muscle weakening.

12. What imaging is best?
    MRI provides the most detailed view of soft tissues, discs, and thecal sac.

13. Can children get thecal sac indentation?
    It’s rare in children and usually due to congenital or traumatic causes.

14. How often should I follow up?
    Typically every 3–6 months if you have symptoms, or sooner if they worsen.

15. Are there emerging treatments?
    Research is ongoing into biologic injections (e.g., stem cells) and minimally invasive endoscopic decompression.

Disclaimer: Each person’s journey is unique, treatment plan, life style, food habit, hormonal condition, immune system, chronic disease condition, geological location, weather and previous medical  history is also unique. So always seek the best advice from a qualified medical professional or health care provider before trying any treatments to ensure to find out the best plan for you. This guide is for general information and educational purposes only. Regular check-ups and awareness can help to manage and prevent complications associated with these diseases conditions. If you or someone are suffering from this disease condition bookmark this website or share with someone who might find it useful! Boost your knowledge and stay ahead in your health journey. We always try to ensure that the content is regularly updated to reflect the latest medical research and treatment options. Thank you for giving your valuable time to read the article.

The article is written by Team Rxharun and reviewed by the Rx Editorial Board Members

Last Updated: May 02, 2025.

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