Traumatic Thecal Sac Indentation

Traumatic thecal sac indentation refers to the inward deformation or compression of the thecal sac—the dural sheath that encloses the spinal cord and cerebrospinal fluid (CSF)—caused by external force such as bone fragments, herniated discs, or hematomas following spinal injury. On imaging (MRI or CT), it appears as a loss of the normal CSF space and a flattening or “pinching” of the thecal sac margin. While mild indentation may be asymptomatic, severe cases can impinge nerve roots, leading to neurological deficits Spine InfoWikipedia.

Anatomy

Structure and Location

The thecal sac is a tubular sleeve of dura mater that extends from the foramen magnum at the skull base down to approximately the second sacral vertebra (S2). It surrounds the spinal cord in the cervical and thoracic regions and the cauda equina in the lumbar and sacral regions, floating within the vertebral (spinal) canal’s epidural space WikipediaRadiopaedia.

Origin and Insertion

Cranially, the thecal sac is continuous with the cranial dura at the foramen magnum. Caudally, the dural tube tapers and ends at S2, enclosing the filum terminale and transitioning into the coccygeal ligament. This configuration ensures a sealed CSF compartment for spinal cord protection WikipediaWikipedia.

Blood Supply

Arterial blood to the spinal dura (thecal sac) is primarily delivered by anterior and posterior radicular arteries, which branch from segmental arteries (e.g., vertebral, intercostal, lumbar arteries) and anastomose longitudinally along the sac’s circumference. These radicular vessels ensure consistent perfusion of the dural sac tissue and adjacent meninges RadiopaediaNCBI.

Nerve Supply

Sensory innervation of the spinal dura comes from the meningeal (recurrent) branches of each spinal nerve. These small nerves re-enter the spinal canal via the intervertebral foramina to supply the dura mater, periosteum, and posterior longitudinal ligament, conveying pain and proprioceptive signals KenhubRadiopaedia.

Functions

1. Protection: Acts as a tough, fibrous barrier shielding the spinal cord and nerve roots from mechanical damage.

2. CSF Containment: Maintains a closed CSF environment, providing buoyancy and nutrients to neural tissues.

3. Shock Absorption: Distributes mechanical forces evenly, reducing focal stress on the cord.

4. Neural Exit Channels: Forms dural root sleeves that guide nerve roots from the cord to the intervertebral foramina.

5. Homeostasis: Preserves consistent intracranial and intraspinal pressure.

6. Barrier to Infection: Limits spread of pathogens from the epidural space into the CSF WikipediaVerywell Health.

Types

Traumatic thecal sac indentations can be categorized by:

1. Severity:

   • Mild: <25% deformation of cross-sectional CSF space, usually asymptomatic.

   • Moderate: 25–50% deformation, possible transient nerve contact.

   • Severe: >50% deformation with clear nerve compression and neurological signs Spine Info.

2. Etiology:

   • Disc Herniation Indentation: Protruding nucleus pulposus exerts focal pressure on the sac Radiopaedia.

   • Spinal Epidural Hematoma: Accumulated blood in the epidural space indents the sac Radiopaedia.

   • Epidural Lipomatosis: Excess fat compresses the sac uniformly Radiopaedia.

   • Bony Fragment Indentation: Retropulsed vertebral fragments from burst or compression fractures.

   • Ligamentous Injury Indentation: Thickened or torn ligaments (e.g., ligamentum flavum hypertrophy) encroach on the sac.

3. Location:

   • Cervical Indentation (e.g., whiplash injuries).

   • Thoracic Indentation (e.g., assault or falls).

   • Lumbar Indentation (e.g., heavy lifting–related disc injury).

   • Sacral Indentation (rare; usually iatrogenic or tumor-related).

4. Configuration:

   • Shape Variants: Polygonal, stellate, Y-shaped, circular, sagittal ovoid, square-stellate, and palm-leaf indentations described in imaging literature jocn-journal.com.

Causes

Any condition or event that narrows the spinal canal can induce thecal sac indentation, especially following trauma or degenerative change Spine InfoRadiopaedia:

1. Burst fractures (axial loading)

2. Compression fractures (low-height falls)

3. Fracture–dislocations (high-energy trauma)

4. Hyperflexion injuries (football, rugby)

5. Hyperextension injuries (whiplash)

6. Axial loading injuries (diving accidents)

7. Pedestrian vs. motor vehicle accidents

8. Sports collisions (football tackles)

9. Stab or gunshot wounds penetrating the canal

10. Crush injuries (industrial accidents)

11. Iatrogenic fractures (spinal instrumentation)

12. Herniated discs (traumatic annular tears)

13. Epidural hematomas (ruptured vessels)

14. Epidural lipomatosis (steroid-induced)

15. Ligamentum flavum hypertrophy (traumatic stress)

16. Osteoporotic vertebral collapse

17. Pathological fractures (tumors, infection)

18. Spondylolisthesis (forward vertebral slip)

19. Facet dislocations (rotational injuries)

20. Spinal tumors with pathological collapse

Symptoms

Symptoms vary by level and severity but often mirror spinal stenosis presentations Spine InfoNCBI:

1. Localized back or neck pain

2. Radicular pain (shooting leg/arm pain)

3. Numbness in dermatome distribution

4. Tingling or “pins and needles”

5. Muscle weakness

6. Diminished reflexes

7. Hyperreflexia and spasticity (cervical involvement)

8. Gait disturbances (ataxic or antalgic gait)

9. Bowel dysfunction (constipation or incontinence)

10. Bladder retention or incontinence

11. Saddle anesthesia (loss of perineal sensation)

12. Sexual dysfunction

13. Loss of proprioception

14. Cold intolerance in extremities

15. Neurogenic shock (hypotension, bradycardia)

16. Respiratory compromise (high cervical injuries)

17. Allodynia (pain from light touch)

18. Hyperalgesia (increased pain sensitivity)

19. Muscle atrophy (chronic cases)

20. Autonomic dysreflexia (in high thoracic injuries)

Diagnostic Tests

A multimodal approach confirms indentation and assesses neural compromise Spine InfoPMC:

1. Plain radiographs (X-ray)

2. Computed Tomography (CT)

3. CT Myelography

4. Magnetic Resonance Imaging (MRI) – T1/T2

5. MRI with gadolinium contrast

6. Dynamic flexion-extension X-rays

7. Ultrasound (epidural hematoma)

8. Bone densitometry (DEXA)

9. Bone scan (for occult fractures)

10. Discography (provocative)

11. Electromyography (EMG)

12. Nerve Conduction Studies (NCS)

13. Somatosensory Evoked Potentials (SSEP)

14. Motor Evoked Potentials (MEP)

15. CSF analysis (if dural tear suspected)

16. Laboratory: CBC, ESR, CRP

17. Coagulation profile (trauma workup)

18. Blood type & crossmatch (pre-surgery)

19. Digital Subtraction Angiography (vascular injury)

20. Clinical neurological examination

Non-Pharmacological Treatments

Conservative care focuses on reducing compression, improving mechanics, and strengthening Spine InfoVerywell Health:

1. Bed rest (short term)

2. Spinal bracing (cervical collars, TLSO)

3. Traction therapy

4. Physical therapy (PT)

5. Aquatic therapy

6. McKenzie extension exercises

7. Core strengthening (Pilates, yoga)

8. Stretching (hamstrings, hip flexors)

9. TENS (transcutaneous electrical nerve stimulation)

10. Ultrasound therapy

11. Manual therapy (chiropractic adjustments)

12. Soft-tissue massage

13. Heat therapy

14. Cold packs (ice)

15. Postural training

16. Ergonomic work modifications

17. Gait training

18. Occupational therapy

19. Cognitive behavioral therapy (pain coping)

20. Weight management

21. Smoking cessation

22. Dietary optimization (anti-inflammatory diet)

23. Acupuncture

24. Biofeedback

25. Prolotherapy

26. Shockwave therapy

27. Dry needling

28. Kinesio taping

29. Vestibular/balance exercises

30. Patient education

Drugs

Medical management aims to control pain and inflammation Spine InfoNCBI:

1. Acetaminophen

2. Ibuprofen (NSAID)

3. Naproxen (NSAID)

4. Celecoxib (COX-2 inhibitor)

5. Tramadol (weak opioid)

6. Morphine (strong opioid)

7. Oxycodone

8. Gabapentin

9. Pregabalin

10. Duloxetine (SNRI)

11. Amitriptyline (TCA)

12. Carbamazepine

13. Baclofen (muscle relaxant)

14. Tizanidine

15. Methocarbamol

16. Cyclobenzaprine

17. Methylprednisolone (steroid)

18. Dexamethasone

19. Lidocaine patches

20. Capsaicin cream

 Surgeries

Indicated when conservative care fails or urgent decompression is needed Spine InfoRadiopaedia:

1. Laminectomy

2. Laminoplasty

3. Discectomy (open or micro)

4. Corpectomy

5. Posterior spinal fusion (e.g., PLIF, TLIF)

6. Anterior cervical discectomy & fusion (ACDF)

7. Vertebroplasty

8. Kyphoplasty

9. Foraminotomy

10. Instrumented stabilization

 Preventions

Proactive measures to protect the spine and maintain bone health Verywell HealthVerywell Health:

1. Proper lifting techniques (bend knees, keep spine neutral)

2. Use of seat belts and airbags in vehicles

3. Protective gear in contact sports

4. Regular weight-bearing exercise

5. Adequate calcium & vitamin D intake

6. Smoking cessation

7. Healthy body weight maintenance

8. Ergonomic workstation setup

9. Fall-proof home environment (grab bars, good lighting)

10. Routine osteoporosis screening

When to See a Doctor

Seek prompt evaluation if any of the following occur Spine-healthVerywell Health:

1. Sudden onset of severe back/neck pain

2. New or worsening limb weakness

3. Loss of bladder or bowel control

4. Saddle anesthesia (perineal numbness)

5. Progressive gait disturbance

6. Unexplained fever with back pain

7. Severe, unremitting night pain

8. Significant trauma history

9. Signs of spinal cord compression

10. Pain unresponsive to 48–72 hours of rest

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Frequently Asked Questions

1. What is the difference between thecal sac indentation and spinal stenosis?
   Thecal sac indentation is a radiologic finding indicating focal sac deformation, whereas spinal stenosis refers to an overall narrowing of the spinal canal that may or may not indent the sac.

2. Can mild thecal sac indentation resolve on its own?
   Yes, if due to transient swelling or a small disc bulge, mild indentation can improve with conservative care over weeks.

3. How is thecal sac indentation diagnosed?
   MRI is the gold standard, showing the degree and location of sac deformation. CT can also detect bone fragment causes.

4. What are common non-surgical treatments?
   Physical therapy, bracing, traction, and pain-modality therapies (TENS, ultrasound) are first-line.

5. When is surgery necessary?
   Surgery is indicated for severe nerve compression signs like progressive weakness, cauda equina syndrome, or failed conservative management.

6. Are steroids useful?
   Short-term high-dose corticosteroids can reduce acute inflammation and secondary edema around the sac.

7. How long is recovery after surgery?
   Typically 6–12 weeks for soft-tissue healing; full functional recovery may take 3–6 months depending on the procedure.

8. Can thecal sac indentation recur?
   Yes, especially if underlying causes (e.g., degenerative disc disease) are not addressed.

9. Is physical exercise safe with indentation?
   Yes, guided low-impact exercise improves strength and spine stability and is often recommended.

10. What lifestyle factors worsen indentation?
    Smoking, obesity, sedentary behavior, and poor posture can exacerbate degenerative processes.

11. How does osteoporosis affect indentation risk?
    Osteoporotic fractures can lead to vertebral collapse and fragment retropulsion, indenting the sac.

12. Can young athletes develop this indentation?
    Yes, repetitive high-impact sports can cause stress fractures or disc injuries leading to indentation.

13. Is there a genetic predisposition?
    Certain connective tissue disorders (e.g., Marfan syndrome) and congenital canal narrowing can increase risk.

14. What’s the role of epidural injections?
    Epidural steroid injections can provide temporary relief by reducing inflammation around nerve roots.

15. How often should imaging be repeated?
    Follow-up MRI every 3–6 months for progressive symptoms; otherwise, as clinically indicated.\

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

Last Updated: May 03, 2025.

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