Contained thecal sac indentation, also known as contained dural sac effacement, refers to a focal compression or “flattening” of the thecal sac—the membranous sheath of dura mater that surrounds the spinal cord and cauda equina—by a lesion that remains within the confines of the spinal canal (i.e., the outer annulus fibrosus or posterior longitudinal ligament remains intact). On MRI, this appears as a subtle inward molding of the normally oval thecal sac without rupture of the annular fibers SpineInfoRadiology Key.
Anatomy
Structure & Tissue Type
The thecal sac is the tubular sheath of dura mater—the tough outer meningeal layer—that envelops the spinal cord and cauda equina, containing cerebrospinal fluid (CSF) WikipediaSpineInfo.
Location
It extends from the foramen magnum at the base of the skull down to approximately the second sacral vertebra (S2), running centrally within the bony vertebral canal and separated from the vertebral periosteum by the epidural space Wikipedia.
Origin & “Insertion”
Origin: Adheres to the margins of the foramen magnum at the skull base.
Insertion: Tapers over the filum terminale at S2, anchoring the dural sac to the sacral canal Wikipedia.
Blood Supply
The spinal dura receives arterial blood principally from:
Posterior meningeal branches of the vertebral arteries.
Radicular (segmental) arteries accompanying spinal nerve roots (including the artery of Adamkiewicz) WikipediaKenhub.
Nerve Supply
Sensory innervation arises from small meningeal branches of the spinal nerves (sinuvertebral nerves) and contributions from upper cervical nerves and vagal meningeal branches; cranially, branches of the trigeminal nerve supply the dura of the foramen magnum region WikipediaRadiopaedia.
Functions
Protection & Cushioning: Encloses CSF, which buffers the spinal cord against mechanical shocks Wikipedia.
Nutrient Delivery: CSF carries nutrients and removes waste from neural tissue Wikipedia.
Structural Support: Maintains the spinal cord’s position within the canal.
Dural Root Sheaths: Extends along exiting nerve roots, forming protective sleeves (dural root sheaths) Wikipedia.
Barrier to Pathogens: Acts as a defense against infections reaching neural tissue.
Pressure Regulation: Helps sustain normal intracranial and intraspinal pressure dynamics.
Types of Indentation
Mild vs. Moderate vs. Severe: Graded by depth of sac molding on MRI.
Focal vs. Generalized Effacement: Localized point indentation versus circumferential flattening.
Ventral (anterior) Indentation: Commonly from disc protrusion Radiology Key.
Lateral Indentation: May narrow neural foramina.
Contained Protrusion: Disc bulge/annular protrusion not breaching all annular layers Radiology Key.
Disc Extrusion without Sequestration: Annulus breached but fragment remains attached.
Sequestrated Fragment: Free fragment indenting sac.
Ligamentum Flavum Hypertrophy: Thickened ligament pressing on sac SpineInfo.
Osteophytic Spurs: Bony outgrowths indent the sac SpineInfo.
Epidural Lipomatosis: Excess fat within epidural space.
Tumoral Indentation: Benign or malignant masses.
Arachnoid Web/Cyst: Dural sac compression by arachnoid pathology Optimal Wellness Health Center (UT).
Epidural Hematoma: Acute blood collection.
Epidural Abscess: Infectious compression.
Congenital Stenosis: Developmental canal narrowing.
Spondylolisthesis: Vertebral slippage indenting the sac SpineInfo.
Diffuse Idiopathic Skeletal Hyperostosis (DISH): Bony overgrowths.
Paget’s Disease: Bone remodeling leading to canal narrowing.
Post-surgical Scar Tissue: Fibrosis after spine surgery.
Metastatic Disease: Epidural spread of cancer.
Causes
Any process that narrows the spinal canal or exerts inward pressure can indent thecal sac. Common causes include:
Lumbar or cervical disc herniation SpineInfo
Broad-based disc bulge (contained) Radiology Key
Disc extrusion (breached annulus) Radiology Key
Disc sequestration Radiology Key
Ligamentum flavum hypertrophy SpineInfo
Osteophyte formation (bone spurs) SpineInfo
Spinal stenosis (degenerative) SpineInfo
Spondylolisthesis SpineInfo
Traumatic vertebral fracture or dislocation SpineInfo
Spinal tumors (primary or metastatic) SpineInfo
Arachnoid webs or cysts Optimal Wellness Health Center (UT)
Epidural hematoma (bleeding) SpineInfo
Epidural abscess (infection) SpineInfo
Epidural lipomatosis (excess fat) SpineInfo
Congenital spinal canal narrowing SpineInfo
Diffuse Idiopathic Skeletal Hyperostosis (DISH) SpineInfo
Paget’s disease of bone SpineInfo
Post-surgical epidural fibrosis SpineInfo
Rheumatoid arthritis with pannus formation SpineInfo
Inflammatory spondyloarthropathies (e.g., ankylosing spondylitis) SpineInfo.
Symptoms
Symptoms depend on location and severity:
Localized back or neck pain SpineInfo
Radicular pain (sciatica, cervical radiculopathy) SpineInfo
Numbness or tingling in limbs SpineInfo
Muscle weakness SpineInfo
Gait disturbances SpineInfo
Neurogenic claudication (leg pain on walking) SpineInfo
Hyperreflexia SpineInfo
Hyporeflexia SpineInfo
Muscle spasm or cramps SpineInfo
Balance or coordination problems SpineInfo
Bladder dysfunction (urgency, retention) SpineInfo
Bowel dysfunction SpineInfo
Sexual dysfunction SpineInfo
Saddle anesthesia SpineInfo
Sleep disruption due to pain SpineInfo
Radicular fatigue (profound limb tiredness) SpineInfo
Postural intolerance SpineInfo
Cold or heat sensitivity in limbs SpineInfo
Unexplained weight loss (tumor-related) SpineInfo
Fever, chills (infection-related) SpineInfo.
Diagnostic Tests
MRI (Magnetic Resonance Imaging): Gold standard for soft-tissue detail Orthobullets
CT scan: Useful for bone and calcified lesions Orthobullets
CT myelogram: Contraindicated for MRI-ineligible patients; shows filling defects Orthobullets
X-ray: Initial screening for alignment, fracture SpineInfo
Discogram: Pain provocation test using contrast SpineInfo
Electromyography (EMG): Assesses nerve root irritation SpineInfo
Nerve Conduction Studies (NCS): Differentiates peripheral neuropathy SpineInfo
Bone scan (nuclear medicine): Detects infection or metastasis SpineInfo
CT-guided biopsy: For suspected neoplasm/infection SpineInfo
Blood tests: CBC, ESR, CRP for infection/inflammation SpineInfo
CSF analysis: Lumbar puncture if infection or hemorrhage suspected SpineInfo
Somatosensory Evoked Potentials (SSEP): Assesses dorsal column function SpineInfo
Motor Evoked Potentials (MEP): Evaluates corticospinal tract integrity SpineInfo
Ultrasound: Rare, for accessible epidural masses SpineInfo
Functional MRI: Research use, maps neural activity under load SpineInfo
Plain Myelography: Historical, uses iodinated contrast SpineInfo
Flexion-extension X-rays: Assesses instability SpineInfo
DEXA scan: Bone density for osteoporotic risk SpineInfo
PET scan: Staging metastatic disease SpineInfo
Physical exam: Neurological exam, straight leg raise, reflex testing SpineInfo.
Non-Pharmacological Treatments
Physical therapy: targeted strengthening & stretching SpineInfo
McKenzie lumbar/cervical exercises SpineInfo
Posture training & ergonomic adjustments SpineInfo
Core stabilization programs SpineInfo
Aquatic therapy (hydrotherapy) SpineInfo
Yoga SpineInfo
Pilates SpineInfo
Tai Chi SpineInfo
Spinal traction therapy SpineInfo
Manual therapy/chiropractic manipulation SpineInfo
Massage therapy SpineInfo
Heat therapy SpineInfo
Cold therapy SpineInfo
Transcutaneous Electrical Nerve Stimulation (TENS) SpineInfo
Ultrasound therapy SpineInfo
Acupuncture SpineInfo
Cognitive Behavioral Therapy (CBT) for pain coping SpineInfo
Mindfulness & relaxation techniques SpineInfo
Biofeedback SpineInfo
Orthotic bracing (e.g., lumbar brace) SpineInfo
Activity modification & pacing SpineInfo
Weight management programs SpineInfo
Ergonomic workplace assessment SpineInfo
Sleeping position optimization SpineInfo
Smoking cessation support SpineInfo
Dietary counseling for bone health SpineInfo
Vitamin D & calcium supplementation (non-drug supportive) SpineInfo
Support groups & patient education SpineInfo
Thermal and mechanical modalities (e.g., waxing, paraffin) SpineInfo
Neural mobilization techniques SpineInfo.
Drugs
Ibuprofen (NSAID) SpineInfo
Naproxen (NSAID) SpineInfo
Diclofenac (NSAID) SpineInfo
Celecoxib (COX-2 inhibitor) SpineInfo
Acetaminophen (analgesic) SpineInfo
Tramadol (weak opioid) SpineInfo
Oxycodone (opioid) SpineInfo
Morphine (opioid) SpineInfo
Cyclobenzaprine (muscle relaxant) SpineInfo
Tizanidine (muscle relaxant) SpineInfo
Methocarbamol (muscle relaxant) SpineInfo
Gabapentin (anticonvulsant/neuropathic) SpineInfo
Pregabalin (anticonvulsant/neuropathic) SpineInfo
Duloxetine (SNRI) SpineInfo
Amitriptyline (TCA) SpineInfo
Prednisone (oral corticosteroid) SpineInfo
Methylprednisolone (injection) SpineInfo
Epidural steroid injection SpineInfo
Capsaicin cream (topical) SpineInfo
Lidocaine patch (topical) SpineInfo.
Surgeries
Laminotomy (removal of part of lamina) SpineInfo
Laminectomy (complete lamina removal) SpineInfo
Microdiscectomy (minimally invasive disc removal) SpineInfo
Open discectomy SpineInfo
Foraminotomy (enlargement of neural foramen) SpineInfo
Posterior lumbar interbody fusion (PLIF) SpineInfo
Transforaminal lumbar interbody fusion (TLIF) SpineInfo
Anterior cervical discectomy and fusion (ACDF) SpineInfo
Artificial disc replacement SpineInfo
Kyphoplasty/vertebroplasty (for compression fractures) SpineInfo.
Preventions
Maintain good posture (sitting/standing) SpineInfo
Ergonomic workstation setup SpineInfo
Regular core-strengthening exercises SpineInfo
Healthy body weight management SpineInfo
Proper lifting techniques (bend knees) SpineInfo
Smoking cessation SpineInfo
Adequate hydration & nutrition for bone health SpineInfo
Frequent movement breaks when seated SpineInfo
Use supportive footwear SpineInfo
Regular medical check-ups for early detection SpineInfo.
When to See a Doctor
Seek prompt medical attention if you experience any of the following red-flag signs:
Severe, unrelenting back or neck pain, especially after trauma SpineInfo
Progressive neurological deficits (weakness, numbness) SpineInfo
Bowel or bladder dysfunction SpineInfo
Saddle anesthesia (perineal numbness) SpineInfo
High fever or signs of infection SpineInfo
Unexplained weight loss SpineInfo
Cancer history or immunosuppression SpineInfo
Pain at rest or nighttime pain SpineInfo.
Early evaluation—including imaging and neurological examination—ensures timely diagnosis and management.
FAQs
What exactly is contained thecal sac indentation?
It’s a focal compression of the dura-lined sac around your spinal cord by a lesion that remains “contained” within the annulus, seen on MRI as inward molding of the sac without annular rupture SpineInfo.How does it differ from thecal sac effacement?
“Effacement” simply means flattening; “contained indentation” emphasizes that the compressing lesion is still held within the disc’s outer layers SpineInfo.What causes it?
Most often disc herniations, spinal stenosis, osteophytes, ligamentum flavum hypertrophy, tumors, cysts, and trauma SpineInfo.Can it resolve on its own?
Mild indentation without nerve involvement often remains stable or improves with conservative care (PT, lifestyle changes) SpineInfo.Is surgery always required?
No—surgery is reserved for severe cases with refractory pain or neurological deficits. Most manage well with non-surgical treatments SpineInfo.What lifestyle changes help?
Ergonomic adjustments, weight management, core strengthening, smoking cessation, and regular exercise reduce spinal load SpineInfo.Can contained indentation cause paralysis?
Rarely—only if severe compression impinges neural elements long enough to cause irreversible injury SpineInfo.What symptoms are most concerning?
Saddle anesthesia, bowel/bladder dysfunction, or rapidly progressive weakness warrant immediate evaluation SpineInfo.How is it diagnosed?
MRI is the gold standard; CT myelogram if MRI contraindicated; supported by neurological exam and electrophysiology Orthobullets.What tests might my doctor order?
MRI, CT, CT myelogram, X-ray, EMG/NCS, blood work for infection or inflammation SpineInfo.What non-drug treatments are effective?
Physical therapy, traction, TENS, manual therapy, yoga, Pilates, acupuncture, bracing, and ergonomic changes SpineInfo.Which medications ease symptoms?
NSAIDs, muscle relaxants, neuropathic pain agents (gabapentin), short-term opioids, and corticosteroids (oral or epidural) SpineInfo.What exercises should I avoid?
Heavy lifting, high-impact sports, forward-bending under load, and extreme spinal rotations until cleared by a therapist SpineInfo.How long does recovery take?
With conservative care, mild cases often improve over 4–12 weeks; severe cases or surgery may require 3–6 months for full recovery SpineInfo.How can I prevent recurrence?
Maintain spinal health with core strengthening, good ergonomics, a healthy weight, and regular exercise SpineInfo.
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 03, 2025.
