Cervical thecal sac indentation at C4–C5 refers to a focal inward pressing of the thecal sac—the protective membrane (dural sac) that surrounds the spinal cord and the cerebrospinal fluid (CSF)—at the level between the fourth and fifth cervical vertebrae. On an MRI scan, this appears as a noticeable “flattening” or “indentation” of the normally round CSF‐filled sac, often caused by structures outside or within the spinal canal pushing inwards. Spine InfoSpine Info
Anatomy of the Thecal Sac at C4–C5
Structure & Location
The thecal sac is a tough, fibrous sleeve of dura mater that begins at the base of the skull (foramen magnum) and extends down to about the level of the second sacral vertebra (S2). In the cervical region, including C4–C5, it occupies the central spinal canal, surrounding and protecting the upper spinal cord and housing CSF. Radiopaedia
Origin & Insertion
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Origin: Continuation of the cranial dura mater at the foramen magnum.
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Insertion: Tethers via the filum terminale to the coccyx area at S2, anchoring the spinal cord.
In cervical imaging, this continuity explains why intracranial pressure changes can transmit to the cervical thecal sac. Radiology Assistant
Blood Supply
The dura mater of the spinal canal (thecal sac) receives small arterial branches from adjacent spinal segmental arteries—primarily the posterior radicular arteries which branch off vertebral and cervical segmental vessels. These penetrate the dura and supply its outer layers. Radiopaedia
Nerve Supply
Sensory fibers to the thecal sac arise from the recurrent meningeal (sinuvertebral) nerves, which originate at each spinal level. These nerves convey pain and proprioceptive signals from the dura and ligaments of the spinal canal. Wikipedia
Functions
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Protection: Shields the spinal cord against trauma.
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CSF Containment: Holds cerebrospinal fluid, which cushions neural tissue.
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Buoyancy: Allows the spinal cord to “float,” reducing its weight and stress.
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Metabolic Exchange: Enables nutrient delivery and waste removal via CSF circulation.
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Barrier to Infection: Limits spread of pathogens between the cord and surrounding tissues.
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Structural Support: Maintains spinal cord alignment within the canal.
Types of Cervical Thecal Sac Indentation
Indentations are classified by location and severity:
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Anterior (ventral) Indentation: Pushed from in front by disc bulge or osteophytes.
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Posterior (dorsal) Indentation: Usually from ligamentum flavum thickening.
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Lateral Indentation: Often from facet joint hypertrophy or foraminal osteophytes.
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Circumferential Indentation: Rare, seen in epidural lipomatosis.
Severity grading (based on percentage of CSF space lost):
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Mild: <25%
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Moderate: 25–50%
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Severe: >50% RadiopaediaRadiology Key
Causes
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Disc Herniation: Gel-like core pushes through an annulus tear, pressing the thecal sac Radiopaedia
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Disc Bulge: Broad-based protrusion of disc material without focal rupture.
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Osteophyte Formation: Bone spur growth from vertebral bodies in spondylosis Radiopaedia
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Ligamentum Flavum Hypertrophy: Thickening of the ligament at the back of the canal.
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Ossification of Posterior Longitudinal Ligament (OPLL): Abnormal bone deposition in the PLL.
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Facet Joint Hypertrophy: Enlargement of facet joints encroaching laterally.
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Epidural Lipomatosis: Excess fatty tissue in the epidural space Radiology Key
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Spinal Stenosis: General narrowing of the spinal canal.
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Tumors: Meningiomas or schwannomas growing into the canal.
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Epidural Abscess: Collection of pus compressing the sac.
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Spinal Hematoma: Blood accumulation after trauma or anticoagulation.
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Tuberculous Spondylitis: TB infection causing vertebral collapse and mass effect Radiopaedia
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Metastatic Cancer: Secondary deposits from breast, lung, or prostate.
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Synovial Cysts: Fluid-filled sacks from degenerated facet joints.
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Rheumatoid Pannus: Inflamed tissue over C1–C2 extending caudally.
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Arachnoid Cysts: Congenital fluid-filled sacs within the arachnoid membrane.
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Congenital Canal Stenosis: Naturally narrow canal from birth.
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Diffuse Idiopathic Skeletal Hyperostosis (DISH): Ligament ossification across multiple levels.
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Paget’s Disease: Abnormal bone remodeling narrowing the canal.
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Trauma/Fracture: Vertebral collapse or dislocation impinging on the sac.
Symptoms
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Neck Pain: Localized aching in the cervical area.
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Radicular Pain: Sharp, shooting pain radiating into the shoulder or arm.
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Numbness/Tingling: “Pins and needles” sensation in the arms or hands.
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Weakness: Difficulty lifting or holding objects.
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Reflex Changes: Hyperactive or diminished tendon reflexes.
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Myelopathic Gait: Unsteady, broad-based walking pattern.
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Balance Problems: Feeling off-balance or clumsy.
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Lhermitte’s Sign: Electric-shock sensation down the spine on neck flexion.
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Arm Clumsiness: Trouble with fine motor tasks like buttoning.
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Muscle Spasticity: Stiff, tight muscles in arms or legs.
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Hyperreflexia: Exaggerated reflex responses.
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Babinski Sign: Upgoing toe reflex indicating spinal cord involvement.
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Sensory Level: A distinct line below which sensation is altered.
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Bowel/Bladder Dysfunction: Rare in C4–C5 but serious if present.
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Headaches: Occipital headaches from upper cervical irritation.
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Shoulder Pain: Often mistaken for rotator cuff issues.
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Scapular Pain: Deep back pain under the shoulder blade.
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Fatigue: Generalized tiredness from chronic pain.
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Muscle Atrophy: Wasting of hand muscles over time.
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Sleep Disturbance: Pain interfering with restful sleep.
Diagnostic Tests
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MRI of Cervical Spine: Gold standard for soft-tissue detail and CSF assessment RadiopaediaRadiopaedia
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CT Scan: Better for bony anatomy and ossification.
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X-rays (AP/Lateral): Initial screening for alignment and degenerative changes Home
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CT Myelography: Contrast-filled CSF study for patients who cannot have MRI.
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Flexion–Extension Radiographs: Assess instability.
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Electromyography (EMG): Tests nerve and muscle function.
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Nerve Conduction Studies: Measures conduction velocity in peripheral nerves.
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Somatosensory Evoked Potentials: Monitors dorsal column function.
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Motor Evoked Potentials: Evaluates corticospinal tract integrity.
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Blood Tests (ESR, CRP): Rule out infection or inflammation.
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CBC: Checks for infection or anemia.
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TB Screening (PPD, IGRA): If tuberculous spondylitis is suspected.
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Rheumatoid Factor/Anti-CCP: For rheumatoid involvement.
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CT Angiography: Rarely, to assess vascular compression.
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Bone Scan: Detects metabolic bone disease or metastasis.
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PET-CT: For staging suspected spinal tumors.
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Ultrasound: Guides detection of superficial abscesses.
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Myelogram with CT: Alternative to MRI in hardware presence.
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Gait Analysis: Observational assessment of walking.
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Physical & Neurological Exam: Hands-on evaluation of motor, sensory, and reflex functions.
Non-Pharmacological Treatments
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Cervical physical therapy exercises (strengthening and stretching) Scoliosis Reduction Center®
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Traction (mechanical or manual neck traction) ProMed Pain Rehabilitation Institute
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Postural training and ergonomic correction
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Heat therapy (warm packs)
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Cold therapy (ice packs)
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Transcutaneous electrical nerve stimulation (TENS)
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Ultrasound therapy
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Massage therapy
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Acupuncture
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Chiropractic mobilization
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Yoga for neck health
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Pilates focusing on cervical stabilization
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Tai Chi for balance and posture
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Mindfulness-based stress reduction (MBSR)
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Cognitive behavioral therapy (CBT) for pain coping
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Cervical collars or soft braces (short-term use)
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Cervical pillows and ergonomic supports
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Activity modification and pacing
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Traction pillows for home use
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Water (hydrotherapy) exercises
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Inversion tables (cautious use)
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Neural mobilization (nerve gliding techniques)
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Kinesio taping for support
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Nutritional optimization (anti-inflammatory diet)
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Weight management
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Smoking cessation (improves vascular supply)
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Sleep hygiene improvements
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Patient education on body mechanics
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Relaxation and breathing exercises
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Ergonomic workstation assessment
Drugs
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Ibuprofen (NSAID) – reduces inflammation and pain.
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Naproxen (NSAID) – longer-acting anti-inflammatory.
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Diclofenac (NSAID) – topical and oral formulations.
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Celecoxib (COX-2 inhibitor) – fewer GI side effects.
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Acetaminophen – first-line mild pain relief.
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Cyclobenzaprine – muscle relaxant for spasms.
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Tizanidine – short-acting muscle relaxant.
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Prednisone – short course for severe inflammation.
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Methylprednisolone – oral taper to reduce nerve root swelling.
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Gabapentin – neuropathic pain agent.
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Pregabalin – similar to gabapentin, better absorption.
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Duloxetine – SNRI for chronic musculoskeletal pain.
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Amitriptyline – tricyclic for neuropathic symptoms.
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Nortriptyline – lower-side-effect TCA option.
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Tramadol – mild opioid for moderate pain.
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Oxycodone – short-term opioid for severe pain.
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Hydrocodone – combined with acetaminophen.
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Topical diclofenac gel – localized NSAID effect.
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Methylprednisolone injection – epidural steroid for radicular pain.
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Vitamin B12 injections – supportive for nerve health.
Surgical Options
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Anterior Cervical Discectomy and Fusion (ACDF) – removes disc and fuses vertebrae.
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Posterior Laminectomy – removes lamina to decompress the canal.
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Laminoplasty – reshapes lamina to expand canal space.
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Posterior Cervical Foraminotomy – enlarges the neural foramen.
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Artificial Cervical Disc Replacement – maintains motion while removing disc.
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Posterior Dorsal Decompression – wide decompression for multilevel stenosis.
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Anterior Cervical Corpectomy & Fusion – removes vertebral body for severe compression.
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Endoscopic Cervical Discectomy – minimally invasive disc removal.
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Microsurgical Discectomy – small-incision, microscope-guided disc removal.
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Instrumented Posterior Fusion – rods and screws to stabilize after decompression.
Prevention Strategies
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Maintain good neck posture while sitting and using devices.
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Use ergonomically designed chairs and desks.
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Regular cervical strengthening and stretching exercises.
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Keep a healthy weight to reduce spinal load.
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Practice safe lifting—bend knees, keep back straight.
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Take frequent breaks from repetitive neck activities.
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Sleep with a supportive pillow keeping neck neutral.
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Stay hydrated to maintain disc health.
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Avoid smoking to preserve microvascular blood supply.
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Attend regular check-ups if you have known cervical degeneration.
When to See a Doctor
Seek prompt medical attention if you experience:
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Progressive arm weakness or numbness that worsens over days.
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Balance problems or trouble walking.
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New bladder or bowel control issues.
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Severe, unrelenting neck pain not relieved by rest or medication.
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Signs of infection (fever, night sweats, chills).
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History of cancer or significant trauma with new neck symptoms. Spine InfoPubMed
Frequently Asked Questions
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What exactly is “thecal sac indentation”?
It means the dural sac has a dent or flattening on imaging, often from outside pressure, but by itself may not always cause symptoms. -
Is indentation the same as spinal stenosis?
No. Indentation describes focal sac compression, while stenosis is overall canal narrowing that can impinge nerves or cord. -
Can mild indentation resolve on its own?
Yes—if caused by a temporary sprain or small disc bulge, it may improve with rest and therapy. -
When does indentation become serious?
When it causes myelopathy (spinal cord dysfunction) or persistent radicular pain despite treatment. -
What imaging is best to see it?
MRI without contrast is the gold standard for visualizing CSF, thecal sac, discs, and soft tissues. -
Can I drive if I have indentation but no symptoms?
Generally yes, if you have full strength, reflexes, and no dizziness or clumsiness. -
Will physical therapy make it worse?
No. A trained therapist will tailor exercises to relieve pressure without harming the canal. -
Is surgery always required for indentation?
No—many people improve with non-surgical care unless there is significant cord compression or neurological decline. -
How long is recovery after ACDF?
Most return to light activity in 4–6 weeks, with full fusion taking 3–6 months. -
Can indentation lead to paralysis?
Rarely, if severe compression causes permanent spinal cord injury and is untreated. -
Are injections effective?
Epidural steroid injections can reduce inflammation around nerve roots and relieve pain temporarily. -
What lifestyle changes help prevent recurrence?
Good posture, regular neck exercises, ergonomic workstations, and smoking cessation are key. -
Does bone spur removal guarantee no return of symptoms?
It reduces pressure, but degeneration can recur, so ongoing self-care is important. -
Can indentation at one level affect other levels?
Yes. Biomechanical changes at C4–C5 can increase stress at adjacent levels, leading to multi-level issues. -
When should I get a second opinion?
If recommended surgery seems premature, or if symptoms don’t match imaging findings, seeking another expert view is reasonable.
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.
