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Sequestered intervertebral disc fragments have the potential to migrate both intramurally and extramurally within the spinal canal. There are no particular clinical features allowing for a clear differentiation between patients with atypical disc herniations and those with tumors [rx]. Free disc fragments were previously only identified during surgery but are still frequently misinterpreted as neoplastic masses, even after the introduction of magnetic resonance imaging (MRI) [rx–rx]. This is because the imaging characteristics of sequestered disc fragments may mimic known characteristics of extramedullary (intra- and extradural) lesions, including neoplasms and other benign epidural lesions (such as synovial cysts, hematomas, and abscesses), further complicating preoperative diagnosis based on imaging findings [rx, rx].
A sequestrated disc, also referred to as a free disc fragment, corresponds to extruded disc material that has no continuity with the parent disc and is displaced away from the site of extrusion. By definition, it corresponds to a subtype of disc extrusion.
The term “migrated” disc refers only to position and not to the continuity of disc substance. So, this term can be used when referring either to extruded discs that still have continuity or those without, i.e. sequestrated (e.g. disc extrusion migrated caudally, sequestrated disc migrated cranially).
Causes of Sequestrated Disc
- Disc herniation and sequestrated disc – are associated terms, being nucleus pulposus herniation a possible evolution from a degenerative disc. Disc degeneration is usually associated with the loss of proteoglycans.[rx] Multiple factors influence the degenerative process such as genetic, mechanical, and behavioral.[rx][rx]
- Mechanical load – is important in maintaining a healthy IVD by generating signals to cells that regulate proper matrix homeostasis.[rx][rx] On the other hand, prolonged exposure to hypo- or hyper-loading correlates with disc degeneration /sequestrated disc induction.[rx][rx]
- Repetitive trauma – such as poor posture, poor ergonomics, or repetitive heavy work can lead to a sequestrated disc. These long term injuries are often also associated with poor muscle strength, obesity, and other factors such as smoking.
- An Injury caused – by sudden forces or load on the disc such as a car accident or an awkward heavy lift. This sudden increase in pressure on the disc can cause damage and tears to the annulus that causes a bulging disc.
- Spinal Degeneration – While some degeneration is a normal part of the aging process, poor spinal function and posture will dramatically speed up disc degeneration with a bulging disc.
- People who have led a sedentary lifestyle or those who smoke – increase the chances for bulging discs sequestrated disc.
- Continuous strain on the disc from injury or heavy lifting – and strain can wear them down throughout the years.
- Weakened back muscles – can accelerate the process and may lead to a sudden herniation of the weakened disc. Although sequestrated disc occur over time, herniated discs may occur quickly by trauma.
- Bad posture – including improper body positioning during sleep, sitting, standing, or exercise are all risk factors that may contribute to the development of a bulging disc.
- High contact sports or activities – are also risk factors.
- Runners who fail to use shoes that provide orthopedic support – may also develop bulging discs.
- Activities that place stress and strain on the spine – can lead to the weakening of the discs.
- Road, traffic accident
Symptoms of Sequestrated Disc
If a sequestrated disc has not yet reached the stage of herniation, a patient may have little to no pain involved. A sequestrated disc may have no pain at all because it has not reached a certain severity level, and this can make it difficult to identify the bulging disc symptoms before the condition becomes more severe.
Most commonly, the sequestrated disc creates pressure points on nearby nerves which create a variety of sensations. Evidence of a bulging disc may range from mild tingling and numbness to moderate or severe pain, depending on the severity.
- Un tolerable pain – patients are unable to walk totally. It may be a loss of motor function and sensory.
- Tingling or pain in the fingers, hands, arms, neck, or shoulders – This could indicate a bulging disc in the cervical area.
- Pain in the feet, thighs, lower spine, and buttocks – This is the most common symptom and could indicate an issue in the lumbar region.
- Difficulty walking or feeling of impairment while lifting or holding things.
- Loss of Bladder or Bowel Function – There are some bulging disc cases where professional care is essential. In some cases, such as when you lose bowel or bladder control, it is deemed an emergency, and you may require immediate surgery. These bulges usually are very significant and affect your nerve control involving your bladder or bowels. You should go straight to your nearest emergency department in these instances.
- Weakness in your limb muscles – is a significant concern. If you experience arm, hand, leg, or foot weakness, please seek prompt medical assessment.
- The reduced or altered sensation – is your next priority. Mild disc bulges can reduce your ability to feel things touching you, e.g. numbness or pins and needles. If you experience any of the above symptoms, you should seek professional assistance.
- Referred Pain – Pain in your limbs, e.g. legs (sciatica) or arms (brachialgia) is usually a more significant injury than when experiencing only spinal pain. We recommend that you seek the professional advice of your trusted spinal care practitioner.
- Spinal Pain – Interestingly, if you are only experiencing spinal pain, bulging discs are generally mild injuries and the most likely to rehabilitate quickly. Please adhere to low disc pressure postures and exercise accordingly. If in doubt, please seek professional advice.
- Intermittent or continuous back pain. This may be made worse by movement, coughing, sneezing, or standing for long periods of time.
- Spasm of the back muscles
- Sciatica. Pain that starts near the back or buttock and travels down the leg to the calf or into the foot.
- Muscle weakness in the legs
- Numbness in the leg or foot
- Decreased reflexes at the knee or ankle
- Changes in bladder or bowel function
Associate clinical feature is
- Severe back pain
- Saddle anesthesia i.e., anesthesia or paraesthesia involving S3 to S5 dermatomes, including the perineum, external genitalia, and anus; or more descriptively, numbness or “pins-and-needles” sensations of the groin and inner thighs which would contact a saddle when riding a horse.
- Bladder and bowel dysfunction, caused by a decreased tone of the urinary and anal sphincters.
- Detrusor weaknesses causing urinary retention and post-void residual incontinence as assessed by bladder scanning the patient after the patient has urinated.
- Sciatica type pain on one side or both sides, although pain may be wholly absent
- The weakness of the muscles of the lower legs (often paraplegia)
- Pain in one leg (unilateral) or both legs (bilateral) that starts in the buttocks and travels down the back of the thighs and legs (sciatica)
- Numbness in the groin or area of contact if sitting on a saddle (perineal or saddle paresthesia)
- Bowel and bladder disturbances
- Lower extremity muscle weakness and loss of sensations
- Inability to urinate (urinary retention)
- Difficulty initiating urination (urinary hesitancy)
- The decreased sensation when urinating (decreased urethral sensation)
- Inability to stop or control urination (incontinence)
- Reduced or absent lower extremity reflexes
- Local pain is generally a deep, aching pain resulting from soft tissue and vertebral body irritation.
- Leg pain (radicular pain) is generally a sharp, stabbing pain resulting from compression of the nerve roots.
- Radicular pain projects along with the specific areas controlled by the compressed nerve (known as a dermatomal distribution).
- Inability to stop or feel a bowel movement (incontinence)
- Loss of anal tone and sensation
- Achilles (ankle) reflex absent on both sides.
- Sexual dysfunction
- Absent anal reflex and bulbocavernosus reflex
- Gait disturbance
These symptoms require immediate medical evaluation as they may be a sign of a potentially life-threatening condition.
Diagnosis of Sequestrated Disc
Proper understanding of anatomical zones and vertebral levels is essential to interpret the clinical manifestations secondary to a sequestrated disc. Wiltse proposed these anatomical zones, based on the following landmarks: medial border of the articular facet, lateral, upper, and medial borders of the pedicles, coronal and sagittal planes at the center of the disc. On the axial plane, these landmarks determine the central zone, the subarticular zone (lateral recess), foraminal, and extraforaminal zones. On the sagittal plane, the levels are termed as follows: The supra pedicular level, the pedicular level, the intravesicular level, and the disc level. The correct knowledge of anatomy and the relationship between nerve roots and disc herniation allows the proper understanding of common clinical findings associated with this problem.
We summarize the anatomy, motor function, sensitive distribution, and reflex of the most commons nerve roots involved in cervical and lumbosacral nucleus pulposus herniation:
C5 nerve root – Exits between C4 and C5 foramina, innervates deltoids and biceps (with C6), sensory distribution: lateral arm (axillary nerve) and is assessed with biceps reflex.
C6 nerve root – Exits between C5 and C6 foramina, innervates biceps (with C5) and wrist extensors, sensory distribution: lateral forearm (musculocutaneous nerve), assessed with brachioradialis reflex.
C7 nerve root – Exits between C6 and C7 foramina, innervates triceps, wrist flexors, and finger extensors, sensory distribution: middle finger, assessed with triceps reflex.
C8 nerve root – Exits between C7 and T1 foramina, innervates interosseus muscles and finger flexors, sensory distribution: ring and little fingers and distal half of the forearm (ulnar side), no reflex.
L1 nerve root – Exits between L1 and L2 foramina, innervates iliopsoas muscle, sensory distribution: upper third thigh, assessed with the cremasteric reflex (male).
L2 nerve root – Exits between L2 and L3 foramina, innervates iliopsoas muscle, hip adductor, and quadriceps, sensory distribution: middle third thigh, no reflex.
L3 nerve root – Exits between L3 and L4 foramina, innervates iliopsoas muscle, hip adductor, and quadriceps, sensory distribution: lower third thigh, no reflex.
L4 nerve root – Exits between L4 and L5 foramina, innervates quadriceps and tibialis anterior, sensory distribution: anterior knee, medial side of the leg, assessed with patellar reflex.
L5 nerve root – Exits between L5 and S1 foramina, innervates extensor hallucis longus, extensor digitorum longus, and brevis, and gluteus medius, sensory distribution: anterior leg, lateral leg, and dorsum of the foot, no reflex.
S1 Nerve – back, radiating into buttock, lateral or posterior thigh, posterior calf, lateral or plantar foot; sensory loss on the posterior calf, lateral or plantar aspect of foot; weakness on hip extension, knee flexion, plantar flexion of the foot; Achilles tendon; Medial buttock, perineal, and perianal region; weakness may be minimal, with urinary and fecal incontinence as well as sexual dysfunction.
S2-S4 Nerves – sacral or buttock pain radiating into the posterior aspect of the leg or the perineum; sensory deficit on the medial buttock, perineal, and perianal region; absent bulbocavernosus, anal wink reflex.
Cervical and the thoracic sequestrated disc can also exhibit symptoms of myelopathy such as spasticity, clumsiness, wide-based gate, and weakness, on physical examination hyperreflexia is the most important sign. The Lhermitte sign is the presence of an electric shock-like sensation towards the back and lower extremities, especially by flexing the neck.[rx][rx] Bowel and bladder dysfunction may indicate a poor prognosis.
A physical exam for diagnosing disc pain may include one or more of the following tests:
- Palpation – Palpating (feeling by hand) certain structures can help identify the pain source. For example, worsened pain when pressure is applied to the spine may indicate sensitivity caused by a sequestrated disc.
- Movement tests – Tests that assess the spine’s range of motion may include bending the neck or torso forward, backward, or to the side. Additionally, if raising one leg in front of the body worsens leg pain, it can indicate a lumbar herniated disc (straight leg raise test).
- Muscle strength – A neurological exam may be conducted to assess muscle strength and determine if a nerve root is compressed by a herniated disc/sequestrated disc. A muscle strength test may include holding the arms or legs out to the side or front of the body to check for tremors, muscle atrophy, or other abnormal movements.
- Reflex test – Nerve root irritation can dampen reflexes in the arms or legs. A reflex test involves tapping specific areas with a reflex hammer. If there is little or no reaction, it may indicate a compressed nerve root in the spine.
- The straight leg raise test – With the patient lying supine, the examiner slowly elevates the patient’s led at an increasing angle, while keeping the leg straight at the knee joint. The test is positive if it reproduces the patient’s typical pain and paresthesia.[rx]
- The contralateral (crossed) straight leg raise test – As in the straight leg raise test, the patient is lying supine, and the examiner elevates the asymptomatic leg. The test is positive if the maneuver reproduces the patient’s typical pain and paresthesia. The test has a specificity higher than 90%.
- A medical history – in which you answer questions about your health, symptoms, and activity.
- Erythrocyte sedimentation rate and C-reactive protein – are inflammatory markers, and they are requested if suspicious for a chronic inflammatory condition or infectious cause as the etiology. A complete blood count is useful when suspecting infection or malignancy.
- A physical exam to assess your strength – reflexes, sensation, stability, alignment, and motion. You may also need blood tests.
- Laboratory testing – may include white blood cell (WBC) count, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP).
- Elevated ESR – could indicate infection, malignancy, chronic disease, inflammation, trauma, or tissue ischemia.
- Elevated CRP – levels are associated with infection.
- X-rays – X-ray is the initial workup study when there is a strong suspicion of a specific cause of cervical or back pain (fracture, infection, tumor) or in the presence of red flags (fever, age more than 50, recent trauma, pain at night or rest, unexplained weight loss, progressive motor or sensory deficit, saddle anesthesia, history of cancer or osteoporosis, failure to improve after six weeks of conservative treatment). Anteroposterior and lateral x-ray is helpful to assess fracture, bony deformity, decreased intervertebral height, osteophytes, spondylolisthesis, and facet joint osteoarthritis.
- Magnetic Resonance Imaging (MRI) scan – MRI is the recommended diagnostic imaging in cases of severe or progressive neurologic deficits, suspicion of an underlying condition such as infection, fracture, cauda equina syndrome, spinal cord compression. In cases of radiculopathy, most of the cases improve with conservative treatment and MRI is indicated in those cases with significant pain or neurologic deficits.[rx]
- A myelogram – is a specialized X-ray where dye is injected into the spinal canal through a spinal tap. An X-ray fluoroscope then records the images formed by the dye. The dye used in a myelogram shows up white on the X-ray, allowing the doctor to view the spinal cord and canal, a bulging disc in detail. Myelograms can show a nerve being pinched and a bulging disc by a herniated disc, bony overgrowth, spinal cord tumors, and abscesses. A CT scan may follow this test.
- Computed Tomography (CT) scan – is a noninvasive test that uses an X-ray beam and a computer to make 2-dimensional images of your spine. It may or may not be performed with a dye (contrast agent) injected into your bloodstream. This test is especially useful for confirming which bulging disc is damaged. CT scan is not usually requested in nucleus pulposus herniation. However, it can be helpful in some cases when there is a suspicion of calcified disc herniation (thoracic disc herniation has a 30 to 70% rate of calcification) which is more challenging especially when surgery is a consideration.
- Electromyography (EMG) & Nerve Conduction Studies (NCS) – EMG tests measure the electrical activity of your muscles. Small needles are placed in your muscles, and the results are recorded on a special machine. NCS is similar, but it measures how well your nerves pass an electrical signal from one end of the nerve to another. These tests can detect nerve damage and muscle weakness and a bulging disc.
- Discogram – A discogram may be recommended to confirm which bulging disc is painful if surgical treatment is considered. In this test, the radiographic dye is injected into the disc to recreate disc pain from the dye’s added pressure.
In the presence of low back pain without symptoms of radiculopathy, there is no need to request studies as most of the patients improve in a couple of weeks, a 4-week follow-up is a usual timeframe.[rx]
Treatment of Sequestrated Disc
There is no conservative treatment. It is a medical emergency condition. So the first choice of surgery as soon as possible.
- Microdiscectomy – for a sequestrated disc, a minimally-invasive procedure in which the sequestrated disc portion of the disc is removed.
- Artificial disc replacement – for degenerative disc disease and herniated discs is a minimally invasive procedure that replaces a damaged disc with a specialized implant that mimics the normal function of the disc, maintaining mobility.
- Spinal fusion – fusion for degenerative disc disease, in which the disc space is fused together to remove motion at the spinal segment. Spinal fusion involves setting up a bone graft, as well as possible implanted instruments, to facilitate bone growth across the facet joints. Fusion occurs after the surgery.
- Open Back Surgery – Traditionally, bulging discs are treated with an open back procedure, meaning the surgeon makes a large incision into the skin and cuts muscle and surrounding tissue to gain access to the problematic disc. This traditional surgical option is invasive, requires overnight hospitalization, general anesthesia, and requires a lengthy recovery coupled with strong pain medication.
- Endoscopic Surgery – Fortunately, you have a second option with endoscopic spine surgery. Thanks to the advancement of surgical technology at bulged disc surgery can be performed using endoscopic procedures, meaning the surgeon makes a small incision to insert special surgical tools. During an endoscopic sequestrated disc operation, the surgeon uses a tiny camera to visualize and gain access to your damaged disc. This minimally invasive new approach offers shorter recovery, easier rehabilitation, and a much higher success rate than open back or neck surgery. A local anesthetic is all that is usually required.
Some patients will not benefit from conservative treatment and will require surgery to decompress the nerve involved. Classical surgical indications are motor deficit, cauda equina syndrome, and persistent pain after conservative treatment.
In cervical sequestrated disc, there is no evidence of effectiveness for conservative treatment compared with surgery.[rx] Different randomized controlled trials (RTC) have compared conservative versus surgical treatment in the sequestrated disc, observing faster pain relief and recovery in the early surgery groups, however, similar outcomes in the long term (one or two years) were found.[rx][rx] In another trial, carefully selected patients who underwent surgery for lumbar disc herniation achieved greater improvement compared to nonoperative treated patients at eight years follow up .[rx]