Vertebral column has 33 vertebrae and the discs separate each vertebra in cervical, thoracic and lumbar segment. Disc is a cushion between vertebra and functions as a shock absorber. Weight is transmitted through vertebral column and thus through disc. Disc is made up of inner circular nucleus pulposus and outer annulus fibrosis. Nucleus pulposus is soft and thick gelatinous substance. Central nucleus pulposus expands with pressure and helps to absorb the shocks during weight transmission and movements of vertebral column. Accelerated pressure changes within disc and horizontal expansion of nucleus pulposus secondary to pressure results in disc bulge into annulus fibrosus. Annulus fibrosus is tough membrane and resist tear in healthy young individual. Illness such as disk degeneration weakens the fibrous annulus and disk bulge herniate through the torn or broken annulus fibrosus known as herniated disc. Lumbar disc herniation is observed in disc between L1 and S1 vertebra. Most common disc herniation is observed at level of L4/L5 and L5/S1 disc.
Disc herniates either into inter-vertebral foramina (figure 1) or spinal foramina (figure 2). Inter-vertebral foramina is a lateral bony tunnel meant to pass the spinal nerve and lumbar spinal canal accommodates lower end of spinal cord and quada equina. Disc herniation into inter-vertebral foramina causes pinch nerve pain or radicular pain. Large disk herniation into spinal canal causes narrowing of spinal canal or spinal stenosis (figure 2). Spinal stenosis causes pressure on spinal cord or quada equina resulting in quada equina syndrome.
What Can Cause A Lumbar Disc Herniation?
Lower Back Injury Resulting In Lumbar Disk Herniation-
- Auto or Car Accident- Whiplash injury caused by car accident changes pressure within disc and shears outer fibrous annulus membrane resulting in disc herniation.
- Improper Weight Transmission- Causes pressure changes in disc and results in herniation of disc e.g. domestic work, weight lifting,
- Work Accident- Repetitive lifting, bending, standing, and driving results in abnormal movements of vertebral column causing disc herniation.
- Contact Sport- Participation in contact sports causes rapid acceleration and deceleration of the body as well as change of direction of shear force results in disc herniation.
Diseases Causing Lumbar Disk Herniation
- Osteoarthritis- Causes disc and cartilage degeneration results in tear of outer annulus fibrosus layer.
- Traumatic Disc Degeneration-Repeated trauma causes disk degeneration. Disc herniation may follow with minimum pressure changes within disc since outer fibrous layer is extremely weak secondary to degeneration.
Chronic Smoking - A Risk Factor For Lumbar Disk Herniation
Chronic smoking is associated with disc degeneration secondary to weak annulus fibrosis, which is often followed by herniation of nucleus pulposus.
Obesity - A Risk Factor For Lumbar Disk Herniation
Obese patient transmits extra weight through the vertebral column. Twist, fall or severe cough can cause disc herniation.
What Are The Symptoms and Signs Of Lumbar Disk Herniation?
Symptoms of Lumbar Disk Herniation
Lumbar (Back) Pain-
- Discogenic Pain- Disc outer surface has sensory fibers. Tear of outer annulus fibrous layer causes inflammation of the disc and secretion of prostaglandin. Prostaglandin causes irritation of nerves lying along the disc and results in severe discogenic pain. Discogenic pain is felt on lower back along the dermatomal spread of lumbar nerves as shown in figure 1.
Lumbar Radicular Pain
- Character of Pain- Unilateral Sharp shooting pain.
- Pain Provoked By- Standing, Bending, Twisting, Coughing and Sneezing.
- Time and Intensity of Pain- Pain is worse with ambulation, bending and at night.
- Pain Radiates to Lower Leg- Dermatomal distribution of pain depends on level of disc herniation causing irritation of one of the following lumbar nerve L1, L2, L3, L4, L5 or S1.
- Radiculopathy is a diagnosis that follows disc herniation if radicular pain is associated with tingling, numbness and/ or weakness.
Cauda Equina Syndrome
- Seen following large disc herniation in spinal canal
- Causes severe pressure on lower segment of spinal cord and bundle of spinal nerve from L2 to S1 known as cauda equina.
- Presented as severe pain, numbness, weakness, urinary incontinence and bowel incontinence.
- Considered medical emergency if severe weakness is associated with incontinence.
- Emergency surgery is necessary to prevent permanent nerve damage and paralysis.
Dermatomal Distribution of Radicular Pain and Radiculopathy
- L1 Radiculopathy- Pain and numbness felt over inguinal dermatome.
- L2 Radiculopathy- Pain, numbness and weakness felt over anterior mid thigh and lateral thigh.
- L3 Radiculopathy-Pain, numbness and weakness felt over inner thigh and anterior lower thigh.
- L4 Radiculopathy- Pain, numbness and weakness is felt over lower leg mostly on inside of the leg on anterior and posterior side of feet.
- L5 Radiculopathy-Pain, numbness and weakness is felt over anterior lateral side of lower leg and dorsal skin of feet of middle three toes.
- S1 Radiculopathy-Pain and numbness is felt over lateral side of feet.
- S2 Radiculopathy-Pain, numbness and weakness is felt over back of the thigh and back of upper 2/3rd of lower leg.
Tingling and Numbness
- Tingling is felt along the dermatome of L1 to S2 nerve as described in dermatomal distribution of radiculopathy.
- Dermatome of tingling depends on level of pinched nerve.
- Numbness often follows tingling if not treated.
- Pain is aggravated and intolerable in lying down position and supine position.
- Patient is unable to sleep because of pain and difficulties to lie down on bed.
- Weight loss is observed during initial phase because of loss of appetite secondary to chronic pain
Clinical Signs- Lumbar Disc Bulge
Paravertebral Muscle Spasm
- Muscle Spasm-
- Muscle spasm is often reflex spasm of paravertebral muscles secondary to irritation or pinch of spinal nerve mostly within inter-vertebral foramina.
- Disc herniation follows inflammation of the disc.
- Inflammatory changes of the disc cause secretion of prostaglandin. Prostaglandin irritates spinal nerve. Spinal nerve supplies a motor branch to paravertebral muscles. Branch of irritated spinal nerve to paravertebral muscles triggers muscle spasm.
- Change of Posture- Change of posture is observed following unilateral contraction of paravertebral muscles. Muscle contraction on one side of vertebral column causes scoliosis or scoliotic bend of vertebral column.
- Change of Gait-Severe paravertebral muscle spasm changes gait. Gait change follows postural abnormality, muscle weakness and atrophy of lower leg muscles.
Muscle Weakness in Lower Leg
- Weakness in Lower Leg- Spinal nerve consists of sensory and motor nerve fibers. Sensory nerve carries sensation of temperature, pain and touch, while motor nerve carries impulses to muscles to contract and coordinate the movements. Pinch or irritation of motor nerve fibers causes weakness in muscles that is receiving these motor fibers. Severe pressure or squeeze can cause permanent damage and permanent weakness in the muscles followed by atrophy of the muscle.
- Lumbar Lesions Resulting In Lower Leg Weakness
- L1 motor nerve lesion results weakness of hip flexion.
- L2 motor nerve lesion results in weakness of hip flexion.
- L3 motor nerve lesion results in weakness in hip flexion and knee Extension.
- L4 motor nerve lesion results in difficulties to extend knee and dorsiflex ankle joint.
- L5 motor nerve lesion results in difficulties to perform hallux extension, planter extension, unable to raise big toe upward.
- S1 lesion causes weakness in knee extension.
- Muscle Atrophy- Motor nerve injury follows weakness of the muscles supplied by the nerve. Inadequate treatment or failure to revitalize the nerve results in muscle atrophy.
Diminished Knee and Ankle Joint Reflexes
- Knee Reflex- L2 and L3 nerve damage causes abnormal knee joint reflex.
- Ankle Reflex (Tendo-Achillis Reflex) - Diminished or absent reflexes when L4, 5 and S1 nerve is damaged.
How is Lumbar Disk Herniation Diagnosed?
- Disc herniation is – evaluated by MRI studies.
- MRI pictures show details of disc, annulus, nucleus pulposus, spinal canal and intervertebral foramina.
- MRI is useful in diagnosis ofDisc herniation, foraminal stenosis caused by disc herniation in foramina, spinal stenosis caused by disc herniation in spinal canal and degenerative disc disease.
- CAT scan study provides sufficient quality images to diagnose disc herniation and other disc pathology.
- Foraminal or spinal canal encroachment of herniated disc is also observed with better quality comparable to MRI.
- CAT scan is also useful following myelogram to diagnose lumbar disc herniation and spinal cord compression.
- Normal- Lumbar Disc Herniation.
- Abnormal- Epidural Abscess or Infected Cancer Tissue Causing Pinch Nerve Pain.
- Normal- Lumbar Disc Herniation,
- Abnormal- Rheumatoid or Psoriatic Arthritis.
White Blood Cell Counts-
- Normal- Lumbar disc herniation.
- Abnormal- Epidural abscess or Osteomyelitis,
- Myelogram study is performed to rule out disc fragments in spinal canal causing pain in addition to disk herniation.
- MRI study if conclusive then myelogram study is avoided. Myelogram study involves invasive procedure.
- Myelogram study involves injection of dye in CSF followed by multiple X-ray pictures to visualize internal structures within spinal canal and CSF.
- Electromyography studies are performed to evaluate radiculopathy and nerve damage.
- Normal- Lumbar disk herniation.
- Normal- Lumbar disk herniation.
- Abnormal- Osteoporosis, osteomyelitis and osteoarthritis
How is Lumbar Disk Herniation Treated?
Medications for Lumbar Disk Herniations-
Nonsteroidal Anti-Inflammatory Drugs (NSAIDs)
- Analgesics for Mild To Moderate Pain- Motrin, Celebrex and naproxen.
- Anti-inflammatory Medications-
- Prescribed for inflammation of nerve.
- Aspirin, Ibuprofen (Motrin, Advil) and Naproxen (Aleve).
Tramadol (Ultram or Ultravcet)
- Analgesics- Prescribed for chronic pain not responding to NSAIDs.
Opioids as Analgesics
Short Acting Analgesics-
- Prescribed for breakthrough pain.
- Hydrocodone- Vicodin, Norco and Lortab
- Oxycodone- OxyIR (Oxycodone Immediate Release)
- Morphine- MS IR (Morphine Sulphate Immediate Release)
Long Acting Opioids-
- Prescribed for long-term analgesics.
- Oxycodone- Oxycontin.
- Morphine- MS Contin.
- Cyclobenzaprine (flexeril)
Neuropathic pain is treated with Antidepressant.
- Antidepressant Analgesics-
- Prescribed for chronic neuropathic pain and depression associated with neuropathic pain.
- Most commonly used antidepressant as analgesics are as follows-Duloxetine
- Tricyclic antidepressants (Elavil)
Neuropathic pain is treated with Antiepileptics or Anticonvulsant medications.
- Antidepressant Analgesics-
- Prescribed for chronic neuropathic pain.
- Prescribed for depression associated with neuropathic pain.
Most common Antiepileptics used as analgesics to treat neuropathic pain are as follows-
- Gabapentin- Neurontin.
- Pregabalin- Lyrica.
Anxiety and muscle pain is treated with anti-anxiety medications.
Most Common Anti-anxiety Medications Used Are
- Diazepam- Valium
Interventional Pain Therapy-
Corticosteroid is injected in epidural space to relieve pain and inflammation.
- Trans-laminar Epidural Corticosteroid Injection-Epidural needle is inserted between two vertebral spines and advanced into epidural space with loss of resistance technique. Epidural space is identified confirming satisfactory dye spread in epidural space using X-ray (image intensifier) images.
- Caudal Corticosteroid Injection-Caudal epidural injection is an alternative choice of technique of injecting corticosteroid in epidural space. Space is identified using dye and X-ray images.
- Trans-foraminal Epidural Injection-Needle tip is placed within the intervertebral trans-foramina. Placement of needle is confirmed with X-ray and dye is spread in epidural space. Trans-foraminal injection is more specific targeted cortisone injection at the bulged disc and irritated nerve pinched at the foramina.
- Chiropractic Treatment- Spinal manipulation may aggravate pain if herniated disc is large and causing severe pressure on nerve. Chiropractic treatment may be beneficial in small disc herniation with only radicular pain and no other symptoms like tingling, numbness and weakness in leg.
- Osteopathic Manipulation- Not recommended to treat severe pain caused by disc herniation.
- Massage Therapy- Massage therapy is recommended for associated pain caused by muscle spasm and not responding to muscle relaxants. Massage therapy also assists in continuing aggressive physical therapy.
Types of Physical Therapy-
- Passive Physical Therapy
- Heat Application.
- Ice Packs
- Electrical Stimulation- Tens Unit
- Active Physical Therapy
- Active Exercises- Specific exercises and massage are stretching. For most low back pain treatments, active exercise is the focus of the physical therapy program.
Surgical Options to Treat Lumbar Disk Herniation
- Percutaneous Discectomy
- Micro Discectomy- Disc is visualized on TV using endoscope or microscope. Herniated disc is identified and peripheral disc is carefully removed with blunt instruments. Advantages- Minimum tissue and muscle trauma. Rapid recovery.
- Laser Discectomy- Microscopic surgery, instead of blunt instrument laser beam is used to evaporate edges of the disc herniating in to foramina. Advantages- Minimum tissue and muscle trauma. Rapid recovery.
- Percutaneous Disc Removal- Small herniated disc is removed through small incision. Microscope may be used, otherwise visual impression of disc is limited.Advantages- Minimum tissue and muscle trauma. Rapid recovery.
- Explorative Discectomy -Skin incision is extended through subcutaneous tissue, muscles and tendon to visualized disc. Extensive surgery. Tissue and muscle trauma prolongs recovery.
- Laminectomy-Lamina is a posterior part of vertebral column. Lamina protects spinal cord and spinal nerve. Large herniated disc often occupies spinal canal and intervertebral foramina resulting in pinch nerve within spinal canal or foramina. Lamina is a part of posterior circle of spinal canal and intervertebral foramina. Removal of lamina decompresses as well as widens the spinal canal and foramina. Surgery of removal of part or total lamina is a known as partial or total laminectomy. Laminectomy also helps to visualize the disc to accomplish discectomy.
- Spinal Fusion Surgery-Spinal Fusion Surgery is performed when multiple attempts of nerve decompression surgery fails. Discectomy and laminectomy are performed to decompress the pinch nerve. Spinal fusion surgery involves total removal of spine and lamina and upper and lower vertebrae then fused using metallic plates in different design and sizes. Extensive surgery, needs prolonged time to recover.