Herniation of ucleus pulposus due to damaged annulus fibrosus compressing the nerves or spinal cord causing pain and spinal cord dysfunction.
Etiology
Intervertebral disc:
Intervertebral disc is composed of annulus fibrous—the annulus fibrous, dense collagenous ring encircling the nucleus pulposus. Disc herniation occurs when part or all the nucleus pulposus protrudes through the annulus fibrous.
Risk factors:
The pathophysiology of herniated discs is believed to be a combination of the mechanical compression of the nerve by the bulging nucleus pulposus and the local increase in inflammatory chemokines.
- Age-related degenerative changes (M/C cause): Nucleus pulposus becomes less hydrated and weakens leading to a progressive disc herniation
- Trauma (#2 M/C cause)
- Other causes: Connective tissue disorders, congenital disorders
Lumbar sites:
Higher rate of disc herniation is seen in lumbar & cervical spine due to biomechanical forces in the flexible part of the spine
- Common sites: Lumbar > cervical spine
- Uncommon site: Thoracic spine
Types of herniation:
Posterolateral herniation:
M/C type as annulus fibrosus is thinner and lacks structural support from anterior/posterior longitudinal ligaments. Due to its proximity, a posterolateral herniation is more likely to compress the nerve root.
- Nerve root compression
Midline herniation:
- Spinal cord compression
- Clinical myelopathy
Presentation
Chief complaint: Localized back pain
Localized back pain is a combination of the herniated disc pressure on the longitudinal ligament, and chemical irritation due to local inflammation.
- Sharp or burning pain often radiating in the distribution of the compressed nerve root
- Numbness and tingling, as well as decreased sensation along the path of the nerve root
- Severe cases: Weakness or a feeling of instability while ambulating may be endorsed.
Cervical Spine
In the cervical spine, the C6-7 is the most common herniation disc that causes symptoms, mostly radiculopathy.
- Cervical radiculopathy
Thoracic Spine
Most thoracic disc herniations are asymptomatic and discovered incidentally with an MRI.Unlike the lumbar and cervical disc herniations, thoracic disc herniations have atypical symptoms and often a diagnosis of exclusion.
- Thoracic discogenic pain syndrome (TDPS): Radicular pain secondary to posterolateral herniations that compress spinal nerves as they exit through the intervertebral foramen
Lumbar Spine
Herniated disc can present with symptoms including sensory and motor abnormalities limited to a specific myotome.
- Lower backache + specific dermatomyotomal involvement
- Straight leg raise test (SLRT): Examiner slowly elevates symptomatic leg at increasing angles on a supine patient, while keeping the leg straight at the knee joint. The test is positive if it reproduces the patient’s typical pain and paresthesia.
- Contralateral (crossed) SLRT: Examiner slowly elevates asymptomatic leg at an increasing angle on a supine patient. The test is positive if the maneuver reproduces the patient’s typical pain and paresthesia.
Management
Conservative management:
Acute cervical and lumbar radiculopathies due to a herniated disc are primarily managed with non-surgical treatments.
First-line modalities:
- NSAIDs
- Physical therapy: Started after 2 weeks as most cases resolve
- Refractory pain: Opioid analgesics
Second-line modalities:
- Translaminar epidural injections
- Selective nerve root blocks
Surgical management:
Benefits are moderate and tend to decrease over time following surgery
- Laminectomies with discectomies
- Artificial disk replacement