Herniated disc is a condition in which there is a lesion or rupture in the outer fibrous ring of the intervertebral disc (annulus), that leads to bulging of the inner portion (nucleus). The discs are fibrocartilaginous pads between the vertebrae which act as a shock absorber and allows for flexible movement of the vertebral column. There exist a spinal canal just at the posterior of the intervertebral disc formed by the vertebrae and consists of the spinal cord and nerve roots. A posterior protruded herniated discs may sometimes cause the stenosis of the spinal canal. Majority of discs herniate in the lumbar region followed by cervical, thoracic disc herniation is extremely rare. The most common level for herniation is L4-5 and L5-S1. This is probably due to a high pressure on the lower vertebrae that forces the nucleus to herniate out that occurs due to degeneration or certain movements.
Following are the risk factors associated with this conditions:
- Age between 30-50
- Males are more commonly affected as compared to females
- Heavy weight lifting
- Obesity; increased body weight can place added stress on the lumbar spine
- Sudden strain from twisting or quick movements/Trauma
- Strenuous activity that is repeated over time
- Improper posture
Cervical Disc Herniation
Cervical disc herniation occurs most commonly in cervical vertebrae C5 and C6 or C6 and C7. It can affect nerves in the cervical or brachial plexus. Leading to symptoms in the upper limbs and neck.
Lumbar Disc Herniation
Lumbar disc herniation occurs most commonly in the lumbar vertebrae L4-L5 and L5-S1. It can affect the sciatic nerve leading to symptoms of sciatica, or can also affect the femoral nerve. The spine has a natural lordosis (forward convexity) in the lumbar and cervical regions. The intervertebral discs between L4 and L5, and L5 and the S1, are wedge shaped, to maintain this lordosis. This results in significantly improved mobility and flexibility, however does compromise on stability. As a result, there are numerous supportive structures, such as the lumbar zygapophyseal joints which provide bony locking mechanism that resist forward displacement, iliolumbar ligaments which extend from the transverse processes of the 5th lumbar vertebra to the iliac crest. The thoracolumbar fascia also supports the lumbar region of the spine, and is formed from the aponeurosis of latissimus dorsi and trapezius. It is dynamic structure that is under tension on hip flexion and/or shoulder abduction/elevation. The transverse processes of the lumbar vertebrae are also shorter and stockier than other vertebrae, and the bodies are large and kidney bean shaped. This allows for better pressure distribution of pressure, after all the load that each vertebra is carrying gets progressively higher the further down the spine you go.
Intradural Disc Herniation
Intradural disc herniation is a rare type of herniation that can be found in the thoracic, cervical or lumbar region and diagnosis is usually found during surgery or on MRI.
Site of herniation
There could be midline, paramedian, posterolateral and anterior disc herniation. It may be unilateral or bilateral. Sometimes there is an intravertebral herniation characterised by the herniation of the nucleus pulposus into the intervertebral body through a fracture, this is also known as Schmorl's node.
Signs and Symptoms
Depending on where the disc herniation has occurred in the spine will determine the symptoms patients present with.
Herniated disc symptoms of the lower back:
- Lower back pain
- Sharp, shooting pain down the back of the leg in conjunction with sciatica
- Numbness in one leg or buttock or feet
- Burning pain
- Pins and needles sensation
- Tingling in legs
- Leg weakness
- Muscle weakness
- Loss of bladder or bowel control
Herniated disc symptoms of the neck:
- Neck pain and back pain
- Pain in trapezius muscle
- Spasm of the neck muscles
- Shooting pains down the arm
- Burning pain in the arm, neck or shoulders
- Arm weakness
- Tingling in arms
- Pins and needles in the arm
- Loss of bladder or bowel control
- Headache in the back of the head
Investigations for diagnosis of herniated disc are firstly done by an x-ray of the spine. This is to see evidence of degenerative discs in the spine. Spinal x-rays can rule out any other causes of symptoms of back pain.
In addition MRI or CT scans of the spine are useful imaging tests to confirm the diagnosis of herniation. MRI is considered as gold standard to identify the condition. It is also helpful in detecting if there is narrowing in the spinal canal.
EMG (electromyography) is a test that involves small needles placed into muscles to measure electrical activity by measuring the response of muscles. It can be useful to detect damage to the nerves and determine where the disc herniation has occurred.
A myelogram is useful test to see what structures are causing pressure on the spinal cord. Contrast is injected into the cerebrospinal fluid spaces and then an x-ray is taken of the spine, CT scan with myelogram may also be ordered as it is more sensitive.
Medical treatments can be effective in treating the symptoms of herniated discs in most patients. Supportive treatments for most back and neck pain will resolve with rest and analgesia, muscle relaxants, and non-steroidal anti-inflammatory medications. Ice or cold compresses can be applied to the back to relieve pain and gentle heat applications may be used after any spasms. Any physical activity should be reduced to not exert too much pressure on the back. Lifting should be avoided and sitting for long periods should be avoided as well. Physiotherapy can be initiated, as certain exercises will strengthen the back muscles.
Epidural injections of a cortisone-like drug can help relieve nerve pain by relieving inflammation and swelling around the nerve roots.
Surgical procedures such a microdiscectomy or laminectomy can be carried out. In microdiscectomy procedure is done by microscopically removing the fragments of herniated disc. Laminectomy is a procedure that removes part of the vertebrae called the lamina that contributes to increasing pressure. Once removed pressure is relieved helping with symptoms and mobility. Microdiscectomy or laminectomy procedures are carried out depending on the size and position of the disc herniation. The procedures are carried out under general anesthetic and will take six weeks to recover from this surgery.
Cauda equina syndrome is a medical emergency, which is loss of function of the lumbar plexus and presents with incontinence, loss of anal tone, saddle anaesthesia, sciatica pain, leg weakness, and ataxic gait.
It is treated with early surgical decompression to prevent long term neurological damage.