Duke-NUS Graduate Medical School | Herniated_Lumbar_Disc

Hi I'm Eunisa from SingHealth EME. Today, I will be talking about a common cause of low , the herniated disc. The objectives for today's session is to understand the anatomy and pathophysiology behind this condition and the basic management of lumbar herniated disc disease. Specifically, my talk will cover the following segments.

What is lumbar disc herniation? It is a condition widely referred to as slipped disc. But, in fact, this term is not medically accurate as the spinal discs are fixed in position between the vertebrae and cannot, in fact, slip. It is actually a result of a tear in the outer casing of the vertebral disc that allows the soft inner portion to bulge out. And that may cause compression of associated nerve roots.

Lumbar pain is responsible for more work absences than any illness except the common cold. The annual prevalence of lower back pain in working adults may approach 50%. In 85% of the, no definite cause of lower back pain can be diagnosed. Some may be attributed to disc herniation. Herniation of the nucleus pulposus is more common in adults. Risk factors include acute trauma, family history of disc herniation, and sports including weightlifting, , gymnastics, and collision sports.

The is the largest avascular structure in the body located in the spinal column between successive vertebral bodies. It is oval in cross section, biconvex in shape, and becomes successively larger by about 11% per segment from cephalad to caudal. The annulus fibrosus is an outer constraining ring, primarily made up of type 1 collagen. The nucleus pulposus refers to the central portion of the disc. It is soft and jelly-like and made up type II collagen, proteoglycan, and hyaluronan long chains.

These components have highly hydrophilic side chains, which hydrate the nucleus by an osmotic swelling pressure effect. If acts as a shock absorber to cushion the spinal column from forces that are applied to the musculoskeletal system. Together with two posterior facets, an anterior disc provides protection for the neural elements within the acceptable constraints of clinical stability.

What causes disc herniation? General wear and tear and degenerative processes due to age, rapid disc strain, or constant sitting with is a common cause of disc herniation. Traumatic like lifting while bent at the waist, rather than lifting with the legs while the back is straight is another common precipitant of disc herniation. It is also important to note that disc herniation has a strong genetic component. Mutation in genes coding for proteins involved in the regulation the extracellular matrix has been implicated in this condition.

Disc herniation can occur at any level of the spine. However, most happen in parts with increased mobility. The most commonly affected being the lumbar region, followed by the cervical region, and then the thoracic region. Two mechanisms may account for the pain associated with herniated lumbar disc. Firstly, mechanical injury, secondly, chemical radiculitis. In mechanical injury, anterior side of the disc is compressed, and the posterior side of the disc is stretched and thinned. While sitting or bending forward, the nucleus pulposus gets pressed against the tightly stretched and thinned annulus fibrosis. The combination of membrane thinning from stretching and increase in internal pressure of the disc results in the rupture of the confining membrane. The jelly-like contents of the disc then move into the spinal canal, pressing against the spinal nerves, thus producing intense and usually disabling pain and other symptoms.

In terms of chemical radiculitis, is released, not only by the herniated disc, but also in cases up annular tear by facet joints and in . This causes pain and and may contribute to disc degeneration. This condition has a wide spectrum of presentation depending on the degree of herniation. It usually has unilateral involvement due to the presence of posterior ligaments, which prevent posterior and favor postero-lateral herniation instead. Herniations may be asymptomatic in up to 50% of cases or may present with pain or a variety of neurological signs. For example, radiating into regions served by affected nerve roots, pain in the , knees, or feet, , sensory changes, weakness, or even syndrome, which may present with loss of bowel and bladder control as well as sexual dysfunction.

The main findings to look out for in a of a patient with lumbar disc herniation are positive test, which has a high sensitivity but low specificity, neurologic testing, we should focus on L5 and S1 nerve roots, because 98% of clinically important disc herniations occurs at these levels. For L5 , it is important to test ankle and great dorsiflexion. To test for numbness in the medial foot and the web space between the first and second toe. For the S1 nerve root, you should test plantarflexion, ankle reflexes, and sensation at the posterior calf and lateral foot.

According to the American guideline, imaging is not necessary for the first four to six weeks in the absence of any of the following: presence of neurologic findings, constitutional symptoms, history of traumatic onset, history of , age above 50 years old, infectious risks, such as an injection drug user, immunosuppression, indwelling urinary catheter, prolonged steroid use, skin, or urinary tract infection, or osteoporosis. If imaging is indeed indicated, x-ray, CT or MRI can be used, although MRI would be most diagnostic. X-ray signs suggestive of disc herniation is decreased intervertebral height. On MRI, the bulging disc can be better visualized, and the degree of nerve root compression can be ascertained.

Treatment can be medical or surgical. Medical treatment is reserved for minor herniations. It includes anti- inflammatory drugs, epidural, as well as, physiotherapy. Symptoms would heal within a few weeks, and it is the first line therapy for at least six weeks. Surgical treatment is reserved for severe herniation or those who have failed medical therapy. This includes , (Hemi), or lumbar fusion procedures. The aim of surgical procedures is to relieve the nerve root compression.

In summary, a is a medical condition affecting this spine due to trauma, lifting or idiopathic causes. A tear in the outer fibrous string or the annulus fibrosis of an intervertebral disc allows the soft, central portion, the nucleus pulposus, to bulge out beyond the damaged outer rings. Tears are always postero- lateral. This tear in the disc ring may result in the release of inflammatory chemical mediators, which may directly cause severe pain, even in the absence of nerve root compression.

Diagnosis is mainly through imaging. The treatment for minor herniation is medical, including physiotherapy and anti-inflammatory drugs. Pain that is refractory to conservative treatment may require surgical intervention, which aims to the relieve nerve compression and restore normal anatomy.