A herniated Lumbar disc is a condition affecting the lumbar spine. It occurs when a gel-like substance in the central core of the intervertebral disc called the nucleus pulposus squeezes out through breaks in the restraining annulus fibrosus. The extruded fragment comes in contact with or compresses the exiting nerve roots resulting in lumbago (Low backache) which maybe followed a week later with sciatica (Pain radiating down the leg) on the affected side. Conservative treatment with bed rest, pain killers and muscle relaxants result in relief in more than 80 percent patients with resumption of normal function within 4 to 6 weeks. If you don’t respond to above measures within a week you should consult your doctor who may advise investigations and based on the findings may recommend surgery.

Anatomy of the normal intervertebral disc

In order to understand the effects of a herniated disc it might be helpful to understand the structure of a normal intervertebral disc. As the name implies an intervertebral disc functions as a joint between two adjacent vertebral bodies. Its major role is mechanical. Eighty percent of the body weight in the standing posture is transmitted through the vertebral bodies and their intervening discs. The flexibility of the spinal column provided by the intervening discs allows for the complex movements allowing bending, flexion and torsion. The average lumbar disc is approximately 7–10 mm in height and 40 mm across in the front to back plane.

The symptoms resulting from herniated lumbar disc are a consequence of the structures compressed in the spinal canal and exit foramen. These pain sensitive structures are nerve roots and their dorsal root ganglion. Your doctor can correlate your symptoms with the findings revealed by imaging.
In a herniated disc the boundary between annulus and nucleus becomes blurred, with the nucleus generally becoming more fibrotic and less gel-like. Often the lamellar structure of the annulus becomes disorganized with fissures forming within the disc, particularly in the nucleus. Your doctor may recommend Magnetic Resonance Imaging of the Lumbosacral spine to allow the study of these degenerative changes in the intervertebral disc and the involved vertebrae which often include: Disc Bulge: This represents an outpouching of the intact annulus with extrusion of the gel-like nucleus resulting from loss of disc height. Your doctor may recommend Dynamic MR Imaging in case your symptoms do not correlate with the radiology to reveal a disc bulge which may occasionally be missed on Static MR. Disc herniation: Your doctor can study the dimensions of the extruded disc fragments on the axial images of Magnetic Resonance Imaging. Axial images are images that are taken in a plane perpendicular to the spinal column. Three different shapes of the disc fragments are possible: protrusion, extrusion or sequestration. Protrusion is when the height of the herniated fragment is less than the length of the base in any of the planes. Extrusion is when the length of the base is less than the height of the hernia. Sequestration is when there is no continuity between the herniated disc fragments and the intervertebral disc. It is as if the degenerate disc fragments have dropped off from the parent intervertebral disc space and become independent bodies occasionally masquerading as tumors. These fragments may move upwards or downwards in the spinal canal.

What are the possibilities following acute herniated lumbar disc? An acute herniated lumbar disc can irritate the exiting nerve roots resulting in lumbago with or without sciatica. In majority of patients the pain if it has to resolve does so within six weeks. This happens because of three possibilities:

  1. The degenerative disc fragments become more dehydrated and shrink resulting in some loss of volume and reduced compression
  2. The compressed nerve root narrows at the site of compression providing some space
  3. The pain is relieved despite no perceivable changes on Magnetic Resonance images over time. It is believed to be due to the reduction in the levels of inflammatory molecules released at the time of acute disc herniation
The symptoms resulting from herniated lumbar disc are a consequence of the structures compressed in the spinal canal and exit foramen. These pain sensitive structures are nerve roots and their dorsal root ganglion. Your doctor can correlate your symptoms with the findings revealed by imaging.

Central disc herniation (Purple): Seen in the elderly or young athletes. More likely to present with acute cauda equina syndrome- a neurosurgical emergency! This presents with severe pain, inequal deficits on the two sides, urinary retention and numbness of genitalia. Posterolateral lumbar disc herniation (Pink): The typical clinical picture includes initial lumbalgia, followed a week later by progressive sciatica in a patient around 40 years of age. Extreme lateral lumbar disc herniations (Green): ELLDH occur more frequently among elderly patients, with a peak incidence in the sixth decade. These occur more frequently at upper lumbar levels and as these extrusions compress the exiting root with its dorsal ganglion, the clinical presentation often involves lancinating leg pain, whereas low back pain is often mild to moderate. ELLDHs are characterized by the compression of the nerve root which exits at the same level and this is in contrast to classic posterolateral disc compression, which affects the nerve root leaving at the level below.

Extraforaminal lumbar disc herniations (Yellow): EFLDH feature cephalad migration of fragments away from their disc space of origin beyond the dorsal root ganglion of the exiting nerve root. EFLDH occur beneath or lateral to the facet joints and are characterized by the compression of the nerve root which exits at the same level. These herniations are uncommon and maybe missed by routine MR Imaging protocols.

The majority of lumbago and sciatica resolve within 6 weeks with conservative measures consisting of restricted physical activity, bed rest, analgesics, muscle relaxants and physiotherapy. In case of persistence of symptoms especially pain your doctor may refer you to an anesthetist for Epidural steroid injections. Surgical treatment is indicated

  1. if pain control is unsuccessful despite these measures outlined above,
  2. if there is a motor deficit greater than grade 3,
  3. if there is radicular pain associated with foraminal stenosis, or
  4. if cauda equina syndrome is present. The latter represents a medical emergency.