What is a Herniated Disc?
Herniation of the nucleus pulposus (HNP) occurs when the nucleus pulposus (gel-like substance) breaks through the anulus fibrosus (tire-like structure) of an intervertebral disc (spinal shock absorber).
A herniated disc occurs most often in the lumbar region of the spine especially at the L4-L5 and L5-S1 levels (L = Lumbar, S = Sacral). This is because the lumbar spine carries most of the body's weight. People between the ages of 30 and 50 appear to be vulnerable because the elasticity and water content of the nucleus decreases with age.
The progression to an actual HNP varies from slow to sudden onset of symptoms. There are four stages: (1) disc protrusion (2) prolapsed disc (3) disc extrusion (4) sequestered disc. Stages 1 and 2 are referred to as incomplete, where 3 and 4 are complete herniations. Pain resulting from herniation may be combined with a radiculopathy, which means neurological deficit. The deficit may include sensory changes (i.e. tingling, numbness) and/or motor changes (i.e. weakness, reflex loss). These changes are caused by nerve compression created by pressure from interior disc material.
Progression of Herniated Disc
The extremities affected are dependent upon the vertebral level at which the HNP occurred. Consider the following examples:
Cervical - Pain in the neck, shoulders, and arms
Thoracic - Pain radiates into the chest
Lumbar - Pain extends into the buttocks, thighs, legs
Cauda Equina Syndrome occurs from a central disc herniation and is serious requiring immediate surgical intervention. The symptoms include bilateral leg pain, loss of perianal sensation (anus), paralysis of the bladder, and weakness of the anal sphincter.
Diagnosis of a Herniated Disc
The spine is examined with the patient laying down and standing. Due to muscle spasm, a loss of normal spinal curvature may be noted. Radicular pain (inflammation of a spinal nerve) may increase when pressure is applied to the affected spinal level.
A Lasegue test, also known as Straight-leg Raising Test, is performed. The patient lies down, the knee is extended, and the hip is flexed. If pain is aggravated or produced, it is an indication the lower lumbosacral nerve roots are inflamed.
Other neurological tests are performed to determine loss of sensation and/or motor function. Abnormal reflexes are noted as these changes may indicate the location of the herniation.
Radiographs are helpful, but Computed Axial Tomography (CAT) or Magnetic Resonance Imaging (MRI) provides more detail. The MRI is the best method enabling the physician to see the soft spinal tissues unseen in a conventional x-ray.
Radiographic Evidence of HNP
The findings from the examination and tests are compared to make a proper diagnosis. This includes determining the location of the herniation so treatment options can be reviewed with the patient.
Dr. Dawson's article on herniated disc is quite informative, and it has been written in such a way for a lay person to understand the content. The description on the extent of herniation is quite accurate and MRI is quite helpful in determining the type and location of herniated disc. It should be remembered that the diagnosis of a herniated disc is frequently made clinically after history and examination, and MRI or CT is recommended only if invasive treatment is considered. Among conservative treatments mentioned, pain relief with nonsteroidal anti-inflammatory medications (NSAIDs) and a gradual exercise program rather than bedrest is important for maximal recovery.
Epidural steroids also should be mentioned as a secondary treatment for radicular pain if NSAIDs are not helping. Surgical indications should be strictly defined as failure to relieve radicular pain or radiculopathy despite appropriate conservative treatment for at least 6 weeks, and imaging study showing herniated disc that correlates clinically.
Dr. Dawson is correct in that about 80-90% of patients with a herniated disc will respond to conservative treatment. One of the reasons for the patient's improvement of symptom associated with herniated discs is the tendency of gradual resorption of the extruded disc frament with time. If surgery is indicated, outpatient microdiscectomy is the gold standard treatment as Dr. Dawson stated.
Other treatment methods such as chemonycleolysis, endoscopic or arthroscopic discectomy, nucleoplasty, etc. have narrower indications, and the success rate is generally lower than microdiscectomy. Long-term outcomes following these newer procedures should be determined prior to general application.