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.
