Etiology of Symptoms
The disk is largely aneural; therefore not all disk protrusions are symptomatic.

Pain. Symptoms of pain arise from pressure of a swollen disk or swollen tissues against pain-sensitive structures (ligaments, dura mater, blood vessels around nerve roots) or from the chemical irritants of inflammation if there is herniated disk material.

Neurological signs and symptoms. Neurological signs arise from pressure against the spinal cord or nerve roots. The only true neurological signs and symptoms are specific motor weaknesses and specific dermatome sensory changes. Radiating pain in a dermatomal pattern, increased myoelectrical activity in the hamstrings, decreased straight-leg raising, and depressed deep tendon reflexes can also be associated with referred pain stimuli from spinal muscles, interspinous ligaments, the disk, and facet joints and therefore are not true signs of nerve root pressure.

Variability of symptoms. Symptoms are variable depending on the degree and direction of the protrusion as well as the spinal level of the lesion.

• Posterior or posterolateral protrusions are most common. With a small posterior or posterolateral lesion, there may be pressure against the posterior longitudinal ligament or against the dura mater or its extensions around the nerve roots. The patient may describe a severe midline backache or pain spreading across the back into the buttock and thigh.

• A large posterior protrusion may cause spinal cord signs such as loss of bladder control and saddle anesthesia.

• A large posterolateral protrusion may cause partial cord or nerve root signs.

• An anterior protrusion may cause pressure against the anterior longitudinal ligament, resulting in back pain. There are no neurological signs.

• The most common levels of protrusion are the segments between the fourth and fifth lumbar vertebrae and between the fifth lumbar vertebra and sacrum, although a protrusion may occur at any level, including the cervical spine.

Shifting symptoms. Symptoms from a disk lesion may shift if there is integrity of the annular wall because the hydrostatic mechanism is still intact.

Inflammation. Contents of the nucleus pulposus in the neural canal may cause an inflammatory reaction and irritate the dural sac, its nerve root sleeves, or the nerve roots. The symptoms may persist for extended periods and are not responsive to purely mechanical changes. The back pain may be worse than leg pain on the straight-leg raising test. Poor resolution of this inflammatory stimulus may lead to fibrotic reactions, nerve mobility impairments, and chronic pain. Early medical intervention with anti-inflammatory agents is usually necessary.

Onset and Behavior of Symptoms from Disk Lesions

Onset. Onset is usually between 20 and 55 years of age but most frequently from the mid-thirties to forties. Except in cases of trauma, symptomatic onset in the lumbar spine is usually associated simply with bending, bending and lifting, or attempting to stand up after having been in a prolonged recumbent, sitting, or forward-bent posture. The person may or may not have the sensation of something tearing. Although cervical disk lesions are not as prevalent, a prolonged flexed spinal position as in a forward head posture may lead to or exacerbate symptoms from a protrusion. Many patients have a predisposing history of a faulty flexion posture.

Pain behavior. Pain may increase gradually when the person is inactive, such as when sitting or after a night’s rest. The patient often describes increased pain when attempting to get out of bed in the morning or when first standing up. Symptoms are usually aggravated with activities that increase the intradiskal pressure, such as sitting, forward bending, coughing, or straining or when attempting to stand after being in a flexed position. Usually, symptoms are lessened when walking except when the bulge is large or the nuclear material has prolapsed and moved beyond the confines of the annulus.

Acute pain. When there is inflammation during the acute phase, pain is almost always present but varies in intensity, depending on the person’s position or activity.
When there is a lumbar disk lesion, initially discomfort is noticed in the lumbosacral or buttock region. Some patients experience aching that extends into the thigh or leg. In the cervical spine, initially pain is noticed in the midscapular and shoulder area. Numbness or muscle weakness (neurological signs) are not noted unless the protrusion has progressed to a degree to which there is nerve root, spinal cord, or cauda equina compression.

Objective Clinical Findings in the Lumbar Spine
• The patient usually prefers standing and walking to sitting.

• The patient may have a decrease in or loss of lumbar lordosis and may have some lateral shifting of the spinal column.

• Forward bending is limited. When repeating the forward-bending test, the symptoms increase or peripheralize. Peripheralization means the symptoms are experienced farther down the leg.

• Backward bending is limited; when repeating the backward-bending test, the pain lessens or centralizes. Centralization means that the symptoms recede up the leg or become localized to the back. If the protrusion cannot be mechanically reduced, backward bending peripheralizes or increases the symptoms.

• If there is a lateral shift of the spinal column, backward bending increases the pain. If the lateral shift is first corrected, repeated backward bending lessens or centralizes the pain.

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