L4 nerve root compression
by Nathan Wei, MD, FACP, FACR
Nathan Wei is a nationally known board-certified rheumatologist and author of the Second Opinion Arthritis Treatment Kit. It's available exclusively at this website... not available in stores.
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The spine consists of 33 vertebrae (bones stacked on top of each other).
There are four separate regions including the cervical, thoracic, lumbar, and sacral spine. Discs separate the vertebrae and act as a shock absorbing system. The disc has a tough outer ring of fibers called the annulus fibrosus and a soft gel-like center called the nucleus pulposus.
The five lumbar vertebrae carry the majority of the body weight. The sacral region helps distribute weight to the pelvis and hips.
The spinal cord runs down the center of this column of vertebrae. Spinal nerves leave the spinal cord and travel through a tunnel or foramen. The nerves provide sensory (allowing you to touch and feel) and motor information (allowing the muscles to function).
The primary symptom of acute or chronic nerve root compression is pain.
The onset of symptoms is characterized by a sharp, burning, stabbing pain radiating down the posterior or lateral aspect of the leg, to below the knee. This type of pain is often referred to as sciatica. Pain is often associated with numbness or tingling. In more advanced cases, motor deficit (muscle weakness)and diminished reflexes occur.
The most common levels for sciatica are L4-5 and L5-S1.
The root pain of sciatica is almost invariably accompanied by back pain (94%). There are usually spasms of the back and leg muscles.
The onset of root pain due to intervertebral disc herniation is often abrupt, but it may also develop over several hours or days after the start of back pain. Radicular pain is induced or aggravated by movement. Pain aggravated by coughing or sneezing is a common complaint.
Sciatic pain usually can be diffuse and difficult for the patient to localize. On occasion, specific areas or points along the course of the sciatic nerve are tender and painful. Dull pain is often felt in the buttock.
The lumbar roots are vulnerable as they exit the foramina as they lie in the immediate path of a lateral disc herniation.
Intervertebral disc herniation and degeneration is the most common source of compressive radiculopathy.
Over 90% of all clinically significant lower extremity radiculopathies due to disc herniation involve the L5 or S1 nerve root at the L4-5 or L5-S1 disc level. The natural history of most disc herniation is that the symptoms are self-limited and do not require surgical therapy.
Current practice is to develop a rehabilitation program for back pain and to proceed with more aggressive treatment only when there is a progressive neurologic deficit or pain that does not improve.
Lumbar intervertebral disc herniation occurs most commonly at L4/5 (L5 root; 50%) and at L5/S1 (S1 root; 46.3%). Therefore, compression of the 5th lumbar nerve root is most common, with the first sacral nerve roots a close second.
A reason for the frequent compression of the L5 root may be the tight fit of the L5 root in its foramen since this root has the largest diameter and its intervertebral foramen is narrower than any other lumbar intervertebral foramen.
Pain which radiates along the posterior thigh and the posterolateral aspect of the leg is due to an S1 or L5 radiculopathy (nerve roots). When caused by S1 irritation it may radiate to the lateral aspect of the foot; pain due to L5 radiculopathy may radiate to the top of the foot and to the big toe.
Pain which radiates along the anterior aspect of the thigh into the anterior leg is due to L4 or L3 radiculopathy. With L4 root compression there is diminished knee jerk reflex and weakness of the quadriceps muscles. L2 pain is antero-medial in the thigh. Pain in the groin usually arises from an L1 lesion.
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