When is an MRI Necessary for Low Back Pain or Neck Pain?

Introduction:

The decision of when to do an MRI for patients with low back or neck pain depends upon assessing the risk of a serious condition being present as revealed by warning symptoms in the history or signs in the physical examination. Back pain and neck pain are common health complaints; almost everybody suffers from these problems. Most of the time, neck and back pain are not caused due to some serious problem or injury, and the cause can be easily diagnosed. Often lower back and neck pain gets better on its own with time. But sometimes, finding the exact cause of such pain is difficult. When nothing helps, an MRI scan comes to the rescue and helps find the exact cause of the pain by providing detailed images of the soft tissue around the spine. However, an MRI scan is usually recommended if there are warning signs along with pain.

How Does an MRI Machine Work?

Unlike traditional X-rays or computerized axial tomography, otherwise known as CT scan, MRI (magnetic resonance imaging) does not use any radiation, and thus as far as scientifically known, it is much safer than X-rays. The patient is placed in a very strong magnetic field which causes the hydrogen protons in the body to become excited and because the magnetic field applied is uniform, these protons become similarly aligned. The magnetic field is rapidly turned on and off repeatedly, which causes the protons to relax and emit radiofrequency waves. From this change, the MRI machine can compute a picture of the tissues of the body, particularly the brain, spinal cord, major nerves, and other soft tissues. MRI detects slight differences in water content in soft tissues to detect abnormalities.

What Abnormalities Can an MRI Detect?

The MRI can show derangements from normal anatomy, including:

• Disc herniation (rupture of fibrocartilagenous material which surrounds the intervertebral disc).

• Spine infection.

• Tumors of the spine, nerves, or spinal cord.

• Compression of the nerves or spinal cord from hemorrhage (bleeding), fracture, infection, or tumor.

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• Changes in the intervertebral disc or soft tissue adjacent to the spine.

MRI is superior to a CT scan in evaluating disorders of the spine as regards nerve compression. However, sometimes a CT scan is needed to evaluate fine detail in the vertebrae because cortical bone, the tough outer layer of bone, has a low water content.

What Is the Importance of Warning Symptoms and Signs?

The vast majority of neck or low back pain sufferers will improve without surgery. Only about two percent will ever need an operation. A physician can usually determine the potential seriousness of a condition causing pain by obtaining a detailed history and performing a thorough examination. If there are no warning symptoms or signs in the history or physical findings suggestive of a dangerous condition, then for most patients, an MRI is not necessary before a trial of conservative treatment for at least a month.

Symptoms that the patient experiences or have as a history that may indicate a serious condition include:

• Progressive and unrelenting pain that is not relieved with rest and worsens at night.

• Progressive weakness of one or more extremities.

• One of the legs feels numb and gets worse with time.

• Difficulty in controlling urination, bowel movements, or erections.

• Weight loss or fever associated with the pain.

• Recent serious illness, especially cancer or infection.

• History of osteoporosis.

• Long-term use of steroids.

• History of cancer.

• Living in an area where tuberculosis is endemic.

• Pain seen under the age of 16 years or over 50 years of age.

• The onset of pain after significant trauma.

Signs seen during the examination which may indicate a serious condition include:

• Numbness in the groin, genital, and anal area, called saddle anesthesia.

• An enlarged bladder can indicate urinary retention.

• Fever.

• Weight gets reduced below average according to height.

• Increased reflexes, positive Babinski sign (extension of the great toe when the sole is stimulated), or clonus (a repetitive contraction of the ankle joint on sudden stretching of the Achilles tendon - a tendon of the posterior leg) can indicate spinal cord compression.

• Bilateral weakness or sensory loss.

• Weakness in one or more extremities against minimal resistance or gravity.

Which Area of the Spine Should Be Studied?

Most of the time, patients with cervical spine problems have neck pain and upper extremity complaints, while those with lumbar spine problems have low back pain and lower extremity complaints, but sometimes it is not so clear.

Pain at the level of the shoulder blades can come from the lower cervical spine or upper thoracic spine. Generally, if it also radiates to the arm, then it comes from the cervical spine. Pain from the lower thoracic region can be similar to pain from the lumbar spine. If there are significant signs of lower extremity weakness, increased reflexes, bladder, bowel, or sexual dysfunction in a setting where the patient complains of low back pain, then it may be wise to do a thoracic MRI if the lumbar does not show the cause. Similarly, a very low cervical problem or serious thoracic problem can be hard to localize with a study of only the cervical or thoracic spine alone. Most MRI scans of the cervical usually show the lower brain, so lesions near the junction of the cervical spinal cord and brain are usually identified somewhat on cervical MRI.

What Are the Risks of MRI Scan?

In rare cases, the dye used in MRI scans may cause severe allergic reactions or damage to the kidneys. The strong magnetic fields used during an MRI scan may cause heart pacemakers not to work well. However, newer pacemakers are MRI-compatible. Hence, it is important to check with a cardiologist whether the pacemakers are MRI-compatible. MRI scans can also make a metal piece inside the body to move. So, inform the technologist about any metal objects present in the body. Pregnant women should go for MRI scans.

Conclusion:

MRI is generally recommended when relief from symptoms is not obtained after giving the first line of treatment. MRI is considered a gold standard for diagnosing the cause of a specific condition and planning treatment. MRI scans are often used in planning back or neck surgery. At times, MRI scans may help in assessing post-surgical healing and recovery.

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