Diagnosis of Low Back Pain

Diagnosis of Lower Back Pain

To arrive at an accurate diagnosis, your doctor will need to consult with you to take a detailed history, perform a physical exam, and possibly order some tests. The history is very important to arrive at an accurate diagnosis. When it comes to low back and leg pain, important questions include:

HISTORY

  • When did the pain begin?
  • What precipitated it? Was there an injury, or did it occur spontaneously?
  • Does it stay in the back, or does it travel down the leg? If so, where in the leg does it go?
  • What makes the pain better? What makes it worse?
  • Is there any weakness associated with the pain?
  • Is there any loss of bowel or bladder control?
  • Do you have any numbness, tingling, or pain in your back or extremities?
  • Does changing position relieve your symptoms?

EXAM

Next, your doctor will need to perform a physical exam. During the exam, specific things the physician will watch for are:

  • Tenderness to palpation (touching by hand) over the lumbar spine
  • Signs of “straight leg raising” or “crossed straight leg raising”: a straight leg raise is an orthopedic test in which the doctor gently raises your leg straight up in the air, extending the knee. If pain shoots down the leg being raised, this is a positive indication that there is likely to be something (quite possibly a herniated disc) putting pressure on the nerve root. A crossed straight leg raise test is a test where, when one leg is raised, the pain travels down the opposite leg. This sign is very accurate in predicting the presence of a herniated disc.
  • Weakness in the lower extremities: the lumbar and sacral plexus nerve roots each supply different muscle groups in the legs and buttocks. Pressure from a herniated disc on a nerve root will often cause weakness in the muscle by the nerve root level. For example, the S1 root supplies the gastrocnemius muscle (calf muscle), and injury or pressure upon the S1 nerve root may cause the patient to have difficulty walking on the toes. Pressure or injury on the L5 nerve root may cause difficulty picking up the big toe, and can result in foot drop.
  • Sensory changes in the lower extremity, in the distribution of the nerve root being affected. The S1 nerve root supplies sensation to the lateral aspect of the foot, and injury to the S1 nerve root can result in numbness to the lateral foot and small toe.
  • Reflex changes can also result from pressure on a nerve root. The S1 nerve root is responsible for the Achilles Reflex, and injury to the S1 nerve root may result in an absent or decreased ankle jerk reflex.

Please keep in mind that these are very general descriptions of the tests and signs. There is a great amount of cross over on these nerve root levels, and everyone is built a little different. Dr. Tunick brings over thirty years of clinical experience in physical examination, neurologic and orthopedic testing, and specializes in managing patients with these difficult spinal disc injuries.

IMAGING TESTS

Common tests a patient with low back and lower extremity pain may undergo include lumbar spine x-rays (films), CT scans (computed axial tomography scans), MRI scans (magnetic resonance imaging), myelograms, post myelographic CT scans, EMG/NCV (electromyogram/nerve conduction velocity) studies, discograms, and bone density tests.

Below is a brief description of each test:

Lumbar spine films: these plain x-rays are good at showing alignment of the spine. Degenerative changes, thinning disc space, any slippage, known as spondylolisthesis or subluxations, are easily visible on plain x-rays of the lumbar spine. Also, compression fractures of the vertebral bodies are easily seen. Tumors can also be detected with plain film radiography.

CT Scans: these show “cross sections” of the spine. They are pictures of the body divided into very small slices. These “slices” of the body can accurately reveal the anatomy within. When used on the spine, they detail bone very well but are not quite as good at showing soft tissue structures such as herniated discs, nerves and tumors. CT scans use x-rays which are sent through the area of interest in numerous directions, then a computer adds the images in 3 dimensions and displays the pictures so they can easily be understood by your doctor.

MRI Scans: the images provided are similar  to CT scans in as far as these images provide serial slices through the spine or other areas of interest. They use magnetism instead of x-rays to obtain the images. In addition to showing information in additional planes the MRI gives much better detail of the soft tissue anatomy of the spine than do CT scans. Discs, nerve roots, joint capsules, muscle tissue and tumors are all seen more clearly. Bone is seen more clearly on CT scans. MRI imaging is rapidly becoming the imaging study of choice in the diagnosis of low back and leg pain as it provides the greatest amount of clinically relevant information for the doctor.

Myelograms: a myelogram is a study in which the radiologist performs a spinal tap, places a dye (which shows up on x-ray and CT scans) into the spinal fluid, this is x-rayed. Following this procedure, CT scans are performed. What is provided is an outline or shadow of the pathology. For example instead of seeing a nerve root sheath filling nicely from the dye in it, it may show nice filling to a point, and then show a ‘bump’ in it. These studies are often performed in patients where the MRI studies are ambiguous or in patients who have a pacemaker implanted for the heart (pacemakers cannot be used in the presence of an MRI machine).

EMG/NCV studies: these studies monitor the electrical functioning of muscles and nerves. Rather than providing images or pictures of the anatomy as MRI, CT scans and plain film radiology, these studies are tests of function and look at how well a muscle or nerve is working.

Bone Density Tests: this test measures the density and strength of bones. Osteoporosis is the leading cause of vertebral compression fractures. A number of tests are available, but the most common is the DEXA (dual energy x-ray absorptiometry) test.

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