Spinal Information - Current Diagnostic Methodologies
The data and diagrams in the section below are courtesy of:
SpineUniverse.com and Spine-Health.com
Diagnostic studies are used to confirm an anatomical lesion (injury) as a cause of back or neck pain. They are particularly useful to pinpoint the source and extent of the injury to assist in the diagnosis and development of an appropriate treatment plan.
Patients are usually advised to complete a period of conservative care, usually at least four to six weeks from the onset of pain, before obtaining any type of diagnostic study. The only instance that an imaging study is immediately necessary is if a patient experiences bowel or bladder incontinence or progressive neurological loss of function, such as progressive weakness.
There are several types of diagnostic imaging technologies and techniques available to assist in accurately diagnosing the anatomical injury that is causing pain. X-rays, the most common and inexpensive form of imaging, are usually obtained first. Then, based on the result of the x-ray, a treatment plan may be developed or increasingly more sophisticated imaging studies may be completed to more precisely define the source and extent of the anatomical structure that is causing pain.
X-rays provide detail of the bone structures in the spine, and are used to rule out:
- instability (such as spondylolisthesis)
They image bones by shooting an x-ray beam through the body. The calcium in bone blocks penetration of the x-ray beam and the image of the bones is picked up as a shadow on a film positioned on the other side of the patient.
X-rays provide for excellent bony detail because bone consists mainly of calcium. However, discs and nerve roots do not have any calcium, so an x-ray does not capture an image of these structures. An x-ray, therefore, cannot be used to diagnose lumbar disc herniation or other causes of nerve pinching. X-rays should not be performed in women who may be pregnant.
1. CT Scan
A CT scan (see image below) is essentially a fancy x-ray that can take cross section images of the body. Such scans provide excellent bony detail through multiple views and are capable of imaging for specific conditions, such as:
(1) lumbar disc herniation
(2) lumbar spinal stenosis
Like an x-ray, a CT scan works by shooting an x-ray beam through the body. A computer is used to reformat the image into cross sections of the spine. This process is repeated at multiple intervals. As a result, the spinal canal can be imaged and assessed for specific conditions. With its excellent bony detail, CT scans are very useful for assessing fractures. Because x-ray beams are utilized, the image does not clearly show nerve roots. CT scans will image large disc herniations, but can miss smaller ones.
2. CT Scan with Myelogram
When combined with a myelogram, a CT scan provides for excellent nerve detail. The myelogram adds some additional risk and expense to the CT scan but provides substantial information about the nerve roots.
A myelogram consists of injecting a radiographically opaque dye (dye that is picked up by x-ray) into the sac around the nerve roots, which in turn lights up the nerve roots.
The CT scan follows and shows how the bone is affecting the nerve roots. This is a very sensitive test for nerve impingement and can pick up even very subtle injuries. The main risk with CT scans is that they use x-ray beams and should not be performed on pregnant women. The main risk with a myelogram is the potential for a spinal headache.
The spinal headache is usually alleviated in one to two days with rest and fluids, and seems to be more common in patients with a history of migraine headaches.
If the patient's headache continues, some blood can be withdrawn from the patient's arm (antecubital vein) and then injected into the epidural space in the back (blood patch). This procedure places pressure over the site that is leaking spinal fluid to stop the leak and in turn alleviates the headache.
3. Magnetic Resonance Imaging ("MRI")
The MRI was developed in the 1980's and has revolutionized treatment for patients with lower back pain. An MRI scan is generally considered to be the single best imaging study of the spine.
Physicians usually have a good idea of what they are looking for on the MRI scan before one is performed. The scans are most commonly used for pre-surgical planning, such as for a decompression or a lumbar spinal fusion. MRI scans are extremely sensitive to picking up information about the health of the discs, as well as the presence of any tumors or a lumbar disc herniation. In addition to pre-surgical planning, MRI scans are also very useful for the following:
- To rule out infection or tumor.
- For patients who have had surgery, to differentiate scar tissue from a recurrent disc herniation.
- Prior to performing an epidural injection to rule out the risk of injecting a steroid into a tumor or infection.
An MRI is a completely different technology from an x-ray and CT scan. It is particularly useful as an aid in the assessment of certain conditions by providing detail of the disc (such as for degenerative disc disease, isthmic spondylolisthesis) and nerve roots (such as for lumbar disc herniation, lumbar spinal stenosis). MRI scans are also useful to rule out tumors or spinal infections.
An MRI images the spine by using a magnet that goes around the body to excite hydrogen atoms. After the atoms return to their normal level of excitation, they emit energy that is picked up on a scanner. Since humans are composed primarily of water (which is two parts hydrogen), MRI's provide highly refined detail of the spine's anatomy.
Unlike an x-ray beam, there is no radiation with the magnet so the scans may be done on pregnant women. However, patients with a pacemaker implanted in their heart should not have a scan because the magnetic field will cause the pacemaker to malfunction. Also, anyone who works around metal should first have an x-ray of their eye sockets to ensure that they do not have any metal filings in their eyes, which the magnetic field may cause to migrate and damage the eye. Because most scanners are fairly tight, certain patients may feel uncomfortable, or may not tolerate lying in a tight tunnel for 45 to 60 minutes while the scan is being performed. To address this issue, newer generation scanners are designed with more open space, although a more open tube does sacrifice the excellent detail provided by the tight tubes.
A discogram is a test to determine the anatomical source of lower back pain for the patient. This procedure is most frequently used to determine if degenerative disc disease is the cause of a patient's pain (discogenic low back pain). Discograms are also performed to assist in preoperative planning for candidates for a lumbar spinal fusion.
In this procedure, the discographer inserts a needle in the patient's back into the center of the disc. Radiographic dye is then injected into the disc, and if injecting the dye recreates the patient's normal pain (concordant), it is then inferred that the specific disc is the source of pain for the patient. If the pain is unlike normal pain (discordant), it can be inferred that even though the disc may look degenerated on an MRI scan, it is in fact not the source of the patient's pain. The test itself is painful, but the patient needs to be awake and aware in order to tell the discographer what kind of pain is generated by the injection (see figure below and note injection from right side of photo into disc space).
As the discogram injection is not for treatment of pain, a steroid (anti-inflammatory medication) is not injected. However, sometimes a discographer will inject lidocaine (a numbing agent) into the disc to decrease the pain of the procedure. Often, after the discogram is completed, a CT scan is performed to check the morphology (anatomy) of the disc.
There are a limited number of risks involved with a discogram. Disc space infection is a serious but rare (<0.1%) potential complication. Because the needle passes close to the nerve, there is also slight risk of nerve root damage with the test.
While each of the aforementioned diagnostic treatment methodologies is adequate, none is exact. Each treatment methodology requires an initial examination of the patient in the psoas relaxed position. In this position the patient is lying down on his back (in the supine position) in a relaxed way.
Because virtually all MRI and CT examinations are performed with the patient lying down and free from the effects of gravity, many spinal diseases, injuries and conditions may be improperly diagnosed. According to several studies published by the Inventors in Spine and in ACTA Radiologica, DynaWell L-Spine considerably increases the accuracy in MRI and CT spinal examinations, and better assists medical professionals in the accurate diagnosis of a number of chronic back pain conditions.
The impact of DynaWell L-Spine can be significant in changing and improving the diagnostic outcome for procedures that utilize the CT and MRI scans. This in turn will result in a more accurate pre-operative diagnosis and allow for better surgical outcomes and a more satisfied patient population.