You have reached the Information Page Lynx Version 2.7 File that you are currently viewing Linkname: Facts about MRI's URL: http://www.hvmconline.com/mri.htm Server: Apache/1.1.3 Debian/GNU Date: Sun, 28 Jun 1998 08:33:35 GMT Last Mod: Sat, 07 Feb 1998 06:05:49 GMT Owner(s): None size: 172 lines mode: normal No Links on the current page HUDSON VALLEY MEDICAL CONSULTANTS MRI Facts A Brief Overview of Disc Herniations [INLINE] lumb-obl.jpg (11335 bytes) Above: Normal anatomic model. When a disc herniation occurs as a result of an accident or injury, the soft disc material extrudes into the spinal canal and causes pressure on an assortment of structures. Some of these structures are significant and can result in debilitating symptoms, but others are not significant and are of no clinical importance. The wording of an MRI report can shed an incredible amount of light on the actual injuries sustained by a claimant. First, consider the following anatomical overview: lum-may.jpg (14907 bytes) The "intraspinal neural structures" (nerve structures located inside the spinal canal) that can result in symptoms if they are touched or compressed by a herniated disc are the spinal cord and the nerve roots that exit from the cord. If a portion of an intravertebral disc makes contact with either of these structures, symptoms may result. The symptoms (pain, numbness, etc.) will be related directly to the nerves in the body that are serviced by the particular level of the herniation. c7.jpg (9879 bytes) ..... c8.jpg (11086 bytes) MRI views showing a disc herniation. Note the compression on the cord. Fortunately, nature provides for protection of these structures by a sack of fluid that surrounds the spinal cord, called the "thecal sac" or "subarachnoid space." To picture this, imagine a balloon of water surrounding a pencil, with the pencil being the spinal cord. If a herniated disc makes contact with the balloon (thecal sac) but does not compress the spinal cord or the nerve roots, then there is no significance to the findings, since only direct compression of the cord or nerve roots will result in significant symptoms. The disc must compress the thecal sac enough to cause cord or nerve root compression to be clinically significant. Keep the above overview in mind when you review MRI reports. Bear in mind that it is the radiologist's responsibility to provide a descriptive overview of the condition of the discs and neural structures, as well as providing a summary of the report. As such, it's important to read these reports carefully! For instance, if the report indicates "disc herniation with compression of the cord", this may account for the claimant's symptoms. However, a report that indicates "compression of the thecal sac" but does not indicate cord or nerve root compression does not necessarily imply a symptomatic disc herniation. Studies have shown that a high percentage of the adult population have asymptomatic disc herniations that are not attributable to a particular accident! cervan-1.jpg (12019 bytes) ..... cervani1.jpg (12118 bytes) Models showing normal wear & tear of a disc - notice the amount of normal compression! Another important aspect to consider is degenerative disc disease. As discs age, whether through a natural process or injury, they begin to lose fluid and become dehydrated (or desiccated). When a disc herniation occurs, the dehydration process is increased and that disc will appear degenerative on MRI earlier than it otherwise would. As such, it's important to watch for signs of degenerative disc disease in the radiologist's report which would indicate that a herniation pre-dated the injury. This is indicated by such terms as disc desiccation, disk dehydration, "hard" disc, osteophytes, spondylosis, ridging, etc. c1.jpg (9574 bytes) ... c3.jpg (9506 bytes) ... c2.jpg (10626 bytes) c4.jpg (9432 bytes) ... c5.jpg (8514 bytes) ... c6.jpg (10137 bytes) The above represent normal MRI images. Although there are no hard and fast rules as to how long it takes for a disc to appear degenerative following a herniation, a safe general rule would be a period of 3-10 months. In other words, if an MRI is performed within the first 3 months of an injury, and the disc is degenerative, then it is very likely that this herniation pre-dated the accident. However, if the disc is described as "soft" or non-degenerated during this period, then there is a likelihood of causal relationship between the accident and the herniation. One last important bit of information is that disc bulges are always degenerative and are rarely trauma related! Finally, it's important to point out that "a little knowledge can be dangerous," and MRI's are not fool-proof! We've seen cases where, despite there being NO MRI indication of cord or nerve root compression, the claimant's clinical symptoms and EMG findings indicated a strong possibility of a disc herniation. When that occurs, further testing - such as a CT/Myelogram - may be necessary to confirm or deny the diagnosis. Although it's out of the scope of this overview to comment on other types of tests, suffice it to say that a CT/Myelogram is a more accurate (but also more invasive) test for a disc herniation. Remember that NO competent physician will base surgery solely on MRI findings without clinical correlation and confirmation of a herniated disc! Remember also that an MRI review is only valid to confirm or deny a diagnosis and/or causal relationship. An MRI review, in and of itself, is NOT a reasonable tool to determine if the MRI test was valid and medically necessary! The fact that an MRI is negative does not necessarily imply that the test itself was not medically indicated. If there is a question of denying payment for an MRI (or any other clinical test for that matter) due to lack of medical necessity, that decision must be based on a clinical analysis (either peer review or IME) by an appropriate specialist. On a side note, particularly from an insurance fraud aspect, it is possible to alter EMG findings, but not MRI films (unless a different patient is substituted for the claimant). In questionable cases, it's interesting to note if the EMG was performed BEFORE or AFTER the MRI. EMG's performed prior to an MRI are more reliable, as opposed to EMG's that are performed following an MRI that could be altered to conform to MRI findings. If in doubt, an independent radiological evaluation is strongly suggested! Remember, also, that about 90 percent of patients with acute low back problems recover within 1 month, with only conservative treatment (ie: rest!). Our nurses will be happy to discuss the needs of your file with you in an effort to obtain a cost effective solution. colormri.jpg (83468 bytes) The above is a color cross-section of a cadaver at about the L4-5 level. Compare with the MRI image below: cmriview.jpg (3555 bytes) [INLINE] [INLINE] SUMMARY: [INLINE] Watch for the duration of time between the injury and the MRI. A "soft" disc identified within a few months of the injury may imply causal relationship. However, a "hard", "dessicated" or "dehydrated" disc implies degenerative disease. If this is identified within a few months of the injury, causal relationship is doubtful! [INLINE] Review the terminology of the report carefully. Cord or nerve root compression are significant findings but "compression of the thecal sac" means very little!. [INLINE] Watch for disc herniations at multiple levels. It would be highly unlikely for a typical MVA to result in multiple herniations! An accident serious enough to cause multiple herniations would most assuredly result in other serious injuries and hospitalization. [INLINE] Do NOT schedule an MRI review for the sole purpose of determining if the test itself was medically necessary. The lack of trauma related findings in the MRI does not necessarily imply that the MRI was not medically indicated. Refer to a clinical evaluation (peer review) of the records to make that determination. [INLINE] Home [INLINE] E-Mail to us [INLINE] Top of Page