Question: Would you please share your opinions about the determination of "MMI" (maximal medical improvement)?" We often hear clinicians and case managers use this phrase but patients-as well as clinicians-seldom seem to understand what it really means.
Answer: Brain Injury Source, Ask the Doctor
By Nathan D. Zasler, MD, FAAPM&R, FAADEP, DAAPM, CIME
Would you please share your opinions about the determination of "MMI" (maximal medical improvement)?" We often hear clinicians and case managers use this phrase but patients-as well as clinicians-seldom seem to understand what it really means.
The issue of maximal medical improvement (MMI) comes up in many different contexts. Often, in a Workers Compensation case or medicolegal context, it may be one of the most important issues in determining someone's ability to return to employment and/or make determinations regarding the permanency of a given condition.
MMI is a term that is used very specifically in the American Medical Association's (AMA's) Guides to the Evaluation of Permanent Impairment. In the typical context in which it is used in clinical settings, it generally is not used in a parallel fashion to that espoused by the AMA Guides. Specifically, in the Guides, MMI is defined as that point in time at which an impairment is not expected to change by more than 3% over the ensuing year for the whole body impairment rating. Unfortunately, many clinicians come up with rather arbitrary definitions to MMI when using the AMA Guides. As an example, I have seen and heard people define MMI in the context of AMA impairment rating as that point in time at which no further (e.g., 0%) change in the impairment rating is anticipated after one year, or no significant (however that is defined) change in impairment is expected from that point forward. Just exactly how one is supposed to determine when using the AMA Impairment Rating System that someone has reached MMI certainly could be questioned. How do you know that someone is not going to make more than a 3% change in total body impairment rating, as opposed to a 4%, 5% or 10% change over the ensuing year? It is necessary for clinicians and lawyers to understand that this percentage change was arbitrarily set, based solely on consensus opinion and not on any sound scientific methodology (which can be said as well for the AMA Guides as a whole).
In a clinical context, MMI typically refers to that point in time at which one can say with a degree of medical probability that an individual's condition (e.g., his/her impairment) will not change significantly. Clearly, such a statement has a large margin of error, on at least two potential levels. On one level, one is stating with a degree of medical probability that someone's condition likely will not change; that is, there is a 51% chance or more that the condition is stable. That means, that if your lowest level of "certainty" is 51%, you have a 49% chance of being incorrect. Additionally, if one states that the condition will not change significantly, then one has the additional factor of how "significantly" is defined. Relative terms have the propensity to be vague and one always should try and obtain some level of quantification. What may be "significant" to one person may not be significant to another.
Another issue that I see often oversimplified is the medicolegal question of whether someone is at MMI. When this question is asked generally rather than specifically, much detail will be lost in the process. Without looking specifically at what an individual's various impairments are and the recovery timeframe for those impairments, making a global MMI statement will tend to produce an overly convergent analysis of the case in question. An example of this might be a person who has been in a multi-trauma crash, sustaining a severe traumatic brain injury with diffuse axonal injury, smell loss, conductive hearing loss, benign paroxysmal positional vertigo and multiple extremity fractures. The recovery timeframe for these various post-traumatic sequelae is different; simply to assume that MMI is reached at the same time for all these different conditions would be erroneous. More specifically, recent literature suggests that following severe traumatic brain injury where the primary neuropathology is diffuse injury, the individual may continue to make ongoing and significant neurological improvement for at least three to five years post-injury. If related to the damage of cranial nerve one, anosmia following traumatic brain injury typically plateaus-at least in terms of its recovery-by six months post-injury. If given enough time (e.g., one to two years), benign paroxysmal positional vertigo most often resolves on its own. As a rule, conductive hearing loss improves over time, typically stabilizing between six and twelve months post-injury. In most cases and assuming there are no significant associated complications of fracture healing, extremity fractures reach MMI much earlier than any of the aforementioned neurological conditions. In conclusion, it is of utmost importance to break down any analysis of post-injury impairment relative to a MMI analysis.
Both common logic and the AMA Guides dictate it also is of utmost importance to understand that impairments cannot be rated until such time as it is deemed that the individual has received appropriate treatment to optimize recovery of any post-injury impairment. If an individual has an affective disorder (i.e., post-traumatic-stress disorder or an organic affective disorder such as depression) as a result of a traumatic life event, one cannot rate the impairment until such time as appropriate psychopharmacologic and psychotherapeutic interventions have been carried out to optimize these psychoemotional conditions.
Although it is not probably a standard practice, I always like to differentiate between MMI as it relates to the impairment level versus the functional level of the individual. For example, someone may have reached MMI with regard to recovery from a stroke or traumatic brain injury but not have reached MMI with regards to his/her ability to cope with that impairment on a functional level. There certainly are cases where an individual has not received appropriate rehabilitation and can, therefore, improve functionally, even though his/her neurologic condition remains static (e.g., his/her impairment rating would not change but his/her disability level might).
All these issues are important to take into consideration when looking at MMI. This is a very important issue in the context of clinical care as it relates to ascertaining ongoing provision of medical and rehabilitation services for people with neurologic injuries. Clearly, it also is an important workers' compensation and/or forensic issue that must be understood in its entirety by clinicians and lawyers alike.
Thanks again for your question.
Nathan D. Zasler, MD, FAAPM&R, FAADEP, DAAPM, CIME, is an internationally respected specialist in brain injury care and rehabilitation. Dr. Zasler is medical director of the Concussion Care Centre of Virginia, Ltd. and is involved with several brain injury rehabilitation programs in the Richmond, Virginia area, including Tree of Life, LLC, a living assistance program for persons with acquired brain injury. Dr. Zasler has lectured and written extensively on neurologic issues with over 500 lectures and publications, including two edited textbooks. Dr. Zasler is a member of numerous editorial boards and is editor-in-chief of the international scientific publication Neurorehabilitation: An Interdisciplinary Journal. He is active in numerous national and international organizations including serving on the Board of Governors of the International Brain Injury Association. He is also grant reviewer for several federal agencies and serves on the Advisory Board for the Department of Head Injury Program. His main areas of interest include low-level neurologic states after brain injury, post-concussive disorders and neuromedical issues in acquired brain injury.