The Expanded Disability Status Scale (EDSS) is a rating system that is frequently used for classifying and standardizing the condition of people with multiple sclerosis (MS). While it has many shortcomings and is complicated to use and understand, I think it is important that people with MS at least know what it is and how it is applied, as this is an important tool in clinical trials – both to determine who can participate as well as in reporting results.
I chose to include the whole scale, rather than condensing it, both to illustrate the complexity of the EDSS, as well as to provide a tool to allow you to interpret findings such as, “the average patient in the trial started with a disability score of 3.5 and after two years of treatment progressed an average of 1.5 points on the EDSS.”
How Is an EDSS Score Calculated?The score is based upon neurological testing and examination of functional systems (FS), which are areas of the central nervous system which control bodily functions. The functional systems are:
- Pyramidal (ability to walk)
- Cerebellar (coordination)
- Brain stem (speech and swallowing)
- Sensory (touch and pain)
- Bowel and bladder functions
- Other (includes any other neurological findings due to MS)
The Expanded Disability Status Scale (EDSS)0.0: Normal neurological exam.
1.0: No disability, but minimal signs in one functional system (FS) are present.
1.5: No disability, but minimal signs in more than one FS are present.
2.0: Minimal disability in one FS is present.
2.5: There is mild disability in one FS or minimal disability in two FS.
3.0: There is moderate disability in one FS or mild disability in three or four FS. However, the person is still fully ambulatory.
3.5: The person is fully ambulatory, but has moderate disability in one FS and mild disability in one or two FS; or moderate disability in two FS; or mild disability in five FS.
4.0: The person is fully ambulatory without aid, and is up and about most of the day (12 hours) despite relatively severe disability. He or she is able to walk 500 meters without aid or rest.
4.5: The person is fully ambulatory without aid, and is up and about much of day. He or she is able to work a full day, but may otherwise have some limitations of full activity or require minimal assistance. This is considered relatively severe disability. Able to walk 300 meters without aid.
5.0: The person is able to walk 200 meters without aid or rest. Disability impairs full daily activities, such as working a full day without special provisions.
5.5: The person is able to walk 100 meters without aid or rest. Disability precludes full daily activities.
6.0: The person needs intermittent or unilateral constant assistance (cane, crutch or brace) to walk 100 meters with or without resting.
6.5: The person needs constant bilateral support (cane, crutch or braces) to walk 20 meters without resting.
7.0: The person is unable to walk beyond five meters even with aid, and is essentially restricted to a wheelchair. However, he or she wheels self and transfers alone, and is active in wheelchair about 12 hours a day.
7.5: The person is unable to take more than a few steps and is restricted to wheelchair, and may need aid to transfer. He or she wheels self, but may require a motorized chair for a full day's activities.
8.0: The person is essentially restricted to bed, a chair or a wheelchair, but may be out of bed much of day. He or she retains self care functions and has generally effective use of arms.
8.5: The person is essentially restricted to bed much of day, but has some effective use of arms and retains some self care functions.
9.0: The person is confined to bed, but still able to communicate and eat.
9.5: The person is totally helpless and bedridden and is unable to communicate effectively or eat and swallow.
10.0: Death due to MS.
Disadvantages of Using the EDSS for MSResearchers and experts have noted the following shortcomings of the EDSS to characterize MS patients and their disease progression:
- The EDSS places too much emphasis on ability to walk.
- It is insensitive to cognitive dysfunction in MS (like most scales based on a standard neurological exam).
- Calculating EDSS scores is complicated, as the rules for how to rate findings on the neurological exam and translating these into scores on the functional system status are ambiguous and complex.
- Because of the way the scale is designed (see preceding points), it is not sensitive to many clinical changes that a person with MS experiences, and people seem to “jump” from one part of the scale to another, rather than exhibiting a smooth decline.
Additional PointsIt is possible to move back and forth on the scale. For instance, a fully functional patient with sensory symptoms might have an EDSS score of 1.0 most of the time. A relapse involving optic neuritis could bump their score up to a 3.0 until they were treated or the symptoms remitted on their own. They would then move back down to a 1.0 (or a 1.5 if there were some lingering symptoms).
While most neurologists do not formally use EDDS scores to monitor patients, my neurologist told me that he watched approximate disability scores to determine when to take action, such as Solu-Medrol treatment or whether physical therapy was warranted.
Kurtzke, Neurology, 1983, 33:1444-52.
Kurtzke, Neurology, 1983, 33:1444-52.