Expanded Disability Status Scale (EDSS) | MS Trust

Last updated: 14 October 2024

The Expanded Disability Status Scale measures your current level of disability. Neurologists use it to benchmark and monitor changes in multiple sclerosis. Since MS is a progressive condition, your EDSS is likely to increase over time though most people will not experience the scale’s highest levels of disability.

Developed by neurologist John Kurtzke to replace his Disability Status Scale (DSS), it is a way of measuring disability and progression in multiple sclerosis. The EDSS is also used widely in clinical trials.

Scores are based on examination by a neurologist, and climb by half unit increments from 0 to 10 as your level of disability increases.

These scores apply to those who can walk unaided. They are based on the level of neurological impairment of eight functional systems in your brain. These functional systems are networks of neurons that are responsible for the specific tasks listed below:

These are defined by walking impairment, which is why the EDSS is sometimes criticised for its reliance on just one aspect for its main measure of disability.

Although the scale takes into account disability associated with advanced MS, most people will never reach these scores. If you feel worried about how your MS might progress, a Canadian study may offer some perspective. It took place when the Disability Status Score was still used, before it was replaced by the EDSS in 1983. This large study of people with MS at a clinic in Ontario, found that 51% of people had a Disability Status Score score of five or lower. 88% had a score of seven or lower. Treatment of MS has greatly advanced in the decades since.

The EDSS is the most widely used measure for disability progression in MS. However, this scale has some limitations. EDSS scores can vary due to the complex scoring rules and the subjective nature of the neurological examination. This means that there is a risk that different health professionals might score you differently.

Some critics argue that the changes between steps on the scale are unequal for example 1.0 to 2.0 and 4.0 to 5.0. From level 4.0 upwards the scale focuses on walking ability and underestimates the importance of upper body function. Arm and hand function is vital in self-care and independence. Some functional areas are not assessed in the EDSS, such as mood, energy levels and quality of life. This means that the EDSS is not always a good measure of the impact MS has on you.