MS outcomes are highly individualized and characterized per the disease subtype.
About 15% of patients will never necessitate assistance with ambulation, while 5-10% will do so within 5 years, and another 10% will do so in 15 years.
Average patient will take about 28 years from the point of diagnosis to necessitate assistance while walking, and will be about 60 years of age.
The rate of disability of MS is slowing down with the advent of science and new treatment options since the late 20th century.
Multiple Sclerosis & Disability
Multiple Sclerosis (MS) is considered the most common disabling disease of young adults. However, when it comes to MS, there is no one-size-fits-all, that is every patient has a different disease course with differing speeds and rates of disability. These differing disease courses are generalized as Relapsing-Remitting MS, Secondary Progressive MS, and Primary Progressive MS.
Relapsing-Remitting MS is the most common MS type, and as can be deduced by its name, it progresses with attacks with incomplete to full recovery. The attacks typically peak within days to weeks, but shattering attacks leading to permanent disability are rare. Of note, one study on more than a thousand patients showed 2587 attacks, however only 7 patients with an attack that resulted in permanent use of a cane, crutch or brace.
Secondary Progressive MS
Secondary progressive MS starts as relapsing-remitting MS, however instead of attacks, there’s gradual worsening of deficits. There are no initial criteria to differentiate secondary progressive from relapsing-remitting MS and the diagnosis is made retrospectively. Studies have shown this transition to typically occur between 10 to 20 years after disease onset.
Primary Progressive MS
This form of MS is defined by progressive accumulation of disability from the get go. There may be brief improvements and acute attacks but the disability will worsen over time with asymmetric spastic paraparesis (partial paralysis of lower limbs) and without a defined sensory level.
How is Disability Measured in MS?
The most commonly used scales to measure disability within the context of MS are the Kurtzke Disability Scale, aka Disability Status Scale (DSS) and the expanded version of it, i.e., Expanded Disability Status Scale (EDSS). Both scales define no disability with a 0 and death due to MS with a 10, however the progression is not linear.
Studies have shown that these scales have bimodal distributions among large numbers of patients, meaning peaks at value 1 (no disability and minimal neurological signs) and 6 (meaning assistance or cane necessity for ambulation). Furthermore, the median time spent with a DSS of 4 or 5 was one and a half years compared with median time at DSS 1 of four years and DSS six of three years.
Speed of Disability
The worsening of disability is highly individualized, however is still categorized within the MS subtypes. The good news is that studies show that most patients have slow rates of worsening. A large study from Canada that followed more than 2000 patients for more than 22000 patient years showed that it took almost 28 years as median for patients from disease onset to reach EDSS 6, i.e., no longer ambulatory without cane/assistance, the median age of EDSS 6 was 59 years. As expected, the primary progressive disease had faster disease progression.
Interestingly, adult males progressed to cane necessity faster, however, the age of requiring a cane was similar for both males and females, 59 years for former and 60 years for latter. Younger age at diagnosis was associated with a slower progression but patients that were diagnosed later were also older when they progressed to EDSS 6.
Aggressive (Malignant) MS
Unfortunately, some patients have MS that is extremely rapidly progressive, termed aggressive MS. Studies have shown us that about 5-10% of MS patients will have such a course and will need assistance with ambulation, i.e., EDSS 6 within 5 years of initial diagnosis.
On the contrary, some patients still retain almost full neurological function at least for 15 years after initial diagnosis and such disease course is termed benign MS. Studies have demonstrated that about 15% of patients will have such disease and will have EDSS scores less than 3.
Studies from the early 1990s have consistently found MS to be much more rapidly progressive than studies conducted today. For example, a 25-year-long study finalized in 1993 elucidated that 50% of patients reaching EDSS 6 within 16 years of diagnosis, compared with a study from 2016 showing only 11% reaching EDSS 6 within that same time frame, meaning only 11% would need assistance walking or a wheelchair 16 years post-diagnosis. A most likely explanation is that the newer medications termed disease-modifying therapies, introduced in the early 2000s have had extremely beneficial effects on long-term outcomes. Thus, time is your friend with MS, and the better we get at researching new treatment options, the better the outcomes will be in the future.