Multiple sclerosis, or MS for short, is the most common autoimmune disorder affecting the central nervous system as well as the most common cause of disability in young adults.
As the central nervous system is in charge of various functions such as movement, cognition or homeostasis of bodily functions, MS can present with differing symptoms to differing degrees.
MS can also be considered the umbrella term covering three main disease subtypes, all with varying prognoses and outcomes: relapsing-remitting MS, secondary progressive MS, primary progressive MS. Thus, it is hard to prognosticate MS without factoring in patient specific characteristics.
Prognosis in general
MS is a progressive disease; thus, the question is the rate of progression and disability.
Most studies have shown that the worsening of neurological function and disability is slow in most patients.
As expected, with the advent of newer treatments, such as the disease modifying therapies, and better understanding of the disease, the progression of MS is being slowed down. A 25-year follow up study done in 1993 showed that more than 50% of patients were using a cane or similar in ambulation at 16 years post diagnosis vs. 11% in a study from 2016 at 17 years post diagnosis.
Although MS is progressive over long periods of time, particularly in well-managed disease, it is still debilitating and has been associated with reductions in life expectancy, particularly after years of disease.
A meta-analysis to that extent done on over 28000 patients with MS elucidated that compared with the general population, patients with MS had a 2.8 times higher mortality ratio mainly due to infections and suicide.
Interestingly, a French study covering 18 MS centers with over 37000 patients identified no excess mortality within the first 10 years of the diagnosis. The excess deaths started thereafter and continued until age 70, whereby they normalized. i.e. After 70 years of age, MS was no longer a factor in excess mortality.
The difficulties in prognosticating MS lie in the individualized outcomes of the patients. Some patients respond well to treatment, where others don’t, some patients have extremely benign courses, where others become disabled rapidly. As such, relapsing-remitting MS is typically associated with better prognosis compared to progressive types.
Additionally, early disease course and extent of symptoms at the onset of disease are considered strong prognostic factors predicting long-term disability. Patients that had strong early attacks and did not recover from them, or had a shorter interval until their second attack had worse outcomes with poorer prognosis in several studies.
Classically derived prognostic factors that have been identified with favorable outcomes such as optic neuritis or unfavorable outcomes such as brainstem or cerebellar symptoms, have all been recently shown by studies to not be independent prognostic factors, but either covered under disease subtypes or extent of disease at onset.
Demographically, there are some racial differences in prognosis. Although African Americans are diagnosed with MS at later ages, they are at increased risk of developing ambulatory disability compared to Caucasians.
Although females are at increased risk for MS, gender does not seem to influence the outcomes from the disease. Several studies have shown that sex was not a prognostic factor for outcomes, however, there are also some studies demonstrating that male sex was associated with a faster disability progression. Thus, until data is clearer, gender is not considered to be of prognostic value.
One would expect age to be a prognostic value, as the earlier the diagnosis, the longer the lifespan with the disease. However, some studies have shown that diagnosis at an older age was associated with faster onset of disability. Though the jury is still out whether age represents a true prognostic factor or not.
Tools to help with prognosis
MRI is the cornerstone of diagnosis, management as well as prognostication, i.e. prediction of development, disability and progression, of MS. In this context, several studies have demonstrated that the bigger the lesion load and the worse the cerebral atrophy, the worse prognosis there is.
However, this prognostication seems to be particularly valuable at the onset of diagnosis as several other studies have demonstrated that the more advanced the disease, the less correlation there is between MRI findings concerning the lesion load and outcomes such as degree of disability and speed of progression.
Ultimately, the location of the MRI findings is also as important as the degree, as a small lesion in a critical area may lead to a much more severe disability then a large lesion in a non-critical area. Thus, the MRI findings and their association with outcomes and prognosis need to be taken with a grain of salt.
It is nearly impossible to prognosticate outcomes of MS without considering patient specific factors, as the disease plays out differently in everyone.
The treatment response as well as the extent of disease early in the disease course will give information about how fast the disease will progress.
Ultimately, MS is not necessarily fatal, however, studies have demonstrated that patients with MS have somewhat lowered life expectancies.
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