Primary-progressive MS (PPMS) is a form of MS characterized by a gradual, but continuous, worsening of symptoms and disease progression from the beginning, or disease onset. PPMS affects a small percentage (about 10%) of patients diagnosed with MS.
There are usually no exacerbations (relapses, flare-ups, or attacks) with PPMS, but there may be periods of time when the disease appears to be stable. The rate of progression with PPMS (how quickly the patient gets worse) differs from patient to patient, and may fluctuate for the same patient over time.
How is PPMS different from disease courses that involve relapses?
Less inflammation and fewer lesions. In relapsing forms of MS, exacerbations generally involve inflammation attacking myelin. With PPMS, there tends to be less inflammation and fewer lesions (plaques) that form within the brain. Although lesions can occur anywhere along the CNS, in patients with PPMS, lesions tend to be located more in the spinal cord, rather than the brain. Additionally, with PPMS, there tend to be fewer inflammatory cells present in the lesions that do form.
Different rates of diagnosis by gender. Another way that PPMS differs from relapsing MS is how likely it is to be diagnosed in males versus females. PPMS affects males and females in equal numbers, while relapsing MS affects females 2 to 3 times as often as it does males.
Diagnosed later in life. PPMS tends to be diagnosed much later in life than relapsing MS. RRMS is most commonly diagnosed in persons aged 20-50. The average age when patients are diagnosed with PPMS is about 10 years older than with relapsing MS.
Associated with greater disability. Patients who have PPMS typically have greater difficulties with motor function, including walking, and are more likely to require help with daily activities. Patients with PPMS, therefore, are more likely to be unable to continue working than those with relapsing MS.
How is PPMS diagnosed?
For types of relapsing MS, diagnostic criteria (the evidence that must be present to make a diagnosis) require evidence of two or more areas of CNS damage that have occurred at different points in time, without any other explanation.
Due to the fact that CNS inflammation and inflammatory attacks (exacerbations, relapses, or flare-ups) are less likely with PPMS, diagnosis must be made using other criteria. The diagnosis of PPMS can be a slow process as gathering evidence of disease requires more time and effort.
Diagnostic criteria for PPMS include:
1. One or more year in which neurologic symptoms typical of MS get progressively worse; and
2. Two out of three of the following:
- At least nine MS-like brain lesions visible using magnetic resonance imaging (MRI), or four or more MS-like brain lesions and positive results on visual evoked potential (VEP) testing showing impairment of transmission of signals in the optic nerve
- MS-like lesions present on the spinal cord visible using MRI
- Analysis of cerebrospinal fluid (taken by lumbar puncture) showing an abnormal immune response in the CNS typical of MS