Multiple Sclerosis Research: PPMS v RRMS what's the difference?

PPMS v RRMS what's the difference?

Besides cost effectiveness of treatment and the fact of loads of treatments for RRMS and only 1 (maybe depending where you live) for PPMS

Dastagir A, Healy BC, Chua AS, Chitnis T, Weiner HL, Bakshi R, Tauhid S. Brain and spinal cord MRI lesions in primary progressive vs. relapsing-remitting multiple sclerosis.eNeurologicalSci. 2018;12:42-46

BACKGROUND:Primary progressive (PP) multiple sclerosis (MS) is considered a clinically distinct entity from the spectrum of relapsing-remitting (RR) forms of the disease.
OBJECTIVE:To compare the presence of brain and spinal cord lesions between PP and RR subjects.
METHODS:We studied people with PPMS [n = 40, 17 (42.5%) men, age 50.7 ± 7.7 years, disease duration 10.1 ± 7.4 years, Expanded Disability Status Scale (EDSS) score 4.6 ± 2.1] and RRMS [n = 40, 12 (30%) men, age 47.9 ± 4.2, disease duration 13.7 ± 5.9, EDSS 1.7 ± 1.3]. MRI of the brain and full spinal cord at 1.5T was analyzed to define patients having: 1. brain only, 2. spinal cord only, or 3. brain and spinal cord MS lesions.
RESULTS: Lesions in the brain only were less common in PP (n = 1, 2.5% of people) than RR (n = 10, 25%) (Fisher's exact p = 0.007). Lesions in the spinal cord only (PP: n = 6, 15%, RR: n = 3, 7.5%, p = 0.481) or brain plus spinal cord (PP: n = 33, 83%, RR: n = 27, 68%, p = 0.196) were similar between groups. PP had higher EDSS and timed 25-ft walk (Wilcoxon tests, both p < 0.001), higher age (t-test p = 0.049), lower disease duration (t-test, p = 0.02), and a similar sex ratio (Fisher's exact p = 0.352) vs. RR.
CONCLUSIONS:We report a topographic difference in MRI lesion involvement between PPMS and RRMS. Lesions restricted to the brain are more common in RRMS. These findings provide support to the notion that PP may have features distinctive from the RR spectrum of the disease. Longitudinal comparisons and quantitative MRI analysis would be necessary to confirm and extend these results.

Compare apples with pears and you get a mush. It was published in illogical neuroscience after all :-)

From a pwMS point of view, PPMS and RRMS differ dramatically. The severity of RRMS waxes and wanes, as symptomatic periods alternate with stretches in which the illness appears to fade or even disappear. In contrast, people with PPMS, who account for about 15% of cases, can expect their condition to continually deteriorate.

PPMS and RRMS also diverge in their demographics and response to drugs. When RRMS patients are diagnosed, they are usually in their 20s or 30s, whereas PPMS patients are around 10 years older. Although RRMS is two to three times more common among women than among men, the gender ratio for PPMS is close to 50:50. When researchers have tested anti-inflammatory and immune-modulating drugs that are beneficial for RRMS they’ve detected little effect on PPMS

Despite these disparities, in some ways PPMS and RRMS are indistinguishable. For example, studies have reported that they overlap in characteristics such as the amount of demyelination and remyelination, the number of cortical lesions, and the extent of acute axon damage

Researchers haven’t been able to pinpoint any imaging finding or pathological change that distinguishes PPMS from RRMS. Under the microscope or in MRI, they look the same. The convergence between the two MS forms also extends to susceptibility genes.

The 1.5-tesla and 3-T MRI scanners used in hospitals and most studies can’t reveal as much detail as ultrahigh-field 7-T MRI scanners, where it was concluded that PPMS and RRMS belong to the same disease spectrum.