Cognition (thinking, memory and learning) is known to be affected in MS. This is more so in progressive MS.
In a study last year, it was found that those with more structural damage to the brain at baseline were more likely to have cognitive issues. And more likely that not cognitive issues were encountered if the brain cortex was involved (the area comprised of the surface of the brain where cell bodies of neurons sit, i.e. the nerve center).
So if the cortex and cognition are so closely inter-linked, it then begs the question whether accelerated cortical volume loss may also accelerate the rate of cognitive decline?
According to the team in Amsterdam, this is a yes.
In a prospective study of 230 PwMS (179 relapsing-remitting and 51 progressive MS), they discovered that cortical volume loss was faster in progressive MS and converting relapsing-remitting MS, than stable relapsing-remitting MS.
Moreover, those with progressive MS there was a 3x greater likelihood of cognitive decline per year compared to stable relapsing-remitting MS (see Figure 1 below). In other words, as MS evolves both cortical volume loss and cognitive decline accelerate over time.
What about other brain areas?
Interestingly, in those with stable MS, cognitive decline was related to yearly increase in lesion size. But not to volume loss in the deep brain (deep grey matter) or cortex. Whilst, in those converting from relapsing-remitting MS, the decline correlated with yearly loss in the deep grey matter only. And finally, in progressive MS cognitive decline correlated with only cortical volume loss.
Clearly, based on these study findings the substrate for cognitive decline in the different sub-types of MS differs, and it would be important to target these areas. Until then cognition will remain a silent victim in MS.
Cortical atrophy accelerates as cognitive decline worsens in multiple sclerosis
Anand J.C. Eijlers, Iris Dekker, Martijn D. Steenwijk, Kim A. Meijer, Hanneke E. Hulst, Petra J.W. Pouwels, Bernard M.J. Uitdehaag, Frederik Barkhof, Hugo Vrenken, Menno M. Schoonheim, Jeroen J.G. Geurts
Objective To determine which pathologic process could be responsible for the acceleration of cognitive decline during the course of multiple sclerosis (MS), using longitudinal structural MRI, which was related to cognitive decline in relapsing-remitting MS (RRMS) and progressive MS (PMS).
Methods A prospective cohort of 230 patients with MS (179 RRMS and 51 PMS) and 59 healthy controls was evaluated twice with 5-year (mean 4.9, SD 0.94) interval during which 22 patients with RRMS converted to PMS. Annual rates of cortical and deep gray matter atrophy as well as lesion volume increase were computed on longitudinal (3T) MRI data and correlated to the annual rate of cognitive decline as measured using an extensive cognitive evaluation at both time points.
Results The deep gray matter atrophy rate did not differ between PMS and RRMS (−0.82%/year vs −0.71%/year, p = 0.11), while faster cortical atrophy was observed in PMS (−0.87%/year vs −0.48%/year, p < 0.01). Similarly, faster cognitive decline was observed in PMS compared to RRMS (p < 0.01). Annual cognitive decline was related to the rate of annual lesion volume increase in stable RRMS (r = −0.17, p = 0.03) to the rate of annual deep gray matter atrophy in converting RRMS (r = 0.50, p = 0.02) and annual cortical atrophy in PMS (r = 0.35, p = 0.01).
Conclusions These results indicate that cortical atrophy and cognitive decline accelerate together during the course of MS. Substrates of cognitive decline shifted from worsening lesional pathology in stable RRMS to deep gray matter atrophy in converting RRMS and to accelerated cortical atrophy in PMS only.