Although cognitive impairment is a common feature of multiple sclerosis (MS), there is not a lot of research available on specific cognitive phenotypes. A study categorized MS cognitive phenotypes and found that doing so may help guide treatment decisions and cognitive rehabilitation techniques.
The study population consisted of patients with MS from eight MS centers in Italy and healthy controls. Eligibility criteria for all participants included not using psychoactive drugs as well as no history of other neurological or medical disorders, learning disability, severe head trauma, and alcohol or drug abuse.
There were 1,212 patients with MS (mean age, 41.1 years [standard deviation (SD), 11.1 years]; 784 were female) and 196 healthy controls (mean age, 40.4 years [SD, 8.6 years]; 130 were female).
The researchers established five cognitive phenotypes: preserved cognition (n=235 patients [19.4%]), mild–verbal memory/semantic fluency (n=362 patients [29.9%]), mild–multidomain (n=236 patients [19.5%]), severe–executive/attention (n=167 patients [13.8%]), and severe–multidomain (n=212 patients [17.5%]) involvement. Patients with preserved cognition and mild–verbal memory/semantic fluency were younger (mean age, 36.5 years [SD, 9.8 years] and 38.2 years [SD, 11.1 years], respectively) and had shorter disease duration (mean, 8 years [SD, 7.3 years] and 8.3 years [7.6 years], respectively) than patients with mild–multidomain (mean age, 42.6 years [SD, 11.2 years]; mean disease duration, 12.8 years [SD, 9.6 years]; P<0.001), severe–executive/attention (mean age, 42.9 years [SD, 11.7 years]; mean disease duration, 12.2 years [SD, 9.5 years]; P<0.001), and severe–multidomain (mean age, 44 years [SD, 11.0 years]; mean disease duration, 13.3 years [SD, 10.2 years]; P<0.001) phenotypes. Patients with progressive MS were more likely to have severe cognitive phenotypes.
MRI evaluation found that, when compared with patients with preserved cognition, patients with mild–verbal memory/semantic fluency had lower mean hippocampal volume (5.42 mL vs. 5.13 mL; P=0.04), patients with the mild–multidomain phenotype had decreased mean cortical gray matter volume (687.69 mL vs. 662.59 mL; P=0.02), those with severe–executive/attention had higher mean T2-hyperintense lesion volume (51.33 mL vs. 99.69 mL; P=0.04), and patients with the severe–multidomain phenotype had decreased volume in all brain structures explored (except for nucleus pallidus, amygdala and caudate nucleus).
“These phenotypes can represent a more meaningful measure of the cognitive status of patients with MS and can help define clinical disability, support clinicians in treatment choices, and tailor cognitive rehabilitation strategies,” the study authors concluded.