Poor PASAT performance correlates with MRI contrast enhancement in multiple sclerosis

Cognitive impairment is increasingly recognized as relevant clinical feature in multiple sclerosis (MS). We applied the Paced Auditory Serial Addition Test (PASAT), a recommended screening tool for cognitive dysfunction in MS, to investigate the relationship between cognitive performance and the presence of gadolinium (Gd)-enhancing lesions on brain MRI.

In this longitudinal correlational research study, 75 patients with relapsing-remitting MS (48 women and 27 men, mean age 36 years, mean disease duration 5 years, mean Expanded Disability Status Scale [EDSS] 1.7) without clinical signs of a relapse underwent 2 MRI measurements (number and volume of T1 contrast-enhancing lesions and of T2 lesions) and clinical examinations (EDSS and Multiple Sclerosis Functional Composite [MSFC]) with a mean interscan interval of 10 weeks. Patients were divided into 3 groups: A (n = 38), Gd on 1 scan; B (n = 12), Gd on both scans; and C (n = 25), Gd on neither scan.

In group A, PASAT was better at the Gd-negative time point (p = 0.002), whereas the other MSFC subscores remained unchanged. Subgroup analysis confirmed the finding in patients with a Gd-positive scan first, whereas this was not the case for patients with a Gd-negative scan first, presumably owing to the small sample size of this subgroup. In groups B and C, there was no difference between both time points regarding MSFC and its subscores. EDSS remained stable in all groups during the investigation.

Paced Auditory Serial Addition Test performance is affected by the appearance of Gd enhancement as surrogate marker of inflammatory activity in otherwise physically stable patients with multiple sclerosis, which may indicate that Gd enhancement causes a diffuse impairment of cerebral connectivity with a negative impact on cognitive functioning.