Cognitive function in primary progressive and transitional progressive multiple sclerosis - A controlled study with MRI correlates

The relative rarity of primary progressive (PP) and transitional progressiv e (TP) multiple sclerosis has meant that little documentation of cognitive function in such patients is currently available. The aim of this study was to investigate the cognitive skills of patients with PP and TP multiple sc lerosis relative to matched healthy controls, and to examine the relationsh ip of this impairment to MRI parameters, Sixty-three patients (43 PP, 20 TP ) were individually matched with healthy controls, who undertook the same c ognitive tasks as the patient group. The neuropsychological assessment comp rised Rao's brief repeatable battery, a reasoning test, and a measure of de pression. Patients also underwent T-1- and T-2-weighted brain MRI, These pa tients were taken from ar larger cohort (158 PP, 33 TP) in whom it had been demonstrated that there were no significant differences between the mean s cores of the PP and TP groups on any of the cognitive variables. The 63 pat ients were therefore taken as one group for comparison with the healthy con trols, These patients performed significantly worse than the controls in te sts of verbal memory, attention, verbal fluency and spatial reasoning. An i mpairment index was constructed and applied to the patient data. This corre lated modestly with T-2-lesion load (r = 0.45, P = 0.01), T-1-hypointensity load (r = 0.45, P = 0.01) and cerebral volume (r = -0.35, P = 0.01), Thus, PP and TP multiple sclerosis patients demonstrate significant cognitive dy sfunction when compared with matched healthy controls, The relationship bet ween this impairment and MRI parameters is moderate, suggesting that cognit ive dysfunction in PP and TP multiple sclerosis has a complex and multifact orial aetiology, which is not adequately explained by pathology as demonstr ated on conventional MRI.