MR spectroscopy changes and neuropsychometric deficits in patients with renal insufficiency

Introduction: Uremic encephalopathy is normally diagnosed by neurological deficits in patients with chronic renal insufficiency. However, neuropsychological deficits may occur long before any overt neurological symptoms can be observed. Little is known about the underlying brain pathology of patients suffering from uremic encephalopathy. We hypothesized that cognitive deficits present in patients with renal insufficiency treated with and without hemodialysis may correspond to neurometabolite changes in distinct brain regions.

Methods: We performed MR-spectrometry in 23 non-dialyzed patients with chronic renal insufficiency (GFR<50ml/min/1.73m2) and 15 hemodialyzed patients. Healthy controls (n=28) were recruited from the social environment of the patient population. Attention, learning and memory, intelligence and executive function were assessed by neuropsychometric testing.

Results: Metabolite alterations predominantly occurred in the posterior white matter. In non-dialyzed patients as well as in dialyzed patients a decrease of creatine was observed. In addition N-acetylaspartate/N-acetylasparteglutamate and choline reduction was measured in dialyzed patients. We found disturbances in intelligence, memory, learning ability and executive function. Patients on hemodialysis in addition showed an impairment of attention, but the overall cognitive performance was higher in this group. MR-spectroscopic changes correlated with memory difficulties in non-dialyzed patients and with attention deficits in dialyzed patients.

Conclusion: Patients with renal insufficiency without overt clinical signs of uremic encephalopathy show metabolic disturbances in distinct brain regions as well as cognitive impairments. The majority of neuropsychological deficits improved on dialysis therapy implying a beneficial effect of early dialysis treatment on cognitive performance.