Cerebral metabolic alterations and cognitive dysfunction in chronic kidney disease

The diagnosis of uraemic encephalopathy is considered if patients with end-stage renal disease present with neuropsychiatric symptoms. However, cognitive deficits may occur in patients with chronic kidney disease (CKD) long before any overt neurological symptoms can be observed. We hypothesized that cognitive dysfunction in patients with CKD both, treated and untreated by haemodialysis, may correspond to metabolic changes in distinct brain regions.

We performed magnetic resonance spectroscopy (MRS) ((1)H-MRS) of the brain in 23 non-dialysed patients with CKD (Stages 4-5) and in 15 haemodialysed patients. Healthy controls (n = 63) adjusted for age and education were recruited from the social environment of the patients' population. Attention, learning and memory were assessed by psychometric testing.

MRS alterations were predominantly found in the white matter. Concentrations of creatine-containing compounds (Cr) were decreased in dialysed and non-dialysed patients. Choline concentration (Cho) and combined N-acetylaspartate and N-acetylaspartylglutamate concentration (NAx) were reduced only in dialysed patients. Disturbance in memory and learning ability as well as attention deficits were observed in both patient groups. Of note, attention deficits were more severe in dialysed patients. MRS results correlated with attention deficits in dialysed patients.

CKD patients without clinical signs of uraemic encephalopathy showed metabolic disturbances in distinct brain regions as well as cognitive impairments. Haemodialysis was accompanied with more severe cognitive dysfunction and metabolic alternations than CKD alone. Although the small sample size limits the interpretation of the data, a negative impact of haemodialysis on cognitive function must be considered.