BACKGROUND: The hippocampus is considered as the main radiosensitive brain structure responsible for postradiotherapy cognitive decline. We prospectively assessed correlation between memory change and hippocampal N-acetylaspartate (h-tNAA) concentration, a neuronal density and viability marker, measured by 1H-MR spectroscopy (MRS). METHODS: Patients with brain metastases underwent pre-radiotherapy (WBRT, 10x3.0Gy) MRS focused on the h-tNAA concentration and memory testing by Auditory Verbal Learning Test (AVLT) and Brief Visuospatial Memory Test-Revised (BVMT-R) was performed. The both procedures were repeated four months after WBRT and the h-tNAA and memory changes were correlated. RESULTS: Of the 20 patients, ten passed whole protocol. The h-tNAA concentration significantly decreased from pre-WBRT 8.9, 8.86 and 8.88 [mM] in the right, left and both hippocampi to 7.16, 7.65 and 7.4, respectively. In the memory tests a significant decrease was observed in AVLT_total-recall, BVMT-R_total-recall and BVMT-R_delayed-recall. The trend toward correlation was between the decreases in the left h-tNAA and BVMT-R_delayed-recall (p = 0.096) and between the right h-tNAA and AVLT_total-recall (p = 0.0885). CONCLUSIONS: A significant post-WBRT decrease in h-tNAA was proven by MRS as a feasible method for the in vivo investigation of radiation injury. Continuing recruitment focusing on other cognitive tests and metabolites is needed. Supported by grants IGA NT/14600, NT/14120 of the Czech Ministry of Health.