BACKGROUND: The hippocampus is considered as the main radiosensitive brain structure responsible for postradiotherapy cognitive decline. We prospectively assessed correlation of memory change to hippocampal N-acetylaspartate (h-tNAA) concentration, a neuronal density and viability marker, by (1)H-MR spectroscopy focused on the hippocampus. METHODS: Patients with brain metastases underwent whole brain radiotherapy (WBRT) to a dose of 30 Gy in ten fractions daily. Pre-radiotherapy (1)H-MR spectroscopy focused on the h-tNAA concentration and memory testing was performed. Memory was evaluated by Auditory Verbal Learning Test (AVLT) and Brief Visuospatial Memory Test-Revised (BVMT-R). Total recall, recognition and delayed recall were reported. The both investigation procedures were repeated 4 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 after WBRT, respectively. In the memory tests a significant decrease was observed in AVLT total-recall, BVMT-R total-recall and BVMT-R delayed-recall. Weak to moderate correlations were observed between left h-tNAA and AVLT recognition and all BVMT-R subtests and between the right h-tNAA and AVLT total-recall. CONCLUSIONS: A significant decrease in h-tNAA after WBRT was proven by (1)H-MR spectroscopy as a feasible method for the in vivo investigation of radiation injury. Continuing patient recruitment focusing on other cognitive tests and metabolites is needed.

Department of Neurosurgery St Anne's University Hospital Brno Faculty of Medicine Masaryk University Kamenice 5 625 00 Brno Czech Republic Department of Neurosurgery St Anne's University Hospital Brno Pekarska 53 656 91 Brno Czech Republic

Department of Radiation Oncology Faculty of Medicine Masaryk University Kamenice 5 625 00 Brno Czech Republic Department of Radiation Oncology Masaryk Memorial Cancer Institute Zluty kopec 7 656 53 Brno Czech Republic

Department of Radiation Oncology Faculty of Medicine Masaryk University Kamenice 5 625 00 Brno Czech Republic Department of Radiation Oncology Masaryk Memorial Cancer Institute Zluty kopec 7 656 53 Brno Czech Republic International Clinical Research Center St Anne's University Hospital Brno Pekarska 53 656 91 Brno Czech Republic

International Clinical Research Center St Anne's University Hospital Brno Pekarska 53 656 91 Brno Czech Republic Department of Clinical Psychology St Anne's University Hospital Brno Pekarska 53 Brno Czech Republic

International Clinical Research Center St Anne's University Hospital Brno Pekarska 53 656 91 Brno Czech Republic Department of Diagnostic Imaging Faculty of Medicine Masaryk University Kamenice 5 625 00 Brno Czech Republic Department of Diagnostic Imaging St Anne's University Hospital Brno Pekarska 53 656 91 Brno Czech Republic

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