Hippocampal proton MR spectroscopy as a novel approach in the assessment of radiation injury and the correlation to neurocognitive function impairment: initial experiences

Abstract

BackgroundThe 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 1H-MR spectroscopy focused on the hippocampus.MethodsPatients with brain metastases underwent whole brain radiotherapy (WBRT) to a dose of 30 Gy in ten fractions daily. Pre-radiotherapy 1H-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.ResultsOf 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.ConclusionsA significant decrease in h-tNAA after WBRT was proven by 1H-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.

The positive effects of high-frequency right dorsolateral prefrontal cortex repetitive transcranial magnetic stimulation on memory, correlated with increases in brain metabolites detected by proton magnetic resonance spectroscopy in recently detoxified alcohol-dependent patients

“…1 H-MRS has been used to evaluate hippocampal brain metabolites in various populations, including patients with mild cognitive impairment, 17 patients with Alzheimer’s disease, 18 cognitively normal older adults, 19 and patients receiving whole brain radiotherapy. 20 Results of these studies show hippocampal brain metabolites to be reliable preclinical markers of cognitive and memory function.…”

Correlation of Magnetic Resonance Spectroscopy Changes in Hippocampal and Perihippocampal Regions and Neuro-Psychologic Evaluation with Various Clinical Factors Following Whole Brain Radiotherapy in Brain Metastasis

“…Hippocampal avoidance WBRT (HA-WBRT) has been the most widely accepted used method to mitigate the adverse neuro-psychologic effects of WBRT (15)(16)(17). It is however essential to understand the basis of patient selection for HA-WBRT (18,19).…”

Hippocampal sparing in brain radiotherapy

“…It is finally worth mentioning about the search for objective methods for assessing cognitive impairment in patients with post-cerebral RT. In a proton MR spectroscopy study on patients that had undergone WBRT 4 months earlier, reduced concentrations of N-acetylaspartate were noted; this being a metabolite of nerve tissue from the hippocampal region [87]. Another study using MR spectroscopy found sub-acute radiation damage to nerve tissue after a month post-WBRT [88].…”