P2–324: Greater frontal than cingulate magnetic resonance spectroscopy abnormalities in early Alzheimer's disease

Recently there has been a great emphasis put on finding early imaging markers for Alzheimer's Disease (AD). In previous imaging studies, abnormal magnetic resonance spectroscopic signals have been found to be limited to the posterior cingulate regions (Kantarci et al, 2000). These studies did not examine other cortical areas. In early AD, executive function has been shown to be deteriorated when compared to normal age matched subjects. We hypothesized that frontal metabolic abnormalities demonstrated by magnetic resonance spectroscopy (MRS) might actually exceed those demonstrated for posterior cingulated cortex. MRS was performed in the left Brodman area (Ba) 44 (inferior frontal gyrus), left Ba 37 (posterior temporal), and left precuneus (this included the mid posterior cingulate gyrus and precuneus areas) in 10 normal elderly controls (NEC) (mean age = 77.9, 4M : 6F, mean MMSE = 27.56) and 6 mild AD patients (mean age = 81.5, 5M : 1F, mean MMSE = 24.00). The N–acetylaspartate and N–acetylaspartylglutamate (NAA+NAAG) / Creatine (Cr) ratios were calculated for these three areas. There was no significant difference found in the Ba 37 region between normal and AD subjects. The precuneus area had minimal significance (p<0.061). The Ba 44 region showed the most significant (p<0.01) difference between AD patients and NEC subjects. MRS performed in the frontal area might demonstrate earlier changes in mild AD patients and may prove to be useful in prognostication. Frontal cortex MRS should be assessed in a pre–dementia state such as Mild Cognitive Impairment (MCI).