In a study that had a 5-year follow-up, hippocampal volume (HV) was shown to be correlated with elevated risk in a cohort of elderly patients with mild cognitive impairment. Individuals who developed dementia had a smaller HV at baseline.

Patients with minimal cognitive impairment (MCI) as identified by the Clinical Dementia Rating scale (CDR) are known to have a conversion rate to dementia of 20%. The CDR Sum of Boxes score (CDR-SB; range 0–18) enables a quantitative evaluation of that impairment. To evaluate HV as a predictor of conversion, this study assessed 28 elderly patients who had a range of impairment at baseline. Impairment was gauged with the instruments of CDR-SB, MMSE (mini mental state examination), and ADAS-cog (Alzheimer assessment scale). Based on these outcomes, patients were stratified as follows:

• CDR=0 (thus CDR-SB=0) = low risk

• CDR=0.5 and CDR-SB=0.5, 1, or 1.5 = medium risk

• CDR=0.5 and CDR-SB=2, 2.5, or 3 = high risk

Hippocampal volume was determined with a brain MRI within a maximum 4-month period after the initial neuropsychological evaluation. Scans were performed with a GE 1.5 Telsa scanner; imaging data were analyzed with Brains 2 software.

Results showed that HV was significantly smaller in high-risk individuals (0.21±0.014) as compared with individuals who were considered to be at low risk (0.28±0.033) or medium risk (0.26±0.037; p<0.001 for both). Those who went on to develop dementia two years before the final neuropsychological assessment had a smaller mean HV at baseline than those who did not (p=0.02); however, after receiver operating characteristic analysis was performed, no discrete HV value emerged as being useful to discriminate between the two groups. The HV correlated negatively with CDR-SB but did not correlate with age or years of education. The finding that individuals who developed dementia had smaller HV at baseline supports the theory that HV may be an important predictor of conversion.