Mild cognitive impairment (MCI) is considered as a transitional state between normal aging and dementia and can be subdivided into amnestic vs. nonamnestic and single vs. multiple domains types. It is suggested that these clinical subtypes may have different underlying etiologies and outcomes. The amnestic MCI differs in the performance profile on memory testing: retention vs. retrieval deficit. Generally, the retention deficit is attributed to the medial temporal dysfunction and the retrieval deficit to the frontal dysfunction. We tried to determine whether there could be distinctive subtypes available even in the amnestic MCI.

Sixty-two patients with amnestic MCI-single domain were included in this retrospective study. They were divided into the retention- vs. the retrieval-deficit groups according to the results of Seoul Verbal Learning Test (SVLT). We compared baseline characteristics including vascular risk factors and neuropsychological profiles. We also measured the medial temporal atrophy (MTA) using a visual rating scale and assessed lacunar infarcts and white matter hyperintensities (WMH).

Of 62 patients, 41 had retention deficit and 21 had retrieval deficit on SVLT. Among baseline clinical and demographic variables, only the frequency of hypertension was higher in the retrieval-deficit group ( p =0.005). There were no differences in neuropsychological profiles between the two groups other than a lower immediate recall score in the retention-deficit group ( p =0.012) and a higher recognition score in the retrieval-deficit group ( p =0.001). Severities of WMH and MTA were not different between the two groups, nor was the number of lacunar infarcts and microbleeds.

We could not find any significant difference except for the frequency of hypertension between the two subgroups of amnestic MCI, suggesting that there may be no further gain in subdividing a single domain amnestic MCI.