Structural MRI volumetric analysis in patients with organic amnesia, 1: methods and comparative findings across diagnostic groups

Background-If they are to be replicable, MRI volume measurements require ex plicit definitions of structures and of criteria for delineating these stru ctures on MRI. Previously published volumes in healthy subjects show consid erable differences in measurements across different studies, including a fo urfold variation in estimates of hippocampal volume. Previous neuroimaging reports in patients with Korsakoff syndrome have generally found widespread or non-specific change, whereas in patients with herpes encephalitis the e xtent of pathological involvement reported beyond the temporal lobes has va ried. Method-In the present study, a clear set of anatomical criteria and detaile d MRI segmentation procedures were applied to measure whole brain, frontal and temporal lobe, and anterolateral and medial temporal volumes, as well a s thalamic areas in patients with organic amnesia (from Korsakoffs syndrome , herpes encephalitis, and focal frontal lesions) as well as healthy contro ls. Results-Patients with Korsakoffs syndrome showed decreased thalamic measure ments but no significant changes in the medial temporal lobes, whereas pati ents with herpes encephalitis showed severe medial temporal but not thalami c atrophy. In the patients with known frontal lobe lesions, quantitative an alysis on MRI showed reduced frontal lobe volume but no significant tempora l lobe or thalamic atrophy. Conclusion-Quantified MRI can be a useful technique with which to examine b rain-cognitive relations, provided that detailed techniques are explicitly described. In particular, specific patterns of volume change can be found i n vivo in patients with Korsakoffs syndrome and those with herpes encephali tis.