["Intrathecal inflammation has been suggested to play an important role in the pathogenesis of Alzheimer's disease (AD). However, there is little clinical evidence in support of this hypothesis in AD patients. We previously reported that the blood-brain barrier permeability represented by the cerebrospinal fluid/serum albumin ratio correlates with medial temporal lobe atrophy (MTA) in AD. The aim of this study was to elucidate the relationship between intrathecal inflammation and the severity of AD.", 'We investigated the correlations between the cerebrospinal fluid/serum IgG index and the indices of AD severity, including Clinical Dementia Rating and Mini-Mental State Examination, and MTA on magnetic resonance imaging in 42 AD patients. Further, the number of apolipoprotein E isoforms and the blood-brain barrier permeability were also examined for the correlation with the IgG index.', 'The IgG index showed a positive correlation with the severity of MTA but not with the other parameters examined.'] Is cerebrospinal fluid/serum IgG index correlated with medial temporal lobe atrophy in Alzheimer 's disease?