Abstract
Hippocampal focal T2 hyperintensities (HT2Hs), also referred to as hippocampal sulcal cavities, are a common finding on Magnetic Resonance (MR) images. There is uncertainty about their etiology and clinical significance. In this study we aimed to describe these HT2Hs in more detail using high resolution 7 Tesla MR imaging, addressing 1) the MR signal characteristics of HT2Hs, 2) their occurrence frequency, 3) their location within the hippocampus, and 4) their relation with age. We also performed an explorative post-mortem study to examine the histology of HT2Hs.Fifty-eight persons without a history of invalidating neurological or psychiatric disease (mean age 64 ± 8 years; range 43–78 years), recruited through their general practitioners, were included in this study. They all underwent 7 Tesla MRI, including a T1, T2, and FLAIR image. MR signal characteristics of the HT2Hs were assessed on these images by two raters. Also, the location and number of the HT2Hs were assessed. In addition, four formalin-fixed brain slices from two subjects were scanned overnight. HT2Hs identified in these slices were subjected to histopathological analysis.HT2Hs were present in 97% of the subjects (median number per person 10; range 0–20). All HT2Hs detected on the T2 sequence were hypointense on T1 weighted images. Of all HT2Hs, 94% was hypointense and 6% hyperintense on FLAIR. FLAIR hypointense HT2Hs were all located in the vestigial sulcus of the hippocampus, FLAIR hyperintense HT2Hs in the hippocampal sulcus or the gray matter. Post-mortem MRI and histopathological analysis suggested that the hypointense HT2Hs on FLAIR were cavities filled with cerebrospinal fluid. A hyperintense HT2H on FLAIR proved to be a microinfarct upon microscopy.In conclusion, hippocampal T2Hs are extremely common and unrelated to age. They can be divided into two types (hypo- and hyperintense on FLAIR), probably with different etiology.
Highlights
On MR images of the hippocampus, focal T2 hyperintensities, referred to as hippocampal sulcal cavities, are a common finding
The inter-rater intraclass correlation coefficient (ICC) for all HT2Hs was 0.79
The intra-rater ICC for HT2H volume assessment was 0.98 and the
Summary
On MR images of the hippocampus, focal T2 hyperintensities, referred to as hippocampal sulcal cavities, are a common finding. They are reported to be hypointense on T1 and hyperintense on T2 weighted images. Argue that the T2 hyperintensities are lesions related to ischemic or hypoxic events [3,4]. This ambiguity concerning their origin is reflected in the various names they received including hippocampal sulcal cavities, low signal foci, and hyperintense lesions. In the present paper we will refer to them as focal hippocampal T2 hyperintensities, abbreviated as HT2Hs
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