Hippocampal T2 hyperintensities on 7Tesla MRI

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.

Stroke and the Connectome: How Connectivity Guides Therapeutic Intervention

“…Due to their small size, in many cases microinfarcts are not detected with standard imaging tools; therefore regional abnormalities in brain structures are assumed to reflect sites of damage, while actual affected networks may be more widely distributed. Nonetheless, there is evidence that regions such as the hippocampus and white matter tracts may accumulate more hyperintense damaged regions compared to the rest of the brain (van Veluw et al, 2013). Animal models of microinfarction can be used to systematically identify sites of damage and also reflect the trend for a greater number of infarcts in vulnerable brain regions (Wang et al, 2012).…”

Ontario Neurodegenerative Disease Research Initiative (ONDRI): Structural MRI methods & outcome measures

“…For ONDRI, the SBHV segmentation has been fully integrated into the SABRE-LE pipeline, and includes left and right hippocampal sub-classifications for parenchyma, hypointensities, and stroke volumes (when present). Currently, there is some controversy over the pathophysiological origin and relevance of small cavities commonly observed in the hippocampus (Bastos- Leite et al, 2006;Maller et al, 2011;Van Veluw et al, 2013;Yao et al, 2014), which are particularly relevant in the ONDRI VAS patients. Additionally, large cortico-subcortical strokes can extend from the cortex into the hippocampus.…”

Hippocampal sulcal cavities: prevalence, risk factors and association with cognitive performance. The SMART-Medea study and PREDICT-MR study

“…According to others, HSCs are dilated perivascular spaces (dPVS), also known as dilated Virchow-Robin spaces (dVRS) (Kwee and Kwee 2007). Previous studies found a higher number of HSCs with an increasing mean arterial pressure (MAP) (Van Veluw et al 2013), and with higher systolic and diastolic blood pressure (Yao et al 2014), suggesting that the etiology of HSCs may be related to vascular factors . However, a review reported that the relation between HSCs and hypertension has been questioned and that some studies excluded patients with hypertension (Maller et al 2011).…”