Hippocampal sulcus remnant: potential cause of change in signal intensity in the hippocampus.

Abstract

A small area of changed signal intensity in the hippocampus is often seen on magnetic resonance (MR) images of the brain in patients without specific clinical signs or symptoms. To ascertain its cause by means of histologic examination, this finding was evaluated retrospectively in 109 patients and correlated with findings in two human brain specimens. This area of change was typically round or curvilinear and 1-2 mm in diameter. Its location was between the hippocampus and dentate gyrus. The signal intensity was the same as that of cerebrospinal fluid (CSF) with all MR sequences used. The incidence of change in signal intensity was greater in elderly patients. Correlation with histologic findings showed that this area of change, a dilated perivascular space, was the residual cavity of the hippocampal sulcus. Whenever an area of CSF-like signal intensity has this shape and topographic features, the possibility of anatomic variation should be considered before the change in signal intensity is diagnosed as brain injury.

Frequency and Location of Dilated Virchow-Robin Spaces in Elderly People: A Population-Based 3D MR Imaging Study

“…Although still controversial, the hippocampal cavities located between the cornu ammonis and dentate gyrus were found at postmortem examination to be covered by a single cell layer, to contain blood vessels, and to be surrounded by intact cerebral parenchyma, which strongly suggest typical dVRS. 24 We found that these cavities are of uniform shape and location, with a frequency of 44.5% in the 3C-Dijon MR imaging cohort, close to the 39% reported by Sasaki et al 24 in 109 patients from 8 to 85 years of age. Whether their severity is related to age and apolipoprotein E4 or E2 alleles as suggested in small samples will need additional investigations.…”

Subcortical Lacunar Lesions: An MR Imaging Finding in Patients with Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy

“…In addition to being confused with Virchow-Robin spaces, SLLs can also be confused with normal variations in the temporal lobe. Hippocampal sulcus remnants are apparent at MR imaging as small circumscribed areas with a signal intensity similar to that of CSF in the hippocampus (21). These structures can be differentiated from SLLs by their location because hippocampal sulcus remnants occur within the hippocampus and are surrounded by hippocampal gray matter, whereas SLLs are seen only at the cortical junction of gray and white matter.…”

Asymmetric Development of the Hippocampal Region Is Common: A Fetal MR Imaging Study

“…7 The fusion of the walls of the hippocampal sulcus continues until GW 30, 4 but focal open remnants may be found even in adult brains. 8 The orientation of the hippocampal sulcus may also change during the inversion process.…”