Anatomical variations of the dentate gyrus in normal adult brain

Abstract

Recent scientific papers indicate the clinical significance of the dentate gyrus. However, a detailed knowledge of the anatomical variations of this structure in normal adult brain is still lacking. An understanding of the variable morphology of the dentate gyrus may be important for diagnostic neuroimaging. Thus, the purpose of this macroscopic cadaveric study was to describe the anatomical variations of the dentate gyrus. Forty formalin-fixed human cerebral hemispheres, obtained from bodies of donors without the history of neuropathological diseases, were included in the study. The dentate gyrus was classified as well-developed, when it protruded completely from under the fimbria of the hippocampus. The gyrus was classified as underdeveloped, when it was covered by the fimbria of the hippocampus (but clearly visible at the coronal section of the hippocampal formation), while the hypoplastic gyrus was not visible macroscopically under the fimbria of the hippocampus. The well-developed type was observed in 27 cases (67.5%). The thickness of well-developed type of the dentate gyrus, measured between the fimbriodentate sulcus and hippocampal sulcus, varied from 2.74 to 5.21 mm (mean = 3.67 mm, median = 5.54 mm, SD 0.65 mm). In the next nine cases (22.5%), the dentate gyrus was underdeveloped. The thickness of underdeveloped type of the dentate gyrus varied from 1.75 to 2.37 mm (mean = 2.02 mm, median = 2.16 mm, SD 0.33 mm). In the remaining four cases (10%), the dentate gyrus was hypoplastic and could not be distinguished macroscopically. In all injected hemispheres, arterial supply of the dentate gyrus was provided by the branches of the posterior cerebral artery. Awareness of normal variations of the dentate gyrus may allow for better correlation of anatomical knowledge with radiological data and for use this knowledge to describe abnormal conditions.

Keywords: Cerebral cortex; Dentate gyrus; Hippocampal arteries; Hippocampal formation; Human brain; Temporal lobe.

Fig. 1

Assessment of the dentate gyrus morphology. The well-developed margo denticulatus of the dentate gyrus (dg) was visualized on the medial side of the fimbria of the hippocampus (fh). The tooth-shaped part of the dentate gyrus is clearly visible. For comparison purposes, horizontal incisions through each hippocampal formation were performed with the aid of a brain knife, in the half-length of the body of the hippocampus (place of the incision was marked by white arrowheads). At this level the thickness of the margo denticulatus was also measured, between the fimbriodentate sulcus and hippocampal sulcus. ph pes of the hippocampus

Fig. 2

The appearance of the well-developed dentate gyrus. a Medial view. The dentate gyrus (dg) was classified as well-developed, when the margo denticulatus protruded completely from under the fimbria of the hippocampus (fh). In those cases, the hippocampal sulcus (marked by white arrowheads) was well-developed and clearly visible along all length of the margo denticulatus. b The coronal section through the hippocampal formation showing the well-developed dentate gyrus (marked by black arrowhead). cf crus of fornix, cs collateral sulcus, fg fasciolar gyrus, h hippocampus proper (Ammon’s horn), pg parahippocampal gyrus, ph pes of hippocampus, scc splenium of the corpus callosum, su subiculum of the parahippocampal gyrus, un uncus

Fig. 3

The appearance of the well-developed dentate gyrus with irregular prominences and less marked hippocampal sulcus. a Medial view. b The coronal section through the hippocampal formation showing the dentate gyrus (marked by black arrowhead). h hippocampus proper (Ammon’s horn), dg margo denticulatus of the dentate gyrus, fh fimbria of the hippocampus, pg parahippocampal gyrus, ph pes of hippocampus, su subiculum of the parahippocampal gyrus

Fig. 4

The appearance of the underdeveloped dentate gyrus. a Medial view. The dentate gyrus was classified as underdeveloped, when the margo denticulatus (dg) was covered by the fimbria of the hippocampus (fh). b The coronal section through the hippocampal formation showing the underdeveloped margo denticulatus (marked by black arrowhead). h hippocampus proper (Ammon’s horn), ph pes of hippocampus, su subiculum of the parahippocampal gyrus

Fig. 5

Hypoplasia of the dentate gyrus. a Medial view. The dentate gyrus was classified as underdeveloped, when the margo denticulatus was not visible macroscopically under the fimbria of the hippocampus (fh). b The coronal section through the hippocampal formation showing the hypoplasia of the dentate gyrus (black arrowhead shows the place with absent or vestigial margo denticulatus of dentate gyrus). cs collateral sulcus, h hippocampus proper (Ammon’s horn), pg parahippocampal gyrus, ph pes of hippocampus, su subiculum of the parahippocampal gyrus

Fig. 6

Arterial supply of the dentate gyrus. Arterial supply of the dentate gyrus is provided by the branches of the posterior cerebral artery (pca), namely by one of the posterior choroidal arteries (pc) and by the middle hippocampal artery (mh). dg margo denticulatus of the dentate gyrus, fh fimbria of the hippocampus, h hippocampus proper (Ammon’s horn), mca middle cerebral artery, ph pes of hippocampus, un uncus