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Hippocampal Subfield Group

16 Jun, 10 tweets, 7 min read

@DrAnaDaugherty

Guest post by @DrAnaDaugherty on hippocampal (Hc) vascularization.

Brought to you by “anastomosis” (noun): a cross-connection between adjacent blood vessels; plural “anastomoses”.

As in, “Wow! 54 years of mapping anastomoses”

#SubfieldWednesday 🧵 1/

The unique features of its arteries make Hc vulnerable to anoxia. Superficial arteries travel long tangential routes, and intrahippocampal arteries have few anastomoses and travel with the rolling CA and dentate gyrus tissue. 2/

#SubfieldWednesday

Posterior cerebral (PCA) & anterior choroidal (AChA) arteries supply Hc. Variations are noted: PCA supply is typical and dominant, AChA supply is not seen in 30-40% of hemispheres.

🚨Anastomosis Alert (arrows) 3/

tinyurl.com/2hjaw6vj

#SubfieldWednesday

PCA supplies middle (body) and posterior (tail) superficial Hc arteries; when present, AChA supplies anterior (head) superficial arteries, otherwise majority blood supply is from PCA branches. 4/
tinyurl.com/85tsx9fw

#SubfieldWednesday

Recent 7T in vivo study replicated past histological observations, and identified when AChA diameter is large, more PCA anastomoses are present (especially in uncus).

Check out the beautifully illustrated paper by Spallazzi et al. 5/
tinyurl.com/p3cd4tn4

#SubfieldWednesday

Ventral intrahippocampal arteries primarily supply CA1, cross DG & end in CA2. Dorsal arteries are short & curve to CA3-DG & sometimes CA2. Large arteries travel long, oblique routes even with right angles; small arteries are straight with small territories. 6/
#SubfieldWednesday

There is individual variability. Commonly CA1 is only supplied by large ventral arteries, all other Hc subfield regions have several supplies. This describes body and tail portions; but the arterial arcade in the head is arranged within each digitation. 7/

#SubfieldWednesday

Hc anastomoses do not efficiently correct for fluctuations in blood supply, causing vulnerability to ischemia; CA1 is least vascularized of all regions and so is most sensitive to this. 8/

tinyurl.com/3rprp6z3

Variation in blood supply by PCA and AChA correlate with cog performance; may contribute to risk for Hc sclerosis and the mixed evidence of aerobic exercise increasing Hc blood flow.

High-res MRI creates new study opportunities! 9/

tinyurl.com/tw6dpjej
#SubfieldWednesday

References

Bartsch et al. (2015) JCBFM
Duvernoy (2005), The Human Hippocampus, p. 73ff
Erdem et al. (1993), JNS
Muller & Shaw (1965), Arch Neurol
Perosa et al. (2020), Brain
Spallazzi et al. (2019), NeuroImage: Clinical

10/fin

#SubfieldWednesday

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Duvernoy, H. M. (2005). The human hippocampus: functional anatomy, vascularization and serial sections with MRI. Springer Science & Business Media.

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