A fascinating new study has been published (Tortora D, et al. Differences in subependymal vein anatomy may predispose preterm infants to GMH–IVH. Archives of Disease in Childhood – Fetal and Neonatal Edition. 2017) looking at cerebral venous anatomy as shown by an MRI trick that I didn’t know about, which is something called susceptibility weighted imaging, or SWI, venography. Using this technique they could map out the venous drainage of the germinal matrix region in former VLBW (<1500 g birthweight) preterm infants when they reached term equivalent age.
You can see some of these interesting images below, they show an image A with the veins labelled, and image B with an angle measured which is called the curvature index, and an illustration in image C one of the two main findings of the study, that babies who had an intraventricular or germinal matrix hemorrhage had an increased curvature of the vein draining into the internal cerebral veins, which is either the thalamostriate vein (the classical pattern) or the direct lateral vein (a fairly common variant).
The other finding was that any of the several anatomic variants were associated with an increased risk of hemorrhage* (although they were also quite common among babies without bleeds). Also the variants weren’t necessarily always symmetrical (as in image A above), in the 14 infants with unilateral bleeds, the venous anatomy on the affected side was characterised by presence of anatomical variations in 12/14 cases. In the contralateral normal hemispheres, they found the classic normal pattern in 13/14 cases.
It is fairly obvious that the neuroradiologists evaluating the anatomy and the venous curvature could easily see the hemorrhages, and cold therefore have been biased, but I think the data are fascinating and suggest that minor abnormalities of venous anatomy could lead to venous congestion in the brain of the preterm infant, and predispose to cerebral injury.
I think it’s great that simple basic findings like this (although they require amazing technology and good quality research) can still be discovered, even after we’ve been looking after preterm babies and worrying about IVH for so many years.
I also think it is an appropriate use of pre-discharge MRI in former very preterm babies, research which increases our understanding and helps to give ideas on how we might improve outcomes.
*As many of you will have noticed my spelling is rather erratic, sometimes American, sometimes UK and sometimes Canadian (which is a mix of the others, but gradually becoming more Americanis(z)ed). Some words always look to me more scientific when you use the older UK, Latin and Greek derived, spellings (which I know isn’t true); like haemorrhage or oesphagus. Often I just forget which is which, like who hospitalises and who hospitalizes with a z (thats a zed, not a zee).