Anatomie et physiologie : recherches en cours
Libre accès
ISSN: 2161-0940
ISSN: 2161-0940
David Talbert
Aim: It has commonly been assumed that the brain “floats” in cerebrospinal fluid, restrained only by the bridging veins. However, modern textbooks show that the brain is actually suspended in CSF by an ultrasonically invisible “cobweb” (arachnoid) of collagen reinforced tissue. This would appear to prevent the cortex-skull relative movement necessary for the shearing action currently thought to cause the injuries diagnostic of Shaken Baby Syndrome. The aim of this study was to investigate brain behavior in everyday (sub-traumatic) conditions.
Method: A study into brain motion in vehicle accidents was found, in which radio-opaque markers were injected into fresh cadaver heads to enable movement of brain tissue during sub-traumatic impact to be recorded. Factors relevant to infants were extracted.
Results: Markers in various parts of the brain moved on different trajectories, indicating that fresh brain tissue is floppy. Markers closest to the meninges followed skull movement closest, indicating that the cortex did not slide under the skull linings. Any lagging movement of the deep brain was accommodated by deformation of the brain.
Discussion: Collagen bundles within trabeculae appear to be continuous with those in the inner aspect of the arachnoid and to those in the subpial space thus “stitching” the arachnoid and pia-maters together. However there are no collagen fibres in the brain, only astrocytes bonding the brain to the basement membrane. Anchor failure will occur first at this (pial) end as the pial mat is lifted off the cortex dragging minor surface vessels with them, forming cortical contusions.
Conclusion: Contrary to current assumptions that the brain is semi-rigid and trabeculae are weak, fresh brain is softly resilient and the Arachnoid and Pia Maters are firmly stitched together with collagen fibres and so cannot slide. The brain is floppy enough to accommodate local movements by deforming.