The human brain breaks down 10 times more easily than polystyrene foam

The researchers used MRI scans and an algorithm to measure the brain’s stiffness and resistance to pressure in living humans.

With Karmela Padavic-Callaghan

Although they look like they are made of rubber, the human brain is softer and squishy. Their ability to withstand pressure is similar to that of a gelatin sheet and they break more easily than polystyrene foam used for packaging.

Nicholas Bennion of Cardiff University in the United Kingdom and colleagues have begun developing a method for obtaining more accurate measurements of the physical properties of the brain in living humans. Much of what we know about how brain tissue responds to tools that touch it during neurosurgery comes from organs that are cut or removed and protected in chemicals that can affect tissue stiffness and flexibility.

Combining a machine learning algorithm with MRI scans of prone and then prone people to reposition the brain in the skull, the researchers were able to decipher the different material properties of the brain and the tissues that connect it to the skull. They measured how much the brain collapsed when stepped on, how it responded to being pushed sideways, and how flexible the connective tissues were.

“If you take a brain that hasn’t been preserved in any way, it’s incredibly low in hardness and breaks down very easily. And it’s probably a lot softer than most people think,” says Bennion.

The team found that brain matter collapsed 10 times more easily than polystyrene foam, and its resistance to being pushed sideways was one-thousandth of what it would have been if it had been made of rubber, meaning its softness was comparable to a sheet of gelatin. . Bennion says the algorithm calculates that the tissues that connect the brain to the skull are also quite soft, probably to protect the brain from too sudden movement.

Ellen Kuhl of Stanford University in California says that although researchers have long known that brains are very soft and very fragile, the new study makes this view precise enough to better inform delicate surgical procedures.

Krystyn Van Vliet of the Massachusetts Institute of Technology, however, said the new method may not fully capture the way the brain deforms during movements more vigorous from changing positions, such as a head injury in a crash sport or a traffic accident. In these cases, the flow of fluids in the brain can change its material properties.

The team hopes their model can now be used to predict brain shifts that will occur during surgery for each patient based on pre-operative MRI scans. This can make procedures less invasive, eliminating the need to insert and re-insert instruments into the brain until they are in the right spot.

Reference: Journal of the Royal Society Interface, DOI: 10.1098/rsif.2022.0557