Blowing air into the brain to look for tumors From bloodletting to big data: the evolution of medical research – part 1

If doctors in the past wanted to detect a brain tumor using an X-ray, they replaced cerebrospinal fluid with air. This provided better contrast and clearer images, but also caused severe vomiting and weeks of headaches. 

Thanks to the discovery of the X‑ray in 1895, doctors could look inside the body for the first time. Hard structures, such as the skull or broken bones, show up well, but soft tissue such as a brain tumor is barely visible.

Doctors in the last century came up with a solution. They injected air into the brain. 'It was actually quite cleverly thought out', says radiologist Ritse Mann of Radboud university medical center. 'Everything in your skull has a similar composition—it’s mostly water. If you inject air, you get much more contrast, making the X-ray image clearer.'

Suctioning out cerebrospinal fluid

But you can’t just inject air into the brain; you have to make space first. So those doctors first removed all the cerebrospinal fluid using a needle inserted low in the back. Sometimes they removed as much as one and a half liters. Then they injected air. To get the air into the right place, they rotated the patient in all kinds of positions—even hanging them upside down.

The air filled the fluid-filled spaces of the central nervous system and the four ventricles of the brain. Then a doctor took two X‑rays from different angles. 'These were two‑dimensional flat images', Mann explains. 'So, you saw almost nothing. Only if the tumor was at least five centimeters in diameter and happened to press against a ventricle could it be seen.'

Weeks of headaches

The procedure, known as the pneumoencephalogram, turned out to be of limited use but caused severe side effects. 'Most of the time this was done without anesthesia', says Mann. 'People often vomited violently and suffered from severe headaches for weeks.' It did eventually resolve: the air slowly disappeared through the blood vessels, and the brain produced new cerebrospinal fluid. But that could take months.

By the late 1970s, this procedure came to an end. It was first replaced by the CT scan. Later, the MRI was introduced—an imaging method that maps all the soft structures in the brain in razor‑sharp detail and in 3D.

On the left, a 2D X‑ray image of the brain after air was injected, from 1919. On the right, images from a 3D MRI scan, in which all structures are visible in detail.

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