Scientists have created a novel transparent skull implant, which may give neurosurgeons a “window to the brain,” according to a study published in the journal Nanomedicine: Nanotechnology, Biology and Medicine.

Researchers from the University of California, Riverside, say they hope the implant will lead to new treatment strategies for those with life-threatening neurological disorders, such as traumatic brain injury and brain cancer.

At present, the majority of neurological procedures involve craniectomies. A craniectomy is a neurosurgical procedure where a part of the skull is removed to give swelling in the brain room to expand.

Laser-based treatments have shown promise for many brain disorders in the past, but most medical lasers are unable to penetrate through the skull. Therefore, the scientists hope this novel implant will take laser-based neurological treatments to the next level.

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Scientists created a transparent skull implant that they have named “window to the brain,” a version of which is pictured.
Photo credit: UC Riverside.

The team created the implant using ceramic material that is currently used in dental crowns and hip implants, called yttria-stabilized zirconia (YSZ).

Although this material is traditionally opaque, the scientists used a process called CAPAD – a technique that reduces the porosity of the material to “nanometric dimensions,” and in turn reduces the “optical scattering” that causes YSZ to be opaque.

The transparent YSZ was then polished, heated and slow cooled to toughen the material, and cut into rectangular implants with the dimensions of 2.1 x 4.2 x 0.2 mm3.

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An illustrated cross section of the head, showing how the skull implant would work with laser-based treatment strategies.
Image credit: Mayo Kodera

To test the implant in action, the researchers performed right-sided craniectomies on anesthetized mice. The left side of the cranium was unmodified to act as a control.

The scientists then fixed the implants to the surrounding skull with dental cement.

Optical coherence tomography (OCT) imaging was used over a 2×2 mm2 area on both the left cranium and the right, with the YSZ implant.

Results showed that the OCT provided significantly clearer imaging on the right cranium with the YSZ implant, compared with the left cranium.

The researchers add that signal strength at nearly every depth was much higher when imaging through the YSZ implant, providing evidence that the implant enhances imaging performance.

Dr. Kevin Binder, clinician and associate professor of biomedical sciences at the University of California, Riverside, says:

This is a crucial first step towards an innovative new concept that would provide a clinically-viable means for optically accessing the brain, on-demand, over large areas, and on a chronically-recurring basis, without need for repeated craniectomies.”

The scientists note that although the YSZ implants are not the first transparent skull implants to be reported, they are the first that could be realistically used in humans. They say this is due to the toughness of the material, which makes the implant more resistant to shock and impact, compared with previously created glass-based implants.

They add that as well as enhancing safety, it could also reduce patient self-consciousness by minimizing the need for noticeable protective headgear.

The researchers say that although this study is in the early stages of the “window to the brain” concept, it is important to note the opportunities the implant could provide.

For example, they emphasize that the implant could be used for chronic monitoring of cerebral edema – excess accumulation of fluid in the brain, which is impossible with current techniques.

“Similarly, it may enable chronic monitoring and more precise targeting of photodynamic therapies for residual gliomas, which could prolong survival and improve quality of life for many suffering from brain cancer,” they add.

“Finally, it could provide a platform for development of new optical neuromodulation modalities, with potential applications ranging from fundamental neurophysiology studies to clinical psychiatry.”