For patients with hydrocephalus, a condition characterized by an abnormal accumulation of cerebrospinal fluid in the brain, treatment often requires neurosurgeons like Johns Hopkins’ Mark Luciano to drill burr holes in the skull and insert shunts. With shunts in place, neurosurgeons must regulate fluid flow carefully to stabilize the size of the brain’s ventricles and check for bleeding. This often requires serial imaging with CT or MRI.

Thanks to a new development, colloquially referred to as “acrylic brain windows,” Luciano can now check his patients’ conditions noninvasively via ultrasound, using these windows to view the brain in the clinic or emergency department. These “sonolucent burr hole covers,” essentially refined plexiglass about 2 centimeters wide, are clear and covered by the skin, allowing ultrasound to pass through and capture images of the brain. They transform routinely performed skull holes made for brain access into permanent brain windows.

The burr hole covers “potentially give us the ability to look at the size of the ventricle and make judgements or see where the shunt is or if there’s any bleeding,” says Luciano, director of the Johns Hopkins Hydrocephalus and Cerebral Fluid Center, whose team to date has implanted the acrylic windows into approximately 190 patients at Johns Hopkins.

In the event of a brain bleed or enlarged ventricles, once verified by ultrasound, Luciano can adjust the shunt magnetically to increase or decrease drainage in a noninvasive manner.

The sonolucent acrylic material has also been used in the form of larger plates to monitor patients after they undergo surgery for Chiari malformation, which involves removing part of the back of the skull.

Johns Hopkins researchers published a proof-of-concept paper in February 2023 in Neurosurgery that showed that there was no increase in rates of infection or shunt failure resulting from the sonolucent burr hole covers. It marks the first publication of practical application of sonolucent material for observation windows. The potential of the sonolucent material was first noted by Johns Hopkins plastic and reconstructive surgeon Chad Gordon and dermatology resident Micah Belzberg in a 2019 paper in the Journal of Craniofacial Surgery.

Luciano says that he and his team will soon publish a retrospective paper that will follow up on the patients who have received the implants at Johns Hopkins. The researchers hope to start a prospective trial in 2024 or 2025.

In the meantime, Luciano is working with medical imaging experts Jerry Prince and Muyinatu Bell, both faculty members in the Department of Electrical and Computer Engineering at Johns Hopkins’ Whiting School of Engineering, on getting better pictures and more quantifiable data from ultrasound