Vignesh Subramanian ’24

Figure 1: A CT scan of a human brain with hydrocephalus, made visible by the enlarged ventricles.

Hydrocephalus is a neurological disorder characterized by the abnormal accumulation of cerebrospinal fluid (CSF), the plasma fluid in which the brain is suspended and cushioned, in cavities of the brain known as ventricles. CSF disorders like hydrocephalus develop when CSF is either excessively produced or has its circulatory path blocked. This imbalance or blockage causes the ventricles to enlarge as CSF builds up, compressing brain tissue from within. Hydrocephalus is treatable with the surgical placement of a shunt (the ventriculoperitoneal, or VP, shunting procedure) or puncturing of a hole in the ventricle floor (the endoscopic third ventriculostomy, or ETV, procedure) to release fluid and relieve pressure. However, such procedures require postoperative neuroimaging to verify that the CSF is indeed draining properly. 

Given the extensive risks of ionizing radiation exposure associated with CT scans, the predominant modality used to image adult brains, alternatives such as radiation-free ultrasound are being increasingly explored. However, transcranial ultrasound imaging is made difficult by the fact that ultrasound waves are blocked or distorted by the skull bone surrounding the brain. Researchers at Johns Hopkins University led by Dr. Mark Luciano thus sought to determine whether creating a “window” through the skull – via the placement of transparent covers over sonolucent (permeable to ultrasound waves) burr holes drilled into the cranium – could allow doctors to examine ventricular tissue damage and fluid levels in real time. 

The researchers recruited 37 patients who had recently undergone ETV or VP shunting procedures for the study, creating and widening burr holes in their skulls and fixing 3D-printed, prosthetic acrylic windows at these surgical sites. Transcutaneous, trans-burr hole Doppler ultrasound imaging was then performed, with multiple planes of ventricular anatomy being captured and evaluated to reconstruct images ordinarily generated by CT and MRI imaging. 

The researchers were able to successfully implant the novel cranial windows, confirming that utilization of burr hole covers does not increase infection or revision rates in their postoperative insertion. The researchers further found that they were able to clearly view and make definitive conclusions about the patients’ ventricular size and the caliber of the imaged cavities, though they acknowledged that the field of visualization did not provide as comprehensive a picture of the full brain as other imaging modalities. Future studies will aim to test these conclusions with larger patient samples and longer follow-up times to establish the broad-based applicability of this means of managing hydrocephalus and CSF disorders. 

Works Cited:

[1] R. Lee, et al., First experience with postoperative transcranial ultrasound through sonolucent burr hole covers in adult hydrocephalus patients. CNS Neurosurgery 92, 382-390 (2023). doi: 10.1227/neu.0000000000002221

[2] Image retrieved from: https://commons.wikimedia.org/wiki/File:Hydrocephalus_(cropped).jpg