In Reply: Contactless Ultrasonic Cavitation for the Prevention of Shunt Obstruction in Hydrocephalus: A Proof-of-Concept Study.

To the Editor: We sincerely appreciate Trumble and Huang's letter1 on our article “Contactless Ultrasonic Cavitation for the Prevention of Shunt Obstruction in Hydrocephalus: A Proof-of-Concept Study.”2 The authors have concisely remarked one of the major problems the neurosurgical community is facing in the treatment of hydrocephalus: the obstruction of implanted ventriculo-peritoneal shunts. Despite the many strategies that have been devised over the last decades to clear blocked shunts, none has been consolidated as a gold standard to restore normal flow, perhaps because of the inherent risks that accessing the interior of the implant carries. We believe the local cavitation produced contactlessly by focused ultrasounds, as described in our work, has an enormous potential for addressing this problem, as clearance of obstructions may be achieved externally thus minimizing side effects. While there are potential risks related to the generation of bubbles outside the implant in neighboring areas, if the acoustic energy is efficiently focused over the blocking materials by an array of emitters provided with numerous ultrasound sources, this method may offer a safe approach to re-establishing normal flow. Trumble and Huang referred to an early attempt to recanalise blocked implants3 by exploiting the emerging imaging techniques—optical endoscopic visualization in the referred case—to localize the obstruction. Said minimally invasive approach enabled an enormous improvement in the diagnosis and treatment of shunt obstructions. We would like to express here our surprise at the lack of refinement one would expect from the significant advances in modern endoscopes. Regarding to our approach, we believe some of the multiple medical imaging modalities available at present may assist with providing the information required for optimal ultrasound focusing. We would like to take this opportunity to thank Trumble and Huang for the recommendation and the motivating view of our work. While we are planning further testing and validation of the technique, this support encourages and inspires our team to bring these findings toward the bedside to assist the neurosurgical community with the delivery of better treatments for hydrocephalus.