Exploring the role of focused ultrasound in neurosurgery and neuro-oncology.

Focused ultrasound (FUS) is an emerging technology that uses ultrasound waves to ablate or modulate tissue. While it has been explored in several different clinical fields for over two decades, it has only recently begun to receive attention in neurosurgery. The neurosurgical field seems primed to benefit from a non-invasive precision technology such as FUS, which could minimise the adverse effects of invasive surgery if it delivers comparable efficacy in treatment. Through thermoablation, the high-intensity form of focused ultrasound (HIFU) can ablate nuclei in the basal ganglia to treat movement disorders and also ablate tumours and other targets. The low-intensity form of focused ultrasound (LIFU), typically delivered in a pulsed mode, can be used in conjunction with microbubbles to transiently open the blood-brain barrier (BBB) to increase the bioavailability of therapeutics into brain tissue in a highly targeted manner. While ultrasound is non-invasive (in terms of access to the point of treatment), relatively cheap and with a well-understood safety envelope, it is challenging to accurately focus ultrasound through the skull. Uncertainties remain about the adverse intracranial effects of HIFU, including overheating and brain swelling. Transient BBB opening with LIFU could be a viable solution to an unmet need in therapy delivery; it has the potential to be part of a broader treatment envelope for patients who require both neurosurgical and chemotherapy treatment. We highlight the potential applications of FUS in neurosurgery, its promises and the challenges it still faces.