Alexandre Boutet
Evolution in neuroradiology, and indeed the wider radiology field, is in part dictated by novel diagnoses, therapies, and imaging techniques. The most frequently encountered indications and imaging modalities have changed drastically over the past decades. The expectations of radiology reports are also changing, with a trend toward the use of standardized reporting and quantitative scales. One clinical specialty in particular has contributed to these changes in neuroradiology: functional neurosurgery. In its broadest sense, functional neurosurgery includes the surgical treatment of pain, movement disorders, epilepsy, and psychiatric conditions. In this edition of the AJNR News Digest, we showcase several articles that highlight recent developments in this field and explore their potential impact on neuroradiology.
Functional neurosurgery is largely dedicated to modulating aberrant circuits associated with a wide range of neurologic conditions. Generally speaking, this can be achieved through stereotactic methods, including lesioning or electrically stimulating key brain structures. As a basic principle, the targeted structure represents a crucial hub of the circuit of interest; the motor circuit is targeted in Parkinson disease whereas structures implicated in mood regulation and cognition are targeted in psychiatric disorders and Alzheimer disease, respectively.1,2 Deep brain stimulation (DBS) has emerged as the dominant stereotactic functional neurosurgical procedure because it is reversible and the postoperative titration of electrical stimulation allows for personalized care. However, the advent of a new technology introduced in the last few years has unexpectedly brought lesioning therapies back to the forefront of functional neurosurgery.3,4 MR imaging–guided focused ultrasound (MRgFUS) uses MR thermometry to create a precisely targeted lesion. Most notably, MRgFUS is minimally invasive and does not require opening the skull. While MRgFUS and DBS rely on different mechanisms of action, both these therapies aim at restoring faulty circuits.
The success of these stereotactic procedures is largely dependent on accurately targeting the structure of interest. Traditionally, planning was based on indirect methods that approximated the target in relation to fixed anatomic landmarks. These methods were used as targets could not be readily visualized on imaging. However, with advances in MRI technology, the direct visualization of certain structures has replaced indirect targeting for preoperative planning in certain cases.5 Increasingly, there has also been a shift in focus from what is being targeted at the local level toward what is being engaged at the network level. In other words, rather than discrete structures, such as deep gray matter nuclei, optimal targets may include white matter pathways or focal hubs within larger functional networks.2,6,7 Beyond its role in the preoperative setting, neuroimaging remains essential in confirming adequate treatment location postoperatively and for excluding complications.