LAUSR

We thank Dr McLean for their comments regarding our recent manuscript “Percutaneous cervical sympathetic block to treat cerebral vasospasm and delayed cerebral ischemia: a review of the evidence”. We agree that the literature in this field is heterogenous with respect to type, dose, volume of local anesthetic, and method of delivery used for cervical sympathetic block (CSB). To highlight this heterogeneity, we specifically mentioned these limitations in our manuscript in the paragraph ‘Drug type, drug volume and drug delivery modality’. Such heterogeneity makes it difficult to draw conclusions on the preferred drug, volume, and delivery modality to use, and we therefore chose to write a narrative review, rather than a systematic review, of the literature. Regarding the possibility of using a periganglionic catheter for continuous infusion of a nerve blocking agent, we acknowledge the lack of evidence to support this technique in the manuscript, and we call for further studies on this topic. It is certainly possible that an indwelling catheter may increase the risk of procedural complications. However, we are not aware of any literature to support this statement, and future studies are warranted to document these theoretical complications. We also dedicate a paragraph to the discussion of sympathetic blockrelated complications, which is subtitled ‘CSB complications’. We agree that the concept of unilateral versus bilateral CSB is intriguing with respect to the treatment of vasospasm and delayed cerebral ischemia, which is delineated in a paragraph on page 6 of our manuscript. We are confused as to whether you might have misunderstood our discussion as your letter copies our call for safety and feasibility for these techniques verbatim, which suggests that this section of our manuscript was read correctly. The role of CSB in influencing cerebral perfusion (and likely intracranial pressure) is intriguing. We would respectfully note that, in our manuscript, we never mention the effect of CSB on intracranial pressure as, to our knowledge, no study to date has assessed the effect of CSB on intracranial pressure. Future studies into this question are certainly warranted. The author raises concern that mean arterial pressure reduction may lead to cerebral hypoperfusion and secondary brain injury, and (s) he cites two papers that describe such a phenomenon in patients who underwent a superficial cervical plexus block. 4 It is imperative that the author and readers of our manuscript understand that a superficial cervical plexus block is a completely different procedure from a CSB. A superficial cervical plexus block targets a different nerve plexus than a CSB, and we neither discuss nor advocate a superficial cervical plexus block for the treatment of vasospasm and delayed cerebral ischemia. Lastly, we agree with the author that the many limitations and gaps in knowledge related to CSB must be addressed in future studies. To emphasize this point, we would refer the author of this letter to the editor and the JNIS readership to the section in our manuscript entitled ‘Roadmap for future studies’. In this section we address these points explicitly and provide a suggested roadmap for future studies to overcome the limitations of our current knowledge. We are pleased that the author found our manuscript of interest and agrees with us on the limitations and need for more research on this novel intervention.