Neurosurgery is an innovative and growing field, and we are just beginning to understand the brain and its functions. Research is a core part of neurosurgery training and practice. It is also an excellent way to learn about the field and display your interest in academic medicine. It is not required to complete research, but there is no question that it helps substantially during the application process. High-quality, basic science work is optimal, and if in the area of the neurosciences, even better. Clinical projects with neurosurgeons are looked upon favorably and can yield very strong letters of recommendation if you have shown interest, initiative and delivered a well-done product.
Ask faculty if you can become involved in research projects, and follow through with a rough draft of a manuscript in a timely fashion. A fast turn-around with a well-written paper makes you stand out and paves the way for more involvement. First authorship is clearly most desirable. If not possible, however, try and at least present a poster as first author to demonstrate your leadership and mastery of the subject.
Taking a year off to perform research is an option but is absolutely not necessary to match and is only worthwhile if you are truly interested in research. The strongest applicants have several neuroscience investigations with publications completed in the first two years, coupled with clinical research publications performed over the latter two years of medical school. Research conducted prior to medical school is also extremely relevant to your application.
According to the 2018 NRMP Charting Outcomes, the average number of abstracts, presentations and publications, for those matching into neurosurgery was 18.3. This is an average, and not a requirement. You should strive for two to five quality publications and demonstrate the effort that you put into the research by presenting these as abstracts and posters at meetings as the first author. It should be stressed, however, that although research is a great plus, many applicants match without significant research contributions.