We are now about a third of a century into the advent of “evidence-based” medicine, a concept that probably stemmed from the burgeoning practice of critical evaluation of the literature, ultimately leading to the development of practice guidelines. The purpose of guidelines is to synthesize the literature about a certain disease or its management and offer neurosurgeons a reasonable clinical path, based on the best available evidence. The rationale behind this process is to deal with the inevitable uncertainty in and around clinical decision-making.

Addressing Uncertainty
The importance of uncertainty in clinical judgment cannot be underestimated and should not be misunderstood. One of my neurosurgical mentors used to say to me, “Neurosurgeons are not always right, but we are never unsure.” The ring of truth to this aphorism will be apparent to anyone trained in the specialty, wherein many of our teachers and mentors, in an effort to reach certainty, gathered anecdotal evidence from their own and colleagues’ practices to steer decision-making. The certainty founded upon such evidence did not take into account the extent to which we could be wrong about our conclusions as a result of biases (systematic error) and chance (random error). (13)

Types of uncertainty in medical decision-making have been quantified and divided into several types:
1. Technical uncertainty — inadequate scientific data
2. Conceptual uncertainty — the difficulty in applying abstract criteria to concrete actions
3. Personal uncertainty — not knowing patients’ wishes (3)

The uncertainty that evidence-based medicine attempts to tackle is that related to technical uncertainty, explained by Beresford as “the paucity of adequate data to predict the effects of certain factors in the progress of a disease or the outcomes of certain interventions.” The focus of evidence-based medicine is gathering evidence in a methodical way and analyzing its quality to minimize uncertainty that arises from not having scientific data that are adequate but are the “best” that has been generated to date. The processes involved include a careful search for the pertinent literature, qualitative review and conclusion generation.

Systematic Reviews
There are three ways in which evidence from various medical reports can be aggregated, critically evaluated and summarized quantitatively: systematic reviews, meta-analyses and practice parameters or guidelines. Unlike the “topic reviews” so popular in neurosurgery journals in the late 20th century, systematic reviews are organized aggregates of the literature that have their own study design, just like any individual study. A search of PubMed in February 2015 using the term “systematic review” produces 1,958,393 citations, and an advanced search of (systematic[Title/Abstract]) AND review[Title/Abstract]) lists 73,060 citations, the earliest of which was published in 1948, that used the term appropriately. (16) Probably the best known series of systematic reviews are the products of the Cochrane Collaboration, spanning every aspect of medical care — even neurosurgery. (9) But these types of publications are now ubiquitous in all the literature, including standard neurosurgical publications. (17, 8)

Meta-analyses
Closely related to the systematic review is the meta-analysis, which differs from the former in that statistical techniques are applied. Like the systematic review, meta-analyses are also becoming more prevalent in the neurosurgical literature (2, 23), although they have been around in neurosurgery for more than 20 years. (14, 15) There now are recommended criteria for creating these reviews, depending upon whether the studies being examined are observational studies (case series, cross-sectional, case-control, etc.) or randomized controlled trials. For observational studies, the MOOSE (Meta-analysis of Observational Studies in Epidemiology) guidelines are fairly rigorously followed in neurosurgical journals by reviewers, and few articles are published that do not demonstrate following those criteria. Of interest, these guidelines were the product of a systematic review. (24) For randomized controlled trials, the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines are more commonly used. (21, 18, 19, 20) Whereas there is significant overlap, PRISMA is more comprehensive. What is important is that there are rigorous standards for aggregating the literature to derive a sense of the truth about effective treatment.

Practice Guidelines
The third formal mechanism for literature review differs from both systematic reviews and meta-analyses. Practice guidelines (practice parameters, practice recommendations) are derived from a careful qualitative review of the literature by a group of stakeholders using established criteria for evaluation. (25, 1, 5) Organized neurosurgery (the American Association of Neurological Surgeons (AANS) and Congress of Neurological Surgeons (CNS)) were early adopters of the evidence-based approach espoused by Woolf and others, who identified the role of uncertainty as a stimulus for their development. (26) Evidence was divided into three main categories: Class I – studies (e.g., randomized controlled trials) producing a high degree of clinical certainty; Class II – studies (e.g., case-control, cross-sectional, case series) supporting a moderate degree of clinical certainty; and Class III – studies with little or no certainty (e.g., flawed comparative studies, case reports, expert opinion). Neurosurgical guidelines were first introduced in the mid-1990s using recommended criteria. (4)

Over the subsequent 20 years, the development of guidelines has been a focus of the organizations, so that now there are many guidelines covering most aspects of neurosurgical care. (6) Most recent guidelines have concerned lumbar fusion (12), degenerative cervical spine disease (10), cervical spine and spinal cord injury (11), deep brain stimulation (DBS) for obsessive-compulsive disorder (7), and management of brain metastases (22) and have rigorously followed recommended strategies for guideline development.

Barriers to Implementation
Although the production of evidence-based guidelines continues, one of the key issues is the implementation of guidelines into the practice of neurosurgeons. There are many barriers: unfamiliarity with the guidelines, distrust of the procedure of guidelines (the perceived focus on the “science” rather than the “art” of medical practice), patient applicability (the perceived “cookbook” approach to decision-making), and the unwillingness to change personal approaches in the face of good evidence. These challenges are not particular to neurosurgery or neurosurgeons; they are national in scope and involve all the stakeholders — not just medical decision-makers. (27) In spite of this, clearly the best approach to clinical decision-making for neurosurgical patients must involve the production and evaluation of the highest quality of evidence possible, in the context of the experienced professional’s keeping in mind the individual patient’s prognosis, needs and wishes.

Beverly C. Walters, MD, MSc, is director of clinical research in the department of neurosurgery at University of Alabama at Birmingham, as well as the Henry Ford Health System. She also is the director of clinical research in the department of neurosciences for Inova Health System. The author reported no conflicts for disclosure.

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