LAUSR

Despite about one hundred years of academic work, the general use of the term Chiari malformation remains unclear and continues to cause disagreement, if not confusion, among experts [1]. The term has been employed variably and is based on an anatomical definition of usually 5 mm or more of caudal displacement of the cerebellar tonsils through the foramen magnum. It is also employed for a clinical syndrome that comprises one or more signs and symptoms such as headaches, neck pain, nausea, vertigo, diplopia or paresthesias, which may be aggravated by Valsalva-like manoeuvres. Beyond this, a multitude of pain, disability and psychological correlates have been associated with this entity [2]. One could therefore view their interrelation in a Venn diagram where there is some consensus in those patients who present with both anatomical and clinical criteria fulfilled. However, measurements of the anatomical metrics as well as predictions of treatment outcomes remain a matter of ongoing investigations [5, 7, 8]. Still, the clinical syndrome as such is not clearly established in all cases, as it appears that there are patients who meet the “clinical core criteria” but fail tomeet the expected anatomical criteria. Other patients meet the criteria, but fail classic treatment approaches [6]. There hence is a true gap of knowledge of underlying causes for the symptoms of a Chiari syndrome. In their extensive single-institution cohort study in this volume, DanHeffetz and colleagues from theUSA [3, 4] investigate the radiographic correlation of the extent of tonsillar ectopia to clinical symptomatology in patients. Interestingly, these are patients who self-referred to their institution for the evaluation of a possible Chiari malformation. The key message of their study is that the extent of tonsillar descent does not correlate with clinical symptomatology. In fact, symptoms appeared more frequently in patients with lesser caudal displacement of the measured radiographic anatomical reference point. There are of course limitations to this study. Admittedly, certain selection criteria and even some bias in inclusion criteria for this study can be discussed, but it appears that the diagnosis was made and meticulously documented by a team of physicians dedicated, or specialized, in this condition. One has to recognize that the mechanism of self-referral and the availability of an institutional service with possible financial gain can influence the selection somewhat. Self-referred patients after all are not a random sample. This may contribute to some selection bias (e.g. patients with higher anxiety scores than seen in the general population and in Chiari patients), which might influence the results, yet professionalism of this established center and national oversight would mitigate against any deliberate unethical practice. It is evident and well documented that a strict selection process was employed among referred patients. The secondary referral structure probably introduces some bias to a more complex patient population, since “easier” cases (conforming to the classic definitions) would be treated at local institutions. It is also relevant to note that institutions in health care systems (e.g. UK’s NHS, Swedish health care, Canada) where patients represent a cost to the health care institutions rather than revenue (e.g. USA) will have an incentive to decrease cost and may hence not offer treatment to patients unless clinical indications are posing an undisputable need. It can therefore be seen as a strength of this study that a sizable group of patients with less overwhelming presentations has been scrutinized. The enormous amount of work that went into this project deserves therefore acknowledgement for the diligent approach the authors have chosen to investigate this problem that bears clinical significance in clinical practice. This article is part of the Topical Collection on Neurosurgery general