LAUSR

Dear Editor, I have read with interest the studies of Heffez et al., recently published in Acta Neurochirurgica [4, 5]. Here, neither the severity of subjective symptoms and objective neurological finding nor the intraoperative findings other than tonsillar pallor correlated with the extent of tonsillar ectopy in patients with Chiari malformation type 1 (CMI). Interestingly, some symptoms were more pronounced in the group of patients having tonsillar ectopy only 0–3 mm. Both studies are severely limited by selection bias: the patients were self-referred and did clearly not represent a typical population with CMI. This was, for instance, reflected by the fact that only 4–7.7% of patients harbored a syrinx, in contrary to close to 50% as reported in most other series. The intraoperative finding of neuroma in continuity along the course of the C1 and XI nerves, as reportedly observed in 45–55% of patients, is another curiosity that would require further exploration. Most importantly, however, I cannot agree with the authors’ premise that the symptoms associated with the CMI and the objective neurological findings only shall be consistent with cervical myelopathy and emanate from the compression of rostral spinal cord and caudal medulla oblongata, analogically as in symptomatic cervical stenosis. In my view, such statement as well as the exclusive focus on tonsillar “herniation” in diagnosis of CMI neglects the obvious complexity of the condition, as recently addressed in our review [3]. Worthwhile to mention in this context, we are counseling an increasing number of patients referred to neurosurgical treatment with newly diagnosed CMI. However, the diagnosis is in some cases “discovered” only by upright (also referred to as kinetic, dynamic, or positional) magnetic resonance imaging (MRI), after a standard, recumbent MRI failed to show any abnormality at the craniocervical junction. These are usually patients suffering from headache, neck pain, and plethora of other more or less unspecific symptoms and not responding to any other therapeutical attempts. In desperate search for a diagnosis possibly explaining their symptoms, these patients often seek information on the Internet, leading them often finally to private companies that offer them an additional investigation in the form of upright MRI. I am not aware of the percentage of these patients that end up with “positive” findings after investigation with an upright MRI. However, as a neurosurgeon, I often struggle to explain these frustrated patients why I consider the indication for a surgical treatment doubtful, when the diagnosis of CMI is based solely on the result of this investigation. In Norway and certainly in many other countries across Europe, where the majority of health care is provided and covered by public health insurance, it is also unfortunate to meet patients who have paid for such an investigation themselves and expect that we will take the therapeutical consequences of their “findings.” It is a seemingly logical assumption that conventional MRI taken in the recumbent position of the patient does not reflect the anatomical changes and physiological forces towards discoligamentous structures that occur during normal upright posture and ambulation [1]. Indeed, an MRI taken in the upright position may potentially demonstrate occult pathology not visualized in the recumbent position. This fact has been utilized particularly in diagnosis of degenerative spine disease, in which axial weight load is of importance, as in assessing the degree of disc degeneration or spinal instability [6]. As for the part of cerebellar tonsillar ectopy and CMI, however, there is – at least to my knowledge – to this date no available evidence or studies demonstrating the benefit of decompression surgery in patients with this reportedly “hidden” form of Chiari malformation that only is revealed by This article is part of the Topical Collection on Neurosurgery general