CHIARI I : The so-called 5-mm rule was rejected by 88.5% of the experts

pattismith

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Chiari I Malformation: Opinions on Diagnostic Trends and Controversies from a Panel of 63 International Experts
Paolo A.Bolognese1
AndrewBrodbelt2
Alexander B.Bloom1
Roger W.Kula1

may2019

Background
Chiari I malformation (CMI) and the topics concerning it have been the subject of numerous discussions and polarizing controversies over the course of the last 20 years.
Methods
The opinions of 63 recognized international CMI experts from 4 continents, with a collective surgical experience of >15,000 CMI cases, were gathered through a detailed questionnaire.
Results
Three facts emerged from the analysis of the results:
1) Most of the replies showed a high level of consensus on most CMI-related topics.
2) Several topics, which had been considered controversial as recently as 10 years ago, are now more widely accepted.
3) The so-called 5-mm rule was rejected by 88.5% of the CMI experts who responded to the questionnaire.
Conclusions
Sixty three recognized international CMI experts from 4 continents, with a collective surgical experience of >15,000 CMI cases were polled about a number of CMI topics. The results showed a high level of consensus, as well as a paradigm shift.
 

pattismith

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who is Dr Paolo Bolognese:

"A native of Torino, Italy, Paolo Bolognese graduated in 1986 from the Medical School of the University of Turin. In 1990, he completed his first neurosurgical training at the same university under the guidance of Professor Victor Fasano. In 1992 he accepted the invitation of Dr Thomas Milhorat to transfer his on-going laser Doppler research to the United States, at the SUNY Health Science Center at Brooklyn. There he completed his second residency in neurosurgery and his fellowship in the management of Chiari I malformation and related disorders. In 2001 Dr. Bolognese joined Dr. Milhorat at North Shore University Hospital in Long Island, New York, where together they founded The Chiari Institute. Dr. Bolognese remained there until 2014, first with Dr. Milhorat and, then with Dr. Harold Rekate.
In 2014 he started the Chiari Neurosurgical Center, where he was later joined by Dr Roger Kula.
Dr Bolognese has performed 1,400 Chiari decompressions, 900 craniocervical fusions, and 900 cord de-tetherings.
He is on the scientific educational advisory board of the Chiari Syringomyelia Foundation and on the board of directors of the American Chiari and Syringomyelia Alliance Project"
 

Hip

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It's not possible to create a precise threshold of hindbrain protrusion to signify when Chiari is diagnosed, because in one study, all patients with greater than 12 mm of protrusion were symptomatic for Chiari, but they found that approximately 30% of those whose protrusion was between 5 and 10 mm remained without symptoms.

So even though the threshold of Chiari is typically set to 5 mm of protrusion, you can have 10 mm of protrusion and still not have any symptoms of Chiari.

Conversely, as this present study indicates, you can have less that 5 mm of protrusion, and have the symptoms of Chiari.
 

pattismith

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@Hip,
So surgery now depends on symptoms, and not on the protrusion size.
The polemic that remains between specialists is about cranio-cervical fusion.
This 2017 paper by Dr Brodbelt says:

"Recently, patients with Ehlers Danlos syndrome (EDS) and a Chiari I malformation have made representation to the UK Department of Health for funding to be treated abroad. This action arises out of the suggestion made by a number of surgeons in the United States (US), that cranio-cervical fixation can significantly help such patients, not only for their classic Valsalva related headaches but also for many of the additional, disabling symptoms associated with EDS of the hypermobile type.1,2
This treatment is not, however, widely accepted, even in the US, where there are a limited number of surgeons who carry out the bulk of these fixations. The contention made by some campaigners in the UK is that neurosurgeons here do not understand the disease and that they are unable to perform the surgery. Emotions are running high in some circles and on social media. There have been national headlines, introducing individual patients stories, some of which claim that the affected individuals’ necks are unstable and that these victims risk rapidly worsening disability, or even death, if not urgently treated. Funds are raised for surgical treatment overseas, on the basis that the NHS is unable to provide this treatment. It is certainly understandable that patients would become very concerned if this were the truth and if these risks were indeed real.
EDS is a genetically determined condition, potentially affecting all connective tissues in the body, with several different phenotypes now recognized.3 Affected individuals do experience many symptoms that affect their quality of life. Not least affected are those people with the hypermobility form of EDS that has been associated with Chiari malformations. Some of their symptoms seemingly arise from associated conditions, such as postural orthostatic tachycardia syndrome (POTS) and irritable bowel syndrome. Indeed, the list of conditions described as being associated with hypermobility related Chiari is increasing, including cognitive impairment and mast cell activation syndrome. Disturbances of autonomic function (dysautonomias), resulting from anatomical distortion of the cervicomedullary junction, have been proposed as the mechanism underlying many of these conditions...
Radiological assessment often includes dynamic imaging (flexion/extension views) and/or upright MRI of the craniovertebral junction. Measurements made from these images include the clival-odontoid angle and pB-C2 (a measure of the extent of basilar invagination), and values of <135 and >9mm respectively have been taken to indicate instability. These radiological measurements are not, however, essential parts of the hypermobility diagnostic criteria and are not accepted internationally as indicating instability……..etc"
 

Hip

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So surgery now depends on symptoms, and not on the protrusion size.
I am not sure what the criteria for Chiari surgery are, but for CCI fusion surgery, you normally need to have the both symptoms of cervical medullary syndrome, as well as pathological measurements on MRI.

Dr H requires at least two pathological measurements before he considers fusion surgery. See this Henderson 2018 video at 18:02.