Asymptomatic or Incidental Chiari Malformation

CHIARI MALFORMATION IS NO LONGER CONSIDERED "RARE".

Once thought to be an "orphan disorder" (less than 200,000 cases in the U.S.), Chiari has become remarkably common. MRI is being more frequently used to diagnose neurological disorders. 1,2 Because of this, radiologists are finding more and more Chiari malformations on MRI scans.

It is estimated that Chiari I malformation is present in somewhere between 0.6% and 1% of MRI scans. 3,4,5 The estimated rate of diagnosis in children is a little higher, around 3%.3 While this might sound low— and, therefore, rare— it actually means that Chiari is quite common. If we apply the estimate of 1% to the total U.S. population (323.1 million people, as of July 2016) 6 , then that means an estimated 3.2 million people may have what experts are starting to call incidental or asymptomatic Chiari.

WHAT IS ASYMPTOMATIC/INCIDENTAL CHIARI?

There are plenty of Chiari patients who wait years to have Chiari recognized as the true cause of their symptoms. When patients go undiagnosed or are misdiagnosed, it makes it hard for them to be appropriately treated. But, there are an even greater number of patients who have these so-called incidental findings . 3,4,5,7

People with asymptomatic/incidental Chiari have a Chiari malformation on their MRI, but the Chiari is either not the main source of their symptoms, or it is not causing their symptoms at all. Statistically speaking, this represents a majority of the population with Chiari. One recent study estimated the number of individuals with Chiari malformation to be 68% asymptomatic or incidental. 7

Most incidental Chiari patients either never have symptoms, or have mild symptoms and live pretty normal lives. Others have symptoms that can be managed with medication and careful follow-up with their doctor. 5 Some incidental Chiari malformations (and the syringomyelia that they have caused) can “spontaneously resolve” on their own, without any surgery or other treatments at all 7,8,9,10 — and even the experts aren’t sure why this happens.

HOW DO I KNOW IF I HAVE SYMPTOMATIC OR ASYMPTOMATIC CHIARI?

The most important thing to do when you see a Chiari malformation result on an MRI is to talk to your doctor and, if applicable, get a second opinion. A good doctor will ask you about the symptoms you are having, how those symptoms are or are not impacting your life, and whether or not surgery or “conservative management” would be more appropriate for you, specifically .

Every Chiari patient is different— some patients need surgery, others need to be watched over time, and many do not require any medical intervention at all. It is important to keep a meaningful dialogue open with your medical team and reach out when something doesn’t feel right.

If you ever have questions, please reach out by phone (718-966-2593 ) or email to CSF or the members of the CSF Scientific Education & Advisory Board to learn how you can advocate for yourself or your little one. We are here to help.

References

  1. Smith-Bindman R, Miglioretti DL, Johnson E, Lee C, Feigelson HS, Flynn M, et al: Use of diagnostic imaging studies and associated radiation exposure for patients enrolled in large integrated health care systems, 1996-2010. JAMA 307: 2400-09, 2012
  2. Smith-Bindman R, Miglioretti DL, Larson EB: Rising use of diagnostic medical imaging in a large integrated health system. Health Aff (Millwood) 27: 1491-1502, 2008
  3. Meadows J, Kraut M, Guarnieri M, Haroun RI, Carson BS: Asymptomatic Chiari Type I malformations identified on magnetic resonance imaging. J Neurosurg 92(6): 920-6, 2000.
  4. Aitken LA, Lindan CE, Sidney S, Gupta N, Barkovich AJ, Sorel M, et al: Chiari type I malformation in a pediatric population. Pediatr Neurol 40: 449–454, 2009
  5. Smith BW, Strahle J, Bapuraj JR, Muraszko KM, Garton HJL, Maher CO: Distribution of cerebellar tonsil position: implications for understanding Chiari malformation. J Neurosurg 119: 812-19, 2013.
  6. US & World Population Clock [Internet]. United States Census Bureau; c2016 [cited 2017 Jul 31]. Avaiilable from: https://www.census.gov/popclock/.
  7. Strahle J, Muraszko KM, Kapurich J, Bapuraj JR, Garton HJL, Maher CO: Chiari malformation Type I and syrinx in children undergoing magnetic resonance imaging. J Neruosurg Pediatr 8: 205-13, 2011.
  8. Nishizawa S, Yokoyama T, Yokota N, Tokuyama T, Ohta S: Incidentally identified syringomyelia associated with Chiari I malformations: is early interventional surgery necessary? Neurosurgery 49: 637–641, 2001.
  9. Sun JC, Steinbok P, Cochrane DD: Spontaneous resolution and recurrence of a Chiari I malformation and associated syringomyelia. Case report. J Neurosurg 92 (2 Suppl): 207–210, 2000.
  10. Sun PP, Harrop J, Sutton LN, Younkin D: Complete spontaneous resolution of childhood Chiari I malformation and associated syringomyelia. Pediatrics 107: 182–184, 2001.

Revised: 8/2017

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