Chiari Malformation Workup

  • Author: Peyman Pakzaban, MD; Chief Editor: Allen R Wyler, MD   more...
 
Updated: Mar 2, 2012
 

Imaging Studies

MRI is the most useful and most widely used imaging study for diagnosing Chiari malformation. In addition to depicting the anatomy of the craniocervical junction, it provides useful information about associated abnormalities, such as syringomyelia and hydrocephalus.

Patients who cannot undergo MRI can be evaluated with CT-myelography/cisternography. However, the increasing availability of high-resolution high-speed (eg, 64-slice) CT scanners allows for making the diagnosis with a noncontrast CT with sagittal reconstructions, obviating the need for myelography.

CSF flow analysis through foramen magnum with phase-contrast cine MRI helps distinguish symptomatic Chiari I from asymptomatic cerebellar ectopia[9] and helps predict response to surgical decompression.[10]

CSF flow study with phase-contrast cine MRI. BrainCSF flow study with phase-contrast cine MRI. Brain pulsations results in caudad and cephalad flow of CSF across foramen magnum during systole and diastole. The reversal in the direction of flow is picked up by alternating light and dark appearance of CSF in front and behind the medulla and upper spinal cord on phase-contrast cine MRI. In this case of Chiari I malformation, note the complete absence of CSF flow behind (arrowheads) and focal constriction of CSF flow (arrows) in front of cervicomedullary junction.
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Laboratory Studies

Lab studies are not applicable for diagnosing Chiari malformations.

Preparation for surgery for Chiari I decompression is the same as for any elective surgery and depends on the patient's general health. The author routinely obtains CBC, basal metabolic panel, PT, aPTT, chest radiograph, and ECG. Blood is typed and screened.

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Contributor Information and Disclosures
Author

Peyman Pakzaban, MD  Consulting Neurosurgeon, Houston MicroNeurosurgery; Chairman, Department of Surgery, Bayshore Medical Center

Peyman Pakzaban, MD is a member of the following medical societies: Alpha Omega Alpha, American Association of Neurological Surgeons, American Medical Association, American Stroke Association, Congress of Neurological Surgeons, Harris County Medical Society, and Texas Medical Association

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD  Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

Ryszard M Pluta, MD, PhD  Associate Professor, Neurosurgical Department Medical Research Center, Polish Academy of Sciences at Warsaw, Poland; Clinical Staff Scientist, Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health (NIH); Fishbein Fellow, JAMA, Chicago ,IL

Ryszard M Pluta, MD, PhD is a member of the following medical societies: Congress of Neurological Surgeons and Polish Society of Neurosurgeons

Disclosure: Nothing to disclose.

Paolo Zamboni, MD  Professor of Surgery, Chief of Day Surgery Unit, Chair of Vascular Diseases Center, University of Ferrara, Italy

Paolo Zamboni, MD is a member of the following medical societies: American Venous Forum and New York Academy of Sciences

Disclosure: Nothing to disclose.

Chief Editor

Allen R Wyler, MD  Former Medical Director, Northstar Neuroscience, Inc

Allen R Wyler, MD is a member of the following medical societies: American Academy of Neurological and Orthopaedic Surgeons, American Association of Neurological Surgeons, and Society of Neurological Surgeons

Disclosure: Nothing to disclose.

References

  1. Koehler PJ. Chiari's description of cerebellar ectopy (1891). With a summary of Cleland's and Arnold's contributions and some early observations on neural-tube defects. J Neurosurg. Nov 1991;75(5):823-6. [Medline].

  2. Speer MC, Enterline DS, Mehltretter L, Hammock P, Joseph J, Dickerson M, et al. Chiari type I malformation with or without syringomyelia: prevalence and genetics. J Genet Couns. 2003;12:297-311.

  3. Dias M. Myelomeningocoele. In: Choux M, Di Rocco C, Hockley A, Walker M. Pediatric Neurosurgery. London: Churchill Livingston; 1999:33-61.

  4. Speer MC, George TM, Enterline DS, Franklin A, Wolpert CM, Milhorat TH. A genetic hypothesis for Chiari I malformation with or without syringomyelia. Neurosurg Focus. Mar 15 2000;8(3):E12. [Medline].

  5. Boyles AL, Enterline DS, Hammock PH, Siegel DG, Slifer SH, Mehltretter L, et al. Phenotypic definition of Chiari type I malformation coupled with high-density SNP genome screen shows significant evidence for linkage to regions on chromosomes 9 and 15. Am J Med Genet A. Dec 15 2006;140(24):2776-85. [Medline].

  6. Milhorat TH, Bolognese PA, Nishikawa M, McDonnell NB, Francomano CA. Syndrome of occipitoatlantoaxial hypermobility, cranial settling, and chiari malformation type I in patients with hereditary disorders of connective tissue. J Neurosurg Spine. Dec 2007;7(6):601-9. [Medline].

  7. Greenberg MS. Chiari Malformation. In: Handbook of Neurosurgery. 6. New york: Thieme; 2006:103-109.

  8. Tubbs RS, Lyerly MJ, Loukas M, Shoja MM, Oakes WJ. The pediatric Chiari I malformation: a review. Childs Nerv Syst. Nov 2007;23(11):1239-50. [Medline].

  9. Hofkes SK, Iskandar BJ, Turski PA, Gentry LR, McCue JB, Haughton VM. Differentiation between symptomatic Chiari I malformation and asymptomatic tonsilar ectopia by using cerebrospinal fluid flow imaging: initial estimate of imaging accuracy. Radiology. Nov 2007;245(2):532-40. [Medline].

  10. McGirt MJ, Nimjee SM, Fuchs HE, George TM. Relationship of cine phase-contrast magnetic resonance imaging with outcome after decompression for Chiari I malformations. Neurosurgery. Jul 2006;59(1):140-6; discussion 140-6. [Medline].

  11. Ulrich Batzdorf. Chiari Malformation. In: M.J. Appuzo. Brain Surgery, Complication Avoidance and Management. 2. New York: Churchill Livingston; 1993.

  12. James HE. Chiari Malformation Type I. J Neurosurg. Aug 2007;107(2):184. [Medline].

  13. James HE, Brant A. Treatment of the Chiari malformation with bone decompression without durotomy in children and young adults. Childs Nerv Syst. May 2002;18(5):202-6. [Medline].

  14. Perrini P, Benedetto N, Tenenbaum R, Di Lorenzo N. Extra-arachnoidal cranio-cervical decompression for syringomyelia associated with Chiari I malformation in adults: technique assessment. Acta Neurochir (Wien). Oct 2007;149(10):1015-22; discussion 1022-3. [Medline].

  15. Guo F, Wang M, Long J, Wang H, Sun H, Yang B, et al. Surgical management of Chiari malformation: analysis of 128 cases. Pediatr Neurosurg. 2007;43(5):375-81. [Medline].

  16. Hoffman CE, Souweidane MM. Cerebrospinal fluid-related complications with autologous duraplasty and arachnoid sparing in type I Chiari malformation. Neurosurgery. Mar 2008;62(3 Suppl 1):156-60; discussion 160-1. [Medline].

 
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Sagittal and coronal MRI images of Chiari type I malformation. Note descent of cerebellar tonsils (T) below the level of foramen magnum (white line) down to the level of C1 posterior arch (asterisk).
Axial MRI image at the level of foramen magnum in Chiari type I malformation. Note crowding of foramen magnum by the ectopic cerebellar tonsils (T) and the medulla (M). Also note the absence of cerebrospinal fluid.
Occipitalization of atlas in a patient with Chiari I.
T2 hyperintense region on MRI (arrow) depicting edema in central cord region of a patient with Chiari I malformation. Left untreated, this patient is likely to develop cavitation of the edematous central cord, resulting in syringomyelia.
CSF hypotension syndrome: Postcontrast MRI before (A) and after (B) treatment with lumbar epidural blood patch. Notice the thick meningeal enhancement (arrows), the relative paucity of CSF in front of the brainstem and behind the cerebellar tonsils, and the engorgement of the pituitary gland before treatment (A). Notice reversal of these abnormalities and ascent of the cerebellar tonsils after treatment (B). In this case, an acquired Chiari malformation was not present, but in some cases it is.
CSF flow study with phase-contrast cine MRI. Brain pulsations results in caudad and cephalad flow of CSF across foramen magnum during systole and diastole. The reversal in the direction of flow is picked up by alternating light and dark appearance of CSF in front and behind the medulla and upper spinal cord on phase-contrast cine MRI. In this case of Chiari I malformation, note the complete absence of CSF flow behind (arrowheads) and focal constriction of CSF flow (arrows) in front of cervicomedullary junction.
Resolution of syringomyelia (asterisk) after decompression of Chiari I malformation (white arrow).
Intraoperative photograph of Chiari type 1 malformation showing descent of cerebellar tonsils well below the level of foramen magnum.
Intraoperative photograph of duraplasty with pericranial graft. The duraplasty provides additional room for cerebellar tonsils at the craniocervical junction, while achieving closure of dura and prevention of cerebrospinal fluid leak.
Table 1. Comparison of Chiari I and II Malformations
CharacteristicChiari IChiari II
Usual age of diagnosisAdults and older childrenInfants and young children
Clinical findings
  • Headache and neck pain (worsened by cough or Valsalva maneuver)
  • Myelopathy
  • Cerebellar symptoms
  • Lower brainstem symptoms (eg, dysarthria, dysphagia, downbeat nystagmus)
  • Central cord symptoms (eg, hand weakness, dissociated sensory loss, cape anesthesia)
  • In infants, signs of brainstem dysfunction predominate: swallowing/feeding difficulties, stridor, apnea, weak cry, nystagmus
  • Weakness of extremities
Primary anatomical abnormalities
  • Herniation of cerebellar tonsils through foramen magnum, producing compression of cervicomedullary junction
  • Herniation of lower brainstem through foramen magnum
  • Cephalad course of cranial nerves
  • Kinking of cervicomedullary junction
  • "Beaking" of tectum
  • Upward herniation of vermis through incisura
  • Nearly vertical tentorium
MyelomeningoceleNoAlways
HydrocephalusLess than 10% of casesVery common
Syringomyelia30-70%Common
Associated abnormalities
  • Craniocervical hypermobility syndromes
  • Klippel-Feil anomaly
  • Hereditary connective tissue disorders and neurofibromatosis type II
  • Callosum corpus pellucidum septum of agenesis
  • Hypoplasia or
  • Enlargement of massa intermedia
  • Heterotopias and gyral abnormalities
Shared associated abnormalities
  • Invagination
  • Basilar
  • Occipitalization of atlas
  • Bifida of C1 posterior arch
  • Foramen magnum variant anatomieses
  • Occipitalization of atlas
  • Bifida of C1 posterior arch
  • Foramen magnum variant anatomieses
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