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Jason Passafiume, MD and Humberto Morales, MD University of Cincinnati Medical Center

Poster #:  eP-117. MR Imaging Findings of Cerebellar Tonsillar Ectopia in Adults: Chiari Type 1 Malformation versus Spontaneous Intracranial Hypotension. Jason Passafiume, MD and Humberto Morales, MD University of Cincinnati Medical Center. Disclosures. The authors have no disclosures.

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Jason Passafiume, MD and Humberto Morales, MD University of Cincinnati Medical Center

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  1. Poster #: eP-117 MR Imaging Findings of Cerebellar Tonsillar Ectopia in Adults: Chiari Type 1Malformation versus Spontaneous Intracranial Hypotension Jason Passafiume, MD and Humberto Morales, MD University of Cincinnati Medical Center

  2. Disclosures • The authors have no disclosures.

  3. Purpose • Downward cerebellar tonsillar displacement or ectopia (CE) has multiple causes. • Chiari Type 1 Malformation (CM) and Spontaneous Intracranial Hypotension (SIH) are important entities presenting with this imaging finding. • Differentiating these conditions, although sometimes challenging, is of upmost clinical importance. • The management differs significantly, with epidural blood patch in SIH and elective suboccipital decompression in some cases of CM.

  4. Materials & Methods • Retrospective review of cases with CE and clinical diagnosis of CM or SIH was performed in our radiology database. • Cebellar ectopia was defined as any displacement of the cerebellar tonsils below the McRae line (radiographic line drawn on a midsagittal MRI joining the basion and the opisthion) • Main Quantitative measurements • Cerebellar tonsil displacement (mm) • Length of Supraocciput (LSO) (mm) • Pontomesencephalic Angle (PMA) • Mammillpontine Distance (MPD) (mm) • Qualitative variables: • Effacement of PMA • Pituitary Prominence (PP) • Dural Enhancement (DE) • Rounded transverse sinus (RTS) • Oval shape of foramen magnum (OFM)

  5. Materials & Methods • SPSS was used for statistical analysis; t-test and exact test were used for quantitative and qualitative differences between groups, respectively. • 63 cases of CM and 23 cases of SIH were selected.

  6. Quantitative Measurements B A Pontomesencephalic angle (A) and mammillopontine distance (B) were measured using midline sagittal image.

  7. D G F C E B A Qualitative measurements include: Length of supraocciput (AE), length of clivus (BC), length of Twining’s line (CE), transverse diameter of foramen magnum MaRae’s line (AB), length of tentorial line (DE), dorsum sella to vein of Galen line (CD), transverse diameter of foramen magnum (FG)

  8. Quantitative Results* *Other measurements did not show statistical difference between groups

  9. Qualitative Results

  10. Case 1 • 51 year-old woman with headache and dizziness

  11. Case 1 • Midline sagittal image shows a prominent pituitary with convex superior margin, diminished pontomesencephalic angle, and cerebellar tonsil ectopia. • Additional sagittal image shows a rounded transverse sinus.

  12. Case 1 • Coronal post-contrast T1 fat-suppressed and FLAIR images show pachymeningeal thickening, likely indicating dural venous engorgement.

  13. Case 1 • Follow up imaging (left) obtained at 13 months shows resolution of pachymeningeal thickening and enhancement. A subsequent exam (right) 3 months later shows recurrence. • Several blood patch treatments resulted in transient relief of symptoms for this patient with a diagnosis of intracranial hypotension.

  14. Case 2 • 40-year-old woman with headache and dizziness

  15. Case 2 • Sagittal T2-weighted image displays prominent pituitary, obliteration of the pontomesencephalic angle and sagging brainstem, and marked cerebellar tonsil ectopia. • Coronal post-contrast imaging demonstrates diffuse pachymeningeal thickening and enhancement.

  16. Case 2 • Axial image through the cervical spine shows a C7 left foraminal pseudomeningocele. • Nuclear medicine cisternogram initial imaging shows radiotracer accumulation in the pseudomeningocele. Delayed images (not pictured) showed relative clearing of the radiotracer, suggesting a CSF leak. • The patient underwent a left C6-C7 foraminotomy for repair of pseudomeningocele.

  17. Case 3 • 36 year-old man with headache, neck pain, subjective weakness

  18. Case 3 • Axial image shows an oval shaped foramen magnum, with AP greater than transverse dimension. • Sagittal image displays a short supraocciput and marked cerebellar tonsil downward displacement. Note preservation of the pontomesencephalic angle, without evidence of brainstem sagging. • Imaging and clinical findings were consistent with Chiari malformation. • This patient had improvement of symptoms following suboccipital and C1 decompression.

  19. Conclusion • Decreased Length of Supraocciput and Oval Foramen Magnum are common characteristics of CM cases, confirming a congenital cause of CE. • Effacement of Pontomesencephalic Angle as well as Pituitary Prominence is seen in the majority of SIH cases; rarely in CM. • In uncertain cases of CE, particularly when overlapping features of CM and SIH are noted, the use of contrast can be helpful, as Dural Enhancement was not seen in CM. • In addition, attention to Rounded Transverse Sinus sign in suspected cases of SIH is helpful, not seen in CM.

  20. Resources • Schievink, Wouter I. "Spontaneous spinal cerebrospinal fluid leaks: a review." Neurosurgical focus 9.1 (2000): 1-9. • Nishikawa, Misao, et al. "Pathogenesis of Chiari malformation: a morphometric study of the posterior cranial fossa." Journal of neurosurgery 86.1 (1997): 40-47. • Milhorat, Thomas H., et al. "Chiari I malformation redefined: clinical and radiographic findings for 364 symptomatic patients." Neurosurgery 44.5 (1999): 1005-1017. • Schievink, W. I., et al. "Diagnostic criteria for spontaneous spinal CSF leaks and intracranial hypotension." American Journal of Neuroradiology 29.5 (2008): 853-856. • Angelo, Franzini, et al. "Spontaneous intracranial hypotension: diagnostic and therapeutic implications in neurosurgical practice." Neurological Sciences 32.3 (2011): 287-290. • Atkinson, John LD, et al. "Acquired Chiari I malformation secondary to spontaneous spinal cerebrospinal fluid leakage and chronic intracranial hypotension syndrome in seven cases." Journal of neurosurgery 88.2 (1998): 237-242. • Franzini, Angelo, et al. "Treatment of spontaneous intracranial hypotension: evolution of the therapeutic and diagnostic modalities." Neurological Sciences34.1 (2013): 151-155. • Mea, Eliana, et al. "Chronic daily headache in the adults: differential diagnosis between symptomatic Chiari I malformation and spontaneous intracranial hypotension." Neurological Sciences 32.3 (2011): 291-294. • Puget, Stéphanie, et al. "Chiari-like tonsillar herniation associated with intracranial hypotension in Marfan syndrome: Case report." Journal of Neurosurgery: Pediatrics 106.1 (2007): 48-52. • Urbach, Horst. "Intracranial hypotension: clinical presentation, imaging findings, and imaging-guided therapy." Current opinion in neurology 27.4 (2014): 414-424.

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