Warning: Declaration of My_Walker::start_el(&$output, $item, $depth, $args) should be compatible with Walker_Nav_Menu::start_el(&$output, $data_object, $depth = 0, $args = NULL, $current_object_id = 0) in /home2/ajnrblog/public_html/ajnrdigest/wp-content/themes/ajnr/functions.php on line 258
Searching for the “Holy Grail” of SIH: Site of CSF Leak - AJNR News Digest
March-April 2020
Introduction
Figure 3 from Kranz

Searching for the “Holy Grail” of SIH: Site of CSF Leak

Shah picture

Lubdha M. Shah

Hutchins picture

Troy A. Hutchins

Peckham picture

Miriam E. Peckham

Spontaneous intracranial hypotension (SIH), caused by CSF leak along the spine, can be challenging to diagnose and treat. The classic patient with SIH will present with positional headache and the characteristic brain MRI findings of SIH: dural enhancement, venous distension, subdural collection, and brain stem slumping.1 However, patients with SIH often have a variable clinical presentation (eg, nonpostural headache and cranial nerve palsies) and may not have the expected brain MRI findings. Frequently, the CSF leak site is difficult to localize.2,3 Increased understanding of the pathophysiology of SIH has contributed to the advancement of diagnostic imaging techniques, allowing earlier treatment of this debilitating condition. Until now, management pathways have shown marked heterogeneity, which may be in part related to a lack of practical experience, unfamiliarity with recent discoveries, or unsubstantiated conceptions of how this disease process should be diagnosed and treated.4

In this edition of the AJNR News Digest, we spotlight recent articles that have informed the way this condition should be approached for diagnosis and treatment. These articles add to our knowledge of diagnostic techniques for SIH by 1) using brain MRI features5 as well as postmyelographic renal contrast patterns,6 2) discussing digital subtraction and CT fluoroscopy myelographic techniques for SIH work-up,7,8 and 3) proposing a systematic imaging approach for CSF leak localization.2

The aforementioned classic imaging features of SIH, such as thin pachymeningeal enhancement, are not pathognomonic for SIH; pachymeningeal enhancement is commonly seen in postoperative or post-lumbar puncture cases.9,10 Other, more specific imaging features, such as brain stem slumping, are only present in approximately 51% of cases and can be subjective.10–13 In an effort to provide more objective imaging criteria for SIH, Wang et al used the interpeduncular angle as a sensitive and specific measure and reproducible parameter on routine clinical MRI.5

Diagnostic procedures, such as CT myelography (CTM), are routinely performed to identify the site of CSF leak. Kinsman et al described a potentially helpful secondary sign of CSF dural leak and/or CSF venous fistula: the presence of early renal contrast on initial CTM.6 They found that early renal contrast was more common in confirmed/suspected CSF venous fistulas compared with dural leaks.

Precise localization of the CSF leak source is vital to guiding directed percutaneous or surgical treatment.7,14 A retrospective review of 5 patients by Kranz et al showed that decubitus positioning during CTM can increase leak detection and diagnostic confidence in some patients with previous supine or prone CTM.7 Fluoroscopic dynamic myelogram followed by decubitus CTM in the right or left decubitus position or bilaterally (based on subtle findings on prior CTM) revealed a CSF venous fistula, with a 507% mean increase in draining vein density (illustrated in Figure 1).7 The authors postulated that increased detection may be due to higher contrast concentration on the dependent side combined with gravity effect.7

A systematic imaging approach for diagnosis and localization was proposed by Farb et al, where both brain and spine MRI were combined with digital subtraction myelography to localize the site of CSF leak.2 This approach stressed the importance of patient positioning during myelography depending on which of the 4 described subtypes of CSF leak was suspected.2,15 Type 1 is a ventral dural tear related to disc degeneration and type 2 is a more lateral dural tear.2,15 Type 3 represents a CSF venous fistula, and type 4 is an extradural leak from the distal nerve root sleeve.2,15 Patients were stratified based on the presence or absence of a spinal longitudinal extradural CSF collection on total spine MRI. They performed digital subtraction myelography prone when present and lateral decubitus when absent.2 This approach enabled the authors to definitively identify the CSF leak in 27/31 (87%) of patients with SIH.2 While some patients with types 1 or 2 improved with an epidural blood patch, none of the patients with types 3 or 4 responded.2

These papers bring us closer to reliably diagnosing and localizing the site of CSF leak for treatment, not only by improving our screening efforts through MRI and CTM, but also by informing the imaging work-up to find the site of CSF leak. For an in-depth look at each paper, and for the author’s commentary, please see the accompanying write-ups.

References

  1. Forghani R, Farb RI. Diagnosis and temporal evolution of signs of intracranial hypotension on MRI of the brain. Neuroradiology 2008;50:1025–34, 10.1007/s00234-008-0445-z
  2. Farb RI, Nicholson PJ, Peng PW, et al. Spontaneous intracranial hypotension: a systematic imaging approach for CSF leak localization and management based on MRI and digital subtraction myelography. AJNR Am J Neuroradiol 2019;40:745–53, 10.3174/ajnr.A6016
  3. Kranz PG, Malinzak MD, Amrhein TJ, et al. Update on the diagnosis and treatment of spontaneous intracranial hypotension. Curr Pain Headache Rep 2017;21:37, 10.1007/s11916-017-0639-3
  4. Kranz PG, Gray L, Amrhein TJ. Spontaneous intracranial hypotension: 10 myths and misperceptions. Headache 2018;58:948–59, 10.1111/head.13328
  5. Wang DJ, Pandey SK, Lee DH, et al. The interpeduncular angle: a practical and objective marker for the detection and diagnosis of intracranial hypotension on brain MRI. AJNR Am J Neuroradiol 2019;40:1299–1303, 10.3174/ajnr.A6120
  6. Kinsman KA, Verdoorn JT, Luetmer PH, et al. Renal contrast on CT myelography: diagnostic value in patients with spontaneous intracranial hypotension. AJNR Am J Neuroradiol 2019;40:376–81, 10.3174/ajnr.A5934
  7. Kranz PG, Gray L, Amrhein TJ. Decubitus CT myelography for detecting subtle CSF leaks in spontaneous intracranial hypotension. AJNR Am J Neuroradiol 2019;40:754–56, 10.3174/ajnr.A5995
  8. Kim DK, Brinjikji W, Morris PP, et al. Lateral decubitus digital subtraction myelography: tips, tricks, and pitfalls. AJNR Am J Neuroradiol 2020;41:21–28, 10.3174/ajnr.A6368
  9. Pannullo SC, Reich JB, Krol G, et al. MRI changes in intracranial hypotension. Neurology 1993;43:919–26, 10.1212/wnl.43.5.919
  10. Mokri B, Piepgras DG, Miller GM. Syndrome of orthostatic headaches and diffuse pachymeningeal gadolinium enhancement. Mayo Clin Proc 1997;72:400–13, 10.4065/72.5.400
  11. Fishman RA, Dillon WP. Dural enhancement and cerebral displacement secondary to intracranial hypotension. Neurology 1993;43:609–11, 10.1212/wnl.43.3_part_1.609
  12. Schievink WI, Maya MM, Louy C, et al. Diagnostic criteria for spontaneous spinal CSF leaks and intracranial hypotension. AJNR Am J Neuroradiol 2008;29:853–56, 10.3174/ajnr.A0956
  13. Shah LM, McLean LA, Heilbrun ME, et al. Intracranial hypotension: improved MRI detection with diagnostic intracranial angles. AJR Am J Roentgenol 2013;200:400–07, 10.2214/AJR.12.8611
  14. Cho KI, Moon HS, Jeon HJ, et al. Spontaneous intracranial hypotension: efficacy of radiologic targeting vs blind blood patch. Neurology 2011;76:1139–44, 10.1212/WNL.0b013e318212ab43
  15. Schievink WI, Maya MM, Jean-Pierre S, et al. A classification system of spontaneous spinal CSF leaks. Neurology 2016;87:673–79, 10.1212/WNL.0000000000002986

Image from: Kranz PG, Gray L, Amrhein TJ. Decubitus CT myelography for detecting subtle CSF leaks in spontaneous intracranial hypotension.