Skull Base CSF Leaks: Potential Underlying Pathophysiology and Evaluation of Brain MR Imaging Findings Associated with Spontaneous Intracranial Hypotension

Ian T. Mark; Jeremy Cutsforth-Gregory; Patrick Luetmer; Ajay A. Madhavan; Michael Oien; Paul Farnsworth; Girish Bathla; Steve Messina; Michael Link; Jamie Van Gompel

doi:10.3174/ajnr.A8333

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RE:
Ian T Mark and Jamie Van Gompel

Published on: 11 February 2025
RE: Are Skull Base CSF Leaks Different From Spinal CSF Leaks?
Alaa Radaideh, Pokhraj P. Suthar and Sumeet G. Dua

Published on: 03 February 2025

Published on: (11 February 2025)
Page navigation anchor for RE:
RE:
Ian T Mark, Neuroradiologist, Mayo Clinic
Other Contributors:
Jamie Van Gompel, Neurosurgeon
Dear Editor,

We thank Dr. Radaideh and colleagues for their interest in our work1. CSF leaks, particularly when spinal in origin, can not only be debilitating but are underdiagnosed, and more awareness will benefit patient care.

Our study found that skull base CSF leaks do not typically present with clinical symptoms or brain MRI findings associated with spontaneous intracranial hypotension (SIH). The correspondence by Dr. Radaideh and colleagues question whether underlying intracranial hypertension accounts for the absence of brain MRI findings that we associate with spinal CSF leaks causing SIH.

Of the 31 patients with skull base leaks included in our study, 3 (9.7%) had the diagnosis of idiopathic intracranial hypertension (IIH), 15 (48.4%) had a history of trauma or temporal bone surgery, and 13 (41.9%) were classified as spontaneous. Of the spontaneous cohort, 7 had CSF pressure measured (mean 18.8 cm H2O, SD 3.1). As a reference, IIH consensus guidelines use >25 cm H2O as a cutoff.2 Patients with baseline IIH who decompress as a CSF leak could potentially fall below the 25 cm H2O cutoff.

We believe that the more convincing evidence in our work contrary to the letter by Dr. Radaideh and colleagues lies in the 48.4% of patients with trauma or surgery, rather than IIH, that led to the skull base CSF leak. One of these patients had a posterior fossa leak with brain MRI findings of SIH, otherwise the remainder did not. That cohort provides...
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Dear Editor,

We thank Dr. Radaideh and colleagues for their interest in our work1. CSF leaks, particularly when spinal in origin, can not only be debilitating but are underdiagnosed, and more awareness will benefit patient care.

Our study found that skull base CSF leaks do not typically present with clinical symptoms or brain MRI findings associated with spontaneous intracranial hypotension (SIH). The correspondence by Dr. Radaideh and colleagues question whether underlying intracranial hypertension accounts for the absence of brain MRI findings that we associate with spinal CSF leaks causing SIH.

Of the 31 patients with skull base leaks included in our study, 3 (9.7%) had the diagnosis of idiopathic intracranial hypertension (IIH), 15 (48.4%) had a history of trauma or temporal bone surgery, and 13 (41.9%) were classified as spontaneous. Of the spontaneous cohort, 7 had CSF pressure measured (mean 18.8 cm H2O, SD 3.1). As a reference, IIH consensus guidelines use >25 cm H2O as a cutoff.2 Patients with baseline IIH who decompress as a CSF leak could potentially fall below the 25 cm H2O cutoff.

We believe that the more convincing evidence in our work contrary to the letter by Dr. Radaideh and colleagues lies in the 48.4% of patients with trauma or surgery, rather than IIH, that led to the skull base CSF leak. One of these patients had a posterior fossa leak with brain MRI findings of SIH, otherwise the remainder did not. That cohort provides evidence that skull base CSF leaks do not typically present with brain MRI findings for the reason outlined in our manuscript.

Furthermore, the claim by Dr. Radaideh and colleagues of, “half of the studied patients potentially never had intracranial hypotension and so the imaging signs were naturally absent”, tying low CSF pressure to SIH is a known myth.3-6 This claim, when perpetuated, can lead to the incorrect underdiagnosis of SIH and have a detrimental effect on patient care.

Ian Mark
Jamie Van Gompel

1. Mark IT, Cutsforth-Gregory J, Luetmer P, et al. Skull Base CSF Leaks: Potential Underlying Pathophysiology and Evaluation of Brain MR Imaging Findings Associated with Spontaneous Intracranial Hypotension. AJNR Am J Neuroradiol. Aug 15 2024;doi:10.3174/ajnr.A8333
2. Mollan SP, Davies B, Silver NC, et al. Idiopathic intracranial hypertension: consensus guidelines on management. J Neurol Neurosurg Psychiatry. Oct 2018;89(10):1088-1100. doi:10.1136/jnnp-2017-317440
3. Kranz PG, Gray L, Amrhein TJ. Spontaneous Intracranial Hypotension: 10 Myths and Misperceptions. Headache. Jul 2018;58(7):948-959. doi:10.1111/head.13328
4. Yao LL, Hu XY. Factors affecting cerebrospinal fluid opening pressure in patients with spontaneous intracranial hypotension. J Zhejiang Univ Sci B. Jul 2017;18(7):577-585. doi:10.1631/jzus.B1600343
5. Luetmer PH, Schwartz KM, Eckel LJ, et al. When should I do dynamic CT myelography? Predicting fast spinal CSF leaks in patients with spontaneous intracranial hypotension. AJNR Am J Neuroradiol. Apr 2012;33(4):690-4. doi:10.3174/ajnr.A2849
6. Kranz PG, Tanpitukpongse TP, Choudhury KR, et al. How common is normal cerebrospinal fluid pressure in spontaneous intracranial hypotension? Cephalalgia. Nov 2016;36(13):1209-1217. doi:10.1177/0333102415623071
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Competing Interests: None declared.
Published on: (3 February 2025)
Page navigation anchor for RE: Are Skull Base CSF Leaks Different From Spinal CSF Leaks?
RE: Are Skull Base CSF Leaks Different From Spinal CSF Leaks?
Alaa Radaideh, Assistant Professor, Rush University Medical Center
Other Contributors:
Pokhraj P. Suthar, Assistant Professor

Sumeet G. Dua, Assistant Professor
Dear Editor:

We read with interest the recent article by Mark et al [1] discussing imaging findings in patients with skull base CSF leaks. The authors found that imaging signs of spontaneous intracranial hypotension (SIH) such as pachymeningeal enhancement, cisternal effacement and venous sinus engorgement were absent in most patients with skull base CSF leaks. The authors concluded that skull base and spinal CSF leaks represent different pathophysiologies. While we agree with the authors, that these patients fall into distinct cohorts, we believe that the reader should be aware of some important caveats in this take-home message.

An increasing body of evidence has emerged over the last few years linking CSF leaks, particularly spontaneous CSF leaks from the skull base to intracranial hypertension (IIH) [2]. Skull base remodeling is commonly seen in patients with IIH and predisposes them to CSF leaks in the form of CSF rhinorrhea or otorrhea [3]. In the group of patients studied by the authors, about 10% had proven IIH. More importantly however, about 40% of the patients had spontaneous CSF leaks from the skull base with no apparent cause such as surgery or trauma. Given the association between spontaneous leaks and IIH, it is likely that a significant proportion of these spontaneous cases had undiagnosed IIH; the study though provides little information about this subset of patients. It is unknown whether these 40% patients had elevated opening pressures or...
Show More

Dear Editor:

We read with interest the recent article by Mark et al [1] discussing imaging findings in patients with skull base CSF leaks. The authors found that imaging signs of spontaneous intracranial hypotension (SIH) such as pachymeningeal enhancement, cisternal effacement and venous sinus engorgement were absent in most patients with skull base CSF leaks. The authors concluded that skull base and spinal CSF leaks represent different pathophysiologies. While we agree with the authors, that these patients fall into distinct cohorts, we believe that the reader should be aware of some important caveats in this take-home message.

An increasing body of evidence has emerged over the last few years linking CSF leaks, particularly spontaneous CSF leaks from the skull base to intracranial hypertension (IIH) [2]. Skull base remodeling is commonly seen in patients with IIH and predisposes them to CSF leaks in the form of CSF rhinorrhea or otorrhea [3]. In the group of patients studied by the authors, about 10% had proven IIH. More importantly however, about 40% of the patients had spontaneous CSF leaks from the skull base with no apparent cause such as surgery or trauma. Given the association between spontaneous leaks and IIH, it is likely that a significant proportion of these spontaneous cases had undiagnosed IIH; the study though provides little information about this subset of patients. It is unknown whether these 40% patients had elevated opening pressures or even other imaging signs of IIH such as empty sella and transverse sinus stenosis. Information on IIH associations, such as gender and obesity status, is also notably absent.

Given the above limitations, it is theoretically possible that as many as 50% of the patients studied by the authors had IIH as the underlying cause of CSF leak. Thus, by extension, it is also plausible that imaging signs such as pachymeningeal enhancement were not seen merely because these patients had IIH. In other words, about half of the studied patients potentially never had intracranial hypotension and so the imaging signs were naturally absent.

In summary, although we agree that the patients with spinal and skull base CSF leak have different pathophysiology, we believe that underlying IIH is a significant confounding factor and arguably the most important reason behind the difference noted by the authors between the two groups.

References:

1. Mark IT, Cutsforth-Gregory J, Luetmer P, et al. Skull base CSF leaks: Potential underlying pathophysiology and evaluation of brain MR imaging findings associated with spontaneous intracranial hypotension. AJNR Am J Neuroradiol 2024;45:1593-96, https://doi.org/10.3174/ajnr.A8333

2. Chen BS, Britton JOT. Expanding the clinical spectrum of idiopathic intracranial hypertension. Curr Opin Neurol 2023;36:43-50, https://doi.org/10.1097/WCO.0000000000001131

3. Leal PRL, Barbier C, Hermier M, et al. Association of intracranial hypertension with calvarial and skull base thinning. Otol Neurol 2019;40:e619-26, https://doi.org/0.1097/MAO.0000000000002249
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Competing Interests: None declared.