Diffuse Pachymeningeal Enhancement and Subdural and Subarachnoid Space Opacification on Delayed Postcontrast Fluid-Attenuated Inversion Recovery Imaging in Spontaneous Intracranial Hypotension: Visualizing the Monro-Kellie Hypothesis: Fig 1.

Abstract

Intracranial volume compensatory changes explained by the MonroKellie hypothesis (MKH) occur in spontaneous intracranial hypotension (SIH) and may be seen on MR imaging. 1 This case illustrates previously unreported findings on postcontrast fluid-attenuated inversion recovery (FLAIR) imaging conforming to the MKH, including diffuse pachymeningeal enhancement and gadolinium diffusion into the subdural space. It also highlights an additional compensatory mechanism of subarachnoid seepage seen as gadolinium opacification of the subarachnoid space.A 52-year-old man had a 3-year history of intermittent orthostatic headache relieved by lying down. Two years ago, he presented to the emergency department with severe headache, at which time brain CT showed bifrontal subdural hematomas, which were surgically evacuated. Following an initial asymptomatic period, his symptoms recurred after a few months. A year later, he presented again with severe headache, this time associated with nausea and vomiting. Brain MR imaging showed diffuse pachymeningeal enhancement and bilateral subdural effusions. FLAIR imaging, in addition, showed hyperintensity and thickening of the pachymeninges. Delayed postcontrast FLAIR showed diffuse pachymeningeal enhancement with gradual opacification of the subdural space followed by the subarachnoid space (Fig 1). Low opening pressure and xanthochromia were noted on lumbar puncture, with CSF showing elevated erythrocyte count, lymphocytosis, and raised protein levels. Renal function test findings were normal. In view of the patient's reluctance to undergo intervention, he was managed conservatively with bed rest, hydration, and medication. At discharge, he was asymptomatic.While postcontrast FLAIR has been useful in various intracranial lesions, its role in SIH has not been studied. The first of our findings on postcontrast FLAIR was diffuse pachymeningeal enhancement, similar to that described on postcontrast T1-weighted images. The mild T1 effect of postcontrast FLAIR allows detection of the increased contrast concentration in the engorged veins and interstitium in the dural border cell layer in SIH.2 If the pachymeningeal venous dilation alone is not sufficient to compensate for the CSF loss, fluid extravasation persists and leads to subdural effusions. 3 Our second finding following pachymeningeal enhancement was gadolinium diffusion into the subdural space with maximal subdural space opacification corresponding to the site of greatest pachymeningeal thickening and subdural effusions, a finding conforming to the MKH. Our third finding on delayed FLAIR was contrast opacification of the subarachnoid space. We hypothesize that this finding of gadolinium gradually opacifying the subarachnoid space suggests increased permeability, which comes into play in ongoing CSF loss when other mechanisms are saturated. This theory is further supported by frequent findings of increased red blood cells and raised protein levels in the CSF and previous reports of increased red blood cell diapedesis with subsequent...

MR Myelography for Identification of Spinal CSF Leak in Spontaneous Intracranial Hypotension

“…5,6 This finding is important because treatment with either directed blood patch, fibrin glue injections, or surgery requires preprocedural knowledge of the site of CSF leak. Although intrathecal administration remains an FDA off-label use of gadolinium, all patients in our study tolerated intrathecal gadolinium without complications.…”

“…3,4 A reduction in CSF volume leads to compensatory dilation of venous structures in the brain, which may result in headache and subdural collections via meningeal traction. 5,6 Severe untreated cases of SIH can lead to coma and stroke. 7 CT myelography (CTM) has historically been considered the study of choice for the detection and localization of CSF leak, though a criterion standard test is difficult to establish, given the varied etiologies for SIH.…”

Fast whole brain MR imaging of dynamic susceptibility contrast changes in the cerebrospinal fluid (cDSC MRI)

“…When gadolinium(Gd)-based contrast medium are used, MR signal contrast between pre-contrast and post-contrast MR images can often be observed in the CSF at certain locations within the intra-cranial space. [11][12][13][14] This is mainly due to the fact that the dural blood vessels lack a blood-brain barrier (BBB) that presents in cortical blood vessels, which enables some of the commonly used Gd contrast agents in human clinical MRI scans to cross the dural blood vessel wall and to enter the CSF. Recent studies have shown that some meningeal lymphatic vessels in the brain can be visualized using MRI with Gd contrast in human brains.…”

“…injection, the Gd contrast leaks out from the dural blood vessels, which lacks a BBB into the CSF. [11][12][13][14] However, this is a very rough estimation, and Gd concentration is known to be a key factor that can have dramatic effects on MR signals. 34 Figure 2 shows simulation results for the relationship between the maximum contrast in the CSF with and without Gd and the concentration of Gd in CSF.…”

Spinal Cerebrospinal Fluid Leakage in Spontaneous Intracranial Hypotension: An Intrathecal Gadolinium Enhanced MR-Myelography Study

“…Lumbar epidural blood patches are commonly applied in patients resistant to conservative therapy. Targeted epidural blood patch, fibrin glue injections and surgical dural repair are treatment options needing correct localization of CSF leakage [1][2][3][4][5][6].…”