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Spontaneous intracranial hypotension with deep brain swelling
Mario Savoiardo1, Ludovico Minati, Laura Farina
1Department of Neuroradiology, Istituto Nazionale Neurologico C. Besta, Via Celoria 11, 20133 Milano, Italy. msavoiardo@istituto-besta.it
Brain : a Journal of Neurology
|May 31, 2007
Summary
Spontaneous intracranial hypotension with brain swelling shows increased diffusivity in deep venous drainage. A narrowed vein of Galen and straight sinus angle suggests venous stagnation, impacting brain volume considerations.
Area of Science:
- Neurology
- Radiology
- Neuroscience
Background:
- Spontaneous intracranial hypotension (SIH) results from cerebrospinal fluid (CSF) leakage, typically presenting with brain sagging and dural changes on MRI.
- Severe SIH cases can exhibit significant brain sagging, diencephalic-mesencephalic swelling, and altered consciousness, sometimes with minimal subdural collections.
- The Monro-Kellie doctrine, which posits constant intracranial volume, may need re-evaluation in SIH with brain swelling.
Purpose of the Study:
- To investigate diffusion changes and the vein of Galen (vG)/straight sinus (SS) angle in patients with SIH and brain swelling.
- To explore the relationship between central herniation, venous stagnation, and altered brain volume in SIH.
Main Methods:
- Retrospective analysis of diffusion-weighted MRI studies in five SIH patients with brain swelling, seven SIH patients without swelling, and ten controls.
- Measurement of the angle formed by the vein of Galen entering the straight sinus (vG/SS angle).
- Comparison of mean diffusivity in deep venous drainage areas across the study groups.
Main Results:
- Increased mean diffusivity was observed in SIH patients with brain swelling, particularly in areas draining into the deep venous system (vG and SS).
- The vG/SS angle was significantly decreased in SIH patients with brain swelling (40.7° ± 12.8°) compared to those without swelling (67.8° ± 10.3°) and controls (73.3° ± 12.3°).
- A narrowed vG/SS angle suggests functional stenosis at the junction, potentially causing venous stagnation due to downward brain sagging.
Conclusions:
- Downward stretching of the vein of Galen and a narrowed vG/SS angle may contribute to venous stagnation in SIH with brain swelling.
- These findings suggest that brain volume may not be invariable in SIH, challenging the traditional application of the Monro-Kellie doctrine.
- Diffusion studies and vG/SS angle measurement are valuable in assessing the pathophysiology of SIH with severe brain sagging.
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