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"Giant" arachnoid granulations just like CSF?: NOT!!
C R Trimble1, H R Harnsberger, M Castillo
1Department of Radiological Sciences, Irvine Medical Center, University of California-Irvine, 101 The City Drive, Orange, CA 92868, USA. agropman@cnmc.org
AJNR. American Journal of Neuroradiology
|June 29, 2010
Summary
Giant arachnoid granulations (AGs) over 1 cm are rare and can mimic venous sinus pathology. Imaging reveals that fluid within these giant AGs often shows signal intensity incongruent with cerebrospinal fluid (CSF).
Area of Science:
- Neuroradiology
- Neuroimaging
- Vascular Neurology
Background:
- Giant arachnoid granulations (AGs), defined as >1 cm, are uncommon venous sinus lesions.
- These lesions are frequently misdiagnosed as neoplasms or venous sinus thrombosis.
- Accurate differentiation is crucial for appropriate patient management.
Purpose of the Study:
- To characterize the imaging features of giant arachnoid granulations (AGs).
- To differentiate giant AGs from other venous sinus pathologies using MRI and CT.
- To establish imaging criteria for diagnosing giant AGs.
Main Methods:
- Retrospective analysis of 19 giant AGs (>1 cm) from 17 patients.
- Review of available MR imaging (all), CT (5/19), and digital subtraction angiography (DSA) (7/19).
- Comparison of intra-AG fluid signal intensity with cerebrospinal fluid (CSF) and non-fluid AG tissue with gray matter.
Main Results:
- Fluid within giant AGs demonstrated CSF-incongruent signal intensity in nearly 80% (15/19) of cases on at least one MR sequence.
- Nine of these 15 AGs showed incongruent signal intensity on two or more MR sequences.
- CSF-incongruent signal intensity was observed in 8/8 AGs on FLAIR, 7/10 on precontrast T1WI, 13/19 on T2WI, and 8/14 on contrast-enhanced T1WI.
- Non-fluid AG tissue showed varied signal intensity, including flow voids and gray matter isointense signals.
Conclusions:
- Giant AGs exhibit distinct imaging characteristics on MRI, particularly regarding intra-AG fluid signal intensity.
- CSF-incongruent signal intensity on MRI is a key finding to differentiate giant AGs from venous sinus thrombosis or neoplasms.
- Multisequence MRI analysis aids in the accurate diagnosis of giant arachnoid granulations.
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