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Arachnoid granulations on high-resolution MR images and diffusion-weighted MR images: normal appearance and frequency
T Koshikawa1, S Naganawa, H Fukatsu
1Department of Radiology, Nagoya University School of Medicine, Japan.
Abstract:
Arachnoid granulations (AGs), protrusions into the cerebral venous sinus lumen, have been reported on cerebral venography, contrast enhanced CT, and conventional MR imaging. Although thin-sliced high-resolution MR images and diffusion-weighted images are frequently obtained, there have been no detailed reports concerning AGs on these images. In this study, the frequency and positional distribution of AGs in the transverse sinus was investigated on thin-sliced high-resolution MR images, and their appearance on diffusion-weighted MR images was evaluated. At least one AG was found in 107 of 151 subjects (70.9%). No statistically significant differences were noticed between males and females or between the right and left sides. No significant correlations between age and size or between age and the number of AGs were noted. On diffusion-weighted images, all AGs showed iso-intensity to normal brain tissue, which was higher than the reported signal intensity of arachnoid cyst and lower than that of epidermoids. In conclusion, AGs are normal structures that are frequently found in the cerebral venous sinuses on high-resolution MR images. Knowledge regarding their frequency and normal appearance would be helpful to avoid confusion between pathological processes and AGs. It is also important to know that AGs are frequently found even in the younger population.
Insights
Arachnoid granulations (AGs) are common, normal structures found in cerebral venous sinuses. High-resolution MRI and diffusion-weighted imaging reveal their frequent presence, aiding in differentiating them from pathological conditions.
Area of Science:
- Neuroimaging
- Radiology
- Anatomy
Background:
- Arachnoid granulations (AGs) are anatomical variations protruding into cerebral venous sinuses.
- Previous imaging modalities like CT and conventional MRI have identified AGs.
- Detailed characterization of AGs on thin-slice high-resolution MRI and diffusion-weighted imaging (DWI) is lacking.
Purpose of the Study:
- To investigate the frequency and positional distribution of AGs in the transverse sinus using thin-slice high-resolution MR images.
- To evaluate the appearance of AGs on diffusion-weighted MR images.
- To provide reference data for distinguishing AGs from pathological findings.
Main Methods:
- Retrospective analysis of thin-slice high-resolution MR images and diffusion-weighted MR images from 151 subjects.
- Assessment of the presence, number, and location of arachnoid granulations in the transverse sinus.
- Evaluation of signal intensity of AGs on diffusion-weighted images compared to normal brain tissue, arachnoid cysts, and epidermoids.
Main Results:
- Arachnoid granulations were identified in 107 out of 151 subjects (70.9%).
- No significant differences in AG presence were found between sexes or sides (right/left).
- No significant correlations were observed between age and AG size or number. On DWI, AGs appeared iso-intense to normal brain tissue, distinct from arachnoid cysts and epidermoids.
Conclusions:
- Arachnoid granulations are frequently encountered normal anatomical structures in cerebral venous sinuses, particularly the transverse sinus.
- High-resolution MRI and DWI are effective in visualizing AGs and characterizing their signal intensity.
- Understanding the prevalence and imaging characteristics of AGs is crucial for accurate radiological interpretation and avoiding misdiagnosis of pathology, even in younger individuals.