Purpose: Although arachnoid granulations (AGs) were initially described by Pacchioni more than 300 years ago, they are still poorly described, especially those in middle cranial fossa. The aim of this study was to identify anatomical features of AGs in middle cranial fossa of cadaver and compare such features with that of 64-slice computed tomography.
Methods: The study involved anatomical dissection of 33 adult cadaveric heads and computed tomographic (CT) examinations of 40 patients with various intracranial diseases. The number, size, distribution, and morphology of the AGs in middle cranial fossa of the cadavers and patients were examined and compared.
Results: The number of AGs observed on the middle cranial fossa of the cadaveric specimens was greater than that of the patients (P < 0.05). While anatomic dissection revealed a total of 228 AGs in 24 of 33 cadaveric heads, CT scans demonstrated only 80 AGs in 23 of 40 patients. In cadavers, the AGs occurred in the following sites in order of frequency: the middle meningeal sinus (144 AGs, 63.2%), sphenoparietal sinus (47 AGs, 20.6%), lateral foramen rotundum (19 AGs, 8.3%), and cavernous sinus (18 AGs, 7.9%). In CT images, the AGs occurred in the following sites in order of frequency: the middle meningeal sinus (50 AGs, 62.5%), sphenoparietal sinus (23 AGs, 28.8%), and lateral foramen rotundum (7 AGs, 8.8%). The AGs of cavernous sinus and venous lacunae adjacent to the middle meningeal sinus were hardly identified on CT images. Most of the AGs were spherical or finger-like in shape. Histologically, the AGs can be divided into two types: single type and lobulated type.
Conclusions: The study provides a detailed description of AGs in or near the middle meningeal sinus, sphenoparietal sinus, lateral foramen rotundum, and cavernous sinus. It also reveals a difference in the ability of detecting cranial AGs between microanatomy and CT scans.