Skull base connections between the middle meningeal and internal carotid arteries

Background: External to internal carotid artery anastomoses are normally found in man. However, such connections at the skull base between the cavernous internal carotid artery and middle meningeal artery are rarely discussed in the literature and when present, are difficult, if not impossible, to see with imaging studies unless pathologically enlarged. Therefore, the aim of the present anatomic study was to investigate such connections via cadaveric dissection. Materials and methods: In 12 latex-injected adult cadaveric heads (24 sides), microdissection was performed to investigate for connections at the skull base between the cavernous part of the internal carotid and middle meningeal arteries. Additionally, neck dissections were performed to observe for atherosclerosis of the internal carotid artery. Statistical analyses were performed for differences between sides and gender. Results: On 14 sides (58.3 %) (nine left and five right sides), arterial anastomoses were identified between the middle meningeal and internal carotid arteries. All connections were small with a mean length of 8 mm and a mean diameter of 0.9 mm. These connections were found between the lateral aspect of the cavernous internal carotid artery and the medial side of the main trunk of the middle meningeal artery on 64.3 % of sides, the anterior branch of the middle meningeal artery on 7 % of sides, and the posterior branch of the middle meningeal artery on 28.6 % of sides. The size of the middle meningeal and internal carotid arteries was within normal limits in all specimens. Although not statistically significant, connections tended to be more frequently found on the left sides. Conclusions: The majority of cadaveric sides in our study were found to have anastomoses at the skull base between the cavernous segment of the internal carotid and middle meningeal arteries. These very small connections would most likely not be visualized on imaging studies. These connections most likely function in times of carotid artery ischemia that is chronic in nature (e.g., Moya Moya disease) and may, in the past, have been misidentified as a human rete mirabile.