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.

Temporohyoid osteoarthropathy in 33 horses (1993-2000).

A retrospective study of the medical records of 33 horses was performed to determine the clinical and diagnostic abnormalities associated with temporohyoid osteoarthropathy. Data collected from medical records included signalment, presenting complaints, history, physical examination findings, laboratory data, results of diagnostic imaging studies, and treatments. Follow-up information was obtained from a review of case records; by telephone conversation with the owner, veterinarian, or trainer; or by both methods. Of 33 horses with temporohyoid osteoarthropathy, 29 presented with facial nerve (cranial nerve VII) deficits and 23 presented with vestibulocochlear nerve (cranial nerve VIII) deficits. Guttural pouch endoscopy was more reliable than radiography for diagnosis. Of horses with unilateral clinical signs, 22.6% actually had bilateral disease. Magnetic resonance imaging and computed tomography identified the lesions in all horses in which these tests were performed. Of 30 horses for which follow-up information was obtained, 20 (67%) were alive. Eight horses were euthanized and 1 died because of problems associated with temporohyoid osteoarthropathy. Nineteen of 20 surviving horses (95%) were considered by the owner or trainer to be suitable for athletic use. Twelve surviving horses (60%) had residual facial nerve deficits; 11 horses (55%) had residual vestibulocochlear nerve deficits. Horses with temporohyoid osteoarthropathy have a fair prognosis for return to some type of athletic function, but there is risk of acute death. The majority of horses would be expected to have some residual cranial nerve dysfunction, and it could take a year or longer for maximal improvement to occur.