The “Mickey Mouse” Sign

Abstract

Objective: In transnasal endoscopic pituitary surgery and transsellar approaches to anterior skull base lesions, a bony sella window is created with the lateral limits being the carotid arteries. Method: Coronal CT scan of the sphenoid sinuses were reviewed in a tertiary referral hospital and compared with intra operative findings. Results: Sphenoid anatomy is variable in terms of the degree of pneumatization and bony anatomy around the pituitary gland and internal carotid arteries. We describe a radiological sign ascertained from computerized tomography (CT) that when present indicates whether the carotid arteries can be readily identified endoscopically on entering the sphenoid sinus. On the axial CT the carotid arteries may produce protuberances either side of the sella which together with the bony sella and dorsum sella appear to form the outline of the head of Mickey Mouse or a teddy bear. Conclusion: When this sign is not present then the junction between the sella and carotids may not be clear and surgeons must be cautious or use neuronavigation.