The Retrosigmoid Craniotomy. A, Cadaverous specimen after retrosigmoid craniotomy in order to perform the far lateral approach. Note the exposition of the whole sigmoid sinus, the vertebral artery, C1 and C2 dorsal roots, the hypoglossus condyle and with its posterior two thirds drilled and the hypoglossus nerve into the hypoglossal canal. B, A closer view of the cadaverous specimen dissection performed while a far lateral approach is intended. Emphasis has been given to the vertebral entrance into the dura mater, the sigmoid sinus, the condyle with its posterior two thirds drilled in order to expose the hypoglossal canal and hypoglossus nerve and the posterior condylar emissary vein. This vein connects the external vertebral venous plexus to the sigmoid sinus. It is located, generally, at the inferior edge of the condyle. (Images courtesy of E de Oliveira)