This chapter discusses in great detail prevention, diagnosis and management of intracranial complication that can occur during the operation or in the post operative period. A detailed account of the important and relevant anatomy is illustrated on soft and hard tissues of the cadaver dissection both in coronal and sagittal views aided by CT scans and intra operative photographs. The anatomy of the skull base in relation to the ethmoid and sphenoid sinus is described so as to avoid complications in the first place. The pathophysiology of the CSF leak is discussed and the repair of the CSF fistula is described step by step including post operative care of the patient. Account of the key points for the endoscopic repair is given in detail. An unusual but serious complication of brain abscess, meningitis, Pneumoencephalus, and cavernous sinus thrombosis along with CT scan photographs and the appropriate treatment is given.