Ans. A. Temporal bone.CSF otorrhea# The most common cause of CSF otorrhea is trauma with fracture involving the tegmen tympani. Tegmen tympani which is formed in part by the petrous portion of the temporal bone, and the squamous portion of the temporal bone, forms the roof of the middle ear cavity. Other etiologies include perilymphatic fistula, surgeries involving the temporal bone, congenital anomalies, and destructive temporal bone tumors.# Fluid leaking from the nose or external auditory canal must first be positively identified as CSF. Drops of fluid from a CSF leak placed on absorbent filter paper may result in the double-ring sign, a central circle of blood and an outer clear ring of CSF. Serum glucose, chloride, and total protein tests of the fluid are not specific or conclusive for CSF.# Confirm or exclude the presence of CSF in leaking fluid by means of an immunoelectrophoretic study of the fluid for beta-2 transferrin or, beta-trace protein.# Methods for detecting CSF fistulas with intrathecal injections of dye pose a risk of chemical meningitis. Methylene blue, indigo carmine, and phenolsulfonphthalein (PSP) dyes are no longer in use. Some use a dilute solution of fluorescein to localize CSF fistulas both preoperatively and during surgery. Typically, is injected into the lumbar subarachnoid space over more than 1 minute. Cotton pledgets are placed in the nose. The dye reaches the skull base in 6 hours and is present over the cerebral convexities in 24 hours. The pledgets are examined for green fluorescence in a dark room with ultraviolet light 6 hours after the intrathecal PSP injection.# CT myelography is used in the detection of spinal CSF leak. CT cranial cisternography is performed with injection of 5-7 mL of nonionic myelographic contrast medium into the lumbar subarachnoid space. The patient is maintained in the prone position until a CT scan is performed. CT cistemographic findings in CSF leak include the concentration of contrast medium in portions of a paranasal sinus or within ethmoid or mastoid air cells. Occasionally, a stream of contrast medium is seen at the fistula site.Most common site for linear skull fracturesis the parietal bone, which is the thinnest of the cranial bones.Temporal bone fracturesclassified as transverse (extending across the petrous portion) or longitudinal (extending lateral to medial). Complication asso with transverse temporal bone fracture include CN VIII and CN VII injury, whereas longitudinal temporal fracture can cause hemotympanum, torn tympanic membrane, CSF leak, and conductive haering loss due to bony disruption.Basilar fracture of the temporal boneresults in "battle sign," which is postauricular ecchymoses and can be associated with CSF otorrhea.A frontal basilar farcture results in"raccoon's eyes", which is periorbital ecchymoses. CSF rhinorrhea can result due to frontal basilar fracture. The majority of CSF leaks resolve within 7 days without surgical intervention.