The cranial nerves are 12 pairs of symmetrically arranged nerve trunks that are attached to the base of the brain. They leave the skull via various foramina at its base and are distributed for the greater part to the head. Some of these nerves may be described as traveling in a direction away from the brain; some of them convey impulses in a reverse direction. On leaving the brain each cranial nerve is invested by a sheath of pia mater, traverses the subarachnoid space, pierces the arachnoid and receives an additional sheath from the latter- mentioned membrane. It next enters a canal in the dura mater; this leads to the foramen in the skull through which the nerve leaves the cranium. It is invested by a sheath of dura which is continuous with the epineurium covering the nerve trunk proper. The dural aperture and the foramen do not necessarily correspond to each other in location since some of the nerves (the 4th and the 6th) run an intradural course of some length before they leave their foramina. These nerves are not only numerically designated from before backward but are also distinguished by their specific names, which are based on their distributions or functions.
KeywordsCranial Nerve Facial Nerve Cavernous Sinus Lateral Rectus Lingual Nerve
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