The first step in the examination of the meninges is the removal of the brain.
The calvaria should be removed as follows : - The bone having been laid bare, a string should be tied round the skull passing from about an inch and a quarter above the external occipital protuberance behind, to an inch above the orbital arches in front. The outer table of the skull should then be sawn through and the inner table afterwards cracked with the mallet and chisel. A slight wrench will now disengage the calvaria. After noticing the Pacchionian bodies and the meningeal arteries, the student will do well to examine the superior longitudinal sinus by laying it open. He should next cut through the dura mater in an antero -posterior direction on each side of the sinus, and then make incisions directed transversely outwards from the central points of the two previous incisions as far as the cut margin of the bone. The four triangular flaps thus mapped out should be turned downwards, and by gently drawing one of the hemispheres aside, the falx cerebri may be seen ifi situ within the great longitudinal fissure, and the veins entering the superior longitudinal sinus may be noted. The falx should then be divided close to its attachment to the crista galli and thrown backwards. The head should next be inclined backwards and the frontal lobes of the brain gently raised. The following structures will then come into view, viz. the olfactory bulbs, the second, third, and fourth nerves, the infundibulum, and the internal carotid arteries. The olfactory bulbs will come away with the brain, but the other structures will require to be divided with scissors, as the nerves are frequently torn away from their connections by using a scalpel for this purpose. The head should next be gently inclined towards the right side, and the tentorium divided close to its attachment to the bone. The sixth, seventh, and eighth nerves should be cut at the same time. This dissection should be repeated on the opposite side. The head should then be tilted backwards, and the remaining cranial nerves, the vertebral arteries, and the commencement of the spinal cord cut through. The latter should be divided as low down as it can be reached with the scalpel. The brain can now be removed from the cranial cavity, the veins of Galen being ruptured by this process.
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