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The examination of the brain requires removal of the head from the rest of the carcass, and opening the calvarium
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To remove the head from the rest of the carcass, severe all attachments at the atlanto-occipital joint
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While doing this, take care not to unnecessarily pull the spinal cord damaging it on the process
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Skin the head and remove all muscles to expose the vault of the cranium
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To open the vault of the cranium and expose the brain, a hacksaw may be used to saw off the overlying bones
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Alternatively, a chisel may be used but take care not to penetrate the cavity and damage the brain
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Grasp firmly the head and press it against one corner of the table and carefully saw the bone slowly
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Hold the head firmly with the aboral surface (occipital bones) slightly tilted and facing the examiner
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Grasp the whole head with one hand pressing the thumb against the nasopharyngeal opening
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Anchor the index finger on the orbital rim and support the nasal region with the rest of the fingers
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Press firmly the head on one corner of the table
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Carefully saw the condyloid fossa just above the occipital condyles
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Continue the cut slightly oblique and forward cutting the junction of the squamous temporal and occipital bones, and up to the supraorbital process of the frontal bones
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Take care when cutting the lateral part of the temporal bone since at this part the bones are relatively thin and lie close to the brain.
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After completing cuts at the right side of the head, rotate the head to cut the bones at the other side
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Grasp the head with the thumb anchored on the orbital rim and the index finger pressed against the nasopharyngeal opening
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Support the head using the rest of the fingers grasping the nasal region. Make a similar cut until both the cuts at both side of the head meet at the median plane
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Place the head on the table and hold it firmly with one hand
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Make a diagonal cut continuing the cuts made at either side, and saw off about quarter thick of the head
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This completes the cuts to open the calvarium
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Hold the head slightly tilted with the foramen magnum facing the examiner
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To remove the sawed portion of the calvarium, pry it open by sticking the knife or a flat instrument onto the sawed portion where the occipital and temporal bones meet forming a ridge
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This part of the skull is relatively thick
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Twist the knife and force open the sawed bone
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If the cuts made were deep enough, this should pry open the calvarium without much difficulty
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Once the sawed portion is lifted and removed, cut the meninges covering the brain
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The brain is now exposed for examination
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Before removing the whole brain from the cavity, examine the surface of the brain and look for evidence of oedema and flattening of the gyri and sulci
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Remove the brain by inverting the head with the palm supporting the falling brain
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With the aid of a pair of scissors, cut all the cranial nerves and attachments until the whole brain drops slowly to the palm of the hand holding the head.
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The whole brain is best fixed in ten-times the brain volume of 10% formalin solution overnight before examination
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This will harden the brain and makes it amenable to slicing and manipulation
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Any alteration on the appearance of one side compared to that of the other side may be a suspect for possible lesion, provided that cuts were made perpendicularly
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When slicing the brain, note any difference on the diameter of the ventricles and any abnormal tissue masses
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Save the slices of the brain in fresh formalin solution. For routine histopathological evaluation of the brain, at least six sections are required composed of the following transverse sections:
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Root of spinal cord
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Mid cerebellum
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Cerebrum at either side (2 sections) including the hippocampus
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Brain stem taken at the level of the pons
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Cerebral peduncle