Examination of brain

EXAMINATION OF THE BRAIN

  • The examination of the brain requires removal of the head from the rest of the carcass, and opening the calvarium
  • To remove the head from the rest of the carcass, severe all attachments at the atlanto-occipital joint
  • While doing this, take care not to unnecessarily pull the spinal cord damaging it on the process
  • Skin the head and remove all muscles to expose the vault of the cranium
  • To open the vault of the cranium and expose the brain, a hacksaw may be used to saw off the overlying bones
  • Alternatively, a chisel may be used but take care not to penetrate the cavity and damage the brain
  • Grasp firmly the head and press it against one corner of the table and carefully saw the bone slowly
  • Hold the head firmly with the aboral surface (occipital bones) slightly tilted and facing the examiner
  • Grasp the whole head with one hand pressing the thumb against the nasopharyngeal opening
  • Anchor the index finger on the orbital rim and support the nasal region with the rest of the fingers
  • Press firmly the head on one corner of the table
  • Carefully saw the condyloid fossa just above the occipital condyles
  • 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
  • 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.
  • After completing cuts at the right side of the head, rotate the head to cut the bones at the other side
  • Grasp the head with the thumb anchored on the orbital rim and the index finger pressed against the nasopharyngeal opening
  • 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
  • Place the head on the table and hold it firmly with one hand
  • Make a diagonal cut continuing the cuts made at either side, and saw off about quarter thick of the head
  • This completes the cuts to open the calvarium
  • Hold the head slightly tilted with the foramen magnum facing the examiner
  • 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
  • This part of the skull is relatively thick
  • Twist the knife and force open the sawed bone
  • If the cuts made were deep enough, this should pry open the calvarium without much difficulty
  • Once the sawed portion is lifted and removed, cut the meninges covering the brain
  • The brain is now exposed for examination
  • 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
  • Remove the brain by inverting the head with the palm supporting the falling brain
  • 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.
  • The whole brain is best fixed in ten-times the brain volume of 10% formalin solution overnight before examination
  • This will harden the brain and makes it amenable to slicing and manipulation
  • 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
  • When slicing the brain, note any difference on the diameter of the ventricles and any abnormal tissue masses
  • 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:
  • Root of spinal cord
  • Mid cerebellum
  • Cerebrum at either side (2 sections) including the hippocampus
  • Brain stem taken at the level of the pons
  • Cerebral peduncle
Last modified: Friday, 23 March 2012, 10:11 AM