Lecture 4

Question 1

What are potential reasons behind removing the brain during necropsy?

Answer 1

-rabies samples
-prion samples
-histopath. samples

Question 2

What are the basic steps to removing the head on necropsy?

Answer 2

-reflect the skin over ventral jaw
-cut through the tissue on either side of the mandible
-cut the hyoid bones to remove the tongue
-access the atlanto-occipital joint and disarticulate it
-cut through the spinal cord
-cut through any remaining tissue attaching head to body
-remove remaining soft tissue from skull

Question 3

What are the two methods for removing the brain from the skull?

Answer 3

Oscillating Saw:
-remove muscle over calvarium
-make first cut across
-make a cut down either side extending into the foramen magnum
-use skull key to remove piece of skull
-allow gravity to help remove entire brain
-use scalpel blade to scoop out remaining pituitary

Band Saw:
-make a longitudinal cut
-gently scoop out each half of the brain with end of scalpel handle or fingers
-cut cranial nerves as needed to remove brain
-retrieve any remaining portion of pituitary

Question 4

What are the steps to obtaining a rabies sample?

Answer 4

-do NOT place brain in formalin
-take cross section through cerebellum and brainstem
-take cross section from each side if brain was cut in half
-submit the section containing cerebellum and brainstem

Question 5

What are the steps to obtaining a prion sample?

Answer 5

-do NOT place brain in formalin
-take cross section bilaterally through the obex
-take cross section from each side if brain was cut in half

Question 6

What are the steps for brain fixation?

Answer 6

-place entire brain (or pieces remaining follow rabies and/or prion testing) into formalin
-do not cut into the brain further
-20:1 ratio of formalin to brain (and spinal cord)

Question 7

Which tools are used for spinal cord removal via dorsal laminectomy?

Answer 7

-rongeurs
-oscillating saw
-band saw

Question 8

What are the steps to spinal cord removal via dorsal laminectomy?

Answer 8

-remove dorsal laminae
-gently remove spinal cord; use scalpel to cut spinal nerves
-inspect spinal cord for lesions; localize relative to vertebrae
-feel the floor of spinal canal to check for bulging discs
-use band saw on vertebral column longitudinally to inspect vertebrae and discs

Question 9

What are the steps to spinal cord removal via longitudinal cut?

Answer 9

-use band saw to carefully make longitudinal cut
-gently remove spinal cord; use scalpel to cut spinal nerves
-inspect spinal cord for lesions; localize relative to vertebrae
-feel the floor of spinal canal to check for bulging discs
-inspect vertebrae and discs