54 • Cut the brain between the cerebral hemispheres to just open the ventricles. This will
allow formalin to access the inside of the brain. Alternatively, the cerebrum can be cut transversely multiple times like a loaf of sliced bread but not full thickness so as to leave
a 2-3 cm depth of tissue along the ventral brain to connect the slices. Immerse the brain and pituitary in 10 buffered formalin.
Common mistakes include cracking cutting too deeply into the bone around the brain, particularly the bone protecting the ventral brain, which can lead to damage of the ventral
brain stem. Insufficient ‘cracking’ of the bones surrounding the brain, particularly the ventral cranium, can make it difficult to lever the cranium apart. One side of the nose breaks.
Levering the head apart too quickly can tear the brain.
7.5 How to remove the brainstem with a modified spoon
The brain stem can be removed without opening the head us ing a ‘prionics spoon’, called
such because they are used to collect samples for prionics or TSE testing. Spoons for sheep and cattle are different sizes.
The procedure is as follows:
• Remove the head and place it with the nose down. Clear fat and muscle from the occipital condyles to allow access to the foramen magnum and brain stem.
• Slide the prionics spoon between the occipital condyles and over the dorsal surface of the brain stem.
• Keep the tip of the spoon pointing dorsally until ¾ of the blade is past the occipital condyles. Then, push the blade ventrally and move the tip of the spoon from side to
side to insure a proper cut. • Once the brain stem is removed examine it to make sure a small section of the spinal
cord, the obex and part of the medulla are present and fix in 10 buffered formalin as soon as possible.
Figure 7.9: Showing spoons and spoon placement
7.6 How to describe gross changes found at necropsy
A good description of your necropsy findings is very helpful to the pathologist examining and testing your samples. Photographs of lesions are a very useful addition to your written
description.
55 Field investigators tend to describe gross findings by providing a specific diagnosis in the
hope that it serves as both a description and provisional diagnosis. Examples include “the lungs had pneumonia
” and “the intestines had haemorrhagic enteritis”. This approach can be misleading and serves as a poor record. Describing and interpreting gross lesions is
relatively simple with a little practice. Below are some guidelines.
Description
Use plain, simple language. Do not record anything for normal organs and tissues unless a normal finding is
unexpected. Use six of the seven senses – 1. sound, 2. sight, 3. smell, 4. touch, 5. feel and 6.
common sense. Don’t use the 7
th
sense, taste.
Use a checklist of features. i.e. DA DE SSSSS CCCCP “dadescp” Displacement - the abnormal location of an organ or tissues
Adhesion
– adjacent tissues stuck together due to inflammation
Distribution
– the spatial arrangement of lesions i.e. random, symmetrical, focal, multifocal, coalescing, miliary, diffuse, segmental
Extent
– the percentage of an organ affected
Size
– described as lesion dimensions in length or weight or size relative to a common object golf ball or fist or relative to another organ in a pair. Lesions can be uniform or
non-uniform in size. Weight can be light or heavy and is often subjective even when weight is measured on scales.
Shape
– describe as circular, rectangular, triangular and so on. Borders are described as distinct, diffuse, irregular, serrated etc.
Surface including cut surface
– smooth, rough, ulcerated, dry, raised and so on
Sound
– what is heard when percussed or auscultated – crepitant gas, sloshing free fluid, knocking solid
Smell
– define the lesion by its odour i.e. sweet, foul, ammonia-like, cider-like, rotten egg like, acetone, odourless
Colour
– the complexion or tincture which distinguishes the lesion such as brown, red, gray, black, green; reddish black, whitish gray. Varieties of one colour are hues e.g. hues
of red or green. Light and dark are not colours.
Contour
– surface irregularities e.g. raised, depressed or flat.
Consistency and texture - Describes degree of density or viscosity of a lesion e.g. gas, fluid, solid.
Content
–Volume and nature of contents of hollow organs particularly bladder, gall bladder and reticulo-rumen; full, half full, empty; colour, smell, texture, particle size,
foreign objects.
pH
– 1-14 of urine and reticulo-rumen contents
56
7.7 How to interpret gross changes found at necropsy
