Practical pathology

by Aldred Scott Warthin

As soon as the sawing is completed, no matter what method is used, the T-chisel or skull-opener (Fig. [12]) is used to spring off the skull-cap. The chisel-blade is inserted into the saw-cut in the right frontal region, and turned sideways with a quick, powerful movement of the right hand. Any portions of the inner table not completely sawed through (usually in the region of the petrous portion of the temporal) are thus broken, and the dura is loosened sufficiently from the inner table to allow the prosector to introduce the fingers of the right hand beneath the skull-cap in the frontal region and to hold down the dura while the fingers of the left hand inserted into the frontal saw-cut pull the skull-cap backward with a powerful tug, completely separating it from the dura, unless the dura is adherent throughout, as is the case in very young children, old people, and in certain pathologic conditions. In the latter case it may be necessary to cut the dura along the line of the horizontal saw-cut and to remove it with the skull-cap, cutting the falx as the skull-cap is lifted. In young children the dura must always be removed with the skull-cap. In the case of pathologic adhesions an attempt should be made first to separate them from the lamina vitrea by cutting them with a knife or chisel-blade inserted through the saw-cut. As the adhesions are severed the skull-cap is lifted gradually backward. Too much force should not be used in jerking off the skull-cap, else the brain may be damaged. Whenever possible the dura should be left intact, as a better judgment is thereby obtained of the intradural pressure, and there is less danger of losing the contents of the subdural space.

Some prosectors use hammer and chisel to remove the skull-cap. This is a bad method, particularly so in the case of medicolegal autopsies, as artificial fractures of the skull may thus be produced. It is safest never to use a hammer in the opening of the skull.

The skull-cap is examined as soon as taken off. If the periosteum was not previously removed it is now scraped off, and the skull-cap examined against the light. After its complete examination the operator proceeds to the removal of the brain.

2. Removal of the Brain. The convexity of the dura is first examined. The narrow-bladed brain-knife or long section knife (Fig. [3]) is now taken in hand, and with the cutting edge directed upward the point of the blade is inserted into the anterior end of the superior longitudinal sinus and the sinus cut open as far posteriorly as the opening in the cranial vault will admit. Its walls and contents are then examined. With cutting edge outward the point of the brain-knife is then inserted through the dura just to the left of the anterior end of the falx and the dura cut around to the left at the level of the horizontal saw-cut. The knife is then inserted through the dura just to the right of the falx and the dura cut in the same way on the right side. The two halves of the dura are now loosened from the convexity of the brain by breaking the blood-vessels connecting the dura with the inner meninges. The index-finger is swept over the convexities and along the sides of the longitudinal sinus, tearing the pial veins. Pathologic adhesions should be carefully worked out. The finger is then used to raise the falx anteriorly so that the point of the brain-knife can be introduced beneath it to cut it upward and forward. The dura is then carefully examined and turned back over the brain and allowed to hang down over the occiput. The inner meninges over the exposed portion of the brain are now examined; and the brain is then removed as follows: The four fingers of the left hand are placed beneath the frontal lobes, lifting these sufficiently for the prosector to be able to cut the I, II, III, IV and VI cranial nerves, the carotids and pedicle of the hypophysis down to the tentorium cerebelli. The tentorium is then cut with the tip of the brain-knife, which is held perpendicularly, by a gentle up-and-down sawing motion, from left to right along the superior border of the petrous bones. The V, VII, VIII, IX, X, XI and XII cranial nerves are then cut as closely as possible to their exits. As they are cut the brain is lifted gradually more and more, and supported by the left hand. When all the connections have been cut except the cord and vertebral arteries these are severed by the myelotome (Fig. [4]), or by the brain-knife, the point of which is put down through the foramen magnum as far as possible, and the cord and vertebral arteries severed by a transverse cut made from left to right as nearly horizontal as possible. The knife is now laid aside and the first two fingers of the right hand put beneath the two cerebellar lobes so that the medulla and portions of cervical cord fall between these fingers, which are then used to lift them upward and backward. The freed brain is now rolled over backward out of the cranial cavity upside down onto the palm of the left hand, and is then placed upon a board, tray or dish ready for examination. If the cord has already been removed, any portion remaining is taken out with the brain. In case the cord has been freed and is to be removed with the brain it is only necessary to cut the vertebral arteries and then to lift up the brain, drawing the cord up through the foramen magnum.

3. Section of the Brain. (Modified Virchow Method.) The brain as it is taken from the cranium is placed upside down, with occipital lobes toward the prosector. The basal meninges and blood-vessels are then carefully examined. The hemispheres and convolutions are separated and the arachnoid torn by the tip of the index-finger or the handle of a scalpel; and the branches of the cerebral vessels to their deepest ramifications are thus exposed, giving a complete picture of the circle of Willis and all of its branches to the point where they enter the brain-substance. The larger vessels are opened by transverse or longitudinal cuts and their walls and contents noted. The brain is then turned over, and the meninges examined over the entire convexity. The pia and arachnoid are then removed together over the entire convex and median surfaces of the hemispheres. If the blood-vessels between the convolutions are seized with the forceps the meninges can be easily stripped off, the fingers aiding the forceps, using great care not to tear the brain substance. The meninges are removed about half-way down the outer sides of the hemispheres and are there left intact so as to hold the pieces of brain together after it has been cut, and so permit orientation. The cortical surface is then examined; if bloody, it should be washed with a weak stream of water.

Fig. 28.—Method of examination of brain. Opening of left ventricle. Line showing direction of cuts. (After Nauwerck.)

The hemispheres are now separated until the corpus callosum comes into view. The left hemisphere is then held by the left hand, with the thumb on the median surface and the fingers on the outer and under sides, so that the hemisphere is turned outward and yet raised slightly at the same time, thus stretching the corpus callosum over the cavity of the left lateral ventricle. The point of the narrow brain-knife (Fig. [3]) with cutting edge upward is then introduced with great care through the corpus callosum about midway between the genu and splenium and close to the gyrus cinguli (gyr. forn., Fig. [28]). The corpus callosum at this point is about 2 to 3 mm. thick and it is gently nicked with the point of the knife until an opening is made into the cavity of the ventricle. The knife-point must not be allowed to slip through to damage the basal ganglia beneath. Into the small opening thus made the brain-knife, held nearly horizontal, with cutting edge upward, is introduced and the corpus callosum cut forward until the anterior horn of the ventricle is reached. The point of the knife is then passed into the horn and the knife-handle raised and turned over forward, cutting slightly outward through the frontal lobe to its apex and disclosing the anterior horn. The knife is then reversed, held horizontally, with cutting edge upward, and the corpus callosum cut posteriorly from the beginning of the first cut, until the posterior horn is reached, when the point of the knife is inserted into the horn and the knife turned over toward the operator, cutting backward and somewhat outward through the occipital lobe to its apex and opening up the posterior horn. (See Fig. [28].) By this method the lateral ventricle is opened first at the highest point of its cavity, and the fluid contents collect in the anterior and posterior horns so that the amount and character can be easily noted.

Fig. 29.—Section of brain. Ventricles opened. Lines show direction of large longitudinal incisions through brain-substance. (After Nauwerck.)