Autopsy of a Head Injury
Most autopsies of the head begin with the pathologist shaving the head to look for bruises (contusions) on the outside surface of the scalp (left). If the autopsy has been done properly, the head should be shaved for careful inspection. Attorneys should obtain photos of this stage from the Medical Examiner for experts to review.
The next step involves a lateral cut of the scalp from ear-to-ear (right).The scalp is then reflected front to back to expose the subgaleal layer to inspect for hemorrhages. Thorough photographic documentation of the subgaleal or intrascalp areas is absolutely required for a forensic autopsy. Make note of whether there is a corresponding external contusion on the child’s head to help determine whether the subgaleal hemorrhage is a true impact site or not. When the scalp is reflected, the pathologist may locate a fracture that escapes visual detection by percussing the exposed skull. Though most fractures can be observed visually, a “cracked pot” sound may indicate one that had been missed.
The pathologist will then remove the skull cap, exposing the brain. The dura may be either adherent to the inner table of the skull, or covering the surface of the brain, depending on whether or not it has been cut when the skull cap is removed.
When the dura is cut and removed, a subdural hematoma may be seen.
This blood will appear bright red if it is “acute.” If the subdural is older itwill appear the color of port wine or “crank case oil.” The pathologist should note if the blood is red/black, brownish, yellowish-orange, “machine oil” or straw colored (or combinations of all of these). The pathologist should weigh (volume), sample and photograph this blood.
Acute Subdural Hematoma
Chronic Subdural Hematoma
“Chronic” or old subdurals will be darker in color and may leave an iron stain on the dura. It will appear the color of port wine, brown or yellow.
It should be noted whether the blood is adherent to the skull cap, dura or elsewhere (and if so, to what degree) to aid in the timing and dating of the subdural. Adherant blood is not accute in nature. If the blood is adherent, care should be taken to properly fix the specimen before attempting to make a tissue section, since the clot and other valuable information may be carried away in the process. Even apparently acute clots may have chronic elements within them that only histological study can reveal.
Timing and Dating of Injuries
Histology Slide of Subacute Subdural Hematoma
7-8 day old or so subdural hematoma membrane…beneath the membranous cellular reaction is a recent hemorrhage, the age of which is 2 days old or less
The pathologist should retain a sample of the dura for examination by a forensic neuropathologist. Dating of a subdural hematoma by visual inspection is unreliable, but histologically, using the Munro and Merritt chart, greater accuracy is possible. Although the Munro and Merritt dating concept was done from limited adult data, it is the most comprehensive study to date. There are no studies to indicate that the process of aging and dating subdurals in children is any different than adults.
The arachnoid is the thin web-like membrane beneath the dura and covering the surface of the brain.
Diffuse Axonal Injury: This condition has had a number of other names (traumatic axonal injury–TAI, inner cerebral trauma, etc.). Classically persons suffering from DAI are in deep coma after suffering major closed head trauma such as major falls, automobile accidents and the like. They may or may not have subdural hematomas or skull fractures or any major bleeding in the brain. Most do not survive when autopsy is done within a few days of trauma the brain is edematous; there are numerous scattered deep brain hemorrhages classically in the corpus callosum, deep white matter around the ventricles and in the cerebral peduncle and upper brain stem-diencephalon. Microscopically, there are swollen axons with various reactions about them.
DAI is often alleged in so-called shaken babies and used to be thought to occur from the rotational forces that accompany shaking. However it was shown that there was no biomechanical evidence that the forces involved in pure shaking can attain the tissue injury threshold needed for production of DAI in experimental animals. It was also shown that regardless of what might have occurred prior to death, once the individual has been on a respirator, with significant hypoxia/ischemia to the brain, with or without edema or any other pathology, the findings of axonal injury by any staining method are unreliable in predicting what form of injury might have preceded death. Put another way, Beta-APP staining or any other method has no forensic significance when there have been 3 or more hours of hypoxia/ischemia and/or edema from any cause before death (Oehmichen; Geddes).
Beta APP stain showing beaded axon to the left
and accumulation in other axons and nerve cells.