**3. Special dissection procedures**

Selected procedures and techniques that differ from or are added to the routine autopsy are performed in certain situations to better demonstrate the diseases or injuries involved.

#### **3.1 Pneumothorax**

Pneumothorax is usually associated with injury to the lung, although pure pneumothorax, although rare, can happen. The pleural cavities, therefore, should be checked for the presence of air in cases of chest injuries.

The skin and muscle on the injured side of the chest are reflected and dissected to form a pocket lateral to the chest wall, just below the level of the axilla. This pocket is then filled with water, and a scalpel is introduced under the water level, incising into an intercostal space through to the pleural cavity. Air bubbles observed exiting through this incision represent presence of pneumothorax. An inverted graduated cylinder filled with water can be held over the pocket prior to the incision into the pleural cavity to collect and measure the amount of air in the pleural cavity if desired [14].

#### **3.2 Posterior leg dissection**

Deep vein thrombosis in the calves is frequently seen associated with cases of death by pulmonary embolism, and is a frequent complication of immobilization and/or trauma. With the body positioned prone, the calf is incised vertically from the heel to the popliteal fossa, and the skin is then reflected. The tendon of Achilles is severed, and the attached calf musculature is then reflected and dissected gently from the underlying tibia and fibula from the heel upward. Transverse sections through the reflected musculature are then performed, and thrombi, if present, will thus be transversely sectioned, and their relationship with the attached vessels can be visualized. Antemortem thrombi typically maintain their sausage-like shape even if they become dislodged from the vessels, and show a concentrically layered cut surface (an indication of antemortem organization) [14]. Postmortem clots are typically soft and collapsible in nature, and do not show concentric laminations on cut surfaces.

#### **3.3 Layered neck and facial dissections**

Examination of the neck structures can aid in determining injuries in the neck that may have medicolegal implications. The neck should be examined at the end of the autopsy following removal of all other organs including the brain so as to create a dry/bloodless field to minimize the possibility of introducing blood seepage into the neck structures during dissection.

The routine Y-incision is extended from the tips of both shoulders upward along the posterior-lateral aspects of the neck and behind the ears toward the level of midear. The skin is then undermined and reflected from the shoulder regions to the ears, proceeding to the level of the mandible on both sides. Layerwise reflection of the muscles of the neck is then carried out and injuries of the anterior neck are documented. Examination of the posterior neck takes on a similar approach, which is most easily done with the body positioned prone. A single vertical incision from the protruding C7 spinous process up toward the midline occiput is coupled with a horizontal incision at the mid posterior neck, effectively creating a cross-shaped incision, where the skin can then be reflected back to expose underlying musculature. The posterior neck muscles are then reflected in a layerwise manner and examined for injuries.

Sometimes it is necessary to examine the soft tissues of the face, and the anterior skin flap can be further reflected by undermining the facial skin from the level of the mandible. Subcutaneous severing of the external auditory meatus will mobilize the skin for better visualization of the facial skull, and will not interfere with the cosmetic appearance of the face as long as midline attachments of skin to subcutaneous tissues are maintained at the midline of the face.

### **3.4 Exploration of middle and inner ears**

The middle and inner ears are encased in the petrous portions of the temporal bones, located at the base of the skull.

Following the removal of the brain, the dura is stripped from the middle fossa, and the petrous regions are dried. Bone cutters are used to excise the petrous ridge from all four sides to produce a roughly rectangular segment. The inner surface of the tympanic membrane is exposed and can be examined for evidence of inflammation. Findings of purulent inflammation should be reported and swabs may be submitted for culture. The entire petrous block can be decalcified and submitted for microscopic examination if so desired [14].

### **3.5 Air embolism**

Air embolism should be suspected in cases involving an open wound to the neck area, diving misadventures, chest trauma, or cases associated with childbirth or abortions. An interrupted blood column at autopsy in cerebral or cardiac vessels is often artefactual and thus is not regarded as evidence of air embolism.

The pericardial sac is opened anteriorly, and the edges are grasped with tools such as forceps or hemostats to create a pocket. Water is poured into the sac and the heart is submerged. A scalpel is then used to incise into the right side of the heart under the water level. Bubbles will arise if air is present. For measurement, an inverted graduated cylinder filled with water can be placed in the water prior to incising the heart [14].

### **3.6 Exploration of the sphenoid sinus**

The presence of water in the sphenoid sinus, although recognized to be present in any body that has been immersed in water, is one extra finding that can lend support to cases of drowning, which remains a diagnosis of exclusion. A large-bore needle attached to a syringe is used to perforate the sphenoid bone on either side of the sella, while it is directed downward and medially at a 45° angle. An average of 2–3 ml (sometimes up to 5 ml) of water may be aspirated [14].

## **3.7 Removal of the spinal cord**

The spinal cord can be visualized or removed for further examination by either an anterior or posterior approach, traditionally by sawing through the pedicles (anterior approach) or the laminae (posterior approach) to expose the underlying spinal cord following the routine autopsy and removal of the brain. Alternatively, an intervertebral disc in the lumbar spine can be transected, as well as another intervertebral disc in the thoracic area. A Stryker saw is used to cut out the segment of vertebral bodies between the two transected discs. The exposed dura is visualized, and can be slit vertically and reflected sideways. The exposed portion of the cord/cauda is then loosened by severing the nerves within the spinal canal, and slow downward traction toward the feet can be applied to retrieve the remaining cord in its entirety [14, 15].

#### **3.8 Examination of the cervical spine/vertebral artery**

Examination of the cervical spine may be warranted in cases of traffic deaths, falls, diving deaths, and suspected shaken baby cases. One radiological study showed that cervical injuries in road crash victims can be above C3 (50% of cases) or below C3 (22% of cases) [16]. Injuries range from severe fractures and dislocations to a few deep hemorrhages in the musculature. Injuries to the vertebral artery can sometimes occur when hyperextension/flexion and rotational forces are in play, with the most vulnerable regions being the third section [17].

The body is placed face down, and a head block is placed under the chest, with the head flexed at the neck. A posterior midline incision is made, and the musculature dissected in a layered fashion down to the vertebral column. The atlanto-occipital joint capsules are incised into, so that the articular surfaces can be examined. The atlas is disarticulated and removed. Laminectomy is then performed on the cervical vertebrae, and the dura mater can be incised and the spinal cord examined prior to removal. The exposed underside of the base of the skull can now be examined for fractures [14].

To begin the vertebral artery examination, the brain should be examined for basal subarachnoid hemorrhage, and if present, the basilar artery can be clamped with a hemostat. The skull cap can be replaced to ensure stability. The vertebral arteries can then be accessed from its branching point from the subclavian artery (most often the first branch) and cannulated with an 8F catheter, and secured and sutured to ensure no leakage around the catheter. An anterior–posterior x-ray is then obtained, and each cannulated artery is injected with 3–5 ml of contrast medium repeatedly until the vessel is visible on x-ray. The lesion, if present, can be established radiographically, and the entire neck block can be excised by cutting around the foramen magnum superiorly and disarticulating the seventh cervical vertebra inferiorly [14]. Fixation and decalcification can then proceed, and the vertebral arteries and surrounding tissues can then be exposed and examined.

#### **3.9 Fixation of the brain**

The brain is a soft structure that goes into decomposition quickly following death, thus making processing and examination difficulty in the fresh state. In addition, many brain findings can be subtle and require the tissue to sbe in optimal condition in order for these findings to be exhibited. Thus, it is advisable for the brain, following removal from the cranial cavity, to be suspended in a bucket of formalin using a string placed under the basilar artery of the circle of Willis, for at least a week and most optimally beyond 2 weeks prior to cutting into the brain parenchyma. The hardened tissue also provides better exhibits for photographing subtle lesions.

#### **4. Other examination/testing**

#### **4.1 Microscopic examination**

Some conditions (such as myocarditis) are diagnosed only on microscopic examination, with no specific corresponding gross findings. Forensic microscopy should be a part of investigations of sudden unexpected deaths, determination of the premortem nature of diseases or injuries, and interpretation and substantiation of gross findings (such as in cases of infections and/or malignancies). In my experience, samples of major organs (heart, lungs, liver, kidneys, and brain) should be microscopically examined in every autopsy.

#### **4.2 Toxicology/biochemical analysis**

Collection of postmortem specimens for toxicological testing has become almost routine for many institutions involved in death investigation, and can be performed

#### *Postmortem Examination DOI: http://dx.doi.org/10.5772/intechopen.92184*

with or without a complete internal examination. The routinely collected specimens include blood from a peripheral source, urine, vitreous humor, and liver tissue [18]. Other specimens that may be of value include bile and stomach contents.

Blood should be collected from a peripheral site such as the femoral vessels to minimize effects of postmortem redistribution of certain drugs. Collection can be achieved by inserting a large bore needle attached to a syringe through the skin, overlying the location of the femoral vessels (medial anterior inguinal regions), or internally by directly visualizing the vessels during the autopsy. Urine can be collected through the skin as well by inserting needle into the suprapubic area. Vitreous humor is collected by inserting needle into the whites (scleral portion) of the eyes, aiming toward the center of the globes.

Fluid specimens should be deposited and stored in glass tubes with sodium fluoride, to preserve the storage stability of drugs such as cocaine [19]. Vitreous fluid is also useful in the evaluation of diabetic complications, in that glucose and ketones are seen to increase substantially in cases of diabetic ketoacidosis [20].
