Reducing Occupational Hazards in Forensic Autopsy: A Novel Approach to Brain Removal via Craniotomy

Introduction

It is not advisable to perform an autopsy on the COVID-19 case, even for diagnosis, let alone the academic interest.^1–4 However, this recommendation may not be feasible in all circumstances in the practice of forensic pathology, as one gets to see unexpected sudden deaths, suicides, custodial deaths, homicides, and other high-profile cases with either a confirmed or suspected COVID-19 diagnosis. Here, it becomes an obligation for the pathologist to perform a complete medicolegal autopsy. Still, there remains a potential risk that the virus could persist on the bodies of the deceased, as viable SARS-CoV-2 has been shown to survive on surfaces for several days.^{5, 6} A complete autopsy on a COVID-19 body needs a team of highly trained forensic pathologists and infrastructures such as a negative-pressure Biosafety Level 3 autopsy suite, which is not available at many autopsy centers, especially in resource-constrained nations.^{3, 7} Hence, minimal invasive autopsy techniques have been recommended in all such cases to minimize unnecessary hazardous procedures.^{8, 9}

Skull vault opening using an electric saw is one such aerosol-generating procedure (AGP) that increases the possibility of transmission of COVID-19. ¹⁰ Even though the electric saws are complemented with vacuum units, they are still considered unsafe because of their inefficiency to completely collect the bone dust and other tissue fragments emanating from high-speed sawing. ¹¹ Though these AGPs are inevitable in cases where the brain is the organ of interest, the authors still believe that there should be some workaround for brain removal, at least in autopsies where surgical craniotomies have already been done. Many methods are being tried to overcome the negative effects of conventional autopsies in these COVID times. ¹² It is in the same context; a new method has been developed and adopted by the authors and discussed in this case study.

Craniotomy, Types, and Indications

Craniotomy, a procedure involving the temporary removal of a section of the skull to access the brain, has a long and evolving history. Its earliest forms can be traced to prehistoric times, where it was believed to serve ritualistic or spiritual purposes, such as releasing malevolent spirits. Ancient Egyptians adapted the fire-making bow drill for cranial procedures as early as 1400 bce, and the earliest known writings on craniotomy are attributed to Imhotep, around 2900 bce. By the 5th century bce, Hippocrates introduced its therapeutic use for treating skull fractures. The technique and associated instruments were further documented in the early 16th century by Berengario in his work “De Fractura Calvae.” The Renaissance period saw an increase in craniotomies due to injuries from firearms and explosives. Significant advancements in antiseptic techniques and the introduction of general anesthesia in the 19th century contributed to the widespread adoption and refinement of the procedure. Today, craniotomy remains a vital neurosurgical intervention, supported by coordinated care from interprofessional medical teams to ensure optimal patient outcomes.^13–15

A craniotomy is the surgical removal of part of the calvarium (skull) to expose the brain. This removed portion of the bone is called the bone flap. The bone flap may be temporarily removed and replaced after the neurosurgical intervention. The bone flap, after removal, may be stored in the abdominal wall or a bone bank.^{16, 17} In cases of compound fractures, where the bone is fragmented, multiple pieces may need to be discarded during the procedure, as they cannot be effectively replaced.

Craniotomy surgeries are performed for a variety of traumatic and non-traumatic skull and brain pathologies, including brain tumors; clipping or repairing an aneurysm; removing arteriovenous malformations; evacuating blood or blood clots from a leaking blood vessel; addressing arteriovenous fistulas; draining brain abscesses; repairing skull fractures or tears in the dura mater; relieving intracranial pressure (ICP) by removing damaged or swollen areas of the brain due to traumatic injury or stroke; treating epilepsy; and implanting stimulator devices to manage movement disorders such as Parkinson’s disease.^{16, 18, 19}

There are several types of craniotomies, categorized based on factors such as the location of the pathology, ease of access, maximum safety, and minimal damage to surrounding organs and tissues. In neurosurgical and forensic practice, various craniotomy techniques—commonly referred to as surgical “corridors”—are selected based on clinical indications, lesion location, and required exposure. The following sections briefly outline several key approaches commonly employed in both therapeutic and postmortem settings.

Surgical FTP Craniotomy Procedure

The surgical FTP (frontotemporal parietal) craniotomy procedure typically begins with a C-shaped or question mark-shaped incision made on either side of the scalp. The upper anterior portion of the incision is usually positioned above the corresponding eyebrow, while the lower posterior end is placed near the upper attachment of the corresponding ear. Once the scalp has been incised, the next step involves removing the bone over the skull vault at the site of interest. This is achieved by creating burr holes at the margins of the area, followed by sawing to connect these burr holes, thereby freeing the bone flap. The excised bone flap is often temporarily stored in the patient’s anterior abdominal wall, thigh, or in a bone bank, and it is typically replaced once the surgery is complete and the patient has sufficiently recovered.^{20, 30}

Autopsy Technique

The initial steps, such as placing the body, positioning the head, and documenting external findings, remain consistent with conventional autopsy procedures.^31–33 Upon examining the head in post-craniotomy cases, one may observe the craniotomy wound margins either fully healed or in various stages of healing. In cases with minimal healing, the wound margins can be manually separated without the use of instruments, and the scalp is reflected away from the wound margins (Figure 1). To facilitate the process, an incision is made from the contralateral mastoid process, intersecting the craniotomy wound perpendicularly. The scalp flaps thus created are reflected anteriorly and posteriorly (Figure 2). If the craniotomy margins are completely or nearly healed, a regular bimastoid incision may be used.

OPEN IN VIEWER Figure 1.

Downward Reflection of the Dura Mater to Expose the Underlying Cerebral Hemisphere.

OPEN IN VIEWER Figure 2.

Scalp Flaps Reflected Anteriorly and Posteriorly at the Midsagittal Region.

After reflecting the scalp, the skull vault, craniotomy defect, and the undersurface of the scalp are exposed. Special care should be taken during this step, as craniotomy involves the removal of a section of cranial bone, and a deep incision may inadvertently injure the brain. Furthermore, when removing staples from the craniotomy wound, attention should be paid to prevent the sharp ends of the staples from injuring gloved fingers.

Through the craniotomy defect, the dura mater is examined. If the dura mater remains intact and covers the brain, it is carefully incised along the craniotomy wound margins, except at its inferior border, and gently reflected downward. The cerebral convexity is exposed, and the ipsilateral half of the brain is retracted outward at the sagittal fissure using a brain retractor. The falx cerebri and corpus callosum are then identified (Figure 3). The corpus callosum is incised along its length and depth in the midline, following the plane of the falx cerebri (Figure 4). A complete axial incision is made anterior to the concave notch of the tentorium cerebelli through the third ventricle, separating the cerebrum from the rest of the brain (Figure 5). This step can be facilitated by lifting the cerebral hemisphere with a spatula or retractor. The ipsilateral half of the brain is then carefully delivered by severing its attachments, such as cranial nerves.

OPEN IN VIEWER Figure 3.

Ipsilateral Half of the Brain Retracted Outward at the Sagittal Fissure to Visualize the Falx Cerebri and Corpus Callosum.

OPEN IN VIEWER Figure 4.

The Corpus Callosum Incised Along its Length and Depth in the Midline, Following the Plane of the Falx Cerebri.

OPEN IN VIEWER Figure 5.

An Axial Incision made Anterosuperior to the Concave Notch of the Tentorium Cerebelli Through the Third Ventricle to Separate the Second Half of the Cerebrum from the Brainstem and Cerebellum.

The next step involves incising the anterior and posterior attachments of the falx cerebri, reflecting it toward the now-vacant side, to allow for further examination of the contralateral brain. Additional incisions are made in the falx cerebri to release tension and facilitate the removal of the other half of the brain (Figure 6). With the previous axial incision having separated the cerebrum from the brainstem and cerebellum, the remaining half of the brain is easily delivered by severing any basal attachments (cranial nerves) with blunt-ended scissors. This is aided by tilting the head to the contralateral side and digitally manipulating the brain by inserting gloved fingers into the subdural space.

OPEN IN VIEWER Figure 6.

Reflection of the Falx Cerebri Away from the Remaining Half of the Cerebrum by Incising it at Multiple Points to Release Tension.

Once both cerebral hemispheres are removed, the tentorial attachment is incised along the petrous edges bilaterally to expose the cerebellum and brainstem (Figure 7). The spinal cord is transected as deeply as possible, and the brainstem–cerebellar complex is removed using conventional methods. The dura can then be stripped as usual, exposing the inner surface of the skull (Figure 8). Use of an external light source may assist in a more detailed examination.

OPEN IN VIEWER Figure 7.

Incision of the Tentorial Cerebelli Along the Petrous Edges Bilaterally to Expose the Cerebellum.

OPEN IN VIEWER Figure 8.

Exposure of the Inner Surface of the Skull by Stripping the Dura Mater.

In this modified approach, the brain is removed in three distinct parts: (a) The right half of the cerebrum, (b) the left half of the cerebrum, and (c) the brainstem–cerebellar complex, all without the need for additional sawing. These parts can then be examined in a manner consistent with conventional autopsy methods (Figure 9).

OPEN IN VIEWER Figure 9.

The Whole Brain Removed in Three Distinctive Parts.

Limitations

Suitability for certain cases: This procedure is feasible only in cases where the brain’s firmness permits digital manipulation. In cases where the brain has already begun to putrefy, handling and removing the brain becomes significantly more challenging.

Risk of transecting the posterior aspect of the circle of Willis: During the separation of the cerebrum from other structures, there is a possibility of transecting the posterior aspect of the circle of Willis. However, in such cases, antemortem radiological investigations are usually available, which mitigates the impact of this limitation.^36–41 Even if these structures are transected, they remain available for gross and histopathological examination.

Size of craniotomy defect: In some instances, the craniotomy defect may be too small to allow for the brain’s easy delivery. In such cases, greater digital manipulation or mechanical nibbling of the craniotomy wound margins may be required to complete the procedure.

Conclusion

The proposed method is particularly beneficial during situations involving highly infectious cases, where the spread of hazardous agents through aerosols poses a significant threat to the health of personnel working in mortuaries. In cases where a complete examination of the brain is essential, such as in highly sensitive autopsies, this technique offers a safer alternative. The novel procedure for brain removal through the craniotomy defect, without sawing the skull, minimizes the risk of aerosolization and potential exposure to infectious agents.

Given its utility, this method can be adopted not only in confirmed cases of highly infectious diseases but also in non-infectious autopsies. The rationale for broader application stems from the high number of asymptomatic cases of infectious diseases, which may go undetected during routine procedures. By incorporating this technique universally, forensic pathologists can ensure a higher level of safety, reducing the risk of inadvertent exposure to undiagnosed infections. Therefore, this method has the potential to become a standard practice in autopsy procedures, contributing to the overall safety of forensic pathology professionals while maintaining the integrity of the examination process.