Dark Side: Head Injuries - Impact

Head and neck pathology defined here as including all structures contained in the area from the level of the clavicles to the sella turcica, has finally come of age and can rightfully take its place among other well-recognized subspecialties, such as hematopathology, neuropathology, and dermatopathology. Considering all the tissues contained in this small area-skin, mucosal surfaces, bone, soft tissue, lymph nodes, salivary glands, odontogenic structures, thyroid. parathyroids, eyes, and peripheral and central nervous system-one may rightfully argue that head and neck pathology is “nothing morc” than the practice of general pathology above the clavicles. The frozen-section tissue examination. performed during surgery while the patient is still under anesthesia, is accepted as an integral part of the proper surgical treatment of a patient. An entire generation of pathologists and surgeons have become familiar with the method and its benefits to then1 and their patients. Although frozen sections may be requested by a surgeon for several specific Reasons all are based on his desire to obtain accurate diagnostic information. from which he will decide on the immediate surgical procedure.

 

Frozen-section diagnosis should be considered a cooperative effort between physicians. because the surgical pathologist’s report carries the same weight as that of any other consulting physician. It is imperative that a sound dialogue be established between the surgeon and pathologist over the need for, limitations of. and consequences of the frozen-section diagnosis: however, the actual decision of whether or not to prepare a frozen section is up to the pathologist, rather than to the surgeon. In some respects, pathologic evaluation of specimens from the central nervous system (CNS) is less complicated than evaluation of other organs, because requests for margins and the need for extensive specimen dissections are unusual. On the other hand, CNS specimens are usually small, and care must be taken to preserve the tissue. Do not use all of the tissue by freezing the entire specimen. This is especially true for specimens of the spinal cord. These can be minute, yet major therapeutic decisions often depend on the results of the pathology studies. In all cases, it is essential to keep the clinical and radiologic findings in mind when processing specimens from the CNS.

 

Needle biopsy specimens need to be interpreted and handled with special care. The evaluation should begin with cognizance of the clinical and radiographic findings. The chance of making an error is vastly increased when these specimens are studied in a vacuum devoid of clinical or radiographic information. Begin your examination with the cytologic preparation as described above. One of the remaining fragments of tissue can then be used for a frozen section if desired. If an abnormality is established by the smear, a frozen section may not be necessary. Unless you are assured of additional tissue, it is generally wise to freeze only one or two cores at the time of initial examination, holding others in reserve. Throughout the process, review these slides in reference to the radiographic images to ensure that abnormal tissue is obtained and that the findings are consistent with the images. Close contact with the surgeon  is extremely important. In frozen section freezing must be accomplished as rapidly as possible to minimize the formation of ice crystals.

 

Ice crystals are generally avoidable in certain neoplasms, such as meningiomas, but frequently not in infiltrating gliomas from edema-rich white matter. The recommended procedure is to establish a base of semi frozen mounting medium on a cold chuck. The medium should not be completely frozen, because solidly frozen medium will slowly freeze the tissue and encourage the formation of ice crystals by gradually drawing heat from the small specimen. Therefore, place the specimen on the partially frozen base, and immediately immerse it in liquid nitrogen. After freezing, the specimen can then be covered with additional mounting medium and refrozen. Cut and stain sections by standard methods. In the case of gliomas, especially the well differentiated variety (e.g., astrocytoma and oligodendroglioma), it is extremely important that blocks be available from tissue that is not subject to prior frozen section. Prior freezing produces nuclear angulation and hyperchromatism, which can make it difficult to distinguish between gliomas and to distinguish reactive or normal brain from an infiltrating glioma. Unless you are assured of more tissue by the surgeon, use only a portion of the specimen for a frozen section. It helps to determine the scope and the type of the injuries which can be categorized as:

 

·       Soft tissue injuries: lacerations, abrasions, and contusions of the scalp

·       Fracture of the skull

·       Contusions of the brain

·       Epidural hematomas

·       Intracerebral hemorrhages

 

 

Acceleration or deceleration injuries are due to sudden movement of the head the instant after injury, with resultant production of intracranial pressure gradients and the subjecting of the brain to both shearing and tensile forces. Two types of injuries are typically produced:  Subdural hematomas and diffuse axonal injury. Subdural hematomas are secondary to tearing of the subdural bridging veins; diffuse axonal injury is secondary to injury to the axons. While acceleration or deceleration injuries are associated with impact, theoretically, impact is not necessary for the production of these injuries, just sudden angular rotation of the head. In situations encountered by forensic pathologists, however, acceleration or deceleration injuries of the brain involve impact.

 

The second type of injury that can be incurred is to the skull. In general, whenever a head is either struck with or strikes an object having a broad flat surface area, the skull at the point of impact flattens out to conform to the shape of the surface against which it impacts. As the skull is flattened and bent inward, adjacent, but more distant areas, are bent outward by a wave of deformation consisting of the central area of inbending and the peripheral outbending. This outbending can occur at a considerable distance from the point of impact. Where the skull curves sharply, the extent of inbending and outbending is not so great as in less-curved areas. If a fracture of the skull occurs, the fracture does not begin at the point of impact, but at the point of outbending. Linear fractures begin on the external surface of the skull by the forces produced by the outbending of the bone. After inbending, the skull attempts to return to its normal configuration. As the inbent portion of the skull does so, the fracture line extends from its originating site toward the area of impact, as well as in the opposite direction. The fracture line may or may not reach the point of impact and could actually continue through it.

 

In any fall or blow to the head, the degree of deformation of the skull, the generation of a fracture and the extent of any fracture produced is dependent on a number of factors:

 

·       The amount of hair

·       The thickness of the scalp

·       The configuration and thickness of the skull

·       The elasticity of the bone at the point of impact

·       The shape, weight, and consistency of the object impacting or impacted by the head

·       The velocity at which either the blow was delivered or the head strikes the object

 

The amount of energy required for production of a single linear fracture from a low-velocity blow or fall depends on whether the head strikes a hard unyielding surface or a relatively soft yielding surface. With a yielding surface, a large proportion of the impacting energy is transferred to the surface by way of the deformation of the surface, thus decreasing the amount of energy available to cause head injury. In the case of a hard unyielding surface, e.g., a steel plate, in which there is essentially no energy transferred to the impacted surface, it takes approximately 33.3–75 ft lb of energy to produce a single linear fracture. If a head strikes or is struck by a deformable object, not all the energy possessed by either the object or head will be available for deformation of the skull. At impact, the object will tend to indent and deform so as to wrap itself around the head. Thus, the energy delivered is no longer in a localized focus but is dispersed over a considerable area, reducing the possibility of a skull fracture. Linear or comminuted fractures of the skull produced by impaction of a head and a relatively soft and flexible object, such as the instrument panel of a motor vehicle, require kinetic energy levels at impact of between 268 and 581 ft lbs. Impact velocities are from 43 ft/s (29 mph) to 65 ft/s (45 mph). In one test, a human head impacting at 577 ft lb of energy did not fracture.

One point that has been stressed by numerous authors and should be repeated is that there is no absolute correlation between the severity of brain injury and the production of a linear skull fracture. Skull fractures can occur without any significant or detectable brain injury or any impairment of consciousness. Conversely, death may result from extensive brain injury without a skull fracture.

 

Acknowledgements:

www.politie.nl  and a Chief Inspector – Mr. Henk van Essen©

www.aivd.nl       AIVD – Mr. Erik Akerboom ©

 

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