Medical Exhibits - Demonstrative Evidence Expert Blog - MediVisuals

By: Robert Shepherd MS, Certified Medical Illustrator, Vice President and Director of Eastern Region Operations,MediVisuals Incorporated

Long before science had advanced to allow imaging of the body in sectional views by computed tomography (CT) and magnetic resonance imaging (MRI), medical illustrators were illustrating the body in sectional views because these views are the best way to appreciate some anatomical relationships. 

Medical illustrators, physicians, and others who have studied anatomy are familiar with sectional views of the body and appreciate the value of these views in explaining the relationship of anatomical structures. However, accomplished and well respected jury consultants and non-medical illustrator legal graphics experts have expressed concerns that sectional views may be difficult for some jury members to understand. These individuals' opinions are valuable to those of us in the legal graphics business, and I agree with their opinions that, when other views can communicate a particular relationship message equally as well or better, sectional views should be avoided. I also believe most of these experts will agree that there are times and places in which sectional views of anatomy are the best way to appreciate some anatomical relationships. Granted, there have been times when we have been working on specific cases and experts have insisted that sectional views be absolutely and unconditionally avoided. Unfortunately, in these situations the experts were unable to suggest a more effective view to communicate the relevant anatomical relationships (at least in a way that was practical in terms of time and expense). That being the case, sometimes the sectional views were used despite the input of the experts, and at other times, the relationships of the structures had to be explained without the benefits of graphics.

A way to perhaps explain how sectional views help decision makers appreciate relevant anatomical and pathological relationships is to compare them to aerial views or photographs of the scene of a collision.  Space is defined in three planes. Only two of these planes can effectively be demonstrated in a two-dimensional rendering. For example, aerial views have long been used to help explain the positions of vehicles and structures that simply can't be appreciate from "street views". When viewing the scene of a collision from a "street view", one can appreciate vertical and horizontal distances, but not depth; distances close to and far from the viewer's perspective are very difficult to appreciate (see the below figures). By comparison, when viewing an operative site through a "surgeon's view", vertical and horizontal distances can be appreciated, but the depth of the incision and the relationships of the various structures within and around the incision are very difficult or impossible to appreciate.

The "aerial view" of the collision scene allows the viewer to appreciate distances in two geographical planes as well (distances right and left, and toward and away from the "street view," but the ability to appreciate up and down is lost). Also, the locations of relevant structures or vehicles that may have been obstructed by nearby structures (such as buildings trees, signs, or other vehicles) can now be appreciated. Similarly, a sectional view of anatomy can help decision makers appreciate depth relationships of structures. Or, a sectional view of a step in a surgical illustration can allow the viewer to appreciate the depth of the surgery as well as the additional structures that may have been injured (or at risk of injury) during the invasive procedure.  These specific depth  relationships could not be appreciated from the "surgeon's view" of the same surgery shown in the above illustration.

Exhibits developed to help explain the invasive nature of a surgery and the disruption of the soft tissues during operative procedures are critical. For that reason, sectional views are critical in aiding a testifying physician to explain these issues. For example, the exhibit panel that demonstrates an anterior cervical discectomy and fusion (ACDF) that does not include a cross-section through the neck fails to emphasize the depth of the incision and disruption of tissues (essentially all the way to the center of the neck). This depth simply cannot be appreciated in a "surgeon's view".

In order to appreciate cross-sections, orientation views that show the level and direction of the section are helpful (see below), or when time, budget, and presentation format (digital as opposed to a physical panel) allow, a short animation showing the sectional view actually coming out of the orientation view such as MediVisuals' "Scan Selector^TM" can be used.

By: Robert Shepherd MS, Certified Medical Illustrator, Vice President and Director of Eastern Region Operations, Medivisuals Incorporated

Brain injuries are classified into two basic categories; those that are associated with obvious, incontestable evidence of intracranial injury and those that are not.

Obvious intracranial injuries include those with evidence of pathology within the brain itself (intraparenchymal injuries) as well as areas of bleeding around the brain but within the skull. The light area in the scan below indicates blood within the brain tissue, and the surrounding dark area shows associated edema. Both of these are considered to be intraparenchymal injuries. Contusions and hematomas found outside the skull are not considered intracranial but are frequently illustrated to help emphasize the force and direction of the trauma to the head. 

The areas of hemorrhage shown in the illustration below are scattered around the junction between the grey and white matter of the brain, which is consistent with injuries from shear forces. The grey and white matter are of different densities, and when the brain impacts the skull during a traumatic event, the subsequent unequal movement between the two causes damage at their junction.

Head trauma can cause tearing of the blood vessels around the brain, which can result in areas of bleeding (hematomas). As the bleeding continues, the hematoma may expand to compress the brain tissue (as shown in the following illustration) and may require an emergency decompression. Significant compression must be relieved quickly in order to avoid further neurological damage and/or death. 

Introducing a ventriculostomy catheter is one approach used to alleviate increased intracranial pressure. A hole is drilled directly into the patient's skull, and a catheter is advanced through the brain tissue into one of the ventricles. The catheter allows some of the cerebrospinal fluid to escape, thereby relieving the pressure on the brain itself.

In other situations, a craniotomy may be performed to allow the blood to be suctioned from the area surrounding the brain. A bone flap is created by first drilling three holes into the skull and then making cuts between them with a saw. This flap is removed and the blood is cleared from the areas above and beneath the dura. In some cases, the bone flap is not replaced if the brain is swollen or if there is a significant concern over recurrence of the hematoma. For a more detailed look at the craniotomy procedure, please review MediVisuals Craniotomy Surgery Animation. 

By: Robert Shepherd MS, Certified Medical Illustrator, Vice President and Director of Eastern Region Operations, MediVisuals Incorporated

Balance and dizziness are often associated with traumatic brain injuries, although the specific cause of these problems is often difficult to explain. Sometimes the injuries may be to the inner ear organs. Other times the injuries may be to the vestibular nerve. When the injury is to the vestibular nerve, the mechanism of injury is similar to injuries to the olfactory nerve resulting in disturbances in smell.

The exhibit shown below demonstrates the mechanism of injury. As the brain stem and skull move in different directions during a violent impact, stretch injuries to the vestibular nerve can occur. This type of injury is especially significant when supporting arguments of brain injuries occurring as a result of traumatic forces to the head. If forces were significant enough to damage the vestibular nerve, the forces were likely sufficient to cause shear or traumatic axonal injury, as well.

For more information on mild and severe traumatic brain injury, please visit: http://www.medivisuals.com/traumatic-brain-injury.aspx For more information on the featured exhibit, please visit: http://www.medivisuals.com/vestibular-nerve-injury-mvi82010-01x.aspx

A very effective way of increasing the effectiveness of expert testimony is by enhancing focus, understanding, and recall by teaming the testifying expert with a qualified medical illustrator, experienced in preparing legal graphics (illustrations, animations, models, etc.). By working together, the medical knowledge and oral skills of the expert can be supported by expertly created medical graphics that greatly clarify complicated anatomical, physiological, and medical subtleties. Together they result in much more effective communication with the decision makers than if verbal testimony or the graphics were used alone (one mode of communication used alone without being supported by the other). In addition, during a period of hours or days of listening to arguments that are typically only verbal, decision makers grasp the opportunity to focus on visuals in the form of illustrations, photographs, models, and/or animations. In fact, information is generally better processed if jury members and other triers of fact can have information presented in a multimodal fashion (i.e. combinations of simultaneous auditory, visual, and tactile stimuli).

The effectiveness of visuals is supported throughout our society by such common phrases as “A picture is worth a thousand words”, and “Seeing is believing.” In addition, numerous manuscripts refer to studies substantiating that recall is greatly increased when the verbal message is supported by visual images. Typically these studies have shown that after varying periods of time information that was delivered by a combination of voice supported by visuals was recalled at a significantly higher percentage than the same message delivered by voice alone.

References

DeBoth, C. J., & Dominowski, R. L. Individual differences in learning: Visual versus
auditory presentation. Journal of Educational Psychology, 1978; Aug 70 (4): 498-503

McCall, J., & Rae, G. Relative efficiency of visual, auditory and combined modes of
presentation in learning of paired-associates. Perceptual and Motor Skills, 1974; June (38) : 955-958.

Multimodal Learning Through Media: What the Research Says. Cisco Web site. http://www.cisco.com/web/strategy/docs/education/Multimodal-Learning-Through-Media.pdf. Accessed August 19, 2008.