The subject is a 64 year old male who was 5 months short of his 59th birthday on March 6th, 2011 when he was rear-ended at approximately 1935 hours while his vehicle was stopped at a light.

At the time of being struck, the subject’s vehicle was positioned on a black ice roadway with an extremely low friction co-efficient. The collision force caused a violent forward acceleration in which the subject’s brain was driven back in relative motion toward the rear of the skull case while at the same time his head underwent an angular acceleration of approximately 90 degrees to the right.

Immediately Post-Accident

Immediately following the accident, the subject experienced confusion, but no other ailments, and he felt competent to proceed to his place of work. As the evening progressed, his condition worsened, The subject began to experience headache, severe somnolence, and nausea which would have resulted in vomiting were it not for the fact of an empty stomach. The subject also experienced pain in a diagonal band across his chest indicative of a soft tissue injury in the area of his seat belt restraint, a pain on flexion of his right wrist (his hand was on the gearshift throughout the accident) and pain in his right ankle (which was on the brake pedal throughout). Due to his increasing headache, nausea and somnolence, the subject made an early departure from work and returned home to sleep just after midnight on March 7th, 2011.

Loss of Consciousness

The subject has no reliable means to determine the duration of loss of consciousness. The best estimate is an LOC range of between 30 seconds and 1 minute 30 seconds. The subject made no attempt at recall of the accident until approximately one week after the event at which point he was able to recall episodic chunks of the accident event with a significant gap between his last memory (immediately prior to LOC) and his first waking memory after regaining consciousness post collision. (See this post for an initial description).

The Reconstruction

The subject has 14 years experience in marine and offshore safety during which period he was regularly involved in accident investigations. The subject’s insurance company interfered with the sole witness to the accident and denied the subject’s lawyer an agreed opportunity to obtain a full witness statement. Despite this, the subject has been able to reconstruct the accident based on the fact that a traffic light at the controlled intersection of Boulevard Saint-Raymond and Avenue des Jonquilles performed a gating function. This traffic signal held the bullet (the vehicle which caused the impact) stationary while the subject’s vehicle (the target) entered the roadway and gained a calculated 1,000 foot lead, a separation of 30 seconds between bullet and target vehicles. If both vehicles had travelled at the maximum roadway speed, this 30 second interval would have been maintained indefinitely. The fact the bullet initiated collision within less than a second of the target coming to a full stop some 3,500 feet from the gated intersection strongly suggests the bullet was exceeding the posted speed limit by a significant margin.

Figure 1 – Brain Relative Motion at Collision Impact

The Impact

The reconstruction demonstrates an impact speed in a range of between 29 and 39 miles per hour. Figure 1 above shows the impact forces transferred to the subject’s skull case. Because the subject had braced himself against an anticipated collision to his front, there was minimal cushion available from the headrest and seat-back. Using the lower range speed limit and plotting the impact forces against the Wayne State Tolerance Curve (WSTC) gives the result shown in Figure 2 below. The left most position (Red dot) is the calculated result based on the transfer of energy at the time of peak acceleration. LOC occurred within 5 ms of being struck as the target was accelerated from 0 to 30 mph within 5 ms. The right most position (Purple dot) is a second calculated position representing the average acceleration over a 10 ms period. The vehicle proceeded 20 to 25 feet forward across a black ice roadway under a full brake application until it entered a roadway segment free of black ice one half second later (500 ms). Both of the calculated results are within the WSTC curve for 100% probability of sustaining a brain injury.

Figure 2 – Wayne State Tolerance Curve for Probability of mTBI

The WSTC is an engineering calculation primarily used in the design phase as a means to estimate and reduce potential occupant risk. It is not an acknowledged form of medical diagnostic . The WSTC is employed primarily within the automobile industry, and is recognized as a valid criterion of injury. It is based on a calculation of the forces required to initiate a skull fracture and, while indicative of injury potential, it does not account for rotational acceleration of the head which is known to be associated with diffuse axonal injury (DAI). The WSTC, and its derivatives (JHTC, SI, AIS, HIC) are based on direct frontal impact tests, primarily drop tests using cadavers and animal subjects, and the results may not be directly applied to non-contact loading conditions and to situations involving rotational accelerations of the head. The WSTC, and its derivatives, do not provide any explanatory power with respect to the detailed neurological insult that is the direct cause brain injury; they only describe a mechanical force threshold above which injury is highly probable. The WSTC is based on the assumption that there exists a correspondence between mechanical force causing skull fracture, and functional brain damage.

These various limitations drove further investigation of the causes of brain injury.

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Posts in the PCS Sequence

PCS Thesis – Index
PCS Thesis – Injury Modalities
PCS Thesis – The Pineal Gland
PCS Thesis – UV Index