How do courts decide whether cognitive issues are the result of a Mild Traumatic Brain Injury or other factors?
In the recent case of Tan v. Mintzler and Mller (2016 BCSC 1183) the plaintiff was struck by a vehicle running a red light. Ms. Tan suffered injuries to her head, neck, shoulders, mid and low back, chest, and left eye. She also had difficulty sleeping, headaches, tiredness, nightmares, anxiety, depression, cognitive and memory issues after the crash. Ms. Tan had not been able to return to her job as a housekeeper at a hotel and was left completely unemployable.
It was the opinion of medical experts testifying on behalf of the plaintiff that many of her symptoms were the result of a Mild Traumatic Brain Injury, an “MTBI”, sustained in the crash. The defence strongly disagreed with this diagnosis and claimed that her soft tissue injuries and psychological injuries were the cause of her memory and cognitive issues. The acceptance of the MTBI diagnosis would greatly alter Ms. Tan’s prognosis going forward in both her recovery and employability and, therefore, impact the award for damages.
Mr. Justice Groves considered the evidence and came to the conclusion that Ms. Tan had, indeed, sustained an MTBI. His reasoning is instructive with regard to what the courts look at when considering this issue:
 For the plaintiff, Drs. Weiss, Cameron, and Kaushansky gave evidence that they believed Ms. Tan had suffered an MTBI. Dr. Weiss recommended Ms. Tan be referred to a neurologist to confirm her suspicion, a recommendation that was followed with her visit to Dr. Cameron.
 One of the most significant factors in diagnosing the MTBI was Ms. Tan’s evidence that she has no recall of the Accident after hearing the initial sound of the impact. The next thing she remembers is the policeman, Cst. Upshall, knocking on her car window. It was also Ms. Tan’s evidence that she has a spotty memory of the events which transpired after she returned home from the hospital that day. It was also relevant to the MTBI diagnosis that Ms. Tan was diagnosed as having a concussion at the hospital the day after the Accident and by Dr. Fong for several months after the Accident. The doctors also relied on an MRI brain scan which showed an abnormality in the plaintiff’s left parietal lobe which Dr. Cameron testified “probably occurred” at the time of the Accident.
 As I have said, Dr. Dost strongly disagreed with the MTBI diagnosis and with the methodology of the other three doctors.
 The reality is that there is little disagreement regarding the symptoms Ms. Tan experiences and the psychological difficulties she is struggling with. The distinction between whether Ms. Tan’s psychological injuries and cognitive difficulties were caused by an MTBI or by Ms. Tan’s chronic pain and sleep disturbances is relevant only to the quantum of general damages and to Ms. Tan’s prognosis going forward.
 In considering all of the evidence, including Ms. Tan’s testimony and clinical history, the evidence of Cst. Upshall, the hospital records, and the testimony of all of the experts, I find that Ms. Tan suffered an MTBI. This is so for several reasons.
 First, I accept Ms. Tan’s evidence that she suffered at least an altered state of consciousness, if not a loss of consciousness, following the impact of the Accident. Cst. Upshall was clear in his evidence that it took him approximately five minutes to get from the coffee shop, to the Accident scene, to secure the Accident scene, and to attend to Ms. Tan. There was some evidence at trial that paramedics attended to Ms. Tan’s vehicle before Cst. Upshall, but I do not have the evidence of those individuals to confirm Ms. Tan’s mental state immediately following the Accident. Dr. Dost suggested that Ms. Tan’s loss of memory during this period of time was due to natural attrition, but under the circumstances I find that suggestion unlikely. Even Ms. Tan’s earliest medical records indicate a loss of memory during that period. I therefore accept the factual assumption made by the plaintiff’s doctors that Ms. Tan suffered a period of retrograde amnesia.
 Second, it was also the evidence of several doctors that Ms. Tan’s MRI was abnormal and that they attributed this anomaly to the Accident. Dr. Dost was critical of the plaintiff’s experts for relying on the MRI results without considering the false positive rate of the test and for linking the abnormality directly to the Accident. It was also his opinion that, according to the diagnostic standards, an MRI should not be used to diagnose a brain injury. However, the plaintiff’s doctors did not consider the MRI results in isolation. There was no evidence in Ms. Tan’s medical history or at trial that Ms. Tan had suffered any previous trauma which may have contributed to or caused the lesion shown in the MRI. The doctors did not utilize the MRI scan alone to come to their diagnoses, but considered it with all of the other evidence.