Instant Diagnosis? Not so fast!
Written by Jane Crosby
Edited by Carolyn Chiu
February 9th, 2023
Edited by Carolyn Chiu
February 9th, 2023
Public Health
Ever hit your head and wonder if you have a concussion? Wouldn’t it be great if you could know for certain right then and there? Head Impact Measurement Devices, a new development in sports technology, aim to provide a quick and objective diagnosis for athletes on the sideline and reduce the chance that they return to play when injured. While these devices are excellent in principle, their true clinical significance has been questioned because different devices differ in data collection techniques and overall accuracy in predicting brain strain. A comprehensive review of Head Impact Measurement devices, conducted by Virginia Tech and the University of Michigan, evaluates their impact measurement strategies.
Researchers examined the non-helmeted X-Patch and X-Guard devices along with the helmeted standard Head Impact Telemetry System(HITS). The HITS device uses accelerometers to record impacts in which linear acceleration(LA), or straight-line force, is greater than a pre-set threshold[1] past which a sudden lag of the brain's motion within the skull cavity occurs. This lag results in stretching and compression of tissue, damaging the neurons that compose it and causing the brain injury we call concussion. When triggered, HITS records pre and post-impact data including peak LA, estimated angular accelerations (AA), and location of impact.[1] The X-Guard and X-Patch, worn as a mouthguard and behind-the-ear patch, use a gyroscope in addition to an accelerometer which allows them to sense the direction of the peak LA and measure the AA directly instead of estimating it.[1]
Unfortunately, there is still considerable error in the recorded data. Non-helmeted devices exhibit up to a 50% error margin in peak LA[2] while both LA and AA estimates are imprecise in helmeted devices, location of impact affects measurement accuracy in HITS, and the ratio of false positive head impact recordings to true positive recordings is on average 5:1 in both non-helmeted devices.[3] These limitations reflect the struggle to obtain accurate in vivo data for humans–there are simply too many factors at play, not all of which are controllable or measurable. Depending on the device, its accuracy can be inhibited by improper fit, skin motion, and saliva build up.[4,5]
Since concussions are a result of strain from the brain’s movement within the cranial vault, any measure of skull movement, no matter how precise, will only be an estimation or prediction of the brain tissue’s actual movement and contortions.[1] And overall, head impact measuring devices are so new that there is not enough data to agree upon any sort of injury threshold.[1] Because of this, clinical evaluation remains the best course of action following impact. Physicians can utilize data to contextualize their symptoms, but it cannot be relied upon as a standalone means of diagnosis. More fine tuning is needed before we can truly rely on these devices, but for now they are helping us to better understand what magnitude and direction of impact causes concussion so that one day diagnosis may be as instantaneous as impact.