A quick vision test that's so simple it can be administered by parents and others on the sidelines of sports fields and arenas helps detect concussion in athletes as young as 5 years of age, a new study suggests.
Results showed that the King-Devick (K-D) test of rapid number naming outperformed tests of cognition and balance in terms of its capacity to distinguish nonconcussed from concussed athletes immediately after an injury.
The results suggest that a vision-based test should be included in the assessment of athletes following an injury to optimally identify a concussion, said study author Steven Galetta, MD, the Philip K. Moskowitz Professor and chair of neurology at New York University Langone Medical Center.
"A vision test absolutely needs to be added," Dr Galetta told Medscape Medical News. "This one has been the most rigorously tested on the sidelines, and it's easy to administer by parents and others."
The study was published online March 3 in the Journal of Neuro-Ophthalmology.
Rapid Eye Movements
The K-D test, which Dr Galetta said was developed in the 1970s by two optometrists as a test for dyslexia, consists of three cards each with 40 single-digit numbers differently spaced. Athletes read each card as quickly as possible while being timed. Higher testing times compared with baseline indicate worsening of performance, which is consistent with a concussion.
The test requires rapid eye movements (saccades) that involve relay of information throughout the brain, including frontal eye fields, supplementary eye fields, dorsolateral prefrontal cortex, intraparietal sulcus, and deeper structures of the brainstem. Studies show that patients with impaired saccades after a concussion have both cortical and subcortical deficits.
"The visual system is a widely distributed system in the brain that accounts for well over 50% of the brain's pathway," said Dr Galetta.
The study included 332 young male and female athletes (243 aged 5 to 17 years and 89 collegiate athletes aged 18 to 23 years) who were members of various local hockey and lacrosse teams.
At preseason baseline, participants completed the K-D; the Standardized Assessment of Concussion (SAC), which is a brief test of orientation, immediate memory, concentration, and delayed recall; and the Timed Tandem Gait Test, which is the balance component of the Sports Concussion Assessment Tool, 3rd Edition (SCAT3) and the Child-SCAT3.
Baseline scores for all tests improved with increasing age in the combined cohort. This age effect was particularly evident for the third K-D card, on which the numbers are close together.
Younger kids tend to have trouble with items crowded together, which may represent a developmental issue, explained Dr Galetta. "It may take time for their brain to process things that are crowded close together."
During the playing season, 12 athletes sustained a concussion. Immediately after injury, the three tests were repeated for these participants on the sidelines.
A group of 14 control nonconcussed athletes (there were 2 extra volunteers), matched for age, playing position, and sport, also completed these tests under the same conditions.
Using calculations of areas under the receiver-operating characteristic (ROC) curves, which represent the probability that a test can distinguish concussed athletes from controls, the researchers determined that the K-D came out on top. The ROC curve areas accounting for age were 0.92 for K-D, 0.87 for timed tandem gait, and 0.68 for SAC (P = .0004 for the comparison).
"We found the K-D to have the greatest ability to most accurately separate control subjects from concussed subjects, followed by the tandem walk test and then the SAC," said Dr Galetta.
There was a 92% probability of correctly distinguishing a concussed from a nonconcussed athlete based on the result of the K-D test alone.
The K-D scores of controls actually improved by an average of 6.4 seconds and the injured athletes worsened from baseline by 5.2 seconds. "So we had a big spread," commented Dr Galetta.
While other experts consider that a 3-second change from baseline might indicate a concussion, "we think that any delay from their baseline should raise the possibility that a meaningful event like a concussion has occurred," said Dr Galetta.
However, he stressed that a confirmed diagnosis of concussion requires a clinical assessment. Concussion is defined as a direct or indirect impulse to the head or body with accompanying neurologic symptoms.
Current sideline testing does not include vision testing, a situation that Dr Galetta called a "major gap."
The K-D test is fast; it takes older athletes less than a minute to complete. It's also simple to learn. This study and other research suggest that parents can easily conduct the test.
Dr Galetta said he is concerned about proposals in New York State and possibly elsewhere that would make it mandatory to have a doctor or trainer at the sidelines of every youth sporting event.
"We don't think that's economically feasible or feasible from a manpower point of view," he said. "There are not enough doctors or trainers to go around and these leagues can't afford them."
Instead, he said, "we need to empower and educate parents in sports leagues on how to use some of these tools that allow them to make decisions about who they need to direct for professional help. We're not taking the professional out of the loop here, but taking them out from the loop at the event because we don't think resources exist to make it possible."
Commenting on the study for Medscape Medical News, Francis Conidi, MD, Florida Center for Headache and Sports Neurology, and coauthor of the American Academy of Neurology's (AAN's) position statement on concussion in sports, said it was well designed and "pretty impressive."
"From what they've demonstrated, certainly vision testing is something that should definitely be included" in sideline evaluations, he said. "They argue that very well."
He pointed out that including controls in the study helps to prove that fatigue wasn't affecting the test results. "They have taken that covariable out of the equation."
Vision testing is being considered as routine practice immediately after an injury only now, partly because the field is just picking up. There has been "an explosion" of good research coming out in recent years, said Dr Conidi.
"As the field evolves, you'll find that the quality of the testing is going to improve and that's what we're seeing here."
Dr Conidi has developed what he thinks is an improvement on the tandem gait test that looks at both gait and finger snapping. This "dual" test, he said, assesses balance and attention-concentration. "Task-switching is one of the last things that resolves" after a concussion, he said.
He will include this test in a longitudinal study of athletes that is being planned along with Dr Galetta's research team. A group of 1000 athletes will undergo a baseline K-D and then be followed using various office-based tests as part of their regular neurological examination. The researchers aim to see how the K-D holds up in predicting total recovery from a concussion, said Dr Conidi.
This new study isn't the first to show the benefits of vision testing for concussion. Given that other sideline tests, such as the SAC and Balance Error Scoring System (BESS), don't assess eye movements, Dr Galetta and others studied whether the K-D would provide additional information in a cohort of University of Florida athletes.
That study was cited in a recent review by a team led by Rachel Ventura, MD, PhD, Department of Neurology, New York University School of Medicine, that included Dr Galetta and was also published in the Journal of Neuro-Ophthalmology.
"We found that the SAC and BESS even when used together as sideline tools failed to show abnormalities in 10% of the 20 concussions under study," those authors noted. "With the addition of the K-D, all of the concussions could be identified. Thus, adding the K-D increased our ability to detect concussed athletes and complements the SAC and BESS as a performance measure."
After reviewing various diagnostic tests for concussion, including symptom checklists and sideline tests such as the K-D, as well as various types of neuroimaging, Dr Ventura and her colleagues concluded that visual performance measures enhance the detection and management of concussion.
Dr Galetta has received honoraria for speaking from Biogen-Idec, Vaccinex, and Genzyme.
J Neuro-Ophthalmol. Published online March 3, 2015. Abstract
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Cite this: Simple Vision Test Detects Concussion in Young Athletes - Medscape - Mar 12, 2015.