Near Point of Convergence Response Can Foretell Concussion Severity

Adolescent and young adult patients with concussion who have a receded near point of convergence (NPC) breakpoint on initial evaluation are more likely to experience an increased burden of concussion symptoms, according to research results published in Vision Research.  

Because concussion profiles may provide some useful clinical insights for the care of adolescents and young adults who experience concussion, researchers compared both the clinical and injury characteristics of patients who were assessed within 14 days of concussion and those who demonstrated and did not demonstrate a receded NPC (>6 cm) breakpoint. Investigators hypothesized that patients who did demonstrate a receded NPC breakpoint would experience a greater symptom burden and longer recovery. 

Data from patients evaluated at a sports medicine clinic during 2019 and diagnosed with a concussion by a board-certified sports medicine physician were included for analysis. Multiple medical and injury history variables were obtained, including time elapsed from injury to evaluation, loss of consciousness at the time of injury, self-reported prior history of concussion, and preinjury diagnosis of ADHD, anxiety, and migraine headaches or headache disorder. 

In total, 123 patients between 11 and 18 years of age were included. All participants underwent a multimodal concussion evaluation within 14 days (mean, 6.9±3.5 days) of injury. Sixty-three percent presented with a receded NPC breakpoint, while 37% presented with normal NPC breakpoint distance. Patients with a receded NPC breakpoint were significantly younger. 

In both groups, there was no significant difference in the proportion of patients who were girls, had a previous history of concussion, a loss of consciousness, a learning disability, a history of ADHD, anxiety, or depression, or a pre-injury diagnosis of vision or hearing disorders. 

In the receded NPC breakpoint group, there was a significantly higher proportion of patients who reported headaches at initial assessment, as well as significantly greater overall, cognitive, and somatic symptom severity. Those who proceeded to experience persistent post-concussion symptoms (PPCS) had a significantly higher NPC breakpoint at the initial evaluation compared with those without PPCS. This group also committed more modified Balance Error Scoring System (mBESS) errors than the normal NPC breakpoint group, but differences in single- or dual-task tandem gait test performance results were not significant. 

In a multivariable model, investigators found that of all potential predictor variables, more severe somatic symptoms had a demonstrably significant and independent association with a greater NPC breakpoint distance. 

Study limitations include the collection of data via usual care leading to multiple personnel collecting data, the measurement of NPC breakpoint through either subjective diplopia or examiner-observed eye deviation, and a lack of generalizability to those outside of a specialty sports medicine care setting. 

“Within 14 days of a concussion, those with a receded NPC breakpoint reported a more severe symptom burden…compared with those without a receded NPC breakpoint,” researchers report. “As such, visual disorders may be an important driver of symptom profiles following concussion in adolescents, and have the potential to provide prognostic post-injury information.” 

Reference

Walker GA, Wilson JC, Seehusen CN, Provance AJ, Howell DR. Is near point of convergence associated with symptom profiles or recovery in adolescents after concussion? Vision Res. 2021;184:52-57. doi:10.1016/j.visres.2021.03.007