Neuro-Ophthalmologic Response to Repetitive Subconcussive Head Impacts

Abstract

IMPORTANCE Subconcussive head impacts have emerged as a complex public health concern. The oculomotor system is sensitive to brain trauma; however, neuro-ophthalmologic response to subconcussive head impacts remains unclear.OBJECTIVE To examine whether subconcussive head impacts cause impairments in neuro-ophthalmologic function as measured by the King-Devick test (KDT) and oculomotor function as measured by the near point of convergence. DESIGN, SETTING, AND PARTICIPANTSIn this randomized clinical trial, adult soccer players were randomized into either a heading group or kicking (control) group. The heading group executed 10 headers with soccer balls projected at a speed of 25 mph. The kicking-control group followed the same protocol but with 10 kicks. Peak linear and rotational head accelerations were assessed with a triaxial accelerometer. The KDT speed and error and near point of convergence were assessed at baseline (preheading or prekicking) and at 0, 2, and 24 hours after heading or kicking.EXPOSURES Ten soccer-ball headings or kicks. MAIN OUTCOMES AND MEASURESThe primary outcome was the group-by-time interaction of KDT speed at 0 hours after heading or kicking. The secondary outcomes included KDT speed at 2 hours and 24 hours after heading or kicking, KDT error, and near point of convergence.RESULTS A total of 78 individuals enrolled (heading group, n = 40; kicking-control group, n = 38). Eleven individuals (heading group: 4 women; mean [SD] age, 22.5 [1.0] years; kicking-control group, 3 women and 4 men; mean [SD] age, 20.9 [1.1] years) voluntarily withdrew from the study. Data from 67 participants with a mean (SD) age of 20.6 (1.7) years were eligible for analysis (heading, n = 36; kicking-control, n = 31). Mean (SD) peak linear accelerations and peak rotational accelerations per impact for the heading group were 33.2 (6.8) g and 3.6 (1.4) krad/s 2 , respectively. Conversely, soccer kicking did not induce a detectable level of head acceleration. Both groups showed improvements in KDT speed (heading group: 0

Does acute soccer heading cause an increase in plasma S100B? A randomized controlled trial

“…An average linear head acceleration from a header ranges between 26 and 32 g [ 2 ], while regular corner or goal kicks (~50mph) yield accelerations above 50 g [ 40 ]. This study agreed with our previous studies [ 2 , 41 ] in that 10 headings did not increase concussion-related symptoms in study participants, ensuring that our intervention is in fact “subconcussive.” All participants stood approximately 40 ft (12.2 m) in front of the JUGS machine. Participants in the heading group were instructed to head the soccer ball with their forehead and aim the ball towards a researcher standing approximately 16 ft (4.9 m) in front of the participant.…”

Subconcussive brain vital signs changes predict head-impact exposure in ice hockey players

“…There is evidence to suggest that even a single practice session involving head contact, such as heading a ball in soccer, can result in impairment. 23 Magnetic resonance imaging studies have demonstrated that players exposed to repetitive head impacts over the course of a season show significant abnormalities compared to controls over the same time period and that these abnormalities are related to the extent of exposure to head impacts. 4 , 5 , 24 …”

Oculomotor response in male collegiate pole vaulters after repeated head impact due to falls from heights: a pilot longitudinal study

“…The NPC was assessed based on protocols published in previous studies [6][7][8][9] . Participants were seated with their heads in an anatomical position.…”

“…Previous studies suggest that oculomotor functions can reflect subtle sensory impairment caused by subconcussive head impact incidents. For example, the near point of convergence (NPC), which measures the closest point of focus before diplopia occurs 5) , has been shown to in-crease from subconcussive head impacts [6][7][8][9] . In one study, 10 acute soccer headings immediately worsened NPC values by as much as 40% compared to baseline values, and this impairment persisted for more than 24 h 6,7) .…”

“…For example, the near point of convergence (NPC), which measures the closest point of focus before diplopia occurs 5) , has been shown to in-crease from subconcussive head impacts [6][7][8][9] . In one study, 10 acute soccer headings immediately worsened NPC values by as much as 40% compared to baseline values, and this impairment persisted for more than 24 h 6,7) . The NPC values were chronically inflicted in college and high school US football players with varying frequencies and magnitudes of subconcussive head impact incidents 8,9) .…”