Neurophysiological and cognitive impairment following repeated sports concussion injuries in retired professional rugby league players

ABSTRACT

Background: Concussion is regarded as a common injury in rugby league, however no studies have explored the long-term neurophysiological and cognitive effects of repeated concussion injuries in this sport.

Methods: Former professional rugby athletes (n = 25) were compared to 25 age-matched participants with no history of a concussion. All participants completed standardised motor dexterity, reaction time, and cognitive tasks for working memory, associative learning and rule acquisition and reversal. Single-pulse transcranial magnetic stimulation (TMS) acquired motor evoked potentials and cortical silent period (cSP), as well as paired-pulse TMS for short latency intracortical inhibition and long intracortical inhibition (LICI).

Results: Compared to controls, dexterity and visuomotor reaction time was slower in the rugby group compared to controls (p = 0.02, p < 0.01, respectively). The rugby group also demonstrated poorer cognitive performance than controls (p range 0.02 to < 0.01). TMS revealed significantly reduced cSP at suprathreshold stimulation intensities (p range 0.02 to <0.01), and increased LICI (p = 0.03) in the rugby group.

Discussion: These findings of motor and cognitive changes, along with neurophysiological alterations, particularly with intracortical inhibition, nearly two decades post-concussion provides evidence for long-term sequelae for athletes with a history of repeated head trauma in contact sports.

KEYWORDS:

• Sport
• concussion
• mild traumatic brain injury
• transcranial magnetic stimulation
• motor cortex inhibition
• motor execution slowness
• rugby league

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Declaration of Interest

The authors report no conflicts of interest.

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Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. AJP is funded, in part, by a grant from Smart Head Play Charity, and Impact Technologies; and has been previously supported by funding from the Australian Football League and Samsung Corporation. AJP has also received equipment support for research from MagVenture and AD Instruments. AC is a director of Necksafe Ltd Charity. JJM has previously been funded by a NHMRC fellowship. Other authors declare no sources of research funding.