Head injury and concussion: where are we now?

By Mr M J POTTS, consultant neuro-ophthalmologist

[THE AWARENESS OF CONCUSSION has come a long way in the past decade. We are much better at recognising it, we have some tools for measuring it and we are more aware of its potential for long-term damage and injury. Preventing it is more difficult and we are developing guidelines in sport and other fields to recognise and manage it, so as to prevent long-term damage.

Some people are more susceptible to it and genetics and long-term research may help explain that. We recognise that unconsciousness is not obligatory for its occurrence: merely a marker of potential risk.

There are many definitions of concussion, but largely a direct or indirect blow to the head results in initial temporary loss of orientation – only 25% may have actual loss of consciousness – with disturbed vision and balance. Concussion only becomes obvious after 10 minutes, which is why players leave the field for a ‘HIA’ (head injury assessment). If concussion is confirmed by HIA then individual and personalised guidelines come into play for management and return to activities.

Long term and/or recurrent concussion results in loss of function in four domains: cognition, physical malaise and headaches, sleep changes and mood changes.

The visual system remains a highly sensitive system with which to detect concussion. Why? Well, because over half the brain pathways are directly or indirectly connected to the visual system. Over three quarters (80%) of patients have visual or vestibulo-ocular symptoms. Eye movements are affected in a high proportion (30% to 60%) and there may be complaints of blurred vision, double vision and photophobia.

Vestibular and vestibulo-ocular systems are also commonly affected. Most symptoms resolve in one to three weeks with rest, but some will persist – with disabling symptoms. A second concussion during the early recovery is very bad, especially in the first 10 days.

Testing for concussion has evolved. Early tests of rapid number naming were 86% sensitive and 90% specific; they have evolved to rapid word and picture naming (Maddocks questions). Immediate examination of vision and eye movements is still often used in the field.

We have developed better more sensitive HIA tests both at the scene and in the immediate post-injury examination. There are now national and sports-specific guidelines for the management and return to activity in place.

Long-term recurrent episodes result in chronic traumatic encephalopathy (CTE) and boxers have been shown to have reduced retinal nerve fibre layer thickness, although it is not seen after one concussion.

We have some treatment options, largely around preventing recurrence and especially early after the first injury. Vitamin B complexes may help. Guidelines for the safe return to activities are in place for both amateur and professional sports. We are now aware that three or more concussions is very ill advised and may be career ending.

New detection techniques, including gumshield accelerometers and saliva or blood-based shock proteins are being trialled.

Medico-legally, there are more cases being pursued due to the increased awareness and assessment. However, it is recognised that there are some challenging issues there. Most of the assessment techniques are subjective tests, making them vulnerable to bias and variable reproduceability.

Individual susceptibility to concussion is a factor we do not fully understand, although it will probably have a genetic component. It has been long known and recognised that the motivation to recover from concussion is another factor affecting long-term outcomes.

How and why Valentino Rossi was able to crash at such high speeds over such a long period with such a high risk of concussion, and yet be able to jump back on his bike with ‘rubber like’ enthusiasm, is amazing. Unfortunately, Marc Marquez – a much younger fellow Moto GP rider – has been less fortunate and has recently succumbed to recurrent double vision as a complication of his numerous crashes.

The final problem for medico-legal aspects of concussion comes in proving causation. Many of the 1960s and 1970s football and rugby players now affected by chronic traumatic encephalopathy who are considering claims for concussion after-effects also drank prodigiously and smoked heavily, making the assessment of causation problematic. Assessment and guidelines were not in place then, either.

No doubt ‘concussion’ will continue to evolve and we will begin to have some more answers to these complex questions, and especially to the genetic predisposition components. q