Concussion

What is a concussion?

A concussion, or mild traumatic brain injury (mTBI), is a disruption of brain function caused by a blow or jolt to the head, or by an impulsive force applied to the body that is transmitted to the head. Unlike severe head injuries, it typically does not cause visible lesions on standard imaging exams such as CT scans or magnetic resonance imaging (MRI). However, advanced techniques, often used in research, have been able to detect functional and microstructural abnormalities in the brain after a concussion.

The physical forces behind an mTBI result from a rapid and sudden movement of the head, intense enough to cause a sudden displacement of the brain inside the skull. This displacement can lead to impacts against the skull walls, causing microtrauma (Meaney et al., 2011).

Common Causes

Concussions can occur in various contexts:

• Contact sports: soccer, football, hockey, horseback riding, cheerleading.
• Falls.
• Road accidents.
• Significant jolts, even without direct impact to the head.

Common Symptoms

Symptoms of a concussion may appear immediately, several hours, or even up to 24 hours after impact. They include:

• Physical: headaches, nausea, dizziness, visual disturbances, sensitivity to light or noise.
• Cognitive: concentration difficulties, confusion, memory loss.
• Emotional: irritability, anxiety, depression.
• Sleep: insomnia or excessive sleepiness.

Certain symptoms, such as prolonged loss of consciousness, repeated vomiting, or extreme drowsiness, require immediate medical consultation.

Diagnosis

The diagnosis mainly relies on clinical evaluation. Standard imaging exams, although helpful in ruling out severe injuries, often show nothing in the case of a concussion. Specific tools, such as questionnaires and neuropsychological tests, can help assess cognitive impact.

Recovery and Management

Most individuals recover completely within a few days or weeks. Management includes:

• Physical and cognitive rest: limit activities that stress the brain or body for a few days.
• Gradual return to activities: progressively resume school, work, or sports activities under medical supervision.
• Specialized consultation: if symptoms persist, medical evaluation or a multidisciplinary team assessment is recommended.

Post-Concussion Syndrome

According to the report from the World Health Organization Task Force and the National Institute of Excellence in Health and Social Services (INESSS) of Quebec, in the vast majority of cases, individuals who have experienced an mTBI no longer show any symptoms after a few days or weeks following the traumatic event (Mayer et al., 2017; Hiploylee et al., 2016; Levin & Diaz-Arrastia, 2015; McCrea et al., 2009).

However, scientific literature indicates that up to 30% of individuals who have suffered a concussion report persistent symptoms beyond the usual recovery period, a phenomenon known as post-concussion syndrome (Max et al., 1991; Sharp et al., 2014; Whitnall et al., 2006; Sterr et al., 2006; McMillan et al., 2012; Voormolen et al., 2018; 2019; Permenter & Sherman, 2020).

A report from the National Center for Injury Prevention and Control (USA) highlights:

• 30% of individuals with an mTBI experience long-term cognitive deficits.
• 20% are unable to return to work.

In some cases, symptoms include:

• Chronic headaches.
• Memory and concentration problems.
• Persistent fatigue.
• Sleep disturbances.
• Depressive or anxious symptoms.

Numerous studies demonstrate that an mTBI can cause persistent cognitive deficits affecting executive functions, including inhibition, flexibility, planning, and long-term memory (Wammes et al., 2017; Broadway et al., 2019; McAllister et al., 1999; McAllister et al., 2001; Sterr et al., 2006; Dean & Sterr, 2013; Xiong et al., 2016; Broadway et al., 2019; Holiday et al., 2020; Kunker et al., 2020; Sorg et al., 2021).

Microstructural Damage and Its Impact

Studies combining cognitive assessment and brain imaging techniques (structural MRI, diffusion tensor imaging, spectroscopy) show microstructural, metabolic, and neurophysiological abnormalities in patients with persistent deficits after an mTBI.

Two recent meta-analyses (Oehr et al., 2017; Zhu et al., 2019) reveal that mTBI damages neurofilaments in brain cells, causing traumatic axonal injuries. These injuries result from misalignments, disconnections, and swelling of axons caused by the physical forces experienced during the trauma.

Neuroimaging studies also show that microstructural damage affects regions involved in executive functions, particularly the frontal cortex and brain connectivity networks (Grossman et al., 2013; Xiong et al., 2016; Sorg et al., 2014; 2021).

Moreover, abnormalities in the thalamus and medial frontal cortex are associated with high levels of fatigue experienced by patients with persistent deficits following an mTBI (Nordin et al., 2016).

Impact on Quality of Life

A longitudinal study by Hiploylee et al. (2017) involving 80 patients with post-concussion syndrome revealed:

• 65% of patients reported concentration difficulties.
• 45% of patients experienced memory problems.

These patients, evaluated more than three years after their mTBI, were not involved in financial compensation claims and had passed an effort validation test. Nevertheless, their symptoms persisted, significantly impacting their quality of life.

Role of Neuropsychological Evaluation

Neuropsychological evaluation plays a crucial role in managing individuals with post-concussion syndrome, particularly when persistent symptoms require objective documentation.

Objectives of Evaluation

1. Identify affected cognitive functions The evaluation helps quantify cognitive deficits related to mTBI, such as:
   • Memory (episodic, short- and long-term).
   • Attention (selective, divided).
   • Executive functions (flexibility, planning, inhibition).
   • Information processing speed.
2. Differentiate the origins of symptoms Some symptoms may be amplified or caused by non-neurological factors, such as:
   • Anxiety or depression.
   • Post-traumatic stress.

The evaluation helps distinguish between these factors and the direct impacts of the concussion.

1. Objectively document symptoms for medico-legal purposes In insurance or legal disputes, it is often crucial to provide a scientific and rigorous assessment of persistent deficits. Neuropsychological reports are essential tools in these situations.
2. Guide interventions Results help design an appropriate intervention plan, including:
   • Compensatory strategies to manage cognitive deficits.
   • School or work accommodations (e.g., adjusted schedules, digital tools).
   • A specific cognitive rehabilitation program.
3. Monitor symptom progression Repeated evaluations allow tracking progress and adjusting interventions based on symptom improvement or persistence.

Common Myths

• “You must lose consciousness to have a concussion”: False. Most concussions do not cause loss of consciousness. In fact, only 10 to 20% of cases involve fainting. Symptoms can appear subtly, such as dizziness or headaches.
• “If imaging exams are normal, everything is fine”: False. Exams like CT scans or standard MRIs typically do not detect functional disturbances associated with concussions. These techniques are not designed to reveal microstructural or metabolic abnormalities, which may still be the source of persistent symptoms.
• “You must have had a direct blow to the head to have a concussion”: False. A concussion can occur even without a direct impact to the head. Violent jolts to the body or a blow to another part of the body can cause rapid acceleration or deceleration of the brain inside the skull, leading to diffuse axonal damage.
• “Symptoms must appear immediately after the incident to have a concussion”: False. Although in most cases symptoms appear immediately, around 20% of individuals may experience symptoms developing gradually over several hours, up to about 24 hours post-incident. This highlights the importance of continuous monitoring after a traumatic event.

Resources and Support

For more information or assistance, consult your doctor, a neuropsychologist, or clinics specialized in head trauma. Appropriate support can make a significant difference in recovery.