Diagnosing sport-related concussion in youth: Clinical criteria, neurobiology, and persisting symptoms

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Clinical definition and diagnostic framework

Sport-related concussion is defined as a traumatic brain injury induced by biomechanical forces transmitted to the head, neck, or body, resulting in transient neurologic dysfunction. Contemporary consensus statements emphasize that concussion is a clinical diagnosis characterized by the rapid onset of symptoms that typically evolve over minutes to hours and resolve spontaneously. Loss of consciousness is neither required nor typical, and structural injury is not expected on routine neuroimaging.

Diagnosis rests on clinical history, symptom assessment, and neurologic examination, supplemented by age-appropriate standardized tools. In pediatric populations, collateral information from parents, coaches, and educators is often essential, as children may underreport or poorly characterize symptoms. Importantly, no single symptom, sign, or test confirms or excludes concussion.

Symptom clusters and time course

Symptoms are heterogeneous and are best conceptualized in clusters rather than as a unitary syndrome:

• Somatic: headache, dizziness, nausea, photophobia, phonophobia
• Cognitive: slowed processing, inattention, memory difficulty
• Sleep-related: hypersomnia, insomnia, circadian disruption
• Affective: irritability, anxiety, mood lability
• Vestibulo-ocular: blurred vision, diplopia, impaired convergence, motion sensitivity

In most children and adolescents, symptoms improve over days to weeks. Recovery is not linear, and transient symptom exacerbation with cognitive or physical exertion is common early in the course. Current guidance favors early, symptom-limited activity rather than prolonged strict rest, with return-to-learn preceding return-to-play.

Cumulative injury and repeat concussion

A prior concussion increases the risk of subsequent concussion. Some studies associate repeat injury with longer recovery, although findings are variable and influenced by injury severity, symptom burden, and individual factors. Repetitive subconcussive exposure remains an area of active research; at present, there are no validated clinical thresholds for cumulative exposure risk in individual patients.

Neuroimaging: clinical use and research findings

Routine neuroimaging does not diagnose concussion. Computed tomography may be used to rule out skull fracture and intracranial or intracerebral hemorrhage in acute settings. Magnetic resonance imaging is reserved for when red flags are present, such as focal deficits, prolonged alteration of consciousness, prolonged or recurrent nausea or vomiting, or CT abnormalities, including cerebral edema.

Advanced neuroimaging techniques—including diffusion tensor imaging, functional magnetic resonance imaging, and magnetic resonance spectroscopy—have demonstrated group-level alterations after concussion in research settings. Diffusion tensor imaging is increasingly used in the evaluation of patients with persistent symptoms for suspected changes in white matter microstructure and network connectivity.

Neuropathology and autopsy considerations

Acute concussion has no pathognomonic gross or microscopic neuropathologic signature. Discussions of chronic traumatic encephalopathy must be framed carefully: it is a neuropathologic diagnosis established postmortem, primarily described in adult exposure cohorts, and it cannot be diagnosed clinically or inferred from isolated concussive events in youth. The relationship between youth sport participation and later-life neurodegenerative pathology remains incompletely defined.

Why immature brains may be more vulnerable

Incomplete myelination is only one contributor to pediatric vulnerability. Additional factors include a larger head-to-body ratio, weaker cervical musculature leading to greater rotational acceleration, developmental differences in axonal microstructure and neuro-metabolic response to injury, and ongoing synaptic pruning and network reorganization. Cognitive and emotional development also influence symptom recognition, reporting, and recovery.

Persisting symptoms after concussion

A subset of youth experience symptoms that persist beyond the expected recovery window. Current consensus favors the term persisting symptoms rather than post-concussion syndrome, emphasizing heterogeneity rather than a single pathologic entity.

Risk factors variably associated with prolonged recovery include high initial symptom burden, vestibulo-ocular dysfunction, sleep disturbance, migraine history, prior concussion, and pre-injury anxiety or mood disorders. Management is multidisciplinary and symptom-targeted, incorporating structured return-to-learn plans, graded aerobic exercise, vestibular and vision therapy when indicated, headache management based on phenotype, sleep optimization, and psychological support.

Clinical implications for neurologists

For neurologists, youth concussion care requires recognition of concussion as a dynamic clinical diagnosis, restraint in imaging use, attention to developmental context, and early identification of patients at risk for persisting symptoms. Clear counseling about expected recovery, uncertainty around cumulative effects, and the limits of diagnostic testing remains central to high-quality care.

Further reading:

Giza CC, Hovda DA. The neurometabolic cascade of concussion. J Athl Train 2001;36(3):228-35. PMID 12937489

Lumba-Brown A, Yeates KO, Sarmiento K, et al. Centers for Disease Control and Prevention guideline on the diagnosis and management of mild traumatic brain injury among children. JAMA Pediatr 2018;172(11):e182853. Erratum in: JAMA Pediatr 2018;172(11):1104. PMID 30193284

McCrory P, Meeuwisse W, Dvořák J, et al. Consensus statement on concussion in sport: the 5^th international conference on concussion in sport held in Berlin, October 2016. Br J Sports Med 2017;51(11):838-47. PMID 28446457

Patricios JS, Schneider KJ, Dvorak J, et al. Consensus statement on concussion in sport: the 6th International Conference on Concussion in Sport, Amsterdam, October 2022. Br J Sports Med 2023;57(11):695-711. PMID 37316210

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