{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,30]],"date-time":"2026-09-30T20:19:42Z","timestamp":1790799582980,"version":"4.1.0"},"reference-count":54,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2025,7,16]],"date-time":"2025-07-16T00:00:00Z","timestamp":1752624000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Brain Sciences"],"abstract":"<jats:p>Background: Post-concussion syndrome (PCS) and Functional Neurological Disorder (FND), including Functional Cognitive Disorder (FCD), are two frequently encountered but diagnostically complex conditions. While PCS is conceptualized as a sequela of mild traumatic brain injury (mTBI), FND\/FCD encompasses symptoms incompatible with recognized neurological disease, often arising in the absence of structural brain damage. Yet, both conditions exhibit considerable clinical overlap\u2014particularly in the domains of cognitive dysfunction, emotional dysregulation, and symptom persistence despite negative investigations. Objective: This review critically examines the shared and divergent features of PCS and FND\/FCD. We explore their respective epidemiology, diagnostic criteria, and risk factors\u2014including personality traits and trauma exposure\u2014as well as emerging insights from neuroimaging and biomarkers. We propose the \u201cFunctional Overlay Model\u201d as a clinical tool for navigating diagnostic ambiguity in patients with persistent post-injury symptoms. Results: PCS and FND\/FCD frequently share features such as subjective cognitive complaints, fatigue, anxiety, and heightened somatic vigilance. High neuroticism, maladaptive coping, prior psychiatric history, and trauma exposure emerge as common risk factors. Neuroimaging studies show persistent network dysfunction in both PCS and FND, with overlapping disruption in fronto-limbic and default mode systems. The Functional Overlay Model helps to identify cases where functional symptomatology coexists with or replaces an initial organic insult\u2014particularly in patients with incongruent symptoms and normal objective testing. Conclusions: PCS and FND\/FCD should be conceptualized along a continuum of brain dysfunction, shaped by injury, psychology, and contextual factors. Early recognition of functional overlays and stratified psychological interventions may improve outcomes for patients with persistent, medically unexplained symptoms after head trauma. This review introduces the Functional Overlay Model as a novel framework to enhance diagnostic clarity and therapeutic planning in patients presenting with persistent post-injury symptoms.<\/jats:p>","DOI":"10.3390\/brainsci15070755","type":"journal-article","created":{"date-parts":[[2025,7,16]],"date-time":"2025-07-16T10:46:05Z","timestamp":1752662765000},"page":"755","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":8,"title":["Post-Concussion Syndrome and Functional Neurological Disorder: Diagnostic Interfaces, Risk Mechanisms, and the Functional Overlay Model"],"prefix":"10.3390","volume":"15","author":[{"given":"Ioannis","family":"Mavroudis","sequence":"first","affiliation":[{"name":"Department of Neuroscience, Leeds Teaching Hospitals, Leeds LS9 7TF, UK"},{"name":"Third Department of Neurology, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece"},{"name":"School of Medicine, University of Leeds, Leeds LS2 9JT, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5617-0346","authenticated-orcid":false,"given":"Foivos","family":"Petridis","sequence":"additional","affiliation":[{"name":"School of Medicine, University of Leeds, Leeds LS2 9JT, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1941-0432","authenticated-orcid":false,"given":"Eleni","family":"Karantali","sequence":"additional","affiliation":[{"name":"Department of Neurology, Democritus University of Thrace, 68100 Alexandroupolis, Greece"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Alin","family":"Ciobica","sequence":"additional","affiliation":[{"name":"Department of Biology, Faculty of Biology, Alexandru Ioan Cuza University of Iasi, Carol I Avenue 20th A, 700505 Iasi, Romania"},{"name":"Center of Biomedical Research, Romanian Academy, Iasi Branch, Teodor Codrescu 2, 700481 Iasi, Romania"},{"name":"Academy of Romanian Scientists, 3 Ilfov, 050044 Bucharest, Romania"},{"name":"Preclinical Department, Apollonia University, P\u0103curari Street 11, 700511 Iasi, Romania"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sotirios","family":"Papagiannopoulos","sequence":"additional","affiliation":[{"name":"Third Department of Neurology, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7319-2045","authenticated-orcid":false,"given":"Dimitrios","family":"Kazis","sequence":"additional","affiliation":[{"name":"Third Department of Neurology, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,7,16]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"173","DOI":"10.1080\/026990599121692","article-title":"Epidemiology and predictors of post-concussive syndrome after minor head injury in an emergency population","volume":"13","author":"Bazarian","year":"1999","journal-title":"Brain Inj."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"893","DOI":"10.1001\/archneurpsyc.1934.02250050011001","article-title":"Head injury, Neurologic and psychiatric aspects","volume":"31","author":"Strauss","year":"1934","journal-title":"Arch. 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