New framework for the continuum of concussion and functional neurological disorder

Over the past 20 years, scientific investigation and public awareness of concussion has expanded exponentially. This has represented a critical swing of the pendulum for a field that previously had been somewhat ignored by the medical establishment, research funders and health policy-makers. Although substantial progress has been made in better identification and management of acute concussion, many knowledge gaps remain.1 One of the largest ongoing conundrums surrounds the 15%–30% of patients who experience persistent postconcussion symptoms (PPCS) that can last months to years.2 3 This editorial explores how better understanding the continuum between concussion/PPCS and functional neurological disorder (FND) could advance concussion care and research. Running parallel over this time has been an evolving understanding of FND (previously termed conversion disorder). FND can be defined as the presence of involuntary neurological symptoms that are incompatible with conventional neurological diseases.4 This can be likened to a ‘software’ (functional) problem of brain circuits rather than a ‘hardware’ (structural) disease of the nervous system. FND is involuntary and should not be conflated with malingering (deliberate production or exaggeration of symptoms for external gain, eg, financial compensation). FND symptom subtypes include functional movement disorders, functional paralysis, functional seizures, functional sensory disorders, functional cognitive disorder and functional dizziness (also known as persistent postural perceptual dizziness (PPPD)). The latter two phenotypes have particular relevance to considerations surrounding PPCS. Recent efforts in the study of FND have focused on transitioning away from a diagnosis of exclusion towards incorporating validated ‘rule-in’ signs based on characteristics of internal inconsistency, distractibility and variability of symptoms (ie, fluctuations with shifts in attention).5 FND is commonly seen across medical practice and is among the most frequent clinical presentations in outpatient general neurology clinics.6 There is a female preponderance (60%–80%) with the mean age of onset being between …