Postconcussion Syndrome in the ED
Much of the confusion relating to head injuries and their sequelae may relate to the variety of different terms used to define different grades of injuries in various different contexts, many of which are used interchangeably. TBI, mTBI, minor head injury and concussion have all been used in similar settings and no single definition is universally accepted.
Similarly, there is no universally accepted definition of PCS, yet the two most often cited diagnostic criteria are those of the diagnostic and statistical manual of mental disorders (DSM-IV) and international statistical classification of diseases (ICD-10). The former has a far tighter criteria for definition, requiring objective cognitive impairment, disturbance in social or occupational functioning and persistence for at least 3 months. It is little surprising, therefore, that the rates of PCS after TBI vary considerably depending on the criteria used with DSM-IV criteria being met by 11% and 64% by the ICD criteria in one study. Some of the diagnostic criteria for these classifications are shown in Table 1 .
The term 'traumatic brain injury' was introduced in the USA following the Traumatic Brain Injury Act of 1966, referring to a brain injury resulting from direct or indirect head trauma. Perhaps counterintuitively, mTBI has a fairly concise definition, beyond what one might expect of just a bang on the head. The defining features of mTBI are a 'traumatically induced physiological disruption of brain function', with at least one of the following features:
Technically, the definition of mTBI does not preclude structural brain abnormalities; however, the clinical sequelae must be transient. Post-traumatic amnesia must not be greater than 24 h, loss of consciousness greater than 30 min or glasgow coma score (GCS) diminished for greater than 30 min. Most recently, TBI has been defined by a working group as 'an alteration in brain function or other evidence of brain pathology, caused by an external force', with concise definitions of the component parts provided.
'Concussion' is derived from the latin 'concutera', meaning to shake violently. The International Conference in Sport has defined this as a 'complex pathophysiological process affecting the brain due to either direct or indirect injury', clearly recognising that significant blows to the torso with forces transmitted to the head are as likely to result in concussion as are direct injuries. The defining feature is a 'brief' neurological deficit that typically resolves spontaneously. The course, however, may be protracted and PCS may result. Concussion probably represents a subgroup of mTBI. Loss of consciousness is not a requirement for the development of concussive symptoms and indeed 75% of concussed sportspersons have no history of loss of consciousness. Characteristically, there will be no abnormality on standard neuroimaging, if performed, emphasising its functional nature, although new, currently experimental modalities such as diffusion tensor imaging may prove useful in the future for detecting the early subtle changes associated with concussion.
PCS refers to a complex constellation of symptoms that follow a concussive injury. By amalgamating these criteria, the syndrome can be defined as the presence of three or more of the symptoms in Table 1, occurring in the weeks and months following a head injury. Such symptoms may persist up to 6 months following the head injury, though in some cases may continue indefinitely. The differences in symptoms required for diagnosis (Table 1) highlight the uncertainty clinicians have regarding this condition and also how differently PCS can manifest itself. Moreover, as many of the symptoms below are subjective and are common to, or exacerbated by, other disorders, there is a significant risk of misdiagnosis.
Definition and Terminology
Much of the confusion relating to head injuries and their sequelae may relate to the variety of different terms used to define different grades of injuries in various different contexts, many of which are used interchangeably. TBI, mTBI, minor head injury and concussion have all been used in similar settings and no single definition is universally accepted.
Similarly, there is no universally accepted definition of PCS, yet the two most often cited diagnostic criteria are those of the diagnostic and statistical manual of mental disorders (DSM-IV) and international statistical classification of diseases (ICD-10). The former has a far tighter criteria for definition, requiring objective cognitive impairment, disturbance in social or occupational functioning and persistence for at least 3 months. It is little surprising, therefore, that the rates of PCS after TBI vary considerably depending on the criteria used with DSM-IV criteria being met by 11% and 64% by the ICD criteria in one study. Some of the diagnostic criteria for these classifications are shown in Table 1 .
mTBI
The term 'traumatic brain injury' was introduced in the USA following the Traumatic Brain Injury Act of 1966, referring to a brain injury resulting from direct or indirect head trauma. Perhaps counterintuitively, mTBI has a fairly concise definition, beyond what one might expect of just a bang on the head. The defining features of mTBI are a 'traumatically induced physiological disruption of brain function', with at least one of the following features:
any period of loss of consciousness
any antegrade or retrograde amnesia
any alteration of mental state at the time of the incident (feeling dazed, disorientated, confused)
focal neurological deficits.
Technically, the definition of mTBI does not preclude structural brain abnormalities; however, the clinical sequelae must be transient. Post-traumatic amnesia must not be greater than 24 h, loss of consciousness greater than 30 min or glasgow coma score (GCS) diminished for greater than 30 min. Most recently, TBI has been defined by a working group as 'an alteration in brain function or other evidence of brain pathology, caused by an external force', with concise definitions of the component parts provided.
Concussion
'Concussion' is derived from the latin 'concutera', meaning to shake violently. The International Conference in Sport has defined this as a 'complex pathophysiological process affecting the brain due to either direct or indirect injury', clearly recognising that significant blows to the torso with forces transmitted to the head are as likely to result in concussion as are direct injuries. The defining feature is a 'brief' neurological deficit that typically resolves spontaneously. The course, however, may be protracted and PCS may result. Concussion probably represents a subgroup of mTBI. Loss of consciousness is not a requirement for the development of concussive symptoms and indeed 75% of concussed sportspersons have no history of loss of consciousness. Characteristically, there will be no abnormality on standard neuroimaging, if performed, emphasising its functional nature, although new, currently experimental modalities such as diffusion tensor imaging may prove useful in the future for detecting the early subtle changes associated with concussion.
Postconcussion syndrome
PCS refers to a complex constellation of symptoms that follow a concussive injury. By amalgamating these criteria, the syndrome can be defined as the presence of three or more of the symptoms in Table 1, occurring in the weeks and months following a head injury. Such symptoms may persist up to 6 months following the head injury, though in some cases may continue indefinitely. The differences in symptoms required for diagnosis (Table 1) highlight the uncertainty clinicians have regarding this condition and also how differently PCS can manifest itself. Moreover, as many of the symptoms below are subjective and are common to, or exacerbated by, other disorders, there is a significant risk of misdiagnosis.
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