Post-concussion syndrome

In the past, the term PCS was also used to refer to immediate physical symptoms or post-concussive symptoms following a minor TBI or concussion.[13] The severity of these symptoms typically decreases rapidly.[14] In addition, the nature of the symptoms may change over time: acute symptoms are most commonly of a physical nature, while persisting symptoms tend to be predominantly psychological.[15][16] Symptoms such as noise sensitivity, problems with concentration and memory, irritability, depression, and anxiety may be called 'late symptoms' because they generally do not occur immediately after the injury, but rather in the days or weeks after the injury.[13] Nausea and drowsiness commonly occur acutely following concussion. Headache and dizziness occur immediately after the injury, but also can be long lasting.[13]

The condition is associated with a wide range of non-specific symptoms: physical, such as headache; cognitive, such as difficulty concentrating; and emotional and behavioral, such as irritability. Many of the symptoms associated with PCS are common or may be exacerbated by other disorders, so there is considerable risk of misdiagnosis. Headaches that occur after a concussion may feel like migraine headaches or tension-type headaches. Most headaches are tension-type headaches, which may be associated with a neck injury that occurred at the same time of the head injury.[17]

The question of the cause or causes of PCS has been heavily debated for many years and remain controversial. It is not known to exactly what degree the symptoms are due to physiological changes or to other factors, such as pre-existing psychiatric disorders or factors related to secondary gain or disability compensation.[28] The subjectivity of the complaints complicates assessment and makes it difficult to determine whether symptoms are being exaggerated or feigned.[18]

PCS may also be exacerbated by psychosocial factors, chronic pain, or an interaction of some or all of these.[29] The majority of experts believe that PCS results from a mix of factors, including preexisting psychological factors and those directly relating to the physical injury.[13]

It is not known what causes PCS to occur and persist,[30] or why some people who have a mild traumatic brain injury later develop PCS while others do not.[31] The nature of the syndrome and the diagnosis itself have been the subject of intense debate since the 19th century. However, certain risk factors have been identified; for example, preexisting medical or psychological conditions, expectations of disability, being female, and older age all increase the chances that someone will have PCS. Physiological and psychological factors present before, during, and after the injury are all thought to be involved in the development of PCS.[13]

Some experts believe post-concussion symptoms are caused by structural damage to the brain or disruption of neurotransmitter systems, resulting from the impact that caused the concussion. Others believe that post-concussion symptoms are related to common psychological factors. Most common symptoms like headache, dizziness, and sleep problems are similar to those often experienced by individuals diagnosed with depression, anxiety, or post traumatic stress disorder. In many cases, both physiological effects of brain trauma and emotional reactions to these events play a role in the development of symptoms.[32]

Symptom	ICD-10[39]	DSM-IV[34]
Headache	Y	Y
Dizziness	Y	Y
Fatigue	Y	Y
Irritability	Y	Y
Sleep problems	Y	Y
Concentration problems	Y	-
Memory problems	Y	-
Problems tolerating stress/emotion/alcohol	Y	-
Affect changes, anxiety, or depression	-	Y
Changes in personality	-	Y
Apathy	-	Y

The International Statistical Classification of Diseases and Related Health Problems (ICD-10) and the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders have set out criteria for post-concussion syndrome (PCS) and post-concussional disorder (PCD), respectively.

The ICD-10 established a set of diagnostic criteria for PCS in 1992.[39] In order to meet these criteria, a patient has had a head injury "usually sufficiently severe to result in loss of consciousness"[34][40] and then develop at least three of the eight symptoms marked with a check mark in the table at right under "ICD-10" within four weeks.[39][41] About 38% of people who have a head injury with symptoms of concussion and no radiological evidence of brain lesions meet these criteria.[42] In addition to these symptoms, people that meet the ICD-10 criteria for PCS may fear that they will have permanent brain damage, which may worsen the original symptoms.[3] Preoccupation with the injury may be accompanied by the assumption of a "sick role" and hypochondriasis.[38] The criteria focus on subjective symptoms and mention that neuropsychological evidence of significant impairment is not present.[43] With their focus on psychological factors, the ICD-10 criteria support the idea that the cause of PCS is functional.[34] Like the ICD-10, the ICD-9-CM defines PCS in terms of subjective symptoms and discusses the greater frequency of PCS in people with histories of mental disorders or a financial incentive for a diagnosis.[43]

The DSM-IV lists criteria for diagnosis of PCD in people who have had a head trauma with persistent post-traumatic amnesia, loss of consciousness, or post-traumatic seizures.[34] In addition, for a diagnosis of PCD, patients must have neuropsychological impairment as well as at least three of the symptoms marked with a check mark in the table at right under "DSM-IV".[34] These symptoms must be present for three months after the injury and must have been absent or less severe before the injury.[44] In addition, the patient must experience social problems as a result, and must not meet criteria for another disorder that explains the symptoms better.[44]

Neuropsychological tests exist to measure deficits in cognitive functioning that can result from PCS.[18][27] The Stroop Color Test and the 2&7 Processing Speed Test (which both detect deficits in speed of mental processing) can predict the development of cognitive problems from PCS.[18] A test called the Rivermead Postconcussion Symptoms Questionnaire, a set of questions that measure the severity of 16 different post-concussion symptoms, can be self-administered or administered by an interviewer.[3] Other tests that can predict the development of PCS include the Hopkins Verbal Learning A test (HVLA) and the Digit Span Forward examination.[18] The HVLA tests verbal learning and memory by presenting a series of words and assigning points based on the number recalled,[45] and digit span measures attention efficiency by asking the examinee to repeat back digits spoken by the tester in the same order as they are presented.[46] In addition, neuropsychological tests may be performed to detect malingering (exaggerating or making up symptoms) .[14]

Management of post-concussion syndrome typically involves treatments addressing specific symptoms;[16] for example, people can take over the counter pain relievers for headaches and medicine to relieve depression or insomnia.[49] Participation in low-risk physical activities that raise the heart rate and mental activities is advised, at a level that does not worsen symptoms.[50] Prolonged rest is not suggested.[50] Physical and behavioral therapy may also be prescribed for problems such as loss of balance and difficulties with attention, respectively.[51]

The prognosis for PCS is generally considered positive, with total resolution of symptoms in many, but not all, cases. For 50% of people, post-concussion symptoms go away within a few days to several weeks after the original injury occurs.[28] In others, symptoms may remain for three to six months,[25] but evidence indicates that many cases are completely resolved within six months.[18] The majority of symptoms are largely gone in about half of people with concussion one month after the injury, and about two thirds of people with minor head trauma are nearly symptom-free within three months. Persistent, often severe headaches are the longest lingering symptom in most cases and are the most likely symptom to never fully resolve.[52] It is frequently stated in the literature and considered to be common knowledge that 15–30% of people with PCS have not recovered by a year after the injury, but this estimate is imprecise because it is based on studies of people admitted to a hospital, the methodologies of which have been criticized.[29][47][58] In approximately 15% of people, symptoms may persist for years or be permanent. If symptoms are not resolved by one year, they are likely to be permanent, though improvements may occur after even two or three years,[44] or may suddenly occur after a long time without much improvement.[59] Older people and those who have previously had another head injury are likely to take longer to recover.[59]

The way in which children cope with the injury after it occurs may have more of an impact than factors that existed prior to the injury.[34] Children's mechanisms for dealing with their injuries may have an effect on the duration of symptoms, and parents who do not deal effectively with anxiety about children's post-injury functioning may be less able to help their children recover.[34]

If another blow to the head occurs after a concussion but before its symptoms have gone away, there is a slight risk of developing the serious second-impact syndrome (SIS).[60][61] In SIS, the brain rapidly swells, greatly increasing intracranial pressure.[60] People who have repeated mild head injuries over a prolonged period, such as boxers and Gridiron football players, are at risk for chronic traumatic encephalopathy (or the related variant dementia pugilistica), a severe, chronic disorder involving a decline in mental and physical abilities.[62]

It is not known exactly how common PCS is. Estimates of the prevalence at three  months post-injury are between 24 and 84%, a variation possibly caused by different populations or study methodologies.[13] The estimated incidence of PPCS (persistent postconcussive syndrome) is around 10% of mTBI cases.[43] Since PCS by definition only exists in people who have had a head injury, demographics and risk factors are similar to those for head injury; for example, young adults are at higher risk than others for receiving head injury, and, consequently, of developing PCS.[44]

The existence of PCS in children is controversial. It is possible that children's brains have enough plasticity that they are not affected by long-term consequences of concussion (though such consequences are known to result from moderate and severe head trauma).[63] On the other hand, children's brains may be more vulnerable to the injury, since they are still developing and have fewer skills that can compensate for deficits.[64] Clinical research has found higher rates of post-concussion symptoms in children with TBI than in those with injuries to other parts of the body, and that the symptoms are more common in anxious children.[38] Symptoms in children are similar to those in adults, but children exhibit fewer of them.[38] Evidence from clinical studies found that high school-aged athletes had slower recoveries from concussion as measured by neuropsychological tests than college-aged ones and adults.[64] PCS is rare in young children.[53]

The symptoms that occur after a concussion have been described in various reports and writings for hundreds of years.[25] The idea that this set of symptoms forms a distinct entity began to attain greater recognition in the latter part of the 19th century.[69] John Erichsen, a surgeon from London, played an important role in developing the study of PCS.[69] The controversy surrounding the cause of PCS began in 1866 when Erichsen published a paper about persisting symptoms after sustaining mild head trauma.[18] He suggested that the condition was due to "molecular disarrangement" to the spine. The condition was originally called "railroad spine" because most of the injuries studied had happened to railroad workers.[18] While some of his contemporaries agreed that the syndrome had an organic basis, others attributed the symptoms to psychological factors or to outright feigning.[69] In 1879, the idea that a physical problem was responsible for the symptoms was challenged by Rigler, who suggested that the cause of the persisting symptoms was actually "compensation neurosis": the railroad's practice of compensating workers who had been injured was bringing about the complaints.[18] Later, the idea that hysteria was responsible for the symptoms after a mild head injury was suggested by Charcot.[18][70] Controversy about the syndrome continued through the 20th century.[70] During World War I many soldiers with puzzling symptoms after being close to a detonation but without any evidence of a head wound. The illness was called shell shock, and a psychological explanation was eventually favoured.[71] By 1934 the current concept of PCS had replaced ideas of hysteria as the cause of post-concussion symptoms.[18] British authorities banned the term shell shock during World War II to avoid an epidemic of cases, and the term posttrauma concussion state was coined in 1939 to describe "disturbance of consciousness with no immediate or obvious pathologic change in the brain".[71] The term postconcussion syndrome was in use by 1941.[71]

In 1961, H. Miller first used the term "accident neurosis" to refer to the syndrome which is now called PCS and asserted that the condition only occurs in situations where people stand to be compensated for the injury.[35] The real causes of the condition remain unclear.[18]

Though no universally accepted definition of postconcussive syndrome exists, most of the literature defines the syndrome as the development of at least three of the following symptoms: headache, dizziness, fatigue, irritability, impaired memory and concentration, insomnia, and lowered tolerance for noise and light.[44] One complication in diagnosis is that symptoms of PCS also occur in people who have no history of head injury, but who have other medical and psychological complaints.[29] In one study 64% of people with TBI, 11% of those with brain injuries, and 7% of those with other injuries met the DSM-IV criteria for post-concussion syndrome. Many of these individuals with PCS were misdiagnosed as having other unrelated conditions due to commonality of symptoms. (see diagnosis above).[72]

Headache is one of the criteria for PCS, but it is notably undetermined where the headache comes from. Couch, Lipton, Stewart and Scher (2007)[73] argue that headaches, one of the hallmarks of PCS, occur in a variety of injuries to the head and neck. Further, Lew et al. (2006)[74] reviewed ample studies comparing headaches to post-traumatic headaches and found that there is wide heterogeneity in the source and causes of headaches. They point out that the International Headache Society lists 14 known causes of headaches, as well. Furthermore, the headaches may be better accounted for by mechanical causes, such as whiplash, which is often mistaken for PCS.[75] An additional possibility is that posttraumatic stress disorder can account for some cases diagnosed as PCS,[76] but for emotional regulation as well.[72][77]

Depression, posttraumatic stress disorder, and chronic pain share symptoms resembling those of PCS.[29] One study found that while people with chronic pain without TBI do report many symptoms similar to those of post-concussion syndrome, they report fewer symptoms related to memory, slowed thinking, and sensitivity to noise and light than people with mTBI do.[13] Additionally, it has been found that neuroendocrinology may account for depressive symptoms and stress management due to irregularities in cortisol regulation, and thyroid hormone regulation.[78] Lastly, there is evidence that major depression following TBI is quite common, but may be better accounted for with a diagnosis of dysexecutive syndrome.[79]

In a syndrome, a set of symptoms is consistently present, and symptoms are linked such that the presence of one symptom suggests that of others. Because PCS symptoms are so varied and many can be associated with a large number of other conditions, doubt exists about whether the term "syndrome" is appropriate for the constellation of symptoms found after concussion.[80] The fact that the persistence of one symptom is not necessarily linked to that of another has similarly led to doubt about whether "syndrome" is the appropriate term.[52]

A longstanding controversy surrounding PCS concerns the nature of its etiology – that is, the cause behind it[34] – and the degree to which psychological factors and organic factors involving brain dysfunction are responsible. The debate has been referred to as 'psychogenesis versus physiogenesis' (psychogenesis referring to a psychological origin for the condition, physiogenesis to a physical one).[34]

• Daniel Amen, post-concussion expert for the National Football League