Post-concussion syndrome

Post-concussion syndrome, also known as postconcussive syndrome or PCS, is a set of symptoms that a person may experience for weeks, months, or even years after a concussion, a mild form of traumatic brain injury. As many as 50% of patients who have experienced concussion have PCS,^[1] and some sources say as many as 90% of patients experience postconcussion symptoms.^[2] Some doctors make a diagnosis of PCS in patients who have symptoms resulting from concussion for more than three months after the injury,^[3] while others make the diagnosis in patients who have symptoms starting within a week of trauma.^[2] In late, or persistent PCS, symptoms last for over six months.^[2]

It is not known what causes PCS symptoms to occur and persist^[4] or why some patients who suffer a mild traumatic brain injury (MTBI) develop PCS while others do not.^[5] It is commonly believed that physiological and psychological factors before, during, and after the injury all take part in the development of PCS.^[6]

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Signs and symptoms

People who have had concussions may experience physical, mental, or emotional symptoms. Symptoms can appear immediately or weeks to months after the initial injury.

Physical symptoms can include:

• headache
• dizziness
• impaired balance^[7]

• nausea and/or vomiting
• fatigue or sleepiness
• inability to sleep
• decreased libido^[8]
• sensitivity to noise or light^[2]
• ringing in the ears
• double or blurred vision^[9]
• decreased sense of taste, smell, or hearing

Emotional symptoms may include:

• irritability
• anxiety^[10]
• restlessness^[11]
• depression^[12]
• lack of emotion^[12]
• emotional lability or mood swings
• lack of ability to tolerate stress or alcohol^[2]
• aggression^[13]

Cognitive or mental symptoms can include:

• amnesia or difficulty remembering things
• confusion or impaired cognition^[10]
• impaired judgment^[6]
• slowed cognitive processing^[14]
• difficulty with abstract thinking^[11]
• difficulty concentrating^[8]
• decrease in work performance^[13]
• decrease in social skills^[13]

History and controversy

The name "post-concussive syndrome" was first coined by S. H. Auerbach.^[15]

PCS is a controversial diagnosis.^[16] Though people have known about the syndrome for hundreds of years,^[10] it is not known to exactly what degree the symptoms are due to microscopic damage to the brain or to other factors, for example psychological factors.^[12] This question has been heavily debated for many years. Psychological factors are known to affect post concussion symptoms; however, it has been shown that structural damage does occur after some concussions.^[10][11]

In the 1860s, a group of doctors began to support the idea that structural features were to blame for symptoms, but the prevailing sentiment was still that psychological factors caused PCS.^[17] It was not until a century later, in the 1960s, that such structural damage could be visualized using new brain scanning technology. Experiments have shown that physiological damage such as apoptosis does occur after minor TBI such as concussion,^[18][19] and brain dysfunction measured by EEG is correlated with post-concussion symptoms.^[20]

Many researchers now believe that PCS does have a physical basis, though the evidence supporting this hypothesis is still not conclusive.^[19] Other researchers doubt the existence of PCS and attribute symptoms to psychological or social factors, such as patients' expectations that they will experience these symptoms.^[21][22] Malingering may be suspected, especially in cases involving litigation or other potential gain for the patient.^[23] Also, symptoms may be psychogenic, that is, they may be a result of the patient's psychological or emotional state, rather than a physiological phenomenon.^[24] It is widely believed that physiological factors are responsible for early symptoms that occur after mild head trauma, whereas symptoms that occur later are due to psychological factors.^[22] PCS is more prevalent in patients who had psychiatric symptoms, such as depression or anxiety, before the injury.^[25]

Another reason that PCS is a controversial diagnosis is that its symptoms may manifest spontaneously in the general population; thus the syndrome may be diagnosed in a patient who is actually healthy. Symptoms that can be indicative of post-concussion syndrome occur spontaneously in the general population of young, healthy adults at a fairly high rate.^[26] In addition, symptoms of PCS may actually be caused by other conditions.

Differential diagnosis

Because of the similarities to other conditions, such as depression, there is a risk that doctors may misdiagnose PCS.^[4] For example, depression may be mistaken for PCS.^[27] Traumatic brain injury may cause damage to the hypothalamus or the pituitary gland. Deficiencies of pituitary hormones (hypopituitarism) can cause similar symptoms to post-concussion syndrome and should thus be considered as a cause for symptoms before diagnosing post-concussion syndrome. Hypopituitarism can be treated by replacing any hormone deficiencies.

Diagnosis in children

Some researchers believe that children's brains have enough plasticity that they are not affected by long-term consequences of concussion (though such consequences are well known to result from moderate and severe head trauma).^[24] Other research has shown that children do experience post-concussion symptoms such as deficits in memory and concentration, though they may be due to psychogenic factors or preexisting conditions individual to the child.^[24]

Treatment

Patients who have suffered a head injury must be examined by emergency medical care providers to ensure that the head injury is not worse than concussion and potentially life threatening. Thus, head injury patients with symptoms that may indicate a dangerous injury are given CT scans or MRIs and are observed by medical staff. Later, the patient may be tested to determine his or her level of cognitive functioning. A test called the Rivermead Postconcussion Symptoms Questionnaire exists to measure the severity of the patient's symptoms. There is no scientifically established treatment for PCS,^[28] so the syndrome is usually not treated, except with pain relievers for headaches and medicine to relieve depression, nausea, or dizziness.^[12] Rest is also advised but is only somewhat effective.^[28]

When patients have ongoing disabilities, they are treated with therapy to help them function at work, socially, or in other contexts.^[9] Patients are aided in gradually returning to work and other preinjury activities as symptoms permit. Since stress exacerbates post concussion symptoms, and vice versa, an important part of treatment is letting the patient know that symptoms are normal and helping the patient deal with impairments.^[11]

Prognosis

For most patients, post concussion symptoms go away within a few days to several weeks after the original injury occurs.^[12] In others, symptoms may remain for three to six months.^[8][10] In a small percentage of patients, symptoms may persist for years or may be permanent.^[8][6] If symptoms are not resolved by one year, they are likely to be permanent (though some people report improvements after even 2 or 3 years time).^[2] However, the prognosis for PCS is generally considered excellent, with total resolution of symptoms in the large majority of cases.

If a patient receives another blow to the head after a concussion but before concussion symptoms have gone away, there is a slight risk that he or she will develop the very rare but deadly second-impact syndrome (SIS). In SIS, the brain rapidly swells, greatly increasing intracranial pressure.

Epidemiology

The incidence of PCS is higher in females than in males.^[2] People over the age of 55 are more likely to have long-lasting symptoms.^[29] Since PCS by definition only exists in people who have suffered 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.^[2] Some studies have questioned the validity of a diagnosis of PCS in children after finding differences in PCS symptoms between head injured and control groups of children not to be statistically significant.^[30] Others have found the incidence of PCS to be quite similar between children and adults.^[31]

References