The Overdiagnosis of "Post Concussion Syndrome"

These days, many health providers are quick to diagnose patients with “post concussion syndrome” if persistent symptoms are reported after a known or suspected mild traumatic injury (also known as concussion). Interestingly, I have seen this diagnosis given to patients who do not meet any operational definition of concussion and/or who are less than three months post-injury. 

While diagnosing “post concussion syndrome” in patients who were never concussed or who are not yet in the persistent symptom phase is problematic, another problem is that many providers fail to realize is that there are no current consensus-based diagnostic guidelines for a condition with that exact name.
To be precise, the correct diagnostic terms are post-concussional syndrome (PCS) per the International Classification of Diseases-10th edition (ICD-10, 1992) and post-concussional disorder (PCD) per the Diagnostic and Statistical Manual of Mental Disorders-IV (APA, 1994). These criteria are listed at the end of this blog entry in Appendix A. 

While this may seem like a purely semantic argument at first, it is actually a distinction with a significant difference. To begin with, whenever a medical or psychological condition is diagnosed, one needs to know the specific criteria required to make the diagnosis. Without such criteria, diagnostic errors rise and confusion results when attempts are made to communicate about a particular condition. This is why, for example, there are clear and specific criteria for diagnosing multiple sclerosis (Polman et al., 2005). 

 Since there are many conditions that can initially present like multiple sclerosis, the use of formal diagnostic criteria helps improve diagnostic accuracy. The same holds true for all other medical and psychological conditions. That is, criteria should to be used to establish a diagnosis and the criteria should help distinguish the condition of interest from similar conditions. 

With this in mind, how can a diagnosis of “post concussion syndrome” have any real meaning if there are no current formal diagnostic criteria that anyone to refer to? The answer is that it can’t. So we then must turn to the diagnostic criteria for PCS and PCD and examine their utility. 

Serious problems with the definitions

The first question one may naturally ask is since there are two different criteria sets, how well do they agree when applied to actual patients? This question was specifically evaluated by Boake et al. (2004, 2005) who only found “limited agreement” to put it nicely. The reason for the limited agreement mainly centers around very different diagnostic thresholds. That is, after a concussion has been established, a PCS diagnosis only requires a patient to report a few symptoms to meet the diagnostic threshold. This is a very liberal diagnostic threshold since all of the symptoms are non-specific to brain injury. That is, the symptoms listed in the criteria set are often endorsed by normal controls without brain injury (e.g., college students), patients with major depressive disorder, patients with chronic pain, and personal injury claimants with no history of brain injury.
In fact, as McCrea (2008) summarized in his text, many of these groups report such symptoms at higher frequencies than patients with a history of mild traumatic brain injury (MTBI). In a fascinating study by Iverson (2006), he showed that about 90% of patients with a depressive disorder (with no recent history of brain injury) met liberal self-report criteria for postconcussional syndrome. 

Although patients may state that their symptoms began after the concussion, this is not always accurate since patients may exaggerate symptoms (particularly in compensation based claims), may unintentionally misattribute symptoms from another condition (e.g., whiplash, psychological conditions) to brain injury, or may underestimate the degree to which symptoms were present before the injury and overestimate the degree to which they were present afterwards due to expectations that people have about symptoms one should experience after a concussion (Mittenberg et al., 1992). 

Turning to DSM-IV criteria, a diagnosis of PCD requires the presence of cognitive difficulty on objective tests. Objective cognitive testing is often not feasible or practical for physicians, nurse practitioners, or other health care providers who do not have training in objective cognitive assessment. The other problem is that numerous prospective research studies consistently show that patients with a single mild TBI (and in some studies, multiple MTBIs) do not show evidence of cognitive impairment more than three months post injury (Belanger et al. 2005a, 2005b; Binder et al, 1997a, 1997b; Bleiberg et al., 2004; Dikmen et al., 1995; Frenchman et. al, 2005; Iverson, 2005; Larrabee, 1997; Pellman et al., 2004; Schretlen et al., 2003). 

Therefore, it is not all that likely that objective testing will reveal evidence of cognitive impairment more than three months post-injury, particularly when factors such as effort and motivation during testing are accounted for and when other possible etiologies are considered such as psychiatric disorders. This is important because DSM-IV requires that a diagnosis of PCD is not given if the presentation can be explained by another mental disorder.  

Since one criteria set is overly liberal (ICD-10) and another is overly conservative (DSM-IV), it should not be surprising that Boake at al. (2005) found that only 11% of TBI patients (90% mild, 10% moderate) met PCD criteria whereas 64% of patients met PCS criteria. It should be noted that the researchers used a liberal threshold to define a cognitive difficulty (one standard deviation below the mean) since the DSM-IV criteria provide no guidance in this area. This liberal threshold results in a higher degree of false positive classifications since many normal controls obtain scores one standard deviation below the mean.

Another problem is that the definitions of concussion put forth by ICD-10 and DSM-IV are inadequate. Specifically, ICD-10 requires a loss of consciousness (LOC), yet national and international definitions (including one later adapted by the World Health Organization, which is responsible for ICD-10) clearly states that LOC is not required for a concussion diagnosis. Strict adherence to the ICD-10 criteria would result in removing vast numbers of patients who were concussed (but who did not lose consciousness) from being eligible for the diagnosis. 

Although DSM-IV does not restrict concussions to those who experienced LOC, the criteria only lists a few manifestations of concussion and does not provide a precise definition. Regardless, both criteria sets make it clear that it needs to be established that a patient suffered a concussion before a diagnosis of PCS or PCD can be made. In clinical practice, however, I have seen many cases where patients who suffered head injuries (yet do not meet operational definition for MTBI) are diagnosed with “post concussion syndrome.” This would be akin to saying that you are having a post-game show without having a game first. It does not make sense.

What to do from here?

Boake et al. (2005) noted that “…further refinement of the DSM-IV and ICD-10 criteria for PCS is needed before these criteria are routinely employed.” My opinion is to avoid use of these terms entirely because the criteria by which they are based upon are too flawed and were only designed for research purposes. Using a term that has no criteria associated with it such as “post concussion syndrome” does not solve the problem either. What most people mean when they use this term is that the patient had a history of a concussion followed by numerous symptoms. However, as was noted earlier by the Iverson (2006) study and in the review by McCrea (2008) such a standard is too non-specific to brain injury and overly-inclusive. This is a significant problem because patients will interpret the term as meaning that all of their symptoms are caused by brain injury when this is likely not the case. 

While the patient may feel better initially when receiving a diagnosis of PCS because it provides medical validation he/she has been seeking, it can also make the situation far worse in the long run because other potentially treatable conditions such as posttraumatic stress disorder, major depressive disorder, personality disorders, as well as psychosocial factors may not be recognized as contributory, causing the patient to continue to suffer with symptoms far longer than is needed. 

My advice to physicians, nurse practitioners, non-neuropsychologists, and other front-line health care providers dealing with patients more than three months post-injury is to document the medical history in the note, state whether there appears to be a history of head injury or MTBI (if appropriately trained to assess this) and to then state that the patient is experiencing persistent symptoms but that the cause is unclear and needs to be further evaluated through a neuropsychological evaluation. A rule out diagnosis of cognitive disorder NOS can be listed for billing purposes. It should be explained to the patient that the cause of the symptoms are unclear and that further evaluation is needed to determine this. 

Disclaimer: The author of this entry is a board certified clinical neuropsychologist..  

REFERENCES
 

American Psychiatric Association (1994). Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition. Washington, DC, American Psychiatric Association. 

Belanger et al. (2005a). The neuropsychological impact of sports-related concussion: A meta-analysis. Journal of the International Neuropsychological Society, 11, 345–357. 

Belanger et al. (2005b). Factors moderating neuropsychological outcomes following mild traumatic brain injury: a meta-analysis. Journal of the International Neuropsychological Society, 11, 215-27. 

Binder, L.M. et al. (1997a). A review of mild head trauma. Part I: meta-analytic review of neuropsychological studies. Journal of Clinical and Experimental Neuropsychology, 19, 421–431.

Binder, L.M. et al. (1997b). A review of mild head trauma. Part II: clinical implications. Journal of Clinical and Experimental Neuropsychology, 19, 432–457.

Bleiberg, J. Duration of cognitive impairment after sports concussion. Neurosurgery, 54, 1073-80.

Boake et al. (2004). Limited Agreement Between Criteria-Based Diagnoses of Postconcussional Syndrome. The Journal ofNeur opsychiatry and Clinical Neurosciences, 16, 493–499.

Boake et al. (2005). Diagnostic Criteria for Postconcussional Syndrome After Mild to Moderate Traumatic Brain Injury. The Journal of Neuropsychiatry and Clinical Neurosciences 2005; 17:350–356.

Dikmen, S.S. (1995). Neuropsychological outcome at one-year post head injury. Neuropsychology, 9, 80–90.

Frenchman, K.A. et al. (2005). Neuropsychological studies of mild traumatic brain injury : a meta-analytic review of research since 1995. Journal of Clinical and Experimental Neuropsychology, 27, 334-51.

Iverson, G. (2006). Misdiagnosis of the persistent postconcussion syndrome in patients with depression. Archives of Clinical Neuropsychology 21, 303–310

Iverson, G. (2005). Outcome from mild traumatic brain injury. Current Opinion in Psychiatry, 18, 301–317.

Larrabee, G. (1997). Neuropsychological outcome, post concussion symptoms, and forensic considerations in mild closed head trauma. Seminars in Clinical Neuropsychiatry, 2, 196-206.

McCrea, M. (2008). Mild traumatic brain injury and postconcussion syndrome. The new evidence base for diagnosis and treatment. New York: Oxford University Press.

Mittenberg et al. (1992). Symptoms following mild head injury: Expectation as aetiology. Journal of Neurology, Neurosurgery, and Psychiatry, 55, 200-4.

Pellman et al. (2004). Concussion in Professional Football: Neuropsychological Testing - part 6. Neurosurgery, 55, 1290-1305.

Polam et al. (2005). Diagnostic criteria for multiple sclerosis: 2005 revisions to the McDonald criteria. Ann Neurol. 58; 840-846.

Schretlen et al. (2003). A quantitative review of the effects of traumatic brain injury on cognitive functioning. International Review of Psychiatry, 15, 341–349.

World Health Organization (1992). International statistical classification of diseases and related health problems - 10th edition. Geneva, Switzerland: World Health Organization.

Appendix A

ICD-10 Definition: Post-concussional syndrome

Listed below are the diagnostic criteria for PCS from ICD-10.

“Note: The nosological status of this syndrome is uncertain, and criterion A of the introduction to this rubric is not always ascertainable. However, for those undertaking research into this condition, the following criteria are recommended: 

A. The general criteria of F07 must be met. The general criteria for F07, Personality and Behavioral Disorders Due to Brain Disease, Damage and Dysfunction, are as follows:

G1. Objective evidence (from physical and neurological examination and laboratory tests) and/or history, of cerebral disease, damage, or dysfunction.

G2. Absence of clouding of consciousness and of significant memory deficit.

G3. Absence of sufficient or suggestive evidence for an alternative causation of the personality or behavior disorder that would justify its placement in section F6 (Other Mental Disorders Due to Brain Damage and Dysfunction and to Physical Disease).

B. History of head trauma with loss of consciousness, preceding the onset of symptoms by a period of up to four weeks (objective EEG, brain imaging, or oculonystagmographic evidence for brain damage may be lacking).

C. At least three of the following:

(1) Complaints of unpleasant sensations and pains, such as headache, dizziness (usually lacking the features of true vertigo), general malaise and excessive fatigue, or noise intolerance.
(2) Emotional changes, such as irritability, emotional lability, both easily provoked or exacerbated by emotional excitement or stress, or some degree of depression and/or anxiety.
(3) Subjective complaints of difficulty in concentration and in performing mental tasks, and of memory complaints, without clear objective evidence (e.g. psychological tests) of marked impairment.
(4) Insomnia.
(5) Reduced tolerance to alcohol.
(6) Preoccupation with the above symptoms and fear of permanent brain damage, to the extent of hypochondriacal over-valued ideas and adoption of a sick role. 

DSM-IV Definition: Post-concussional disorder

 

 A. A history of head trauma that has caused a significant cerebral concussion.

Note. The manifestations of concussion include loss of consciousness, post-traumatic amnesia, and less commonly, post-traumatic onset of seizures. Specific approaches for defining this criterion need to be refined by further research.

B. Evidence from neuropsychological testing or quantified cognitive assessment of difficulty in attention (concentrating, shifting focus of attention, performing simultaneous cognitive tasks) or memory.

C. Three (or more) of the following occur shortly after the trauma and last at least 3 months.

1. becoming fatigued easily (2) disordered sleep (3) headache (4) vertigo or dizziness, (5) irritability or aggression on little or no provocation, (6) anxiety, depression, or affective liability (7) changes in personality (e.g., social or sexual inappropriateness) (8) apathy or lack of spontaneity.

D. The symptoms in criteria B or C have their onset following head trauma or else represent a substantial worsening of preexisting symptoms.

E. The disturbance causes significant impairment in social or occupational functioning and represents a significant decline from a previous level of functioning. In school age children, the impairment may be manifested by a significant worsening in school or academic performance dating from the trauma.

F. The symptoms do not meet criteria for Dementia due to Head Trauma and are not better accounted for by another mental disorder (e.g., Amnestic Disorder due to Head Trauma, Personality Change Due to Head Trauma.