Concussion is a diagnosis that is increasingly controversial in primary care. The purported link to chronic traumatic encephalopathy1–3 has heightened anxiety among patients, practitioners, and sports administrators.4 Current accepted definitions of concussion characterize it as a brain injury. However, based on the current medical evidence, we would suggest that the constellation of symptoms presently defined as concussion does not have to involve the brain.
The 2008 definition proposed in the Zurich Consensus Statement on Concussion in Sport defines concussion as “a complex pathophysiological process affecting the brain” with the “onset of short-lived impairment of neurologic function that resolves spontaneously.” The definition allows for “a graded set of clinical symptoms that may or may not involve loss of consciousness.” However, the definition affirms that standard brain imaging does not yield any abnormality and that neuropathological changes are not required to make a diagnosis.5 Another guideline, such as that proposed by Veterans Affairs and the American Department of Defense (VA/DoD) in 2009, uses stricter criteria for the diagnosis of concussion, requiring confusion, immediate amnesia, and/or loss of consciousness at the time of impact.6 Nonspecific symptoms such as headache, dizziness, or fatigue can be used to support the diagnosis but do not allow for a diagnosis to be made on their appearance alone. The VA/DoD definition goes on to reiterate that the “symptoms associated with concussion/mTBI are not unique,” “occur frequently in day-to-day life among healthy individuals,” and are “highly subjective in nature.” However, within that definition is a foundational reference to the 1993 definition put forth by the American College of Rehabilitation Medicine that again refers to concussion as a “disruption of brain function.”7 The World Health Organization also offers a definition that characterizes concussion as a brain injury.8 Common to all these definitions is the fundamental concept that concussion is a brain injury.
Our position is that the current syndrome described as concussion does not require brain involvement. Concussion symptoms can emanate from the cervical spine. First, whiplash mechanisms of injury are identical to the “impulsive forces” described in concussive injuries. Second, the symptoms of concussion and whiplash-associated disorders (WAD) display remarkable similarity. Notably, symptoms such as headache, neck pain, disturbance of concentration or memory, dizziness, irritability, sleep disturbance, and fatigue, have been described in both concussion6,9,10 and whiplash11–13 patients. Symptom inventories initially designed for WAD patients have demonstrated application to patients diagnosed with concussion.14 Furthermore, cervical zygapophyseal joints have been implicated as generators of headache and dizziness, with diagnostic and therapeutic anesthetic blocks in whiplash patients.15–17 If the headache associated with concussion can potentially be of cervical spine origin, we would suggest that there is no certainty that any of the common concussion symptoms are specific to brain injury.
No readily available clinical test has been identified to confirm concussion as a brain injury. Despite significant effort in the quest for a validated and practical neuroimaging or biomarker test for concussion as a brain injury, the diagnosis remains clinician based. There is some evidence that imaging with Proton Magnetic Resonance Spectroscopy and functional magnetic resonance imaging demonstrates reproducible changes following a concussive injury,25 but these tests are not practically available and it is not clear that the changes seen represent injury. The diagnostic armamentarium available to clinicians does not generate a compelling argument to attribute concussion symptoms to a brain injury. Essentially, although concussion has been defined as a brain injury, there is a paucity of evidence to attribute the symptom cluster known as concussion to a process exclusively involving the brain.
The removal of injury to the brain as a fundamental construct in the definition of concussion has implications regarding management. Based on current guidelines and evidence, the management of concussion and WAD is very different. The Zurich definition allows for the presence of virtually any symptom following a trauma with forces applied to the head to be attributed to a concussive brain injury and subsequent (and perhaps inappropriate) application of strict management guidelines involving cognitive and physical rest. A diagnosis of “brain injury” and prescription of rest has potentially dangerous consequences as it relates to perception of disability.18 On the other hand, WAD have been treated with radiofrequency neurotomy19–22 and a variety of manipulative techniques.23 Also, the management of WAD includes encouraging patients to engage in their regular daily activity,24 even in the presence of symptoms. The recognition of WAD and other treatable conditions as part of the concussion syndrome would move treatment guidelines away from strict rest-based protocols and the disability that they have the potential to perpetuate.
The current clinical manifestation described as concussion might be more appropriately defined as a syndrome; a constellation of symptoms and potential physical findings seen in patients with injuries involving impulsive forces to the head and neck. Potential sources for symptoms include the brain, neck, vestibular system, and affective disorders. The overlap with neck/whiplash injuries is evident. Incorporating this understanding into the definition of concussion would direct the clinician to determine the most probable source of the concussion symptoms and acknowledge treatable non–brain-based pathology, if present. Furthermore, redefining concussion as a clinical syndrome and not synonymous with "brain injury" might attenuate some of the emerging paranoia and fear surrounding the long-term consequences of concussion as it relates to brain pathology and chronic traumatic encephalopathy.
In conclusion, we suggest that the moniker cranio-cervical shake syndrome (CCSS) is more appropriate for the disorder currently known as concussion. We assert that the constellation of signs and symptoms does not have to involve the brain. This has implications for the management and prognosis of this syndrome.
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