Mild traumatic brain injuries are also known as concussions. It is estimated that these injuries have a prevalence of 3.8 million per year in the
United States (1). Despite this high incidence, mild traumatic brain injuries and concussions are one of the least understood injuries facing the sports healthcare and the neuroscience communities today (2).
In the majority of patients sustaining a concussion, symptoms resolve within 7–10 days. However, approximately 10–15% of these patients develop persistent symptomatology lasting weeks, months or even years after injury (3). This phase of chronic symptoms is known as the post-concussion syndrome. The patient is considered to be chronic when symptoms persist longer than 4-12 weeks.
It is assumed that the post-concussion syndrome manifests secondary to brain injury leading to alterations in brain biochemistry, neurophysiology, and metabolism; the problem is assumed to be in the brain. However, four lines of evidence challenge this assumption:
First Line of Evidence
The standard treatment for mild traumatic brain injury and the post-concussive syndrome is rest (4). This approach works well for 85-90% of these patients, but not for those suffering from the post-concussive syndrome. This suggest that perhaps an etiology other than brain injury is responsible for the ongoing symptomology.
Second Line of Evidence
There is considerable overlap of the signs and symptoms of mild traumatic brain injury and of whiplash associated disorders. This would suggest the possibility that the post-concussive syndrome symptoms may in fact be arising from the cervical spine (3).
Signs and Symptoms of
Signs and Symptoms of Whiplash Associated Disorders
Pressure in Head
Reduced/painful neck movements
Sensitivity to Light
Feeling Like “In a Fog”
Sensitivity to Noise
Ringing in Ears
Feeling Slowed Down
“Don’t Feel Right”
Nervous / Anxious / Irritable
Sadness / More Emotional
Fatigue / Low Energy /Drowsiness
Trouble Falling Asleep
Reduced/painful Jaw Movements
Numbness, Tingling or Pain in Arm or Hand
Numbness, Tingling or Pain in Leg or Foot
Lower back pain
“Injury or dysfunction of the cervical spine has been shown to cause headaches, dizziness and loss of balance, nausea, visual and auditory disturbances, reduced cognitive function, and many other signs and symptoms considered synonymous with concussion.” (3)
Third Line of Evidence
There is a probability that the forces required to cause a mild traumatic brain injury will also injure the soft tissues of the cervical spine. The range of linear impact accelerations causing concussion injury is between 60—160 G, with the peak occurring at 96 G (5). Whiplash injuries can occur at accelerations of 4.5 G (6). Thus it is highly likely that individuals who experience the G forces to sustain a concussion will also experience cervical spine injury.
In 2015, Cameron Marshall DC, Howard Vernon DC, John Leddy MD, and Bradley Baldwin DC published an article in The Physician and Sportsmedicine, titled (3):
The Role of the Cervical Spine in Post-concussion Syndrome
A proposed mechanism for persisting symptomatology following concussion (the post-concussive syndrome) is “concomitant low-grade sprain–strain injury of the cervical spine occurring concurrently with significant head trauma.”
“Any significant blunt impact and/or acceleration/deceleration of the head will also result in some degree of inertial loading of the neck potentially resulting in strain injuries to the soft tissues and joints of the cervical spine.”
“Acceleration/deceleration of the head–neck complex of sufficient magnitude to cause mild traumatic brain injury is also likely to cause concurrent injury to the joints and soft tissues of the cervical spine.”
It is “well established that injury and/or dysfunction of the cervical spine can result in numerous signs and symptoms synonymous with concussion, including headaches, dizziness, as well as cognitive and visual dysfunction; making diagnosis difficult.”
“The symptoms of headache and dizziness, so prevalent in concussion-type injuries, may actually be the result of cervicogenic mechanisms due to a concomitant whiplash injury suffered at the same time.”
It seems unlikely, if not impossible, for the forces required to produce a mild traumatic brain injury not to also cause an injury to the soft tissues of the cervical spine.
Fourth Line of Evidence
Anatomically and physiologically, the cervical spine is connected to the brain and brainstem.
In 2006, researchers from the University of Guelph, Ontario, CAN, published a study in the journal Brain Injury, titled (10):
Is there a relationship between whiplash-associated disorders and concussion in hockey? A preliminary study
The authors examined the relationship between the occurrence of whiplash-associated disorders and concussion symptoms in hockey players. The study design was a prospective cohort observational study. Twenty hockey teams were followed prospectively for one season. Team therapists completed acute and 7-10 day follow-up evaluation questionnaires for all of the players who received either a whiplash mechanism or a concussion.
The authors found that essentially all patients who received a whiplash-mechanism injury also sustained some degree of mild traumatic brain injury. Likewise, all patients who received a mild traumatic brain injury also showed evidence of cervical spine injury. The authors concluded:
“There is a strong association between whiplash induced neck injuries and the symptoms of concussion in hockey injuries.”
“Both should be evaluated when dealing with athletes/patients suffering from either injury.”
In 2013, researchers from the University of Calgary, Calgary, Alberta, CAN, published a study in the Clinical Journal of Sport Medicine, titled (11):
Preseason reports of neck pain, dizziness, and headache as risk factors for concussion in male youth ice hockey players
The objective of this study was to determine the risk of concussion in youth male hockey players with preseason reports of neck pain, headaches, and/or dizziness. The authors pooled data from 2 prospective cohort studies. A total of 3,832 male ice hockey players aged 11 to 14 years (280 teams) participated.
Participants recorded baseline preseason symptoms of dizziness, neck pain, and headaches on the Sport Concussion Assessment Tool. Concussions that occurred during the season were recorded using a validated prospective injury surveillance system. The findings were as follows:
The authors concluded:
“Male youth athletes reporting headache and neck pain at baseline were at an increased risk of concussion during the season. The risk was associated with dizziness and any 2 of dizziness, neck pain, or headaches.”
The implication of this study is that athletes with neck pain are at an increased risk for concussion. They suggest all such athletes should be identified prior to the season.
Four studies have concluded that injuries of the cervical spine are responsible for post-concussion syndrome, and have shown excellent clinical outcomes as a consequence of treatment to the cervical spine.
In 1990, researchers from the Department of Rheumatology, County Hospital of Aarhus, Denmark, published a study in the journal Cephalalgia, titled (12):
An open study comparing manual therapy with the use of cold packs in the treatment of post-traumatic headache
“Manual therapy used in this study seems to have a specific effect in reducing post-traumatic headache.”
“The result supports the hypothesis of a cervical mechanism causing post-traumatic headache and suggests that post-traumatic dizziness, visual disturbances and ear symptoms could be part of a cervical syndrome.”
In 1994, researchers from the Department of Physiotherapy, University of Queensland, Australia, published a study in the journal Cephalalgia, titled (13):
Cervical musculoskeletal dysfunction in post-concussional headache
The authors note, “persistent headache is a common symptom following a minor head injury or concussion, possibly related to simultaneous injury of structures of the cervical spine.”
This study measured aspects of cervical musculoskeletal function in a group of twelve patients with post-concussional headache and in a normal control group. The post-concussional headache group was distinguished from the control group by the presence of painful upper cervical segmental joint dysfunction, less endurance in the neck flexor muscles and a higher incidence of moderately tight neck musculature. The authors concluded:
“As upper cervical joint dysfunction is a feature of cervicogenic causes of headache, the results of this study support the inclusion of a precise physical examination of the cervical region in differential diagnosis of patients suffering persistent headache following concussion.”
Cervicovestibular rehabilitation in sport-related concussion: A randomized controlled trial
These authors note “concussion is a common injury in sport. Most individuals recover in 7-10 days but some have persistent symptoms. The objective of this study was to determine if a combination of vestibular rehabilitation and cervical spine physiotherapy decreased the time until medical clearance in individuals with prolonged post-concussion symptoms.”
This study was a randomized controlled trial. Consecutive patients with persistent symptoms of dizziness, neck pain and/or headaches following a sport-related concussion (12-30 years, 18 male and 13 female) were randomized to the control or intervention group.
Both groups received weekly sessions with a physiotherapist for 8 weeks or until the time of medical clearance. Both groups received postural education, range of motion exercises and cognitive and physical rest until asymptomatic followed by a protocol of graded exertion. The intervention group also received cervical spine and vestibular rehabilitation. The primary outcome of interest was medical clearance to return to sport, which was evaluated by a study sport medicine physician who was blinded to the treatment group.
In the treatment group, 73% of the participants were medically cleared within 8 weeks of initiation of treatment, compared with 7% in the control group. The authors concluded:
“A combination of cervical and vestibular physiotherapy decreased time to medical clearance to return to sport in youth and young adults with persistent symptoms of dizziness, neck pain and/or headaches following a sport-related concussion.”
In 2015, researchers from Canadian Memorial Chiropractic College and State University of New York at Buffalo, published a study in the journal The Physician and Sportsmedicine, titled (3):
The Role of the Cervical Spine in Post-concussion Syndrome
The symptoms of concussion are due to neuronal dysfunction and not due to structural damage of the involved neurons, which is “why conventional structural imaging techniques such as CT and MRI are typically unremarkable.”
This paper reviews the existing literature surrounding the numerous proposed theories of post-concussive syndrome and introduces another potential, and very treatable, cause of this chronic condition; cervical spine dysfunction due to concomitant whiplash-type injury.
The authors discuss the cases of 5 patients with diagnosed post-concussive syndrome, who experienced very favorable outcomes following various treatment and rehabilitative techniques aimed at restoring cervical spine function; treatment included spinal manipulation.
These authors propose that a cervical injury, suffered concurrently at the time of the concussion, acts as a “major symptomatic culprit in many post-concussive syndrome patients.”
These authors present 5 case studies of patients diagnosed with post-concussive syndrome who were treated successfully in a chiropractic clinic. Their improvement was rapid and documented using standard measurement outcomes, and the results were long lasting. Treatment included:
These authors conclude:
“Management of persistent post-concussion symptoms through ongoing brain rest is outdated and demonstrates limited evidence of effectiveness in these patients.”
“Instead, there is evidence that “skilled, manual therapy- related assessment and rehabilitation of cervical spine dysfunction should be considered for chronic symptoms following concussion injuries.”
Explanations of the biological mechanisms for the improvement and resolution of the signs and symptoms of the post-concussive syndrome by treating the cervical spine typically involve the improvement of either cervical spine nociceptive or proprioceptive input into the central neural axis (3). However, an alternative yet biologically plausible explanation was published in 2011, and is explored below.
There is evidence that the post-concussive syndrome symptoms are caused by cerebral vasospasm, resulting in suboptimal production of cerebral ATP (3, 15). This cerebral vasospasm is caused by increased sympathetic tone. Continued reductions in cerebral blood flow and oxygenation secondary to sympathetic nervous system dysfunction is known as cerebral hypoperfusion.
In 2011, researchers from the Division of Cyclotron Nuclear Medicine, Tohoku University, Sendai, Japan, published a unique study, showing the best evidence to date evaluating the mechanism of chiropractic spinal adjusting (specific manipulation) to the cervical spine of human volunteers (16). Eight of the nine authors are credited with the degrees MD and PhD. The article is titled: