The Role of the cervical spine in post-concussion syndrome
“Based on previously established tissue injury thresholds, acceleration/deceleration of the head–neck complex of sufficient magnitude to cause mTBI is also likely to cause concurrent injury to the joints and soft tissues of the cervical spine. It has also been 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.”
-Phys Sportsmed, 2015; Early Online:1–11
Brain or Strain?
Symptoms Alone Do Not Distinguish Physiologic Concussion from Cervical/Vestibular Injury
“Symptoms after head injury, including cognitive symptoms, have traditionally been ascribed to brain injury, but they do not reliably discriminate between physiologic PCD and cervicogenic /vestibular PCD.”
“It is possible that the symptom overlap between whiplash and concussive injuries is related to rotational forces imparted to the head and neck during head injury, with effects on nerve tracts in the brain as well as on the proprioceptive fibers in the cervical soft tissues.26,33 Other possible sources of cervical symptoms include the cervical zygoapophyseal joints, which may cause headache and dizziness in patients with whiplash.”
“In conclusion, the results of this study show that symptom reports from patients with delayed recovery after head injury, including cognitive symptoms, do not discriminate between those with a physiologic PCD and those with a cervical/vestibular injury.”
-Clin J Sport Med Volume 0, Number 0, Month 2014
Neck Muscle Strength Training in the Risk Management of Concussion in Contact Sports:
Critical Appraisal of Application to Practice
“ … has provided evidence that higher absolute total isometric neck strength is a significant predictor of concussion incidence in contact sports in high-school athletes. Therefore, strength-training programs that facilitate increased gains in short-latency rate of isometric force development may be an important component of neck strength training programs to lower the risk for concussion.”
-Gilchrist et al., J Athl Enhancement 2015, 4:2
The Role of the Cervical Spine in Post-Concussion Syndrome
Cameron M. Marshall1, Howard Vernon1, John J. Leddy2 and Bradley A. Baldwin3
1Department of Graduate Studies, Canadian Memorial Chiropractic College, 6100 Leslie Street, Toronto, Ontario, Canada, 2Department of Physiology and Family Medicine, State University of New York at Buffalo, University Sports Medicine, 160 Farber Hall – SUNY, Buffalo, NY, USA, and 3Private Practice – Sports Medicine and Rehab Centres, 199 Mill Street, Angus, Ontario, Canada
Head Impact Telemetry system have demonstrated that the range of linear impact accelerations causing concussion injury is between 60 and 160g (where ‘g’ represents gravity), with the highest predictive occurrence occurring at 96.1g [18]. Studies examining whiplash associated disorders (WAD) have demonstrated two very important features for our discussion: 1) biomechanical studies have demonstrated that as little as 4.5g of neck acceleration can cause mild strain injury to the tissues of the cervical spine [19] and 2) the signs and symptoms reported by these patients, with the exception of a few key differences (i.e. radicular symptoms), appear strikingly similar to those experienced in mTBI (Table 1) [20-28]. If an individual is to sustain an injury where the head is accelerated between 60 and 160g, it is highly likely that the tissues of the cervical spine have also reached their injury threshold of 4.5g.
Biomechanics of Concussion
“These focal brain injuries are common in moderate and severe brain injury but are largely absent in mild TBI.10,11 For this reason, the remainder of this review focuses on the inertial forces that cause the concussive injuries common in mild TBI.”
“There is considerable evidence showing that the primary cause of concussive injuries is the inertial, or acceleration, loading experienced by the brain at the moment of impact. With the head/neck motions that occur during a typical impact, there are two components of acceleration that occur in nearly every instance of concussion — linear and rotational acceleration.”
“Similarly, the effects of these pressure gradients on the deformations that can occur within the brain are also better known. Early studies using photoelastic gelatin indicate that pressure gradients during linear acceleration-based motions can create strains at the craniocervical junction. Subsequent work studying common models of pressure-induced brain injury in animals show a similar type of ability to enhance strains in the brain-stem.”
-Clin Sports Med. 2011 January ; 30(1): 19–vii. doi:10.1016/j.csm.2010.08.009.
CONCUSSION IN PROFESSIONAL FOOTBALL:
BIOMECHANICS OF THE STRUCK PLAYER—PART 14
“Thirty-one NFL collisions involving helmet-to-helmet and helmet-to ground impacts were reconstructed involving 25 concussions of struck players.”
“Our question is, if concussion occurs by strains in the midbrain and the maximum strains occur late after the high impact forces, do late responses of the head and neck influence injury?”
“Increasing neck stiffness reduces peak head acceleration and ∆V. The effect makes a large difference in HIC because the difference in ∆V is raised to the fourth power. Because HIC is the strongest correlate with concussion in the NFL reconstructions.”
“Serious brain injuries occur as a result of diminished tone of the neck muscles (35). A series of blows to the head may result in a “groggy state” in which “the muscle tone, most obviously that of the neck, is reduced, and the head moves like a pendulum under the blows. It sustains, therefore higher accelerations and, consequently, more severe effects.”
“These strains occur late, after the high forces of the helmet collision, during the period of time during which the neck is being deformed by head displacement.”
“It also may be possible to engineer protective equipment that limits head displacement and rotation in younger football players, thus lowering their susceptibility to concussion.”
-Neurosurgery 61:313–328, 2007
Effect of Neck Muscle Strength and Anticipatory Cervical Muscle Activation on the Kinematic Response of the Head to Impulsive Loads
“Greater isometric neck strength and anticipatory activation were independently associated with decreased head DV and Dv after impulsive loading across all planes of motion (all P.001). Inverse relationships between neck strength and head DV and Dv presented moderately strong effect sizes”
-Am J Sports Med. 2014 March; 42(3): 566–576