Whiplash Induced TMJ Injuries and Delayed Onset of Symptoms
By Dr. Brad Eli and Dr. James Elliott
The incidence or prevalence of whiplash injury and TMJ where patients report jaw locking and facial pain indicates a need for speed to treatment.
Whiplash-induced jaw injuries occur with sudden hyperextension and hyperflexion of the neck, typically in the context of low-energy motor vehicle collisions (MVC). The neck is the most common site of injury, but there is growing appreciation that whiplash injuries can affect the temporomandibular joint (TMJ) complex and be the initiating event in chronic TMJ pain disorders.
Whiplash from a motor vehicle accident commonly triggers TMJ injuries
Because the lack of direct impact to the jaw, this connection has been historically poorly understood and controversial, especially given the litigious context of car accidents. Now, a greater understanding of the mechanisms that drive chronic pain disorders clarifies the connection between whiplash and temporomandibular disorders (TMDs). Across multiple studies, the median prevalence of TMDs in patients with a history of whiplash injury is 23% .
The greatest impediment to treatment in whiplash-associated TMJ injuries is the delayed onset of symptoms. One prospective study concluded that one in three patients with whiplash injury are at risk for developing delayed TMD symptoms  “TMJ pain in 30% of whiplash subjects vs 2.5% controls, limitation of mouth opening 37.5% vs 7.5%, and same percentages in muscle masticatory muscle tenderness were found”, accoring to The relationship of whiplash injury and temporomandibular disorders: a narrative literature review article published by NIH.
Preventive measures can interrupt the development of chronic TMDs when administered in the aftermath of injury, but there is rarely a clinical opportunity to recommend these measures. “Awareness of a significant risk for delayed onset of TMJ symptoms after whiplash trauma is crucial for making adequate diagnoses, prognoses and medicolegal decisions,” concludes Charles E. Fernandez, DC, MAppSc, in NIH’s December 8, 2009 publication.
Here we present the mechanisms of whiplash triggered injuries and how they may translate into chronic TMJ syndromes. We discuss the clinical features of whiplash associated TMDs, including important points to remember in the initial patient evaluation. Finally, we recommend a rational treatment program aimed at treating jaw symptoms in the acute setting with the goal of preventing TMD development.
Mechanisms of Whiplash-Associated Temporomandibular Joint Injuries
How a whiplash type injury may impact the jaw joint and cause severe tension exerted on the muscles and tendons involved with a TMJ Injury.
The proposed mechanisms of how the flexion-extension motion of a whiplash injury can affect the TMJ complex:
- Impact to the joint space.
- Indirect trauma to the muscles of mastication.
- TMJ ligamentous injury.
- Disruption of coordinated jaw-neck functionality.
The disc space is the most frequently injured site of the TMJ complex in whiplash injuries, according to Yeon-Hee Lee’s April 1, 2021, MRI-Based Assessment of Masticatory Muscle Changes in TMD Patients after Whiplash Injury NIH article. This trauma is documented by magnetic resonance imaging (MRI) studies of patients with TMD following a history of whiplash.
Depending on the cause of TMD, a treatment strategy may include the following:
- Disc space effusion.
- Anterior disc displacement.
- Disc deformity.
- Condylar degeneration.
There are also significant changes after whiplash injury to the lateral pterygoid muscle (LPM), the jaw muscle responsible for stabilization and depression. Changes in the LPM on MRI include reduced muscle volume, fatty infiltration, and fibrosis, according to Dr. Yeon-Hee Lee .
In addition to these injuries, whiplash can also cause microtrauma to the ligamentous structures of the jaw. The tensile force from the whiplash motion can stretch the ligaments and tendons of the TMJ apparatus, leading to a href=”https://www.orofacialtherapeutics.com/jamss/” title=”jaw and muscle sprain/strain (JAMSS) injuries”>jaw and muscle sprain/strain (JAMSS) injuries.
Finally, TMD symptoms can arise after whiplash due to disrupted jaw-neck functional connections. There is normally an integration of jaw-neck motor and sensory function. When the neck is injured in whiplash, the jaw function can be indirectly affected. Restricted jaw motion due to cervical injuries from whiplash can compromise speaking, eating, swallowing, and yawning. These functional impairments can be detected as soon as one month of the time of injury .
Clinical Aspects of TMJ Injuries
When compared with people who have TMDs from other causes, people with TMDs have significantly higher levels of headache, sleep disturbance, and psychological distress .
One significant challenge in treatment of whiplash injuries is the onset of delayed TMD symptoms. As stated above, one in three patients with whiplash injury are at risk for developing delayed TMD symptoms . Risk factors for TMD development after whiplash injury should be asked about in the patient history, as well as assessing potential intrinsic Jaw injuries.
Questions to ask a patient with whiplash when diagnosing possible TMD:
- Any prior TMJ related issues (e.g. crepitus, TMD symptoms)
- History of mental illness (anxiety, depression, PTSD, somatic symptom disorder)
- Prior jaw parafunction (bruxism)
- Other pain disorders
- Chronic or recurring headaches
- Sleep disturbances
- Poor overall medical status
What symptoms typically accompany a whiplash-triggered jaw injury?
Common TMJ-related symptoms after whiplash injury often include:
- Jaw tenderness.
- Subjective occlusion issues.
- Jaw fatigue with eating.
- Pain with eating and yawning.
- Stiffness or numbness in the jaw-face region.
- TMJ clicking or popping sounds.
Physical examination on an injured jaw should include the following:
- Assessment for trismus
- Oral examination for any tooth fractures or evidence of bruxism
- Assessment of occlusion
- Examination of jaw range of motion and symmetry
- Point tenderness over the joint and muscles
- Palpation for crepitus over the TMJ
- Trigeminal nerve exam
- Cervical exam
Treatment of Whiplash Associated TMJ Injuries
Because of the strong association between whiplash injury and TMD development, basic clinical guidelines for early detection can be followed in the first months after injury. Because roughly 2 out of 10 are at risk of TMD , the clinician must have the right tools to accurately and efficiently identify those falling into a high-risk category. All patients with suspected whiplash injury should be educated about the possibility of TMD development and what measures can prevent it.
As discussed above, the major sites of injury in whiplash-triggered TMJ injuries are the disc space, the LPM, ligamentous structures, and jaw-neck coordinated functions. Driving factors in TMD development are central sensitization after the initial injury, the guarding reflex, the stress response, and mental health issues.
The presence of multiple targets for TMD prevention calls for a multimodal approach to facial pain therapy.
This approach may include any of the following conservative jaw injury interventions:
• Cryotherapy: Cold therapy causes peripheral vasoconstriction, slowing any bleeding into the joint space. Cold also reduces inflammation, has an analgesic effect, and decreases muscle tension. Cryotherapy is most important in the acute setting.
• Thermotherapy: Heat increases circulation, tissue oxygenation, and waste elimination. It is soothing, promotes muscle relaxation, and facilitates mobility.
• Physical Therapy: Early mobility exercises in cases of joint space trauma to help prevent ankylosis and fibrosis of the joint. Mobility helps circulate synovial fluid and remove metabolic waste.
• Behavioral Pain Management: Guided behavioral pain management is well supported in the literature. It helps especially with post-traumatic stress issues and improves patient self-efficacy.
• Oral appliance therapy: Oral appliances are excellent in helping ease muscle guarding and TMJ pain via bite inhibition and joint unloading. Anterior bite plane splints are ideal for this purpose.
All these interventions can be started remotely before an initial evaluation, with the understanding that speed to treatment is critical in preventing chronic jaw pain from developing.
Pathogenesis of Whiplash Associated TMDs
How do jaw and facial pain triggered by a whiplash develop into TMD?
Macro trauma to the disc complex and LPM, microtrauma to the ligamentous structures, and compromised jaw-neck functionality are initiating factors in TMD pathogenesis. However, chronic pain is in essence a central neuropathologic phenomenon. Acute trauma is a necessary, but not sufficient condition for its development. It is now understood that chronic TMD pain develops through the process of “central sensitization” or “central nocioplastic pain”.
How chronic TMD pain develops as described by CJ Woolf:
Central sensitization [is] where the central nervous system (CNS) can change, distort, or amplify pain, increasing its degree, duration, and spatial extent in a manner that no longer directly reflects the specific qualities of peripheral noxious stimuli, but rather the particular functional states of circuits in the CNS… This does not mean that the pain is not real, just that it is not activated by noxious stimuli.” – National Academies of Sciences, Engineering, and Medicine (NASEM) .
On a neurobiological level, central sensitization consists of synaptic plasticity of the nociceptive system, wherein the neuron membrane is hyperexcitable, synaptic connections are strengthened, and signal inhibition is reduced.
These neuroplastic changes result in the following cardinal symptoms of chronic pain syndromes:
- Hyperalgesia: Exaggerated response to noxious stimuli.
- Allodynia: Pain response to normal stimuli.
- Secondary hyperalgesia: Pain response to stimuli outside of the site of injury.
The critical inference here is that since these neuroplastic changes take time to develop, prompt intervention with conservative measures has the potential to interrupt central sensitization and the resulting chronic pain. The therapeutic window for the prevention of central sensitization is from the time of injury to 4 weeks after injury, according to both pre-clinical models and clinical data .
Aside from the initiating traumatic insult, another important mechanism in chronic TMD development is the guarding reflex. This is where the muscles of mastication become tonically active in an attempt to brace the injured TMJ complex. This tonic activation causes a buildup of inflammatory mediators in the muscle, tissue deoxygenation, soreness, and fatigue. Guarding thus becomes a source of constant peripheral pain signaling, which in turn leads to central sensitization and chronic pain.
In the context of traumatic injury, the neuroendocrine system also plays an important role in TMD pathogenesis. Cortisol and pro-inflammatory cytokines are released in response to the psychological stress of an accident. These hormones and cytokines then amplify and perpetuate pain signaling pathways. This is clinically evidenced by the strong association between symptoms of post-traumatic stress and TMD symptom severity.
Other mental health states such as anxiety or depression can also be important in TMD pathogenesis. A pre-existing mental disposition to anxiety or depression, a history of somatization, and a tendency to catastrophize can all contribute to the development, processing, and perpetuation of chronic pain. All these features are consistent with the biopsychosocial model of chronic TMD development .
TMJ injuries are common, with up to a third of patients with whiplash at risk for TMD development. This should prompt medical professionals to educate patients about the possibility of delayed TMD symptom development. Education about patient-directed conservative treatment should also be shared;it is necessary to ensure the patient understands their options and has a say in what options are explored and delivered.
The therapeutic window is narrow if TMD symptoms do arise, where the phenomenon of central sensitization and chronic pain development can be interrupted. A TMJ providers multimodal approach to care has the best chance of accomplishing this. This multimodal approach can include cryotherapy, thermotherapy, physical therapy, behavioral pain management, and dental oral appliance therapy.
All these interventions are conservative, non-invasive, and patient-directed therapies and can be started at once, consistent with the goal of speed to treatment.
Dr. Brad Eli, DMD, MS is a graduate of UCLA’s post-doctoral Orofacial Pain program. The field of orofacial pain, temporomandibular disorders, and treatment of sleep disorders became the 12th specialty of dentistry in 2020. Over the past 29 years of clinical practice specializing in orofacial pain and sleep, Dr. Eli has also been on the educational staff at university hospitals, pain centers, and the clinical staff of Southern California hospitals.
Dr. James Elliott, PT, PhD, FAPT is a global expert in neck pain, whiplash injuries, and the management of acute and chronic post-traumatic musculoskeletal pain. Dr. Elliott is the Acting Executive Director of the Kolling Institute in Australia, is currently a Professor of Allied Health in the Faculty of Health Sciences at the University of Sydney, and is an adjunct professor, principal investigator for the Neuromuscular Imaging Research Laboratory at Feinberg School of Medicine, Northwestern University, Chicago.
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