Cervical Sprain

Etiology

Whiplash-associated disorders describe a constellation of neck-related clinical symptoms manifesting after an MVA or car crash-related mechanism.  The pathophysiologic cascade remains poorly understood and ultimately elusive.  Previous speculated underlying mechanisms had attributed multifactorial elements including vertebral distraction to the facet joint capsule region of the cervical spine causing pain.  Other plausible explanations can include any combination of minor (i.e., clinically irrelevant) injuries to either the facet joint(s), spinal ligaments, dorsal root ganglia/nerve roots, intervertebral discs, cartilage, and paraspinal muscle spasms or contusions of the intraarticular meniscus hemarthrosis may cause symptoms consistent with WADs or "whiplash" injuries.[10][4]  

Epidemiology

As of 2018, whiplash injuries are estimated to affect 0.3% of people a year in the US sustained during sporting injuries, falls, and most commonly motor vehicle accidents.[8]  Approximately 1 million people suffer from a whiplash-associated disorder from a motorcycle accident each year.[4] Before the introduction of seatbelts in 1990 in the UK, the rate was 42.5% of patients seen for automobile collisions with neck injuries[4] British Columbia reported that 61% of claimants to insurance companies were for neck claims in 1995.[4] The incidence is higher in women with females representing almost two-thirds of the population.[4] There is little consistency in the literature regarding epidemiology partially because of poor quality studies compounded by the complex interconnection of other factors including individual, legal, and socioeconomic factors that may influence outcomes.[11]

Pathophysiology

The injury occurs in three stages with a rapid loss of lordosis.  Both the upper and lower spines experience flexion in stage one. In stage two the spine assumes an S-shape while it begins to extend and eventually straighten to make the neck lordotic again. The final phase shows the entire spine in extension with an intense sheering force that causes compression of the facet joint capsules.[4]  Studies with cadavers have shown the whiplash injury is the formation of the S-shaped curvature of the cervical spine which induced hyperextension on the lower end of the spine and flexion of the upper levels, which exceeds the physiologic limits of spinal mobility.[4]  The Quebec task force (QTF) defined whiplash as bony or soft tissue injuries as a result of rear-end or side-impact in road traffic accidents, and from other injuries resulting in “an acceleration-deceleration mechanism of energy transfer to the cervical spine”.[12] The Quebec task force proposed a classification system to define the severity of the whiplash injury.  Stage In Grade 1 the patient complains of neck pain, stiffness, or tenderness with no positive findings on physical exam.  In Grade 2 the patient exhibits musculoskeletal signs including decreased range of motion and point tenderness.   In Grade 3 the patient also shows neurologic signs that may include sensory deficits, decreased deep tendon reflexes, muscle weakness. Grade 4 the patient shows a fracture.[12]  Most WADs are considered to be minor soft tissue-based injuries without evidence of fracture.  

History and Physical

The mechanism of injury is essential in the diagnosis of a whiplash-associated disorder. Typically the patient will report a history of an injury that shows rapid acceleration and deceleration forces such as an MVC, or a sports injury with a collision similarly affecting the neck.[8] The patient may present immobilized with a hard-cervical collar by EMS rescue personnel or the triage provider to prevent further injury until seen and cleared by the appropriate healthcare provider. Patients can present with varied symptoms, including but not limited to, neck pain and stiffness, interscapular pain, upper limb pain and paresthesias, temporomandibular dysfunction, occipital headache, visual disturbances, psychological distress. Also, memory and concentration could be affected.[13] A myriad of psychosocial symptoms has been reported with whiplash injuries, including anxiety, depression, and hypochondriasis.[14]

A comprehensive examination and trauma evaluation are necessary with the cervical spine in a neutral position and while the provider palpates the spine and the paraspinal muscles.  Any midline tenderness or step off dictates further imaging and that the collar remains in place. Distracting injuries or intoxication are prohibiting factors that serve as absolute contraindications to c-spine clearance in the acute traumatic setting. Serial and follow-up examinations are warranted once the patient is appropriately alert and oriented to participate in a comprehensive physical examination.

In otherwise normal patients presenting with a low clinical suspicion of injury with no midline tenderness and unremarkable physical examination allows for clearance of the c-spine precautions without additional imaging. A neurological exam of the upper extremities including strength and sensation is necessary to rule out any deficits. NEXUS [Neuro Emergency X-ray Utilization Study], validated cervical spine criteria or Canadian Cervical Spine Rule are used to help rule in and rule out the need for additional imaging.[7]

Evaluation

The Canadian cervical spine rules or NEXUS criteria are useful for the evaluation of cervical spine injuries in the emergency department.[15]  These criteria determine the need for imaging based on the mechanism of injury, physical presentation at the time of the accident, symptomatic presentation in the emergency department, as well as the physical exam.[16]  The NEXUS c-spine criteria recommend imaging if there is posterior midline cervical-spine tenderness,  focal deficits,  altered mental status,  intoxication or distracting injuries. The Canadian c-spine rules define the need for imaging with patients greater than 65 years of age, dangerous mechanism of injury, paresthesia, midline tenderness, immediate onset of neck pain and impaired range of motion.[17]  Additional imaging such as MRI may be necessary for abnormal findings on CT to evaluate for cord injury.  Flexion and extension films can help rule out ligamentous injury.[18]

Treatment / Management

Immobilization with a soft cervical collar, resumption of normal activity, and mobilization exercises are generally the treatment of choice.  Immobilization has shown the least improvement[12][19] Ultrasound has also been shown to relieve muscle pain for whiplash-associated disorders.[20]  First-line treatments include analgesics, nonsteroidal anti-inflammatories, ice, and heat.[21]  Other controversial analgesic measures include muscle relaxants, which have been shown to have some therapeutic effect in limited studies.[22]  Biofeedback has also demonstrated effectiveness when used in conjunction with other modalities in acute WAD.[23]  Injection of lidocaine intramuscularly was also found to relieve pain symptoms.[24]  Most treatments alone appeared to have moderate effectiveness with combinations of treatment measures improving efficacy and early mobilization consistently most effective.[22](A1)

Differential Diagnosis

The differential diagnosis for cervical spine injuries includes cervical spine fracture, carotid artery dissection, herniated disc, spinal cord injury, subluxation of the cervical spine, muscle strain, facet injury, ligamentous injury.  Whiplash is an injury associated with trauma; remote trauma should dictate evaluation for other causes, such as mass, tumor, infection, etc.  

Prognosis

Prognosis varies secondary to comorbidities prior to the injury, severity of WAD, age and socioeconomic environment.  Full recovery has been shown to occur in a few days to several weeks.[11]  However, disability can be permanent and range from chronic pain to impaired physical function.[11]  There have been inadequate studies that incorporate mitigating factors, such as socioeconomic and legal, which can impact an accurate assessment of recovery.  In regions where there is little or no litigation, the prognosis is more favorable lending that economic gain for disability may play a role in determining the patient's reports of full recovery.[11]

Complications

Though cervical pain is the most common symptom, dizziness and/or headaches can be chronic, persistently reported symptoms.[8]  Chronic pain, subsequent interference with work, and physical function can cause loss of income and lifestyle.[25]