Differential Diagnosis for Car Accident Injuries: An Urgent Care Guide

Motor vehicle accidents (MVAs) are a significant cause of emergency department (ED) visits, accounting for nearly 5 million in 2006 alone, as reported by the National Center for Health Statistics. Victims can experience a spectrum of injuries, ranging from minor and temporary to severe, debilitating, and even life-threatening. In the urgent care setting, a unique patient population presents – often individuals who have self-selected this level of care, sometimes days after the incident, presuming their injuries to be less serious, typically from low-speed, low-impact accidents. However, it is crucial for urgent care providers to maintain a high degree of vigilance to identify potentially severe injuries that may not be immediately obvious. While avoiding unnecessary extensive and expensive radiological investigations is prudent, a systematic approach to differential diagnosis is paramount.

This article provides a practical guide for urgent care clinicians on the differential diagnosis of common complaints following motor vehicle accidents. It emphasizes a structured approach to patient history, physical examination, and risk stratification to ensure timely and appropriate management.

Table 1. Common Injuries Following Motor Vehicle Accidents |

|—|
| Body Region | Specific Injuries |
| Face and Head | Scrapes, bruises, lacerations, fractures (facial, skull), temporomandibular joint (TMJ) injury, dental injuries |
| Brain | Concussion, post-concussion syndrome (PCS), closed head injury, traumatic brain injury (TBI), epidural hematoma, subdural hematoma |
| Neck | Sprains, strains, whiplash-associated disorders (WAD), fractures (cervical spine), cervical radiculopathy, disc injuries |
| Shoulder and Arm | Lacerations, sprains, strains, fractures (clavicle, humerus, forearm), dislocations, rotator cuff injuries |
| Back | Sprains, strains, fractures (vertebral), disc injuries, lumbar radiculopathy |
| Leg, Knee, Foot | Lacerations, sprains, strains, fractures (femur, tibia, fibula, foot bones), dislocations, ligament injuries (ACL, MCL, PCL), meniscal tears |
| Psychological | Post-traumatic stress disorder (PTSD), acute stress reaction, anxiety, depression |
| Source: Adapted from www.all-about-car-accidents.com/car-accident-injuries.html. |

Chief Complaint and Comprehensive History Taking

A detailed history is the cornerstone of accurate differential diagnosis in patients presenting after a car accident. Understanding the mechanism of injury provides crucial context for the patient’s symptoms and guides the diagnostic process. Essential questions to elicit include:

Patient Role: Were they the driver, front passenger, or rear passenger? This can indicate potential injury patterns based on impact direction and restraint systems.
Accident Nature: Was it a head-on collision, rear-end collision, side-impact, or rollover? The type of collision influences the forces exerted on the body and the likely injury patterns.
Restraint Use: Was the patient wearing a seatbelt? Seatbelt use significantly reduces severe injuries but can also cause specific injuries like seatbelt sign bruising. Were airbags deployed? Airbag deployment can indicate higher impact forces and potential associated injuries, but also protection from more severe trauma.
Vehicle Speed and Damage: What were the estimated speeds of the vehicles involved? Was there significant vehicle damage or passenger space intrusion? High-speed, high-impact accidents with extensive vehicle damage raise suspicion for more severe injuries.
Steering Wheel and Windshield Interaction: Did the steering wheel collapse? Was the windshield broken? These details can suggest head and chest trauma.
Time of Accident: When did the accident occur? Delayed symptom onset, particularly for headaches or abdominal pain, can be crucial in diagnosing conditions like subdural hematoma or hollow viscus injuries.

A lower threshold for advanced imaging or ED referral is warranted for patients describing high-speed, high-impact accidents with significant vehicle damage. Certain presenting complaints also carry higher risk and necessitate a thorough and cautious approach.

Headache: Differentiating Benign from Serious Etiologies

Headache is a prevalent complaint after MVAs, estimated to affect 25% to 78% of individuals with mild traumatic brain injury (TBI). In the US, MVAs are responsible for approximately 45% of TBIs. The differential diagnosis for post-MVA headache is broad, ranging from benign conditions like post-concussive syndrome, tension headache, or migraine, to serious and potentially life-threatening conditions such as epidural hematoma, subdural hematoma, or carotid/vertebral artery dissections.

In urgent care, tension headaches related to cervical strains are commonly encountered. These may present as persistent throbbing headaches. However, this presentation is non-specific and cannot rule out more serious underlying pathology that may have a delayed presentation. Therefore, a careful examination for concerning signs is crucial.

Red Flags for Serious Headache:

History:
- Loss of consciousness (even brief) at the scene
- Altered mental status or confusion
- Worsening headache severity
- Headache onset immediately after injury
- Headache accompanied by neurological symptoms (weakness, numbness, vision changes, speech difficulty)
- History of bleeding disorders or anticoagulant use
Physical Exam:
- Scalp hematoma or extensive bruising
- Lateral neck hematoma or bruit (suggesting vascular injury)
- Focal neurological deficits
- Papilledema (swelling of the optic disc)
- Signs of basilar skull fracture (raccoon eyes, Battle’s sign, CSF rhinorrhea or otorrhea)

Epidural Hematoma: This is a neurosurgical emergency occurring in 5% to 10% of severe head injuries. A classic “lucid interval” presentation involves initial loss of consciousness followed by a period of normalcy before neurological deterioration. However, not all patients present classically. Any history of altered consciousness post-accident should raise suspicion.

Subdural Hematoma: These can be acute, subacute (6-20 days), or chronic (>20 days). Symptoms may be non-specific, especially in subacute and chronic cases, including headache, irritability, balance issues, and concentration problems. Importantly, patients may not always recall or associate trauma with their current symptoms, particularly in chronic subdural hematomas, more common in elderly patients or those on anticoagulants.

Post-Concussive Syndrome (PCS): PCS is a common sequela of TBI. Symptoms like headache, dizziness, cognitive difficulties (concentration, memory), and irritability can persist for weeks. PCS is often a diagnosis of exclusion, after ruling out intracranial bleeding or structural injuries, often requiring initial neuroimaging. Management is primarily supportive, with reassurance, education, and symptom-based treatment.

Assessment and Discharge for Headache: Clinical decision rules like the Canadian CT Head Rule (Table 2) help guide imaging decisions. For outpatient management of patients with low-risk headaches, clear discharge instructions are critical. Patients and caregivers should be educated on “red flag” symptoms warranting immediate medical attention:

Inability to awaken
Severe or worsening headache
Somnolence or increasing confusion
Restlessness or seizures
Vision changes
Vomiting, fever, or stiff neck
Weakness or numbness

Table 2. Canadian CT Head Rule |

|—|
| High Risk (Neurological Intervention Needed) | Medium Risk (Brain Injury on CT Likely) | Rule Not Applicable |
| – Glasgow Coma Scale (GCS) score < 15 at 2 hours post-injury | – Amnesia before impact ≥ 30 minutes | – Non-traumatic case |
| – Suspected open or depressed skull fracture | – Dangerous mechanism of injury⁺ | – GCS < 13 |
| – Any sign of basal skull fracture* | | – Age < 16 years |
| – ≥ 2 episodes of vomiting | | – Coumadin or bleeding disorder |
| – Age ≥ 65 years | | – Obvious open skull fracture |
| * Signs of basal skull fracture = hemotympanum, “raccoon eyes,” CSF otorrhea/rhinorrhea, Battle’s sign ⁺ Dangerous mechanism = pedestrian struck by vehicle, occupant ejected from motor vehicle, fall from elevation ≥ 3 feet or 5 stairs Note: Rule originally excluded patients with neurologic deficit, seizure, bleeding diathesis, or oral anticoagulants. Their presence may also indicate need for head CT. Source: Stiell IG, Wells GA, Vanderheen K, et al. Lancet. 2001; 357: 1391-1396. |

Neck Pain: Ruling Out Cervical Spine Injury

Evaluation of post-traumatic neck pain requires a thorough history, physical exam, and consideration of radiography. Observe the patient’s posture and neck movement. Palpate the trapezius and paraspinal muscles for tenderness and spasm, and individually palpate each spinous process for point tenderness. Cervical range of motion (ROM) should be objectively assessed and documented, as restricted ROM is associated with poorer outcomes in whiplash injuries. Normal cervical ROM includes approximately 90° rotation, 45° lateral bending, 60° forward flexion, and 75° extension.

Differential Diagnosis for Neck Pain:

Cervical Strain (Whiplash): The most common injury in urgent care settings post-MVA. Caused by abrupt flexion/extension or rotational forces on the cervical spine. Symptoms include pain, muscle spasm, limited ROM, and often occipital headache. Pain is typically midline or paraspinous, potentially radiating to shoulders, periscapular region, or occiput.
Cervical Sprain: Ligamentous injury of the cervical spine, often occurring with whiplash. May present with similar symptoms to strain but potentially more localized pain and instability.
Cervical Radiculopathy: Nerve root compression in the cervical spine, often due to disc herniation or bony impingement. Presents with radiating pain, numbness, tingling, or weakness in a dermatomal distribution.
Cervical Fracture or Dislocation: Less common in low-impact MVAs but must be considered, especially in high-speed collisions or with significant neck pain or neurological deficits.

Red Flags for Cervical Spine Injury:

History:
- High-speed MVA, rollover, ejection
- Significant neck pain, especially midline
- Neurological symptoms (weakness, numbness, tingling in extremities)
- Loss of consciousness
Physical Exam:
- Midline cervical tenderness
- Focal neurological deficits
- Limited cervical ROM, especially with pain
- Neck deformity or step-off
- Muscle spasm

In patients with severe pain, restricted ROM, or radicular symptoms, advanced imaging is indicated. Plain radiographs are often insufficient to exclude significant injury. CT scanning is preferred when bony injury is suspected without cord involvement. MRI is indicated if spinal cord injury is a concern (e.g., bilateral paresis, paresthesia). A negative neurological exam reduces the likelihood of significant neurological injury, but does not rule out unstable bony injuries when suspicion is high. Transfer to an ED may be necessary for further evaluation and management.

Clinical Decision Rules for Cervical Spine Imaging: The NEXUS Low-risk Criteria (NLC) and Canadian C-Spine Rule (CCS) are validated tools to guide cervical spine imaging decisions.

NEXUS Low-risk Criteria (Table 3): Radiography is unnecessary if all five criteria are met. High sensitivity for ruling out cervical spine injury.
Canadian C-Spine Rule (Figure 1): Identifies patients requiring radiography. High sensitivity. (Note: Figure 1 not provided in this text, refer to original source).

Table 3. NEXUS Low-Risk Criteria |

Chest Pain and Blunt Chest Trauma: Identifying Life-Threatening Conditions

The chest contains vital organs vulnerable to serious injury from MVA-related trauma, including direct impact, rapid deceleration, and crush mechanisms. Injuries range from chest wall trauma (rib fractures) to life-threatening conditions like cardiovascular contusion, aortic injury, pulmonary contusion, lacerations, and pneumothorax. Risk factors for severe thoracic injury include high speed, lack of seatbelt use, extensive vehicle damage, and steering wheel deformity.

History and Examination for Chest Trauma:

Mechanism: Inquire about steering wheel contact, chest pain location and characteristics, palpitations, and dyspnea.
Visual Inspection: Look for paradoxical chest wall movement, wounds, and ecchymosis on the chest and back. Document wound location, appearance, number, and type.
Auscultation: Assess for diminished or absent breath sounds, suggesting pneumothorax or hemothorax.
Palpation: Carefully palpate the chest wall for subcutaneous emphysema or bony crepitus (rib fractures).
ECG: Obtain an electrocardiogram in all patients with anterior chest trauma, chest pain/tenderness over the mid-anterior chest, elderly patients, and those with a history or signs/symptoms of cardiac disease.

Differential Diagnosis for Chest Pain Post-MVA:

Chest Wall Contusion: Bruising of chest wall muscles and soft tissues. Common after blunt trauma. Pain is typically localized to the area of impact, worsens with deep breathing or coughing.
Rib Fractures: Common, especially in older individuals. Pain is often sharp, localized, and exacerbated by breathing, coughing, or movement. Multiple rib fractures increase the risk of underlying lung injury.
Pneumothorax: Air in the pleural space, causing lung collapse. Can be traumatic (from rib fracture or lung laceration) or tension pneumothorax (life-threatening). Presents with chest pain, shortness of breath, decreased breath sounds on the affected side, and hyperresonance to percussion.
Hemothorax: Blood in the pleural space. Often associated with chest trauma. Presents similarly to pneumothorax, but with dullness to percussion.
Pulmonary Contusion: Bruising of lung tissue. May be asymptomatic initially, but can progress to respiratory distress. CXR findings may lag behind clinical presentation.
Cardiac Contusion: Bruising of the heart muscle. Suspect in anterior chest trauma, especially with steering wheel impact. ECG findings (unexplained tachycardia, new bundle branch block, dysrhythmias) are concerning.
Aortic Injury (Transection): Life-threatening, often from rapid deceleration injuries. May have delayed presentation. Suspect in high-speed MVAs. Wide mediastinum on chest X-ray is a key finding.

Life-Threatening vs. Non-Life-Threatening Chest Injuries:

Life-Threatening: Aortic injury, tension pneumothorax, hemothorax, cardiac contusion, flail chest (multiple rib fractures causing paradoxical chest wall movement).
Typically Non-Life-Threatening (in ambulatory MVA patients): Chest contusions, isolated rib fractures, simple pneumothorax (small, stable).

Red Flags for Life-Threatening Chest Injury:

Rapid deceleration mechanism
Persistent chest pain or dyspnea
Hypoxia, tachypnea, abnormal lung sounds
Paradoxical chest wall movement
Wide mediastinum on chest X-ray
Unexplained tachycardia, new bundle branch block, dysrhythmia on ECG

Patients with concerning mechanisms, severe symptoms, or worrisome chest X-ray findings (multiple rib fractures, hemo-pneumothorax, pulmonary contusion, wide mediastinum) should be transferred to the ED. Clinically stable patients with non-concerning mechanisms may not require further evaluation beyond ECG and chest X-ray. Discharge instructions should emphasize the need to return for worsening pain, dyspnea, or lightheadedness.

Abdominal Pain and Blunt Abdominal Trauma (BAT): Recognizing Intra-abdominal Injury

MVAs are a leading cause of BAT in the urgent care setting. Trauma can result in solid organ laceration (spleen, liver, kidney), vascular disruption, or hollow viscus rupture. Splenic injury is the most common significant intra-abdominal injury.

Assessment of Blunt Abdominal Trauma:

History: Mechanism of injury, seatbelt use, abdominal pain characteristics.
Physical Exam:
- Inspection: Ecchymosis (seatbelt sign), distention, visible wounds.
- Auscultation: Bowel sounds (decreased sounds may indicate ileus or peritonitis).
- Palpation: Assess for tenderness (localized or generalized), peritoneal signs (rebound tenderness, guarding, rigidity). Note: Abdominal tenderness can be unreliable in conscious patients, and intra-abdominal injury can occur without significant tenderness.

Differential Diagnosis for Abdominal Pain Post-MVA:

Abdominal Wall Contusion: Muscle and soft tissue bruising of the abdominal wall. Pain is localized to the area of impact, worsens with movement or abdominal muscle contraction.
Splenic Injury: Most common significant BAT injury. Left upper quadrant pain, referred left shoulder pain (Kehr’s sign), hypotension (in severe cases).
Liver Injury: Right upper quadrant pain, right shoulder pain, hypotension.
Renal Injury: Flank pain, hematuria.
Bowel Injury (Hollow Viscus Perforation): Less common but serious. Can have delayed presentation. Abdominal distention, diffuse tenderness, peritoneal signs, decreased bowel sounds. “Seatbelt sign” (abdominal ecchymosis) increases suspicion.
Mesenteric Injury: Injury to the mesentery and associated blood vessels. Can lead to bowel ischemia or infarction.

Red Flags for Intra-abdominal Injury:

Significant abdominal pain or tenderness (especially generalized)
Peritoneal signs (guarding, rigidity, rebound tenderness)
Abdominal distention
Decreased bowel sounds
“Seatbelt sign” ecchymosis
Hematuria (especially with abdominal tenderness)
Hypotension or tachycardia
Distracting injuries

Physical examination alone has limited accuracy in diagnosing BAT (55% to 65% sensitivity). Therefore, it should be combined with observation and diagnostic testing.

Diagnostic Evaluation for BAT:

Laboratory Studies: Individualize based on clinical suspicion. Pregnancy test for women of childbearing age. Urinalysis to assess for hematuria. Non-specific enzyme elevations may occur with trauma.
Imaging:
- Ultrasound (FAST exam): First-line in stable patients. Non-invasive, no radiation, sensitive for detecting intraperitoneal fluid (hemoperitoneum).
- Abdominal CT scan: Indicated if ultrasound is positive, or if solid organ injury is suspected. More sensitive for solid organ injury and retroperitoneal injuries. ED evaluation is needed if hollow viscus injury is suspected.

Conclusion

While major MVA victims are typically evaluated in the ED, urgent care centers frequently encounter patients with post-MVA complaints. Recognizing the spectrum of potential injuries, including delayed presentations of life-threatening conditions, is crucial. A meticulous history and physical examination are paramount in guiding appropriate diagnostic testing, imaging, and referrals. Thorough documentation of each MVA visit, including patient complaints in their own words and objective findings (using diagrams or pictures when helpful), is essential for medical and potential legal purposes. Familiarity with the differential diagnosis of common MVA injuries in the urgent care setting enhances clinician confidence and ensures optimal patient care.

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Assessing Patients in the Wake of Motor Vehicle Accidents

Jill C. Miller, MD

Urgent Care Physician, Senior Clinical Instructor of Medicine for CWRU School of Medicine

Tagged on: Clinical Motor Vehicle Accidents