Temporal Bone Fracture is Most Associated with Epidural Hematomas
Temporal and parietal skull fractures, particularly those crossing the middle meningeal artery trajectory, are the fracture types most strongly associated with epidural hematomas, occurring in approximately 80% of cases.
Epidemiologic Association
The strongest evidence comes from a prospective study of 158 consecutive patients with epidural hematomas, which found:
- Skull fractures were present in 126 patients (80%) 1
- Parietal, temporal, or temporo-parietal location accounted for 99 cases (63%) of all epidural hematomas 1
This anatomic predilection occurs because the middle meningeal artery runs in grooves along the inner surface of the temporal and parietal bones, making it vulnerable to injury when fractures cross its trajectory 2, 3.
Mechanism of Injury
The pathophysiology explains the fracture-hematoma relationship:
- Fractures crossing the middle meningeal artery trajectory consistently cause vascular injury 3
- In a study of 24 patients with small epidural hematomas and cranial fractures crossing the middle meningeal artery, 100% demonstrated vascular lesions on angiography 3
- Two patterns predominate: active contrast extravasation (71%) and pseudoaneurysms (29%) 3
The middle meningeal artery enters the skull through the foramen spinosum in the temporal bone and branches along the temporal and parietal regions, creating the anatomic substrate for this association 2, 4.
Clinical Implications
High-Risk Fracture Patterns
- Linear fractures extending from parietal to temporal regions bilaterally can cause simultaneous bilateral epidural hematomas from injury to both middle meningeal arteries 4
- Fractures extending to the mastoid air cells may be associated with pneumocephalus within the epidural hematoma 5
- Depressed fractures in the mid-parietooccipital region with extension to temporal regions carry particularly high risk 4
Diagnostic Considerations
When skull fractures are detected on plain radiography but fail to show on initial imaging, half of these patients may subsequently develop epidural hematomas 1. This underscores why CT has replaced plain radiographs as the primary imaging modality 1.
Monitoring Requirements
Even with initially small epidural hematomas and temporal/parietal fractures:
- Repeat CT scanning is essential as delayed expansion can occur 1
- Cases have been documented with deterioration occurring 6-30 hours after initial presentation despite initially normal or near-normal CT findings 1
- Angiographic evaluation of the ipsilateral external carotid circulation should be considered when fractures cross the middle meningeal artery trajectory, given the high prevalence of pseudoaneurysms and active extravasation 3
Important Caveats
While temporal/parietal fractures are most common, epidural hematomas can occur without skull fractures in approximately 20% of cases 1. Additionally, the presence of a skull fracture alone does not predict outcome or need for intervention—the associated intracranial injury determines prognosis 1.
In pediatric populations, any skull fracture warrants heightened suspicion, as skull fractures in infants 0-11 months require skeletal survey to evaluate for non-accidental trauma 6.