Filling Defect at Torcula and Transverse Sinus After Trauma
The most likely cause of a filling defect at the torcula and transverse sinus after head trauma is traumatic venous sinus thrombosis, particularly if there is an associated skull fracture extending to the dural sinus. 1
Primary Diagnostic Consideration: Traumatic Venous Sinus Thrombosis
Traumatic venous sinus thrombosis is the leading diagnosis when a filling defect is identified in the torcula or transverse sinus following head trauma, especially in the presence of skull fractures involving these structures. 1
Key Evidence Supporting This Diagnosis:
In patients with closed head trauma and skull fractures extending to a dural sinus, the rate of acute traumatic venous sinus thrombosis is 41%. 1
Traumatic venous injury includes epithelial injury with thrombus formation and venous laceration with compressive hematoma. 1
Hemorrhagic venous infarctions occur in 55% of all cases with occlusive dural venous sinus thrombosis after trauma. 1
Critical Differential: Extrinsic Compression vs. Intrinsic Thrombosis
A filling defect on CTV can result from either intrinsic thrombosis (the "empty delta" sign) or extrinsic mass effect from compressive epidural hemorrhage. 1
Distinguishing Features:
Sinus compression from external mass effect can be distinguished from true thrombosis on MDCT venography and is likely more prevalent than previously estimated. 2
Fractures involving the transverse sinus-sigmoid sinus complex or multiple dural sinuses are more likely to be affected by thrombosis than fractures involving the superior sagittal sinus alone. 2
On contrast-enhanced CT, true thrombosis shows enhancement of the dural lining with a central filling defect, while compression shows external mass effect without intraluminal thrombus. 3
Imaging Characteristics of Post-Traumatic Venous Sinus Thrombosis
On Non-Contrast CT:
- Hyperdensity of the dural sinus may be visible acutely, representing acute thrombus. 3
On Contrast-Enhanced CT/CTV:
- The "empty delta" sign appears as central hypointensity surrounded by contrast enhancement in a triangular configuration. 3
- This finding may not appear for several days after symptom onset but persists for several weeks. 3
On MRI/MRV:
- MRI is more sensitive than CT for detecting cerebral venous thrombosis at each stage after thrombosis. 3
- Gradient echo T2 susceptibility-weighted imaging combined with MRV improves diagnostic accuracy. 3
Important Pitfalls to Avoid
Normal Anatomical Variants That Mimic Thrombosis:
Non-thrombotic filling defects can result from normal anatomical structures and must be distinguished from true thrombosis to avoid dangerous misdiagnosis. 4
- Asymmetrical lateral (transverse) sinuses occur in 49% of normal patients. 3
- Partial or complete absence of one lateral sinus occurs in 20% of normal individuals. 3
- Prominent arachnoid granulations and intrasinus septa can create filling defects that mimic thrombosis. 3, 4
- Flow gaps are commonly seen on time-of-flight MRV images and can affect interpretation. 3
Key Distinguishing Strategy:
The lack of identification of thrombus within the venous sinus on MRI or the absence of a true filling defect on contrast-enhanced MRV or CTV helps clarify the diagnosis and exclude normal variants. 3
Clinical Context and Risk Factors
High-Risk Scenarios:
- Skull fractures (particularly skull base fractures) are present in 97.3% of patients with traumatic venous sinus thrombosis. 5
- Multiple venous sinus involvement increases the likelihood of requiring interventions for refractory intracranial hypertension (94.1% of such patients had multiple thromboses). 5
Prothrombotic States:
When sinus thrombosis occurs after mild closed head injury, investigation for inherited or acquired procoagulant factors (such as antiphospholipid antibodies) is necessary, as this has implications for long-term management. 6
Recommended Diagnostic Approach
In the acute trauma setting, CTV is the most useful initial study for evaluating suspected intracranial venous injury. 1
Imaging Algorithm:
- CTV head is the first-line imaging modality in acute trauma with suspected venous sinus injury. 1
- MRV is a second-line option, useful outside the acute setting or when CTV is inconclusive. 1
- Catheter cerebral angiography can be useful when CTV or MRV are inconclusive but clinical suspicion remains high. 3
Follow-Up Imaging:
Follow-up CTV or MRV at 3 to 6 months after diagnosis is reasonable to assess for recanalization of occluded sinuses in stable patients. 3
Clinical Implications
Symptoms of traumatic venous injury are highly variable and nonspecific (headache, papilledema from intracranial hypertension, or focal neurologic deficits from venous ischemia) and may be mistakenly attributed to other traumatic injuries. 1
Ischemic lesions that cross usual arterial boundaries (particularly with hemorrhagic component) or in close proximity to a venous sinus are suggestive of cerebral venous thrombosis. 3