Diagnosing and Managing Dural Venous Sinus Thrombosis Complicating Acute Mastoiditis
What You're Dealing With
When a patient with acute mastoiditis develops new neurologic symptoms, immediately suspect dural venous sinus thrombosis and obtain MRI with gadolinium-enhanced MR venography—this is your gold-standard diagnostic test, and you must start therapeutic anticoagulation even if hemorrhagic venous infarction is present. 1
Let me walk you through this step-by-step since you're new to ENT.
Step 1: Recognize the Clinical Picture
What Makes You Suspect Thrombosis?
The key is that neurologic signs dominate over typical mastoiditis symptoms when thrombosis complicates the infection 2. Here's what to look for:
Classic neurologic presentations include:
- Lethargy (seen in 60% of pediatric cases) 2
- Nuchal rigidity (stiff neck, 60% of cases) 2
- Abducens nerve palsy (sixth cranial nerve—causes diplopia and inability to look laterally, 60% of cases) 2
- Ataxic gait (unsteady walking, 20% of cases) 2
- Papilledema and diplopia from elevated intracranial pressure 3
General cerebral venous thrombosis symptoms:
- Headache (present in nearly 90% of CVST cases—typically diffuse and progressively worsening over days to weeks) 3
- Seizures (40% of patients, either focal or generalized) 3
- Focal deficits like hemiparesis or aphasia 3
- Altered mental status, especially if deep venous system is involved 3
Important clinical clue: These patients often have prolonged symptoms before admission compared to uncomplicated mastoiditis 2. Between 33-81% may have already received antibiotics for acute otitis media, so prior antibiotic treatment does NOT exclude this diagnosis 1.
Step 2: Order the Right Imaging (Critical Decision Point)
Initial Imaging: Start with Temporal Bone CT
First, get a high-resolution contrast-enhanced CT of the temporal bone to confirm mastoiditis and look for bony erosion of the tegmen (roof of the mastoid) or sinus wall 1. This tells you if there's a structural pathway for infection to reach the dura.
Definitive Diagnosis: MRI with MR Venography
MRI with gadolinium-enhanced MR venography (MRV) is your diagnostic test of choice 1. Here's why this matters:
- Sensitivity advantage: MRI detects venous infarction/hemorrhage in 25% of cases versus only 8% on CT 1
- Diagnostic accuracy: Gradient-echo T1-weighted post-contrast MRI has 92.5% sensitivity and 100% specificity 1
- The "empty delta sign": Look for central hypodensity with peripheral enhancement on contrast-enhanced images—this confirms sinus thrombosis 1
- Anatomic variability: CT is insensitive because of normal anatomic variations in venous sinuses 3
If MRI is unavailable or contraindicated (e.g., pacemaker, severe claustrophobia), use CT venography with IV contrast as your backup—you'll see lack of contrast filling in the occluded sinus 1.
If MRV is equivocal but you still strongly suspect thrombosis, digital subtraction angiography (DSA) remains the gold standard, particularly for isolated cortical vein thrombosis 3.
Which Sinuses Are Affected?
In otogenic (ear-related) thrombosis, the lateral sinuses (sigmoid/transverse) are involved in approximately 73% of pediatric cases, while the superior sagittal sinus is affected in about 35% 1.
Step 3: Laboratory Workup
Obtain these labs:
- CBC, chemistry panel, PT, aPTT (baseline coagulation studies before starting anticoagulation) 3
- D-dimer may be elevated, but a normal level does NOT exclude thrombosis, especially with limited clot burden 3
- Blood cultures (often positive, commonly Staphylococcus aureus) 4
- Thrombophilia screening is recommended because over 50% of children with otogenic sinus thrombosis have an underlying prothrombotic disorder 1
Consider lumbar puncture if elevated intracranial pressure is suspected—this is performed more often in complicated cases 2. However, be cautious about LP if there's significant mass effect on imaging.
Step 4: Medical Management (The Critical Treatment Decision)
Anticoagulation: The Cornerstone of Treatment
Start therapeutic anticoagulation immediately, even if hemorrhagic venous infarction is present on imaging 1. This is counterintuitive but critical to understand:
- Intracerebral hemorrhage secondary to venous thrombosis is NOT a contraindication to anticoagulation 1
- The American Heart Association/American Stroke Association gives a strong recommendation for anticoagulation to prevent thrombus propagation and promote recanalization 1
- The Cochrane systematic review and European Paediatric Neurology Society conclude anticoagulation is safe and reasonable in otogenic sinus thrombosis absent specific contraindications 1
Duration of anticoagulation: 3-12 months is standard, extending to lifelong therapy if persistent thrombophilia or recurrent thrombosis is identified 1.
Antibiotic Therapy
Start IV broad-spectrum antibiotics immediately 1. The American Academy of Otolaryngology recommends high-dose amoxicillin-clavulanate as an alternative option 1.
Important caveat: Cultures from mastoid infections may be negative in 33-53% of cases, so empiric broad-spectrum coverage is essential 1.
Step 5: Surgical Intervention
When to Operate
Surgical management is indicated if:
- No improvement after 48 hours of appropriate IV antibiotic therapy 1
- Subperiosteal abscess is present (though some can be managed with needle aspiration) 1
- Evidence of intracranial complications like brain abscess or meningitis 1
In the thrombosis series, 4 out of 5 children required surgery 2. Surgical options include:
- Mastoidectomy with delamination of sigmoid sinus and puncture of sinuses 5
- Myringotomy with or without tympanostomy tube placement to provide drainage and obtain cultures 1
Endovascular Therapy
Consider catheter-directed thrombolysis or mechanical thrombectomy for patients with absolute contraindications to anticoagulation or those who fail to improve on initial anticoagulant therapy 1.
Step 6: Follow-Up Imaging
Obtain control MRI with contrast 7-14 days after intervention to assess recanalization and detect secondary complications like brain abscess formation 1.
In follow-up studies, 15 of 18 cases showed lessening of mastoid findings with resolving thrombosis 6, so improvement on imaging correlates with clinical recovery.
Critical Pitfalls to Avoid
Don't Mistake Effect for Cause
Mastoid fluid can be secondary to dural venous sinus thrombosis rather than the cause 6. Here's how to tell the difference:
- If mastoid shows fluid but middle ear is clear, the mastoid changes are likely the effect of venous obstruction (obstruction of mastoid venous drainage causes transudation into air cells) 6
- If both mastoid and middle ear have fluid with clinical signs of infection, then mastoiditis is likely the primary problem 6
- This distinction matters because it changes your treatment approach 6
Don't Be Falsely Reassured by Prior Antibiotics
33-81% of mastoiditis patients had received prior antibiotics for acute otitis media 1, so recent antibiotic use does NOT exclude progression to complicated disease.
Don't Delay Anticoagulation for Fear of Hemorrhage
The most common mistake is withholding anticoagulation when hemorrhagic venous infarction is seen on imaging. Hemorrhagic infarction from venous thrombosis is an indication FOR anticoagulation, not against it 1.
Don't Rely on D-Dimer to Rule Out Thrombosis
A normal D-dimer cannot exclude cerebral venous thrombosis 3. If clinical suspicion is high, proceed with MRI/MRV regardless of D-dimer results 3.
Special Considerations in Pediatrics
Hemorrhagic venous infarction occurs more frequently in neonates (≈72%) than in older children (≈48%) 1, so be especially vigilant in very young patients.
Brain abscess remains the most common intracranial complication of otitis media with an incidence of 1 per million per year 1, so always consider this in your differential.