What is dural venous sinus thrombosis as a complication of acute mastoiditis?

Dural Venous Sinus Thrombosis as a Complication of Mastoiditis

Dural venous sinus thrombosis is a life-threatening intracranial complication of acute mastoiditis where infection spreads from the mastoid air cells to adjacent venous sinuses (most commonly the sigmoid and transverse sinuses), causing blood clot formation that can lead to venous infarction, elevated intracranial pressure, brain abscess, and death if not promptly recognized and treated. 1, 2

Pathophysiology and Anatomic Considerations

The mastoid air cells lie directly adjacent to the sigmoid and transverse (lateral) sinuses, separated only by thin bone. 3 When acute mastoiditis develops—either from acute otitis media or infected cholesteatoma—the infection can erode through this bony barrier or spread via emissary veins, causing thrombophlebitis of the dural venous sinuses. 4

• The lateral sinus (sigmoid and transverse) is involved in 73% of pediatric cases, while the superior sagittal sinus is affected in 35%. 1
• Temporal lobe parenchymal changes on imaging correspond to lateral and sigmoid sinus thrombosis, distinguishing this from superior sagittal sinus thrombosis which affects frontal, parietal, and occipital lobes. 1

Clinical Presentation: Why It's Easily Missed

The critical pitfall is that neurological signs dominate over typical mastoiditis symptoms, often delaying recognition. 2 Unlike uncomplicated mastoiditis where you expect retroauricular swelling, mastoid tenderness, and protruding auricle, patients with sinus thrombosis present primarily with:

• Lethargy (60% of cases), nuchal rigidity (60%), and sixth cranial nerve palsy causing abducens paresis (60%) 2
• Headache, visual disturbances, vomiting, and ataxic gait 2, 5
• Prolonged symptoms prior to admission (significantly longer than uncomplicated mastoiditis) 2
• Papilledema on fundoscopic examination indicating elevated intracranial pressure 5
• Fever and signs of sepsis, particularly with sigmoid sinus involvement 3, 4

A common mistake is attributing these neurological symptoms to meningitis alone rather than recognizing the underlying venous thrombosis. 2

Diagnostic Approach

When to Suspect It

Order brain imaging in any mastoiditis case that fails to improve after 48 hours of appropriate IV antibiotics, shows clinical deterioration, or presents with any neurological signs. 1, 6

Imaging Algorithm

MRI with contrast plus MR venography (MRV) is the diagnostic study of choice and superior to CT for detecting both the thrombosis and intracranial complications. 1

• MRI demonstrates the thrombosed sinus with absent flow void and altered signal intensity, plus superior visualization of brain parenchymal lesions including venous infarction and hemorrhage (detected in 25% on MRI vs only 8% on CT). 1
• Gradient-echo T1-weighted post-contrast MRI has 92.5% sensitivity and 100% specificity for dural venous sinus thrombosis. 1
• The "empty delta sign" (central hypodensity with peripheral enhancement) is visible on contrast-enhanced imaging. 1

CT venography (CTV) with IV contrast is an acceptable alternative when MRI is unavailable or contraindicated, showing lack of contrast filling in the affected sinus. 1

• High-resolution CT temporal bone with IV contrast should be performed first to confirm mastoiditis and assess for bony erosion of the tegmen or sinus wall. 1

Laboratory Evaluation

• Blood cultures (often positive for Staphylococcus aureus) and elevated inflammatory markers 7
• Lumbar puncture with opening pressure measurement—expect ICP >20 cm H₂O in the majority of complicated cases 5
• Thrombophilia workup, as prothrombotic disorders are present in over 50% of pediatric cases 1, 8

Management Strategy

Medical Treatment

Anticoagulation is the principal therapy and should be initiated even in the presence of hemorrhagic venous infarction, as intracranial hemorrhage that occurred as a consequence of cerebral venous sinus thrombosis is NOT a contraindication. 1

• The American Heart Association/American Stroke Association recommends therapeutic anticoagulation to prevent thrombus propagation and promote recanalization. 1
• While the role of anticoagulation in otogenic sinus thrombosis remains somewhat controversial, multiple retrospective reviews show no complications from anticoagulation, and both Cochrane and the European Pediatric Neurology Society conclude it is safe and reasonable in the absence of contraindications. 1, 6
• Duration: 3-12 months or lifelong depending on underlying etiology and presence of thrombophilia 1

Broad-spectrum IV antibiotics must be continued for at least 2 weeks, targeting mixed bacterial flora including S. aureus. 6, 4

Surgical Management

Mastoidectomy with exposure of the lateral sinus should be performed to eliminate the infectious source and assess sinus blood flow. 6, 3, 4

• Surgery is indicated when patients fail to improve after 48 hours of IV antibiotics, have evidence of subperiosteal abscess, or show intracranial complications. 6
• Intraoperative assessment of sinus patency is essential—if septic thrombus is present, thrombectomy and internal jugular vein ligation may be necessary. 4
• Myringotomy with or without tympanostomy tube placement provides drainage and allows culture collection. 6

Managing Elevated Intracranial Pressure

Elevated ICP can cause irreversible brain and optic nerve damage without treatment. 5

Treatment options in order of invasiveness:

• Serial pressure-lowering lumbar punctures to evacuate CSF 8, 5
• Acetazolamide therapy 5
• Optic nerve sheath fenestration if vision deteriorates 5
• Ventriculoperitoneal or lumboperitoneal shunt for persistent symptoms despite other measures 8, 5

Critical Follow-Up

Obtain control MRI scans 7-14 days postoperatively to exclude secondary brain abscess formation, which developed in 2 of 4 patients in one series despite immediate surgery. 3

• Brain abscess is the most common intracranial complication of otitis media overall, with an estimated incidence of 1 per million per year. 1
• MRI with contrast demonstrates recanalization status and any evolving complications. 3

Key Clinical Pearls

• 33-81% of mastoiditis cases had received prior antibiotics for acute otitis media, so don't be falsely reassured by antibiotic treatment history. 1, 6, 9
• Hemorrhagic infarction is more common in neonates (72%) than older children (48%). 1
• The presence of neurological signs rather than typical mastoiditis signs should immediately raise suspicion for venous sinus thrombosis. 2
• Endovascular therapy may be considered in patients with absolute contraindications to anticoagulation or failure of initial anticoagulant therapy. 1