What is the recommended initial evaluation and treatment approach for lateral sinus thrombosis?

Diagnosis and Management of Lateral Sinus Thrombosis

The recommended initial evaluation for lateral sinus thrombosis requires venographic imaging with either CT venography (CTV) or MR venography (MRV) following a plain CT or MRI, as a negative plain CT or MRI alone does not rule out lateral sinus thrombosis. 1

Clinical Presentation

• Patients with lateral sinus thrombosis may present with neurological rather than otologic symptoms, including dizziness, headache, meningism, hearing loss, and facial nerve paresis 2
• Many patients have a history of acute otitis media treated with antibiotics in the weeks preceding admission, though they may deny high fevers or active otomastoid symptoms 3
• Lateral sinus thrombosis is a rare but threatening complication of acute mastoiditis or infected cholesteatoma 2
• Children may present with cranial neuropathies and signs of raised intracranial pressure 3

Diagnostic Approach

Initial Imaging

• Plain CT or MRI is useful for initial evaluation but insufficient to rule out lateral sinus thrombosis 1
• A venographic study (either CTV or MRV) should be performed when lateral sinus thrombosis is suspected, even if the plain CT or MRI is negative 1
• CTV of the head is a useful, rapid initial evaluation with high sensitivity and specificity for detection of cerebral venous thrombosis 1

Key Imaging Findings

• On direct cerebral venography, intraluminal thrombus appears as a filling defect within the lumen (nonocclusive thrombosis) or as complete nonfilling (occlusive thrombosis) 1
• Complete thrombosis may demonstrate a "cupping appearance" within the sinus 1
• On noncontrast CT, sinus hyperdensity may be seen, though only 30% of noncontrast head CT examinations are abnormal in lateral sinus thrombosis 1
• Contrast-enhanced CT may demonstrate the "empty delta sign" in some cases 1
• Gradient echo T2 susceptibility-weighted MR images can improve the accuracy of diagnosis 1

Potential Diagnostic Pitfalls

• Anatomic variants of normal venous anatomy may mimic sinus thrombosis, including sinus atresia/hypoplasia, asymmetrical sinus drainage, and normal sinus filling defects 1
• Flow gaps are commonly seen on time-of-flight MRV images, which can affect interpretation 1
• Angiographic examination has shown a high prevalence of asymmetrical lateral (transverse) sinuses (49%) and partial or complete absence of one lateral sinus (20%) in patients with no venous pathology 1
• Direct cerebral venography may be difficult to interpret due to retrograde flow of contrast 1

Treatment Approach

Medical Management

• Immediate initiation of therapeutic anticoagulation with low molecular weight heparin (LMWH) or unfractionated heparin (UFH) upon diagnosis 4
• Anticoagulation is recommended even in the presence of intracranial hemorrhage, as the benefits of preventing thrombus progression outweigh bleeding risks 4
• Broad-spectrum intravenous antibiotics, particularly when lateral sinus thrombosis is associated with otitis media or mastoiditis 5
• Common organisms include mixed anaerobes and Bacteroides species 5

Surgical Management

• Mastoidectomy with exposition of the lateral sinus to scrutinize its blood flow when lateral sinus thrombosis is associated with mastoiditis or cholesteatoma 2
• Myringotomy tube placement may be required in cases associated with otitis media 3
• The decision for surgical versus medical treatment must be based on clinical features of each case 6

Advanced Interventions

• Chemical thrombolysis should be reserved for severe cases with neurological deterioration despite anticoagulation 4
• Catheter cerebral angiography can be useful in patients with inconclusive CTV or MRV in whom clinical suspicion remains high 1
• Direct endovascular thrombolysis involves catheter-directed delivery of thrombolytic agents directly into the thrombosed sinus 4

Follow-up and Monitoring

• An early follow-up CTV or MRV is recommended in patients with persistent or evolving symptoms despite medical treatment 1
• A follow-up CTV or MRV at 3 to 6 months after diagnosis is reasonable to assess for recanalization of the occluded sinus 1
• Control MRI scans 7-14 days postoperatively are recommended to exclude a secondary brain abscess, which can develop despite immediate surgery 2
• Continuous neurological assessment is essential during treatment 4

Special Considerations

• Children with lateral sinus thrombosis may require different management approaches, with a higher index of suspicion needed for timely diagnosis 3
• The prognosis of lateral sinus thrombosis is good if treatment is instituted early with broad-spectrum intravenous antibiotics and appropriate surgical intervention 5
• Patients with previous lateral sinus thrombosis who present with recurrent symptoms suggestive of thrombosis should undergo repeat CTV or MRV 1