What are the complications and management options for subdural hygromas in patients with idiopathic intracranial hypertension (IIH)?

Subdural Hygromas in Idiopathic Intracranial Hypertension: Complications and Management

Subdural hygromas in idiopathic intracranial hypertension (IIH) should be managed conservatively while treating the underlying increased intracranial pressure, with surgical intervention reserved only for symptomatic cases with significant mass effect. 1

Relationship Between Subdural Hygromas and IIH

• Subdural hygromas can occur as a complication in patients with IIH, particularly following interventional procedures or as a consequence of the altered CSF dynamics 1
• Subdural hygromas/hematomas may develop as a rare complication of neurovascular stenting procedures used to treat IIH 1, 2
• The pathophysiology involves altered CSF dynamics and pressure gradients that can lead to accumulation of fluid in the subdural space 3

Complications of Subdural Hygromas in IIH

• Most subdural hygromas are clinically insignificant, with only a small percentage causing symptomatic problems 4
• Potential complications include:
  • Headache exacerbation distinct from typical IIH headache 1
  • Mass effect causing neurological symptoms in severe cases 1
  • Potential progression to subdural hematoma 2
  • Rarely, they may contribute to cerebral venous thrombosis, which occurs in some IIH patients 1

Diagnostic Approach

• MRI brain with contrast is the preferred imaging modality to identify subdural hygromas in IIH patients 5
• CT brain may be used if MRI is unavailable urgently 5
• Imaging should evaluate for:
  • Size and extent of the hygroma 1
  • Mass effect on adjacent structures 1
  • Signs of increased intracranial pressure 6
  • Potential venous sinus thrombosis (requiring CT or MR venography) 1

Management Options

Conservative Management

• Small or asymptomatic hygromas should be managed conservatively while treating the underlying CSF leak or increased ICP 1
• Treatment of the underlying IIH should include:
  • Weight loss program with low-salt diet for all overweight IIH patients (goal 5-10% weight loss) 7
  • Acetazolamide as first-line medical therapy for symptomatic patients 7
  • Topiramate may be considered as an alternative, which has carbonic anhydrase activity and can suppress appetite 1

Surgical Intervention

• Symptomatic hygromas with significant mass effect may require burr hole drainage 1
• In cases with persistent visual decline despite medical therapy, CSF diversion procedures should be considered:
  • Ventriculoperitoneal (VP) shunt is the preferred CSF diversion procedure due to lower reported revision rates 7
  • Optic nerve sheath fenestration (ONSF) may be considered, especially in cases with asymmetric papilledema 1
• Serial lumbar punctures are not recommended for long-term management of IIH 1

Special Considerations

• If subdural hygroma occurs after neurovascular stenting, long-term antithrombotic therapy is required for at least 6 months 1
• In patients with concurrent cerebral venous thrombosis, epidural blood patch should be prioritized as initial treatment, with careful consideration of anticoagulation balancing bleeding risks 1
• Patients should be monitored closely for any changes in headache pattern or neurological examination, which may indicate complications 1

Follow-up and Monitoring

• Follow-up intervals should be based on papilledema grade and visual field status 7
• More frequent monitoring is needed for severe or worsening cases 7
• Repeat neuroimaging should be performed if there are any new or worsening symptoms 5
• Treatment failure rates include worsening vision after initial stabilization in 34% of patients at 1 year and 45% at 3 years 7

Pitfalls and Caveats

• Subdural hygromas may be more frequent when intracranial pressure monitors are placed, possibly due to opening of the arachnoid 4
• The headache phenotype in IIH is highly variable and can mimic other primary headache disorders, making it difficult to distinguish symptoms caused by the hygroma versus underlying IIH 5
• Patients with IIH often develop migrainous headaches superimposed on headaches from raised intracranial pressure, requiring specific treatment approaches 6