Can we use contrast-enhanced Computed Tomography (CT) in patients with cerebrospinal fluid (CSF) rhinorrhea and meningitis?

Imaging for CSF Rhinorrhea in Patients with Meningitis

High-resolution CT (HRCT) of the paranasal sinuses without IV contrast should be used as the first-line imaging modality for patients with CSF rhinorrhea and meningitis, as it provides superior spatial resolution and excellent bony detail essential for identifying skull base defects. 1

Initial Imaging Approach

• HRCT without IV contrast is the most appropriate initial study with reported sensitivity of 88-95% for identifying skull base defects 1, 2
• HRCT correctly identified the site of CSF leak in 100% of surgically confirmed cases in validation studies, demonstrating superior accuracy (93%) compared to other modalities 2, 3
• There is no relevant literature to support the use of contrast-enhanced CT in the evaluation of CSF leak 4
• HRCT alone is sufficient if only one osseous defect is identified and corresponds with clinical symptoms 4

Secondary Imaging Considerations

• MRI with heavily T2-weighted sequences (MR cisternography) should be performed in conjunction with HRCT when additional characterization is needed, with combined sensitivity reaching 90-96% 1, 5
• MRI provides superior soft-tissue contrast and can better identify:
  • Contents of any associated cephalocele 4, 2
  • Dural enhancement and distinction between meningoceles and sinus secretions 4, 1
  • CSF extending from subarachnoid space into sinonasal cavity 1, 6
• MRI without IV contrast with inclusion of heavily T2-weighted images is typically sufficient for CSF leak evaluation 4
• MRI without and with IV contrast may be useful for identifying dural enhancement in cases with meningitis 4

Important Contraindications and Caveats

• CT cisternography should NOT be the first-line imaging study in a patient with active meningitis, as it requires lumbar puncture for intrathecal contrast administration, which could potentially worsen meningitis 1
• CT cisternography should be reserved for cases where:
  • Multiple osseous defects are identified on HRCT and specific localization is needed 1
  • The patient has an active CSF leak at the time of examination 1
  • Other imaging modalities have failed to identify the source of the leak 1, 3
• β2-transferrin analysis of nasal fluid should be performed to confirm the presence of CSF before imaging when possible 1
• In patients with active meningitis, imaging should not delay appropriate antibiotic therapy 1

Comparative Effectiveness of Imaging Modalities

• The combination of HRCT and MR cisternography has been shown to be accurate in 96% of patients with CSF leaks 5
• HRCT outperforms other imaging modalities in localizing CSF leaks, correctly identifying all leak sites in surgical validation studies, compared to radionuclide cisternography and CT cisternography 2, 3
• MR cisternography alone has sensitivity of 87-94% and specificity of 57-100% for identifying CSF leak sites 4, 7
• Non-invasive imaging with HRCT and MR cisternography should be considered before invasive techniques like CT cisternography 8

Imaging for Intracranial Complications

• In patients with meningitis, MRI head without and with IV contrast can accurately identify intracranial complications with 97% diagnostic accuracy compared to 87% for CT 4
• MRI is superior for the diagnosis of meningitis compared to CT 4
• Combined pre- and post-contrast MRI provides the best opportunity to identify and characterize potential intracranial complications 4

By following this imaging algorithm, clinicians can effectively diagnose CSF rhinorrhea in patients with meningitis while minimizing invasive procedures that could potentially worsen the patient's condition.