What is the preferred diagnostic imaging modality, Magnetic Resonance (MR) cisternogram or Computed Tomography (CT) cisternogram, for suspected cerebrospinal fluid (CSF) leaks?

CT Cisternogram vs MR Cisternogram for CSF Leaks

High-resolution CT (HRCT) is the preferred first-line imaging modality for suspected CSF leaks with laboratory confirmation, with superior accuracy (93%) and sensitivity (92%) compared to MR cisternography (89% accuracy, 87% sensitivity). 1

Diagnostic Algorithm for CSF Leak Evaluation

First-Line Imaging

• High-resolution CT (HRCT) should be the initial imaging study for patients with laboratory-confirmed CSF leak (positive β2-transferrin or β2-trace) 1
  • Request thin-section bone algorithm images of the skull base with multiplanar reformation
  • For rhinorrhea: maxillofacial CT
  • For otorrhea: temporal bone CT
• HRCT correctly identified the site of CSF leak in 100% of cases in a retrospective study of 21 patients who underwent surgical repair 1

Second-Line Imaging (when HRCT is inconclusive)

• MR cisternography (89% accuracy, 87% sensitivity) is recommended as a second-line noninvasive option when: 1

  • A meningoencephalocele is suspected on HRCT 1
  • Soft tissue detail is needed to evaluate for associated complications 1
  • MR cisternography utilizes high-resolution T2-weighted or steady-state free precession sequences 1

• CT cisternography should be considered when: 1

  • Multiple potential CSF leak sites are identified on HRCT
  • HRCT fails to identify a defect despite strong clinical suspicion

Third-Line Imaging

• Contrast-enhanced MR cisternography (92-100% sensitivity for active leaks) may be considered when HRCT and CT cisternography fail to localize a laboratory-confirmed CSF leak 1

  • Requires intrathecal administration of gadolinium-based contrast (off-label use)
  • More sensitive than CT cisternography but less commonly performed 1

• Radionuclide (DTPA) cisternography is most useful for: 1

  • Confirming the presence of a CSF leak when laboratory tests are negative 1
  • Not recommended for preoperative planning due to lower spatial resolution 1

Comparative Effectiveness

• HRCT outperforms other imaging modalities in localizing CSF leaks:
  • In surgical validation studies, HRCT correctly identified all leak sites (21/21 cases) 1
  • By comparison, radionuclide cisternography was positive in only 16/21 cases and CT cisternography in only 10/21 cases 1
  • The combination of HRCT and MR cisternography has been reported to have 96% accuracy 2

Clinical Considerations and Pitfalls

• MRI provides superior soft-tissue contrast and can better identify the contents of a cephalocele if present 1
• CT cisternography requires lumbar puncture and intrathecal contrast administration, making it more invasive than HRCT or MR cisternography 1
• Contrast-enhanced MR cisternography requires off-label use of intrathecal gadolinium, which should be discussed during informed consent 1
• The sensitivity of both CT and MR cisternography depends on whether the leak is active at the time of imaging 1
• When multiple imaging modalities are used, the combination of HRCT and MR cisternography provides complementary information about bone defects and soft tissue details 2, 3

Special Situations

• For intermittent or inactive leaks, contrast-enhanced MR cisternography may have lower sensitivity (approximately 70%) 1
• In cases where sufficient fluid cannot be collected for β2-transferrin testing, radionuclide cisternography may help confirm the presence of a leak 1
• 3D T2 DRIVE MR cisternography offers advantages of effective bone and fat suppression with high spatial resolution for localizing CSF leaks 4