CT CISTERNOGRAPHY

Overview

CT cisternography is a specialized imaging technique that uses computed tomography (CT) along with an intrathecal contrast agent (contrast injected into the cerebrospinal fluid, or CSF) to create detailed images of the basal cisterns and subarachnoid spaces around the brain and brainstem. This technique is primarily used to evaluate CSF leaks, blockages, and certain structural abnormalities involving the cranial base and CSF pathways. By highlighting the flow and distribution of CSF, CT cisternography helps radiologists and neurosurgeons visualize small defects or leaks that may not appear on standard CT or MRI scans.

Purpose of CT Cisternography

CT cisternography is typically performed for specific diagnostic reasons where other imaging methods may not provide enough information, including:

1. Detection of CSF Leaks

• Most commonly used to locate the site of a suspected cerebrospinal fluid leak, especially when the leak leads to CSF rhinorrhea (leak into the nasal cavity) or otorrhea (leak into the ear).

2. Evaluation of Basilar Skull Defects

• Identifies small fractures, congenital bony defects, or erosions in the base of the skull that could allow CSF leakage.

3. Assessment of Spontaneous Intracranial Hypotension

• Helps identify sites where CSF is leaking, which can explain symptoms like headaches worsened when standing.

4. Pre-Surgical Planning

• Helps neurosurgeons plan repairs of skull base defects or other interventions by accurately showing the defect’s location and size.

5. Evaluation of Obstructed CSF Flow

• In rare cases, used to study blockages within the subarachnoid space affecting CSF circulation.

Procedure for CT Cisternography

This scan is a more specialized procedure than routine CT and typically involves two steps: contrast administration and CT imaging.

Before the Scan

• You may be asked to fast for several hours.
• Inform the medical team if you:
  • Have allergies to contrast dye or anesthetics
  • Have bleeding disorders or are on blood thinners
  • Are pregnant or suspect pregnancy
• Baseline neurological evaluation and sometimes blood tests are performed to ensure suitability.

Contrast Injection (Lumbar Puncture)

• A lumbar puncture (spinal tap) is performed by a radiologist or neurologist under sterile conditions.
• Through a needle placed in the lower back, a small amount of iodinated contrast dye is injected into the CSF space.
• You’ll then be asked to move or tilt gently to help the contrast move towards the brain’s cisterns.

CT Imaging

• After contrast has reached the basal cisterns, you will lie on the CT table.
• The scanner will take high-resolution thin-slice images, often focusing on the skull base and paranasal sinuses.
• The scan itself is quick, usually lasting around 10–15 minutes.

After the Scan

• You may be monitored for a short time to watch for headaches or discomfort.
• Drink fluids to help clear contrast from the CSF.
• Avoid heavy physical activity or bending over for the rest of the day.

Benefits of CT Cisternography

• Precise localization: Identifies even very small CSF leaks.
• Detailed bone imaging: CT shows skull base defects or fractures clearly.
• Guides surgery: Helps neurosurgeons accurately repair leaks.
• Dynamic evaluation: Shows active leaks by visualizing contrast escape.

Conditions Commonly Evaluated

• Traumatic or spontaneous CSF leaks
• Basilar skull fractures
• Congenital skull base defects
• Postsurgical leaks or complications
• Spontaneous intracranial hypotension due to CSF leaks
• Blockages or abnormalities in subarachnoid spaces

Risks and Considerations

CT cisternography is generally safe when performed by trained specialists, but certain risks and considerations apply:

Radiation Exposure

• Uses ionizing radiation, though limited to the head region.

Lumbar Puncture Risks

• Headache (most common), infection, bleeding, or rarely, nerve injury.

Contrast Dye Risks

• Allergic reactions, though rare.
• The dye may irritate nerves if injected incorrectly, which is extremely uncommon.

Pregnancy

• Usually avoided unless absolutely necessary.

Post-Procedure Care

• Some people experience mild headaches after the procedure, relieved by rest and hydration.

Conclusion

CT cisternography is a highly specialized imaging technique that plays a vital role in diagnosing cerebrospinal fluid leaks and skull base defects that can be missed by routine imaging. By combining detailed CT images with intrathecal contrast, it offers unmatched accuracy in localizing leaks and understanding CSF flow dynamics. While it involves additional preparation and a lumbar puncture, the information gained often guides effective treatment—particularly surgical repair—helping patients recover from conditions that might otherwise remain unresolved. If your doctor recommends CT cisternography, it’s because this advanced technique offers answers that standard CT or MRI scans may not provide, ensuring your care is guided by the most precise and reliable diagnostic information.