Cisternogram - Imaging The Cerebrospinal Fluid

  1. Hydrocephalus (water on the brain) occurs when CSF pressure builds up in the brain - Normal Pressure Hydrocephalus
    1. CSF is produced by the choroid plexuses and enters the ventricles
    2. Flows caudally to the third ventricle
    3. Passes to the posterior portion of the spinal cord and descends
    4. Crosses into the anterior portion of the spinal cord and then heads cephalically near the base of the spine
    5. (Point where the radiopharmaceutical injection will occur, intrathecally, into the lumbar sub-arachnoid space) - (xx) indicate normal flow time of the radiotracer
      CSF Flow
    6. Also refer to the image above
    7. Also refer to the image above
    8. (1 hour) CSF reaches the basal cisterns
    9. (2 - 6 hours) CSF arrives at the frontal poles and Sylvia fissure
    10. (12 hours) CSF is at the cerebral convexities
    11. (24 hours) CSF arrives at the arachnoid villi in the area of the sagittal sinus
    12. At this point the CSF is then absorbed back into the venous system
    13. Note - Normal CSF pressure will not cause CFS (or radiotracer) to flow back into the ventricles
  2. Review of the Cisternogram procedure

    Intrathecial Injection

    1. 500 µCi of 111In-DTPA is injected intrathecally
      1. Injection is done using sterile technique
      2. Should be done by a trained physician, not the technologist
      3. In some situations the procedure needs to done under fluoroscopy
    2. Immediately following the injection, the injection site should be scanned to assure that the radiotracer is in with the CSF compartment
      1. 100k image
      2. 128 or 256 matrix
      3. Collimator ME
      4. Dual energy peak setting
        1. 173 keV at 20%
        2. 247 keV at 20%
    3. 4 - 6 hour later imaging maybe done again and/or a 24 hour scan
    4. 24 hour delays images
      1. Use the same above protocol for all images: matrix, collimator, and energy peak
      2. Acquire ANT and a LAT
      3. 57Co source maybe used to mark the scalp or a 200 µCi technetium source maybe used to outline the skull
    5. 48 and 72 hour imaging maybe required when normal pressure hydrocephalus is present
      1. Repeat the above imaging protocol as stated in the 24 hour delays
      2. Note increased scanning time will be required
    6. Normal images should indicate the activity exiting the arachnoid villa within 24 hours
  3. Types of hydrocephalus or normal pressure hydrocephalus
    1. Hydrocephalus1
      1. Increased pressure of CSF can be caused by: over production by the choroid plexus, obstruction of flow to the arachnoid villa, or reduced absorption at the site of the arachnoid villa.
      2. Enlargement of the is usually noted and observed with CT
      3. Associated with communicating hydrocephalus
      4. Non-communicating
      5. Communication is the delay of the radiotracer >24 hrs to the arachnoid villa. It may or may not show activity in the ventricles. May also be referred to as normal pressure hydrocephalus
      6. Non communicating shows no ventricle activity
      7. Note: Considering the flow of the radiotracer - activity should not be seen in the ventricles
    2. Hydrocephalus defined Sodee (1994)
      1. Normal
      2. Type I: delayed reduced clearance/no ventricle uptake
      3. Type II: reduced clearance/ventricle uptake
      4. Type III: significant reduced clearance/no ventricle uptake
      5. Type IV: significant reduced clearance/ventricle uptake
      6. Type V: Foramen Magnum Block

    3. Hydrocephalus update - NHP patterns are noted in Types IIIB and IV2
      1. Type I - can be either normal or non-communicating hydrocephalus - key activity is seen over the convexities at 24 hours
      2. Type II - there is a delay in activity flowing over the convexities and no ventricle filling
      3. Type IIIA - delay in activity over the convexities with reflux into the ventricle
      4. Type IIIB - no activity seen over the convexities at 24 hours with intermittent ventricle filling
      5. Type IV - If activity within the ventricles is consistent
  4. Imaging results

    Normal 3 hour and 24 hour post injection

    1. This case is an example of what normal CSF flow should look like. You should also appreciate lack of activity in the ventricles at 24 hours and at the same time the activity has surrounded the exterior portion of the head (exiting out)

      2. Abnormal Cisternogram with ventricle filling

    2. Here is an example of a 48 hour delay cisternogram. Questionable activity has reached the superior sagittal sinus and there is definite accumulation within the ventricles
    3. SEE normal - https://fluidsbarrierscns.biomedcentral.com/articles/10.1186/1743-8454-6-5/figures/1

      4. Abnormal vs. normal ventricles

    4. From the above abnormal scan I thought it would be appropriate to look at what this patient's CT looks like. In addition, a normal brain CT is placed next to it. Note the differences in ventricle size. If you wish to know more abut the specific CT, click that section of the image

  1. CSF leaks
    1. There are two types - Rhinorrhea and Otorrhea
    2. How do they occur?

      Where the CSF leak usually starts

      1. Leaks usually occur at the cribiform plate where the anterior fossa turns upward to join the orbital plate of the frontal bone to form the roof of the ethmoid resulting in rhinorrhea
      2. Temporal bone defect may result in Otorrhea
      3. Trauma to the above areas is the most common reason for a leak to occur
      4. Non traumatic causes include hydrocephalus and tumors (result from high pressure buildup)
    3. Methods for diagnosing leaks (non-nuclear)
      1. Usually leaks produce a some amount of fluid, however, if enough volume can be collected, the contents can be examined
        1. CSF is high in glucose
        2. Glucose oxidase strip measures glucose content, however, mixture of other secretions may have a high level of glucose which may result in a false positive diagnosis. Absence of glucose definitively rules out a leak
        3. If an adequate sample can be obtained and compared with serum glucose levels and the glucose level is 60% of the serum level, this leads to a positive diagnosis
      2. High resolution CT (HRCT) is perhaps the method of choice since it will define the exact location of the leak for surgical repair. However, if the leak doesn't produce enough fluid, this method will be unable to its presents (sensitivity is 81 to 89%)
      3. Cisternography/fluoroscopy and MRI have also been used and are not as effective as HRCT
    4. The use of nuclear medicine to diagnose a CSF leak
      1. While NMT is sensitive to determine if a leak is present, the limiting factor is the localization of the leak
      2. Following the injection of 111In-DTPA, pleglets are placed into the nasal sinuses for a period of time, removed and counted. The pleglets with the highest amount of activity indicates the area closest to the leak
      3. SPECT may also be used, however, a significant amount of activity/leak must be present in order to visualize a positive diagnosis
    5. Procedure - Cisternogram
      1. 500 μCi of 111In-DTPA is injected intrathecally
      2. Injection is done using sterile technique
      3. Immediately following the injection, the injection site should be scan to assure that the radiotracer in with the CSF compartment
      4. 100k image
      5. 128 or 256 matrix
      6. Collimator ME
      7. Dual energy peak setting
        1. 173 keV at 20%
        2. 247 keV at 20%
      8. Keep the patient in the supine position until scanning time
      9. Once the radiotracer reaches the basal cisterns (usually the area of the leak) the patients internal jugular vein should be stimulated or the patient should Valsalva . This should stimulate the CSF leak, if it is present
      10. Scan the patient with the lateral view being the most sensitive to identifying the leak
      11. SPECT may also be considered (remember, we do a poor job in finding its location)

        12. CSF Leak

      12. This is an exception to the rule, where the location of the leak can be determined via NMT
    6. Procedure - Pleglet method
      1. 2 - 3 pleglet are placed within the right and left sides of the nasal sinuses (total pleglets = 4 to 6) if Rhinorrhea is suspected
      2. 1 pledge is placed in each external auditory meatus if Otorrhea is suspected
      3. Pleglets are placed in the patient following the intrathecal injection of 111In-DTPA and then removed 4 - 6 hours later
      4. Pleglets size should absorb 0.5 mL of fluid
      5. 0.5 mL sample of the patients serum is taken when the pleglets are removed
      6. Set the well counter to a 10 minute acquisition with a 150 to 250 keV window
      7. Counts are expressed in counts per gram
      8. Normal pleglet to plasma ratio should be 1.3 or less
      9. 1.5 to 10 ratio is considered positive
      10. If it is negative, a new set of pleglets maybe implanted for a longer period of time to further determine the presence of a CSF leak
      11. There is almost a 100% accuracy in this technique, however, the limiting factor is identifying the exact location of the leak
  2. Comments on the types of radiopharmaceuticals used
    1. 111In-DTPA
      1. Agent of choice
      2. The production of this radiopharmaceutical is considered to be more sterile
      3. T ½ is long enough for scanning times of 72 hours or more
    2. 99mTc-DTPA
      1. Can be considered but maybe "less sterile"
      2. T ½ will not allow for delayed imaging at 72 hours
      3. Note: CSF is more sensitive to pathogens so administration of the radiotracer via sterile technique is very important!
  3. What is the treatment for hydrocephalus?
    1. Usually an internal shunt is place inside the skull to relief CSF pressure
      1. A catheter is then inserted which connects the shunt where the CSF fluid flows from the brain to the peritoneal cavity
      2. Solving the excessive pressure of CSF


        3. http://tech.snmjournals.org/content/37/1/1.full

      3. The above images show a normal flowing shunt where the arrow in A is the pump and arrows in are pointing to the patent tubing


        4. http://tech.snmjournals.org/content/37/1/1.full

      4. The above images show an abnormal shunt exam where the activity just stops flowing downward, via no activity in the peritoneum
    2. Problems occur when this system becomes blocked and a nuclear medicine procedure can be preformed to determine shunt patency
    3. Shunt Patency Procedure - See procedure. This will be covered next semester

Cisternogram Procedure
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1 - Radiopharmaceuticals in Nuclear Pharmacy and Nuclear Medicine by RJ Kowalsky and SW Falen, 2nd edition. APhA 2004
2 - Thut DP, Kreychman A, and Obando JA. 111In-DTPA Cisternography with SPECT/CT for the Evaluation of Normal Pressure Hydrocepalus. JNMT March 2014, 42(1) 70-74.

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