Case Author(s): Jeff Chesnut, D.O. and Henry Royal, M.D. , 6/25/99 . Rating: #D2, #Q3

Diagnosis: Cerebral Spinal Fluid Leak

Brief history:

15 month old female with rhinorrhea following resection of a nasal mass.

Images:

Images obtined 1 hour after the injection of the radiopharmaceutical into the lumbar subarachnoid space.

View main image(cl) in a separate image viewer

View second image(cl). Same 1 hr. image with increased intensity.

View third image(cl). 3 hr. delayed images over the abdomen.

View fourth image(cl). 1 hr. lateral view over head with pointer.

Full history/Diagnosis is available below

Diagnosis: Cerebral Spinal Fluid Leak

Full history:

15 month old female who had cribiform plate resection and resection of a nasal mass. Pathologic evaluation of the mass revealed normal brain tissue (anterior encephalocele.) She is now experiencing constant rhinorrhea.

Radiopharmaceutical:

Tc-99m DTPA by lumbar subarachnoid injection.

Findings:

Prior to the injection of the radiopharmaceutical, the patient underwent placement of cottonoid pledgets in the nasal cavity by an otolaryngologist.

Images obtained 1 hour after the injection of the radiopharmaceutical into the lumbar subarachnoid space reveals symmetric ascent of tracer in the cerebral subarachoid space. There is no ventricular reflux. A small amount of activity is seen anteriorly in the superior aspect of the nasopharynx (see 4th image.)

Anterior and posterior images over the abdomen were obtained approximately 3 hrs. after the injection. Activity is seen within the stomach due to swallowed CSF.

The pledgets were removed, weighed and counted in a well counter along with a simultaneously obtained plasma sample. The ratio of pledget activity per gm of accumulated fluid to that of plasma activity per ml was 40:1 in the right pledget. The ratio in the left pledget was 1.5:1.

Discussion:

Radionuclide cisternography is a sensitive method of determining CSF leak. The images are useful if a leak is seen; however small leaks may be only detected by the pledget counts and abdominal images. In an adult, normally 3 pledgets are placed in each nasal cavity by an otolaryngologist. The pledgets must be labeled so that, upon removal, the location of each pledget may be identified. Strict attention to technique must be observed in performing the pledget counts. A dry pledget must be weighed so that an accurate measurement of of accumulated fluid on the pledget can be obtained. A plasma sample drawn simultaneously with the pledget removal is used as a control.

Normally, in adults, In-111 DTPA is used instead of Tc-99m DTPA. One of the concerns with Tc-99m DTPA is that if there is improper labelling, or dissociation of the Tc-99m, one may see gastric uptake as a result of free Tc-99m pertechnetate. The absence of thyroid and salivary gland activity in this case, however, indicates that this has not occurred.

Major teaching point(s):

1. Radionuclide cisternography is a sensitive method for the detection of active CSF leaks.

2. The major value of radionuclide cisternography for the detection of CSF leaks is in the pledget count.

3. Meticulous attention to detail is required when performing the pledget count.

4. Coordination between multiple departments is required for this study. Nuclear medicine performs the imaging and counting while otolaryngology is required to place the pledgets. In many institutions, neuroradiology will perform the intrathecal injection.

ACR Codes and Keywords:

References and General Discussion of Cerebral Spinal Fluid Leak (Anatomic field:Skull and Contents, Category:Effect of Trauma)

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Case number: cl001

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