The test, however, is not typically used, he said, “if the surgeon is going to remove a tumor and the removal of that tumor results in a CSF leak or if the surgeon is performing a routine endoscopic sinus surgery and inadvertently causes a CSF leak.”
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November 2010The test, which is not approved by the U.S. Food and Drug Administration (FDA) for this indication, must be used correctly to avoid complications. According to Dr. Kennedy, seizures have been reported with doses as low as 0.2 cc of 10 percent fluorescein. Because of this potential complication, he emphasized the need for otolaryngologists to inform their patients that this test is not FDA approved for intrathecal use.
When used appropriately, however, the test carries little risk of complications. Both Drs. Welch and Kennedy use the test at its suggested dose of 0.1 cc of 10 percent fluorescein mixed with 10 cc of the patient’s CSF or preservative-free saline and slowly injected over five minutes.
For Dr. Kennedy, this test is superior to the radioactive intrathecal tracer test. “Those tests have a significant false positive rate,” he said, “and that is something which probably many otolaryngologists are not aware of.”
Although intrathecal fluorescein is currently the most sensitive test used to identify CSF leaks, Dr. Kennedy said that a colleague of his, Erica Thaler, MD, has demonstrated efficacy with an electronic nose to detect these leaks (Laryngoscope. 2002;112(9):1533-1542); the same technology, he said, is used currently in agriculture and bioterrorism.
“Otolaryngologists must understand the difference between routine cerebrospinal fluid leak repairs of small defects…as opposed to large defects seen with endoscopic skull base resections that require extended, multi-layer reconstruction.”—Rodney J. Schlosser, MD
Closing from Above
Although otolaryngologists are now able to close most CSF leaks endoscopically, they may still have to team up with a neurosurgeon or hand a case off to a neurosurgeon in some cases.
“There are some situations in which the intracranial approach is necessary,” said Dr. Marple, noting that some of these situations are dictated not by the defect in the skull base but by what is associated with that defect. “For example,” he said, “if there was a large encephalocele associated with an important structure, that may be addressed from above, not because of the defect, but because of the encephalocele.”
Dr. Welch emphasized that even patients with very large defects with meningoencephaloceles may be candidates for endoscopic CSF repair, however.
A Successful Closure
To successfully repair even the most routine CSF leak, otolaryngologists need to keep in mind several basic tenets of repair. For Dr. Kennedy, the issues that get otolaryngologists into trouble most often are knowing when to close a leak created during an endoscopic procedure and the importance of preparing the surface on which to lay a graft.