CT Scan Instead of Fluoroscopy For Placement of Lumbar Drains of Cerebrospinal FluidLumbar spinal drainage using a needle to draw out the cerebrospinal fluid (CSF) is a procedure done during brain surgery. The procedure is called a lumbar drain. Removing CSF helps the brain relax. The technique can also be done when there is a spinal CSF fistula. A fistula is an abnormal connection or passageway between two areas that normally do not connect.
Usually the needle used to tap into the CSF is put in place using fluoroscopy. Fluoroscopy is a type of real-time X-ray that allows the surgeon to see the needle moving through the tissue. One advantage of the fluoroscopy technique is that a portable unit can be brought to the patient's bedside. The procedure can be completed without moving the patient. This type of X-ray improves accuracy but exposes both the patient and the surgeon to radiation.
In this report, doctors from the Departments of Radiology and Neurosurgery at the Albert Einstein College of Medicine in New York report on the use of computed tomography to guide the lumbar drain. They used the case of a 62-year old man with a brain aneurysm as an example. An aneurysm is an abnormal thinning and dilation (or ballooning) of an artery (blood vessel).
Surgery was done to remove the aneurysm. But there was a leak in the CSF after the operation. The surgeons were unable to get a lumbar drain placed using fluoroscopy. After multiple attempts to place a lumbar drain using bedside fluoroscopy, this patient was transported to the CT scan suite. The lumbar drain was placed in one attempt.
The CT scan allows safe and accurate placement of the needle from skin to spinal canal. The needle enters the thecal sac where the CSF is located. The thecal sac is made up of two separate but closely linked layers of lining called the dura mater and the arachnoid mater. The sac protects the nerve roots from pressure injury while the fluid supplies nutrients.
Each cross-sectional slice provided by the CT image allowed the surgeon to choose the right needle angle. Measurements to gauge distances are given in millimeters. If there is any doubt about correct placement of the needle, a contrasting dye can be injected through the needle into the CSF. The dye is taken up by the CSF and confirms proper needle placement.
When standard bedside fluoroscopy has been done with multiple punctures of the dura (lining around the CSF), it may not be possible to get the CSF to flow. This is because tears in the dura allow leakage of the CSF, which reduces the pressure within the CSF. Low CSF prevents CSF flow. This is another situation when computed tomography can be used for lumbar drain placement.
And there is the added advantage of being able to see the needle enter the thecal sac with the option of using a contrast dye to confirm proper needle placement. CT scan also shows if there have been any blood vessels punctured along with the formation of a hematoma (collection or pool of blood). Hematomas must be treated immediately to prevent further complications.
The authors suggest using CT-guided lumbar drain placement in complicated cases. CT scans give the surgeon a chance to examine and study the patient before surgery. The lumbar drain placement technique can be planned down to the millimeter.
Menachem M. Gold, MD, et al. Computed Tomography -- Guided Lumbar Drain Placement. In Journal of Neurosurgery. October 2008. Vol. 9. No. 4. Pp. 372-373.
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