Fall 2003, Volume 16, Number 2
Looking at the trajectory of Alessandro Olivi's biopsy needle is something that could curl the hair of the uninitiated. The needle traverses the brain diagonally, barely skirting a ventricle. And then, passing into no man's land, it enters the brain stem, site of nerve centers for breathing, regulating blood pressure and heart rate, eye movement and swallowing, among other functions.
Olivi (left) gently eases a
biopsy needle into the brain
"Because of the concentration of high-function brain tissue in a small area, the brain stem's been thought off limits for any kind of biopsy," says neurosurgeon Olivi. And while retrieving tissue there isn't novel, it is uncommon.
Olivi's performed 24 of the procedures, however, with next to no difficulties. "The greatest worry with brain biopsy is hemorrhage," he explains. Some pathologies make blood vessels tissue-fragile. Even a small bleed can be devastating in the brain stem. "We tell patients there's a 3 percent risk of that, but so far, we've had no hematomas, no hemorrhagic complications."
Brain stem biopsy is the method of choice to identify and grade tumors and distinguish them from localized inflammation. And while subsequent surgery is typically ruled out in the brain stem-save for tumors that extend beyond it-biopsy is key to making a prognosis and planning the usual option, radiation therapy.
Prior to the biopsy, a patient is fitted with a stereotactic headframe. Next comes an MRI, which Olivi uses to plot his path, measuring distance and angle while at the MRI console, to trace the least risky approach. The patient then moves to the OR for the biopsy. That, surprisingly, is done under local anesthetic and sedation.
Affixing a metal arc to the patient's headframe, Olivi slides a moveable holder around the arc, aligning the biopsy needle so it becomes the radius of a circle whose center is the target tissue. After he's made a pea-size burr hole in the posterior frontal skull, Olivi slowly feeds the needle into the brain, extracting a bit of tissue via an interior stylet. A quick pathologist's report tells if the tissue's right for analysis. In the rare instance it isn't, Olivi can remove a second, smaller sample. Because the needle's housing remains in place, he won't have to make a new pass through the brain.
"All the while," he says, "the patient's awake and not uncomfortable."
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