Volume 16, Number 2
For Brain Outcomes:
Cognitive Testing's Chance to Shine
A dark idea has been making the rounds about people treated for ruptured aneurysms. It says that surgery itself-the craniotomy that opens the skull and the handling of brain tissue that follows-can disturb brain function. "People think, You're manipulating the brain," says neurologist Argye Hillis, M.D., "Sure, patients will have cognitive impairment."
But,
she says, that's not the case. Her study with neurosurgeon Rafael Tamargo,
M.D., and medical student Elizabeth Tuffiash that appeared in last October's
issue of Stroke used cognitive tests and tight design to de-bunk the myth.
Moreover, Hillis believes the bedside cognitive testing she used may well
become standard for evaluating outcomes in all manner of brain- injured
patients. It's accurate, inexpensive and quick.As for the craniotomy myth: "The idea that surgery causes cognitive defects," Hillis explains, "came, in part from a controversial study that said people with small aneurysms do better to avoid surgery because of cognitive risk. But that study had no pre-surgery testing of patients and used post-surgery telephone interviews, which can be unreliable."
In Hillis' study, patients were checked both before and after with simple but comprehensive cognitive tests, from word association to visual memory. To reveal possible surgical effects without the complications hemorrhage would bring, she recruited only patients with unruptured aneurysms. The result: No cognitive defects, subtle or otherwise, surfaced from aneurysm clipping.
A second study, out last November, pitted neurocognitive testing against a widely used NIH stroke scale. It compared the two in reflecting the extent of compromised cerebral cortex and in telling when treatment moved still-salvageable areas in patients' brains out of danger. Hillis' team evaluated 74 stroke patients the day after their mishap. Patients also underwent perfusion-weighted imaging, a type of MRI that highlights at-risk tissue.
"We found that the NIH stroke scale didn't at all reflect the extent of salvageable tissue," says Hillis. The cognitive tests-language tests for patients with left brain stroke and spatial attention tests for those with right brain stroke-did so admirably. Further, in a smaller group of patients recommended for treatment, the cognitive tests were head and shoulders better than the stroke scale at telling when they'd improved.
"That's really no surprise," Hillis explains, because the NIH scale mostly measures motor function whose primary control is deep in the brain. By contrast, the cognitive tests report on far more vulnerable cortical abilities. "Because using the NIH scale to evaluate therapy is widespread, that's worrisome," she says. "We may be ruling out good treatments for stroke.
"You may not be able to restore motor function, but there's often a chance to help other things. Improve patients' ability to speak or to hold attention and you make a huge difference in their lives."
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