Neurology Now:
doi: 10.1097/01.NNN.0000333836.93556.0a
Department: the Waiting Room: Frequently Asked Questions

Brain Imaging

Smolinsky, Mike

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In June 2007, a group of medical experts convened at Stanford University to discuss improved technology for imaging patients with “disorders of consciousness,” such as vegetative and minimally conscious states, that can occur after brain injury. “One of the challenges we identified is responding to desperate calls from families requesting an fMRI scan for a loved one in a limited state of consciousness,” says Judy Illes, Ph.D., formerly at Stanford and now professor of neurology and Canada Research Chair in neuroethics at the University of British Columbia in Vancouver. Dr. Illes and her colleagues developed this FAQ for families.

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1. What is brain imaging?

Brain imaging allows doctors to view and monitor areas of the brain. Images can be produced using structural imaging techniques—magnetic resonance imaging (MRI) and computed axial tomography (CAT)—or functional imaging strategies such as positron emission tomography (PET) and functional MRI (fMRI). Structural imaging identifies abnormalities such as strokes, bleeding, and tumors, while functional imaging evaluates how the brain is working. These measurements are based on the flow of blood and levels of oxygen in specific brain regions.

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2. Can brain imaging be used to determine whether someone is conscious?

There are currently no diagnostic tests capable of detecting whether someone is conscious. Specialized rating scales and imaging techniques have been developed to investigate the likelihood that someone is processing information consciously, but neither approach provides definitive evidence of consciousness or unconsciousness. Doctors currently rely on bedside exams to diagnose disorders of consciousness.

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3. Should I enroll a family member who has brain injury in an imaging study?

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Find out what is involved before enrolling your family member by talking to your doctor and the scientist requesting your consent. Most studies pose minimal risk to the patient, whose participation can add important knowledge to the understanding of disorders of consciousness. Knowledge is gained every day about how the brain works, so you can expect ever-improving diagnosis of and treatment for brain injury. However, these studies are experimental, which means you can't expect to learn new information about the person's condition or to use the information to make decisions about his or her care. Make the choice by thinking about whether the person would have volunteered.

—Mike Smolinsky

©2008 American Academy of Neurology

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