Functional brain imaging reliably predicts which vegetative patients have potential to recover consciousness

April 16, 2014

A functional brain imaging technique known as positron emission tomography (PET) is a promising tool for determining which severely brain damaged individuals in vegetative states have the potential to recover consciousness, according to new research published in The Lancet. It is the first time that researchers have tested the diagnostic accuracy of functional brain imaging techniques in clinical practice.

"Our findings suggest that PET imaging can reveal cognitive processes that aren't visible through traditional bedside tests, and could substantially complement standard behavioural assessments to identify unresponsive or "vegetative" who have the potential for long-term recovery", says study leader Professor Steven Laureys from the University of Liége in Belgium.

In severely brain-damaged individuals, judging the level of consciousness has proved challenging. Traditionally, bedside clinical examinations have been used to decide whether patients are in a minimally conscious state (MCS), in which there is some evidence of awareness and response to stimuli, or are in a (VS) also known as unresponsive wakefulness syndrome, where there is neither, and the chance of recovery is much lower. But up to 40% of patients are misdiagnosed using these examinations.

"In patients with substantial cerebral oedema [swelling of the brain], prediction of outcome on the basis of standard clinical examination and structural brain imaging is probably little better than flipping a coin," writes Jamie Sleigh from the University of Auckland, New Zealand, and Catherine Warnaby from the University of Oxford, UK, in a linked Comment.

The study assessed whether two new techniques—PET with the imaging agent fluorodeoxyglucose (FDG) and functional MRI (fMRI) during mental imagery tasks—could distinguish between vegetative and MCS in 126 patients with severe brain injury (81 in a MCS, 41 in a VS, and four with locked-in syndrome—a behaviourally unresponsive but conscious control group) referred to the University Hospital of Liége, in Belgium, from across Europe. The researchers then compared their results with the well-established standardised Coma Recovery Scale–Revised (CSR-R) behavioural test, considered the most validated and sensitive method for discriminating very low awareness.

Overall, FDG-PET was better than fMRI in distinguishing conscious from unconscious patients. Mental imagery fMRI was less sensitive at diagnosis of a MCS than FDG-PET (45% vs 93%), and had less agreement with behavioural CRS-R scores than FDG-PET (63% vs 85%). FDG-PET was about 74% accurate in predicting the extent of recovery within the next year, compared with 56% for fMRI.

Importantly, a third of the 36 patients diagnosed as behaviourally unresponsive on the CSR-R test who were scanned with FDG-PET showed brain activity consistent with the presence of some consciousness. Nine patients in this group subsequently recovered a reasonable level of consciousness.

According to Professor Laureys, "We confirm that a small but substantial proportion of behaviourally unresponsive patients retain brain activity compatible with awareness. Repeated testing with the CRS–R complemented with a cerebral FDG-PET examination provides a simple and reliable diagnostic tool with high sensitivity towards unresponsive but aware patients. fMRI during mental tasks might complement the assessment with information about preserved cognitive capability, but should not be the main or sole diagnostic imaging method."

The authors point out that the study was done in a specialist unit focusing on the diagnostic neuroimaging of disorders of consciousness and therefore roll out might be more challenging in less specialist units.

Commenting on the study Jamie Sleigh and Catherine Warnaby add, "From these data, it would be hard to sustain a confident diagnosis of unresponsive wakefulness syndrome solely on behavioural grounds, without PET imaging for confirmation…[This] work serves as a signpost for future studies. Functional brain imaging is expensive and technically challenging, but it will almost certainly become cheaper and easier. In the future, we will probably look back in amazement at how we were ever able to practise without it."

Explore further: PET predicts outcomes for patients with cervical spinal cord compression

More information: Paper: www.thelancet.com/journals/lan … (14)60042-8/abstract

Related Stories

PET predicts outcomes for patients with cervical spinal cord compression

September 4, 2013
For patients with degenerative cervical myelopathy, imaging with 18F-FDG positron emission tomography (PET) could act as a marker for a potentially reversible phase of the disease in which substantial clinical improvement ...

PET/CT bests gold standard bone marrow biopsy for diagnosis and prognosis of lymphoma patients

August 1, 2013
A more precise method for determining bone marrow involvement in patients with diffuse large B-cell lymphoma (DLBCL)—a key factor in tailoring patient management plans—has been identified by researchers in a study published ...

Can new diagnostic approaches help assess brain function in unconscious, brain-injured patients?

May 9, 2012
Disorders of consciousness such as coma or a vegetative state caused by severe brain injury are poorly understood and their diagnosis has relied mainly on patient responses and measures of brain activity. However, new functional ...

EEG can detect awareness in people previously thought to be in permanently vegetative state

November 9, 2011
A study published Online First by the Lancet shows that -- using a cheap, portable electroencephalography (EEG) device -- awareness can be detected in people previously thought to be in a permanently vegetative state. The ...

Combination of two imaging techniques allows new insights into brain function

August 26, 2013
The ability to measure brain functions non-invasively is important both for clinical diagnoses and research in Neurology and Psychology. Two main imaging techniques are used: positron emission tomography (PET), which reveals ...

PET more sensitive than CT for merkel cell carcinoma

May 15, 2012
(HealthDay) -- Fluorine-18-fluorodeoxyglucose (F-18-FDG) positron emission tomography (PET) is significantly more sensitive and equally specific compared with traditional computed tomography (CT) imaging for evaluation of ...

Recommended for you

Faulty support cells disrupt communication in brains of people with schizophrenia

July 20, 2017
New research has identified the culprit behind the wiring problems in the brains of people with schizophrenia. When researchers transplanted human brain cells generated from individuals diagnosed with childhood-onset schizophrenia ...

Scientists reveal how patterns of brain activity direct specific body movements

July 20, 2017
New research by Columbia scientists offers fresh insight into how the brain tells the body to move, from simple behaviors like walking, to trained movements that may take years to master. The discovery in mice advances knowledge ...

Team traces masculinization in mice to estrogen receptor in inhibitory neurons

July 20, 2017
Researchers at Cold Spring Harbor Laboratory (CSHL) have opened a black box in the brain whose contents explain one of the remarkable yet mysterious facts of life.

Scientists discover combined sensory map for heat, humidity in fly brain

July 20, 2017
Northwestern University neuroscientists now can visualize how fruit flies sense and process humidity and temperature together through a "sensory map" within their brains, according to new research.

New study reveals contrasts in how groups of neurons function during decision making

July 19, 2017
By training mice to perform a sound identification task in a virtual reality maze, researchers at Harvard Medical School and the Istituto Italiano di Tecnologia (IIT) have identified striking contrasts in how groups of neurons ...

Healthy heart in 20s, better brain in 40s?

July 19, 2017
Folks with heart-healthy habits in their 20s tend to have larger, healthier brains in their 40s—brains that may be better prepared to withstand the ravages of aging, a new study reports.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.