Israeli scientists have developed a “sniff test” that they say can predict the likelihood that an unconscious brain-injured person will regain consciousness in the future.
The study, conducted by researchers from the Weizmann Institute at the Loewenstein Hospital Rehabilitation Center in Ra’anana, observed how patients who were defined as unconscious and unresponsive reacted to smells with a change in their nasal airflow pattern, Weizmann Institute said in a statement last month.
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The findings were published in the scientific journal Nature in late April.
According to the study, 100 percent of the unconscious brain-injured patients who responded to the “sniff test” later regained consciousness during the four-year study period.
The scientists believe that this simple, inexpensive test can aid doctors in accurately diagnosing and determining treatment plans according to the patients’ degree of brain injury.
Dr. Anat Arzi, who began the research during her doctoral studies in the group of Prof. Noam Sobel of the Weizmann Institute of Science’s Neurobiology Department, and continued it as part of her postdoctoral research at the University of Cambridge’s Department of Psychology, explained why it is important to determine the patient’s degree of consciousness.
Dr. Anat Arzi led the sniff test research. Courtesy.
One of the challenges in patients with severe brain injury is that “it’s really difficult to tell sometimes whether the person is conscious or unconscious,” she tells NoCamels.
So how do you know if someone is consciously aware following a severe brain injury? This is the task, Dr. Arzi says. The gold standard diagnostic tool to assess patients with a disorder of consciousness is the Coma Recovery Scale (Revised) she explains. This is a battery of tests that are conducted in order to see if the patient has any type of behavioral response to stimuli. Responses include eye movements, turning the head towards a sound, or tone of voice, or a response to pain.
Dr. Arzi describes the differences in levels of consciousness: the patient could be in a vegetative state — unresponsive and unaware of themselves and the external environment — or minimally conscious, meaning they have partial preservation of conscious awareness.
“Because it’s so challenging, the misdiagnosis rates could be relatively high,” she tells NoCamels, noting that current diagnostic tests can lead to incorrect diagnosis in as much as 40 percent of cases.
“Misdiagnosis can be critical as it can influence the decision of whether to disconnect patients from life support machines,” said Dr. Arzi sin a Weizmann Institute statement.
With regard to treatment, “if it is judged that a patient is unconscious and doesn’t feel anything, physicians may not prescribe them painkillers that they might need,” she explains.
How does the sniff test work?
Dr. Arzi says there are ways to can scan the brain activity of the patient through an MRI or an EEG (Electroencephalogram) that can uncover cases where the person appears unconscious but is actually conscious.
The problem is that “these procedures are relatively expensive, and many times require that the patient would have to move to another location, which could be complicated or risky for some patients,” she notes.