Olfactory sniffing signals consciousness in unresponsive patients with brain injuries

Anat Arzi (), Liron Rozenkrantz, Lior Gorodisky, Danit Rozenkrantz, Yael Holtzman, Aharon Ravia, Tristan A. Bekinschtein, Tatyana Galperin, Ben-Zion Krimchansky, Gal Cohen, Anna Oksamitni, Elena Aidinoff, Yaron Sacher and Noam Sobel ()
Additional contact information
Anat Arzi: University of Cambridge
Liron Rozenkrantz: Weizmann Institute of Science
Lior Gorodisky: Weizmann Institute of Science
Danit Rozenkrantz: Loewenstein Hospital Rehabilitation Center
Yael Holtzman: Weizmann Institute of Science
Aharon Ravia: Weizmann Institute of Science
Tristan A. Bekinschtein: University of Cambridge
Tatyana Galperin: Loewenstein Hospital Rehabilitation Center
Ben-Zion Krimchansky: Loewenstein Hospital Rehabilitation Center
Gal Cohen: Loewenstein Hospital Rehabilitation Center
Anna Oksamitni: Loewenstein Hospital Rehabilitation Center
Elena Aidinoff: Loewenstein Hospital Rehabilitation Center
Yaron Sacher: Loewenstein Hospital Rehabilitation Center
Noam Sobel: Weizmann Institute of Science

Nature, 2020, vol. 581, issue 7809, 428-433

Abstract: Abstract After severe brain injury, it can be difficult to determine the state of consciousness of a patient, to determine whether the patient is unresponsive or perhaps minimally conscious1, and to predict whether they will recover. These diagnoses and prognoses are crucial, as they determine therapeutic strategies such as pain management, and can underlie end-of-life decisions2,3. Nevertheless, there is an error rate of up to 40% in determining the state of consciousness in patients with brain injuries4,5. Olfaction relies on brain structures that are involved in the basic mechanisms of arousal6, and we therefore hypothesized that it may serve as a biomarker for consciousness7. Here we use a non-verbal non-task-dependent measure known as the sniff response8–11 to determine consciousness in patients with brain injuries. By measuring odorant-dependent sniffing, we gain a sensitive measure of olfactory function10–15. We measured the sniff response repeatedly over time in patients with severe brain injuries and found that sniff responses significantly discriminated between unresponsive and minimally conscious states at the group level. Notably, at the single-patient level, if an unresponsive patient had a sniff response, this assured future regaining of consciousness. In addition, olfactory sniff responses were associated with long-term survival rates. These results highlight the importance of olfaction in human brain function, and provide an accessible tool that signals consciousness and recovery in patients with brain injuries.

Date: 2020
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DOI: 10.1038/s41586-020-2245-5

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