Olfactory Stimulation and the Diagnosis of Patients With Disorders of Consciousness: A Double-Blind, Randomized Clinical Trial

Olfactory response is a potential sign of consciousness: electroencephalogram findings

Objective

This study aimed to explore whether olfactory response can be a sign of consciousness and represent higher cognitive processing in patients with disorders of consciousness (DoC) using clinical and electroencephalogram data.

Methods

Twenty-eight patients with DoC [13 vegetative states (VS)/unresponsive wakefulness syndrome (UWS) and 15 minimally conscious states (MCS)] were divided into two groups: the presence of olfactory response (ORES) group and the absence of olfactory response (N-ORES) group according to behavioral signs from different odors, i.e., vanillin, decanoic acid, and blank stimuli. We recorded an olfactory task-related electroencephalogram (EEG) and analyzed the relative power and functional connectivity at the whole-brain level in patients with DoC and healthy controls (HCs). After three months, the outcomes of DoC patients were followed up using the coma recovery scale-revised (CRS-R).

Results

A significant relationship was found between olfactory responses and the level of consciousness (χ²(1) = 6.892, p = 0.020). For olfactory EEG, N-ORES patients showed higher theta functional connectivity than ORES patients after stimulation with vanillin (p = 0.029; p = 0.027). Patients with N-ORES showed lower alpha and beta relative powers than HCs at the group level (p = 0.019; p = 0.033). After three months, 62.5% (10/16) of the ORES patients recovered consciousness compared to 16.7% (2/12) in the N-ORES group. The presence of olfactory response was significantly associated with an improvement in consciousness (χ²(1) = 5.882, p = 0.023).

Conclusion

Olfactory responses should be considered signs of consciousness. The differences in olfactory processing between DoC patients with and without olfactory responses may be a way to explore the neural correlates of olfactory consciousness in these patients. The olfactory response may help in the assessment of consciousness and may contribute to therapeutic orientation.

Study protocol: Developing telephone follow-up scale for patients with disorders of consciousness

Background

The significant lack of rehabilitation prognostic data is the main reason that affects the treatment decision-making and ethical issues of patients with disorders of consciousness (DoC). Currently, the clinic's consciousness assessment tools cannot satisfy DoC patients' follow-up needs.

Objective

The purpose of this study is to construct a sensitive, professional, and simple telephone follow-up scale for DoC patients to follow up on the prognosis, especially the recovery of consciousness, of prolonged DoC patients transferred to community hospitals or at home.

Methods

This study is to adopt expert consultation to construct and to verify the validity and feasibility of the scale on-site.

Conclusion

At present, there is a strong demand for portable, accurate, and easily operated scales. It is helpful to improve the rehabilitation data of prolonged DoC patients and provide more basis for their treatment and rehabilitation.