A Case of Delirium Following Bear‐Related Injury Treated With Yokukansan

Numerous injuries were caused by Asiatic black bears in Japan in 2025, with the highest number of incidents recorded in Akita Prefecture. Injuries inflicted by large wild animals such as black bears can be severe and life-threatening. These traumatic experiences may result in a wide range of psychoneurological symptoms, such as acute stress reactions, post-traumatic stress disorder, delirium, and insomnia. Therefore, the psychological and psychiatric effects must be considered early, with physical treatment provided for managing bear-related injuries [1, 2]. However, evidence supporting the appropriate pharmacological management of delirium in patients following wildlife-related trauma is limited. Yokukansan (YKS) is a traditional Japanese medicine that alleviates neuropsychiatric symptoms. YKS has been investigated for treating intensive care unit (ICU)-related and postoperative delirium. This report describes a patient with delirium following bear-related trauma, who experienced symptom improvement after YKS treatment, while acknowledging the interpretive limitations inherent to a single-case observation with concurrent pharmacotherapy. A 69-year-old man with a remote history of cerebral hemorrhage at 22 years of age encountered a bear while jogging. He was attacked prior to laying prone and sustained a facial injury. The patient was transported to a hospital and transferred to our institution by helicopter for comprehensive management. He had no known history of dementia, psychiatric illness, or alcohol abuse. The initial laboratory evaluation revealed no major electrolyte imbalance or systemic infection. Computed tomography revealed bilateral open zygomatic and nasal bone fractures. Subcutaneous emphysema of the neck, associated with the facial lacerations, was also observed, and an emergency tracheostomy was performed. The wound was irrigated and debrided under general anesthesia. The patient was postoperatively admitted to the ICU and placed on mechanical ventilation. On Day 2 of hospitalization, mechanical ventilation was discontinued, and oxygen was administered via a nasal cannula. At approximately 6:00 p.m., the patient exhibited increased agitation, requiring dexmedetomidine (0.6 mg/kg/h) for sedation. The patient was discharged from the ICU on Day 4. That night, he reported visual disturbances he described as “seeing strange things,” and 5 mg haloperidol was administered. On Day 5, abnormal behaviors such as crawling on the bed and removing the nasogastric tube were observed, and 5 mg lemborexant was administered twice to treat sleep disturbance. On Day 6, persistent nocturnal awakening prompted administering 25 mg trazodone. However, the patient experienced visual and auditory hallucinations. Delirium was clinically diagnosed by the treating physicians based on acute onset, fluctuating attention disturbance, agitation, and perceptual abnormalities, consistent with the diagnostic features in the DSM-5. However, standardized delirium assessment tools were not prospectively applied. On Day 8, the patient showed marked irritability in response to environmental stimuli such as nurse call buttons and monitor sounds. YKS (TJ-54; Tsumura & Co., Tokyo, Japan) was initiated at 7.5 g/day, divided into three doses. On Day 9, the patient achieved adequate sleep with lemborexant monotherapy, and the abnormal nocturnal behaviors ceased. On Day 10, the tracheostomy tube was replaced with a speech cannula. As delirium symptoms did not recur, YKS was discontinued on Day 10 (Figure 1). YKS modulates multiple neurotransmitter systems including the serotonergic, glutamatergic, and gamma-aminobutyric acid pathways. These pharmacological effects may help mitigate agitation, hallucinations, and other neuropsychiatric symptoms [3]. Previous findings on the role of YKS in treating delirium in the ICU and postoperative settings are mixed [4]. Some studies suggested YKS is beneficial in treating delirium; however, systematic reviews yielded inconsistent conclusions, underscoring the need for cautious interpretation and individualized clinical decision-making [5]. In our case, the delirium symptoms improved after initiating YKS treatment. However, the patient received multiple psychotropic medications prior to YKS, and the synergistic or delayed effects of these treatments cannot be excluded. Additionally, the course of delirium often fluctuates, and spontaneous improvement is possible. Therefore, the causality of the improvement in symptoms cannot be definitively attributed to YKS based on the observations from a single case. We do not suggest using YKS as a replacement for established delirium management strategies. Rather, the case highlights a potential adjunctive option in select patients in whom symptoms persist despite the use of conventional measures, particularly in complex trauma settings associated with considerable psychological stress. Another limitation of this case is that standardized delirium assessment tools were not used, which limited the objectivity of the evaluation and the comparability of the case with those in the literature. The generalizability of the findings is inherently restricted as this is a single case report. In this case, delirium following severe bear-related trauma improved after initiating YKS as part of a multimodal management strategy. Although the temporal association is noteworthy, the concurrently administered pharmacotherapy and the natural variability in delirium preclude drawing definitive causal inferences. YKS shows potential as an adjunctive option in selected cases; however, further systematic investigations are required to clarify the role of YKS in treating delirium. We thank Editage (https://www.editage.jp) for proofreading the manuscript. The authors have nothing to report. The authors have nothing to report. Informed consent was obtained from the patient and his family members. Hajime Nakae received honoraria from the Tsumura & Co. The other authors declare no conflicts of interest. Research data are not shared.