Amelioration of pathological yawning after tracheostomy in a patient with locked‐in syndrome: a thermoregulatory approach – authors' reply

Sir, We are encouraged to read the Letter of Dr. Prasad [1] referring to the thermoregulatory approach for amelioration pathological yawning after tracheostomy in a patient with locked-in syndrome. As we pointed out in our original case report [2], although our patient s dead space was reduced by tracheostomy which may be one of the major factors capable of terminating the pathological yawning, the stimulated phrenic nerve influenced by vagus nerve stimulation during the surgery might also ameliorate pathological yawning in our patient. Besides, similar treatments using tracheostomy and cauterization were applied in the treatment of epilepsy in the literature [3]. Regardless of the patient s dead space we suggested that excessive yawning not only appears to be symptomatic of conditions that increase brain and/or core temperature, such as cerebral ischemia, traumatic brain injury, and sleep deprivation [1] but also might be secondary to peripherally phrenic nerve irritation like cardiac tamponade-related [4]. The patient s excessive yawning completely resolved immediately after emergency pericardiocentesis [4] which might be hard to explained as a result of the increase of brain and/or core temperature [1]. In other words, the cause of pathological yawning could be categorized as thermal-related or non-thermal-related and the treatment protocol would thus be different from each other. In summary, it seems that there should be three possible points of view on the termination of the pathological yawning: 1. Reduction of the dead space. 2. Vagus nerve stimulation (phrenic nerve irritation). 3. Thermoregulation.