Repetitive hyperbaric oxygen therapy for paroxysmal sympathetic hyperactivity after acute carbon monoxide poisoning

Delayed neuropsychological sequelae (DNS) are relatively common complications of acute carbon monoxide (CO) poisoning, and usually develop within several days to weeks after the initial clinical recovery from acute CO poisoning. DNS can consist of various symptoms such as memory loss, confusion, ataxia, seizures, urinary incontinence, fecal incontinence, emotional lability, disorientation, hallucinations, mutism, cortical blindness, psychosis, parkinsonism, gait disturbances, rigidity, bradykinesia, and other motor disturbances. Paroxysmal sympathetic hyperactivity (PSH) is a potentially life-threatening disease secondary to acute acquired brain injury. It is characterized by episodic and simultaneous paroxysmal increases in sympathetic and motor activities, not rare in patients with a severe traumatic brain injury. The term PSH is clinically more accurate than the previously used ones describing such conditions as non-stimulated tachycardia, hypertension, tachypnea, hyperthermia, external posturing, diaphoresis, and paroxysmal autonomic instability with dystonia. Development of PSH typically prolongs the length of hospital stay and potentially leads to a secondary brain injury or even death. To date, the occurrence of PSH in the DNS after acute CO poisoning has not been reported in the literature. Potential mechanisms underlying the development of DNS in the deep white matter of the brain are immune-related inflammation and vasodilatation. Repetitive hyperbaric oxygen therapy, combined with methylprednisolone administration, may inhibit DNS progression by inducing cerebral oxygenation, inhibiting inflammation, and reducing cerebral edema. Herein, we report three cases in which the patients recovered from the PSH as DNS after CO poisoning after receiving repetitive hyperbaric oxygen therapy.