LAUSR

A 28-year-old male developed episodes of tachycardia (150–170 beats per minute), fever (38.6 C), diaphoresis, tachypnea, and non-stereotypical episodes consistent of involuntary hip and foot flexion followed by arm flexion and neck extension 6 days after a suicide attempt by hanging, which caused cerebral anoxia. These episodes occurred spontaneously or provoked by touch, lasting 1 to 2 minutes (Video S1). He opened his eyes spontaneously but did not track and was not following any commands. Brain MRI demonstrated findings suggestive of anoxic brain injury (Fig. 1). No epileptiform activity was associated with these episodes as per 24-hr video electroencephalography (EEG). Neither fentanyl nor continuous intravenous infusion of dexmedetomidine eliminated the episodes. A CT scan of the chest suggested pneumonia, but blood cultures and COVID-19 testing by PCR were negative. The diagnosis of paroxysmal sympathetic hyperactivity (PSH) was made after excluding sepsis, epilepsy, pulmonary embolism, and other metabolic abnormalities. The abnormal episodes of motor hyperactivity disappeared without further relapses with a combination of gabapentin 300 mg three times a day, propranolol 20 mg three times a day, and clonidine 0.1 mg twice a day 6 days after their onset. He was discharged to a rehabilitation facility after a 21-day hospitalization. At a follow-up clinic visit 2 months after discharge, clonidine had been discontinued but aripiprazole (20 mg a day) was prescribed by his psychiatrist for bipolar disorder. He only had mild slowness in the right upper extremity on examination (Video S2). A repeat brain MRI showed attenuated persistence of thalamic hyperintensities. PSH is the preferred term for episodes of hyperadrenergic activity following severe acute brain injury. Initially, the disorder was considered epileptic, reported as “diencephalic seizures.” The response to intravenous morphine sulfate rather than to anticonvulsants and the absence of epileptiform activity on EEG warranted its reclassification as a sympathetic storm rather than an epileptic disorder. Sympathetic storms have been associated with posturing suggestive of dystonia (eg, PAID, for “paroxysmal autonomic instability with dystonia”). However, several clues suggest the term dystonia is inappropriate: the movements occur during states of wakeful unresponsiveness, are not sufficiently stereotypic between episodes, do not worsen by certain positions or tasks, and, by virtue of the setting in which they arise, cannot exhibit overflow phenomena or response to closed-loop sensory feedback. These features provide the rationale for using the generic term motor hyperactivity or pseudodystonia over dystonia. The most common etiologies of PSH are, in order of prevalence, traumatic brain injury, hypoxia, and stroke. Medical disorders such as pulmonary embolism and sepsis may mimic PSH by inducing a hyperadrenergic state. PSH may be more common in younger patients and has been associated with prolonged hospitalizations and higher use of critical care resources, such as tracheostomy. In contrast with the delirium-associated persistent agitation and picking-like behaviors, PSH movements are episodic, tend to be provoked by touch, and are uniquely associated with increased sympathetic activity. PSH can be treated with morphine sulfate but gabapentin, opioids, propranolol, or clonidine have been reported to reduce the frequency of episodes. Antidopaminergic medications are best avoided to minimize the risk of neuroleptic malignant syndrome, which can potentially mimic PSH (dysautonomia). Finally, avoidance of nociceptive stimuli is encouraged to prevent triggering sympathetic storms. In sum, PSH is a non-epileptic paroxysmal motor hyperactivity associated with sympathetic hyperactivity. The disorder can be treated with drugs that dampen the sympathetic tone. It is