Febrile myoclonus jerk in children with COVID-19 infection: letter to editor

Dear Editor The new coronavirus infection has spread rapidly around the world. The range of symptoms of this disease in children is from asymptomatic infection to severe respiratory or multiple systems failure, the common symptoms of which were different in each peak and in each strain. In Omicron strain fever without localize sign; involvement of the nervous system (seizures, headache, encephalopathy, etc.) is more common. Myoclonus caused by fever or an underlying infection (Para infectious myoclonic jerks) is a transient, sudden, and often benign finding. This finding is not common and is often not well diagnosed. This complication has been reported following fever from other viral infections, but its association with COVID-19 infection has not yet been established. We introduce two children with myoclonus caused by COVID-19 infection who were admitted to the emergency department of Ali Asghar Hospital in Tehran and were evaluated and treated. First patient was a 36-month-old girl with normal neurological development who admitted to the pediatric emergency department due to the onset of fever and suspicious movements from one hour before the visit. There has been a history of three generalized tonic-colonic seizures following fever. In the morning of the referral, she had a fever and shortly after the onset of the fever jumping movements of four limbs. According to the mother, she was conscious during the attack, not cyanotic, staring and it lasted about 20 to 30 seconds, after which she did not fall asleep. She had no complaints other than fever. At the time of admission, the patient was fully conscious, her vital signs were stable, and there was no evidence of meningeal stimulation. About 7 hours after the patient was referred to the emergency department, he had a similar attack. Second patient was a 23-month-old boy who referred to the pediatric emergency department with a complaint of fever at midnight and suspicious movements. A history of generalized myoclonic movements following fever has been diagnosed after complete evaluation. In terms of neurological development, except for speech delay, it has not had a positive point. About 10 hours after the onset of the fever, the frequency of his generalized myoclonus movements intensified. He had no complaints other than fever. At the time of admission, the patient was fully conscious, his vital signs were stable, and there was no evidence of meningeal stimulation. About 7 hours later, the patient showed another attack of generalized tonic-colonic seizures in the emergency department, which was not accompanied by cyanosis and urinary incontinence, and lasted about 20 seconds. The clinical features of our patients are similar to those described by previous authors. The age range was comparable to those developing febrile seizures (6 mo. to six y). None of the index patients had behavioral changes. The first patient had a history of febrile seizures. In most of the reported cases, the duration of myoclonic jerks varied from 15 min to several hours, lasting as long as a day in one patient. The incidence of fever and seizures and fever-induced myoclonus attacks appears to increase at this peak (2022March-April) of the disease. The outcome of febrile myoclonus seems to be similar to that of simple febrile seizures. All reported cases were healthy on follow-up with no recurrence of the myoclonus .The pathophysiology of febrile myoclonus is not well understood. Rothwell and Hopkins suggested that fever is regulated in the hypothalamus by cytokines induced by infection. Onoe and Nishigaki postulated that cytokines also modulate hypothalamic function and elicit the emotional changes, which so commonly accompany febrile myoclonus. Since fever and myoclonus do not always represent a benign disorder, infectious processes such as encephalitis and drug toxicity such as that seen with tricyclic depressant over-dose that cause both symptoms should be considered in the differential diagnosis. Diagnostic procedures such as a lumbar puncture or an EEG study are not indicated in the absence of previous abnormal neurological history or a family history of epilepsy in an otherwise healthy infant or child. However, these children must be closely followed up for recurrence of the symptoms especially for those occurring without fever. Continued reporting of febrile myoclonus is needed to improve awareness of the condition as a benign neurological symptom occurring occasionally during a febrile illness. Due to the different treatment and management of these two diagnoses, familiarity with the symptoms of each of them seems necessary. Also, given the concurrence of myoclonus attacks at the onset of fever, it may make sense to control the fever more effectively with the goal of stopping it completely and preventing it from escalating with NSAIDs or a higher but safe doses of acetaminophen.