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Pediatric Oncall Journal

Isolated Myoclonus Following Dengue Infection 04/08/2020 00:00:00

Isolated Myoclonus Following Dengue Infection

Sai Chandar Dudipala, Krishna Chaithanya B.
Department of Pediatrics, Star Children’s Hospital, Karim Nagar, Telangana, India.

Sai Chandar Dudipala, MD (Pediatrics), Fellowship in Pediatric Neurology, Consultant Pediatric Neurologist, Department of Pediatrics, Star children’s hospital, Karim Nagar, Telangana, India 505001.
Myoclonus is a sudden, brief, involuntary muscle jerk. Myoclonus is highly prevalent but rarely occurs as an isolated finding in children. It can be due to various etiologies like hypoxia, metabolic disorders, storage disorders, post-infectious, and neurodegenerative disorders. In the literature, myoclonus has been reported with viral encephalitis, upper respiratory tract infections, or streptococcal infection. Opsoclonus myoclonus syndrome can develop after dengue infection. We present an 11 years old girl with isolated myoclonus following dengue viral infection which was a transient benign phenomenon and it completely recovered over a period of time.
post infectious, myoclonus, dengue
Myoclonus is defined as a sudden, brief, shock-like involuntary movement caused by muscular contractions or interruptions of tonic muscle activity.1 This movement disorder affects all the age groups and can appear as an isolated finding or as a symptom of different diseases.2 Myoclonus has been described in acute encephalitis due to a variety of viral agents which either directly invade the central nervous system (CNS) or by an immunological process (post-infectious).3 In either case, the clinical picture is of an acute illness characterized by seizures, alterations in consciousness, and focal neurological signs. Dengue viral infection is one of the common viral agents causing encephalitis and other neurological complications. Neurological manifestations of dengue infection are variable from encephalitis to transient opsoclonus myoclonus syndrome (OMS)4,5 Here, we present an 11 years old girl with myoclonus, as an isolated phenomenon, after dengue infection without any features of encephalitis or OMS.
Case Report
An 11 years old girl presented with myoclonic jerking of both upper limbs and neck for one month. She was recovered from dengue fever (Dengue ELISA IgM positive) one week before the onset of jerks. Initially, child had 2-3 jerks per day, involving upper limbs only, each lasting for up to 20 seconds, without loss of consciousness or other epileptic phenomena. These jerks gradually increased in frequency up to 10-15 episodes per hour and spread to the neck also. She was otherwise normal between attacks. Jerks were always present in the wake state only. She was the only child of non-consanguineous parents with normal developmental history. There was no family history of similar illness. She had completed her immunization according to the Indian Academy of Pediatrics (IAP) schedule. General and systemic examination revealed no abnormalities. The child’s weight was 32 kg. Magnetic resonance imaging (MRI) of the brain was normal. Electroencephalogram (EEG) showed runs of polyspike/spikes at about 5/6 per second, associated with the episodes of jerking. Cerebrospinal fluid (CSF) analysis was normal. CSF measles IgG antibody was negative. The anti-nuclear antibody profile was negative. Serum copper and ceruloplasmin levels were normal. The child was treated with clonazepam. Treatment with clonazepam improved the jerks but made her very drowsy. When clonazepam was discontinued, the jerks became more intense and exacerbated to noise, sudden movement. She was advised to take sodium valproate 300 mg two times a day and piracetam 400 mg three times a day. She showed an excellent response to these drugs and the myoclonus subsided almost completely in four months. Valproate was tapered and stopped slowly over four months. The child has remained normal without any jerks for the past six months.
Myoclonus is a paroxysmal event occurring in a great amount of disorders of different nature. Myoclonic movements have many possible etiologies, anatomic sources, and pathophysiologic features. Myoclonus is often symptomatic, related to several conditions such as hypoxia, infective encephalitis, metabolic disorders, drug-induced and toxic disorders, storage diseases, and neurodegenerative disorders.2 However, myoclonic jerks can also appear as a transitory phenomenon after an infectious illness such as influenza or chicken pox6 or gastrointestinal infections by Enterovirus 717 and even after infections of the upper respiratory tract or influenza-like syndromes.8 The interval between the initial illness and onset of myoclonus is short. Myoclonus developed in our patient following dengue viral infection. In our patient, the interval to the onset of myoclonus was one week.
Neurological features of dengue infection have been reported in 0.5% to20% of patients in recent years.9,10 Neurological complications of dengue virus infection are classified into three categories based on pathogenesis as proposed by Murthy, Marzia and colleagues:1 metabolic disturbance, e.g., encephalopathy;2 viral invasion, including encephalitis, meningitis, myositis, and myelitis;3 autoimmune reactions, including acute disseminated encephalomyelitis, neuromyelitis optica, optic neuritis, myelitis, encephalopathy, and Guillain-Barre syndrome (GBS).9,10 Verma et al reported two patients with OMS followed by dengue viral infection which completely recovered on follow up period.5 Our patient had only isolated myoclonus without any other manifestations. As per the literature review, this is the first report of isolated myoclonus followed by dengue viral infection.
Why some patients should develop myoclonus without clinical or investigative evidence of structural damage of the CNS following non-specific or uncomplicated infectious illnesses is unclear. The pathophysiological origin of the myoclonus in our case is uncertain. As might be expected therefore it appears that post-infectious myoclonus is a heterogeneous entity and probably an immune-mediated phenomenon.
Myoclonic jerks can occur as isolated phenomenon, after a dengue viral infection without any features of encephalitis or OMS.

Contributors: SC- Data collection, literature review, and preparation of the manuscript, guarantor of the article. KC- Literature review and follow up, Conceptualized, and supervised the data, critically reviewed the article.
Compliance with Ethical Standards
Funding None
Conflict of Interest None
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Cite this article as:
Dudipala S C, B K C. Isolated Myoclonus Following Dengue Infection. Pediatr Oncall J. 2020;17. doi: 10.7199/ped.oncall.2020.25
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