Myoclonus is defined as a brief, sudden contraction or interruption of ongoing muscular activity, caused by abnormal electrical discharges in the central or peripheral nervous system (1). Its classification, based on the underlying physiology and the diversity of causes, guides therapeutic decisions (2). It can occur at any age, either as an isolated phenomenon or associated with other neurological diseases (3).

Myoclonus can be further classified by distribution (focal, multifocal and generalized), by provoking factors (spontaneous, reflex) or by site of generation (cortical, subcortical, spinal or peripheral) (4). A detailed clinical assessment is critical to determine the site of onset, patterns, sensitivity to stimuli, and associated neurological signs. This is supported by diagnostic tools such as electromyography (EMG), EEG-EMG polygraphy, jerk-locked back averaging, evoked potentials, and long-latency reflex (C-reflex) (1).

In children, myoclonus is often transient and underrecognized, particularly when associated with fever. Despite being described in literature (5–12), FM remains frequently misinterpreted, leading to unnecessary investigations and treatment. Prompt clinical recognition is therefore crucial to avoid misdiagnosis. This report presents a case of febrile generalized myoclonus in a previously healthy 1-year-old child, accompanied by a narrative review to support clinicians in identifying this rare condition, alongside video and audio material of the events.

An extensive literature search was conducted in PubMed in January 2025 to identify English-language case reports of pediatric FM. The search strategy employed keyword combinations using the terms: (febrile myoclonus) AND (“pediatric” OR “child” OR “infant” OR “toddler”), yielding a total of 115 articles. Inclusion criteria were case reports describing episodes of myoclonus occurring in pediatric patients during febrile illness. Exclusion criteria encompassed articles not written in English and those not relevant to the topic. After the screening, 9 articles were deemed suitable and included in the final analysis.

We present the case of a male patient, born at 40 + 1 weeks of gestational age via operative vaginal delivery. The APGAR scores were 9 at 1 min and 10 at 5 min. Pregnancy history and fetal ultrasound follow-up were unremarkable. Auxological parameters were within normal limits. Neurodevelopmental milestones were appropriately achieved according to the expected timeline. Past medical history included bronchiolitis requiring ventilatory support in the neonatal intensive care unit. Family and personal medical histories were negative for epilepsy or any other significant neurological disorder.

At 1 year of age the patient presented with paroxysmal episodes occurring during febrile peaks (39°C), predominantly when falling asleep. Upon presentation, the patient exhibited rhinitis and cough consistent with an upper respiratory tract infection. Blood tests and blood cultures were within normal limits, pharyngeal swab tested positive for Bocavirus. Neurological examination was otherwise unremarkable, and therefore lumbar puncture was not performed. These manifestations were characterized by rapid, massive muscle contractions involving all four limbs, sporadically associated with eye-rolling, followed by crying. During these episodes, altered mental status was observed. The episodes lasted a few seconds, occurred in clusters, resolving concomitantly with antipyretic administration and subsequent defervescence.

Given the high frequency of episodes initially interpreted as seizures, and the close succession of febrile peaks during recovery, a continuous infusion of midazolam at subanesthetic dose was initiated (0.04 mg/kg/h) but promptly discontinued due to sedation and suspicion of FM. After washout of the benzodiazepine, EEG recording during fever revealed a brief episode of muscle contractions not associated with epileptiform discharges (Figure 1a). The clinical features, combined with EEG findings, supported a diagnosis of a paroxysmal non-epileptic manifestation, specifically febrile generalized myoclonus.

Since admission, the patient experienced four episodes with similar characteristics. Follow-up EEG demonstrated normal background activity, regional differentiation, and normal sleep-phase architecture, without epileptiform activity (Figure 1). After resolution of the upper tract infection and defervescence no more paroxysmal episodes occurred. Audio and video recordings, along with EEG tracings collected during recovery, are included in this manuscript with informed consent from the patient's family (Supplementary Video S1). At last follow-up in July 2025 (1 year and 5 months of age) the child experienced additional myoclonus episodes isolated during febrile events, negative EEG and no neurological sequelae, including signs of neurodevelopmental stagnation or regression (Table 1).

This report is limited by its anecdotal nature, short follow-up (5 months), and lack of jerk-locked EEG or long-term EEG/video EEG. Although the clinical features and EEG findings suggest a benign course, longer follow-up is necessary to exclude progression to epileptic disorders. The literature lacks standardized diagnostic criteria for FM, with diagnosis primarily relying on clinical expertise and phenotypic observation.

FM is a rare, benign, and likely underdiagnosed paroxysmal event in children. Differentiating it from epileptic seizures is essential to avoid unnecessary treatments, as misdiagnosis may lead to prolonged use of antiseizure medications with potential adverse effects and challenges in discontinuation. Although follow-up is advisable, most cases resolve without sequelae. By reporting this case and reviewing the available evidence, we aim to raise awareness among clinicians and highlight the need for further research into the incidence and underlying mechanisms of FM.