Objective: We aimed to investigate clinical and electrophysiological features myoclonus in the pediatric age group.

Background: Myoclonus is a movement disorder characterized by sudden, brief and irregular jerks. One classification groups myoclonus according to its origin in the nervous system. Myoclonus may develop secondary to various genetic causes, neurodegenerative disorders or systemic diseases.

Methods: We retrospectively assessed the medical records of patients who were referred to the electromyography laboratory. From these records, we included all patients who were under the age of 18 years and in whom it was confirmed by polymyography. Demographic features (age, gender), and clinical features (clinical diagnosis, accompanying neurological findings including cognitive findings, systemic findings) were retrieved from the medical records. In all patients, surface electromyography during rest, arms outstretched, goal-directed movement, brainstem reflexes and long-latency reflexes (LLR) were done. NMyoclonus was classified based on clinical and electrophysiological findings.

Results: There were 27 patients (16 male, 59.3%) who fulfilled the inclusion criteria. Mean age was 14.5±3.4 years. The clinical diagnoses were subacute sclerosing panencephalitis (SSPE, n=7), epilepsies including progressive myoclonic epilepsies (n=9), movement disorders and epilepsy attributed to mitochondrial mutation (n=2), myoclonus-dystonia (n=1), catatonia (n=1), demyelinating disease (n=1), a genetic motor neuron disorder (n=1). In five children, no final diagnosis was done. Types of myoclonus were cortical myoclonus (n=14) and probable cortico-subcortical myoclonus involving upper extremities (n=13). Eight out of 14 patients with cortical myoclonus and four out of the remaining patients displayed reflex sensitivity. There was polyminimyoclonus in six cases which had a tremor-like appearance in the distal parts of extremities. Two patients with SSPE (28.6%) had cortical myoclonus. Patient with myoclonus-dystonia had short-duration myoclonic bursts without C reflex or high-amplitude LLRs suggesting cortico-subcortical subtype.

Conclusions: Myoclonus in the pediatric age in our cohort was mostly associated with SSPE and epilepsy. The frequency of movement disorders such as myoclonus-dystonia is rare in this age group in comparison to epilepsy syndromes. Different types of myoclonus in SSPE are seen probably in relation to the level of involvement.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/myoclonus-in-the-pediatric-age-group-a-retrospective-analysis-of-clinical-and-electrophysiological-characteristics-of-patients-referred-to-an-electrophysiology-laboratory/