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Myoclonic Epilepsy Beginning in Infancy or Early Childhood Clinical Presentation

  • Author: Michael C Kruer, MD; Chief Editor: Amy Kao, MD  more...
 
Updated: Mar 14, 2016
 

History

Once myoclonus is identified and confirmed to be associated with abnormal generalized discharges on EEG, it is important to ascertain the frequency and course of the patient’s myoclonus, as well as the time of onset. In order to better characterize the patient’s electroclinical syndrome, it is important to distinguish whether other seizure types co-occur, to carefully delineate neurodevelopmental progress (paying attention to evidence of regression), and to identify systemic manifestations of disease. Identification of a distinct epilepsy syndrome may guide diagnostic testing and management, and it may aid in prognostication and long-term care decisions.

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Physical Examination

Brief, abrupt myoclonic jerks typically occur several times a day, but they may or may not be observed during an office-based examination. Manifestations often include head nodding, abrupt abduction of the arms, or sudden falls. Eyelid or facial muscles are affected commonly, although axial myoclonic jerks are most common and occur in 90% of patients. The differential diagnosis of rapid, brief, hyperkinetic movements includes tics and stereotypies. As with many paroxysmal episodic disorders of childhood, in questionable cases, having caregivers videotape spells of concern may be helpful, particularly if direct observation is not possible.

Myoclonic seizures commonly occur on awakening, and some may be precipitated by photic stimuli. In neurodegenerative disorders, myoclonic jerks may be precipitated by abrupt stimuli. Rarely, myoclonic seizures occur continuously as myoclonic status epilepticus with partial preservation of consciousness. This is a particularly prominent feature of Alper syndrome associated with POLG1 mutations.[8]

Although myoclonic seizures may occur as the sole type of seizure in some patients, they more commonly are associated with other forms of generalized seizures. Generalized tonic-clonic seizures are most common. Brief generalized clonic seizures or unilateral clonic seizures also may be seen. Atypical absence seizures occur in 40%, and pure atonic seizures may also occur.

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Contributor Information and Disclosures
Author

Michael C Kruer, MD Assistant Professor, Departments of Pediatrics and Neurosciences, Sanford School of Medicine, University of South Dakota; Physician in Pediatric Neurology and Neurogenetics, Sanford Children's Specialty Clinic, Sanford Children's Hospital

Michael C Kruer, MD is a member of the following medical societies: American Academy for Cerebral Palsy and Developmental Medicine, American Academy of Neurology, American Academy of Pediatrics, American Society of Human Genetics, Child Neurology Society, Society for Neuroscience

Disclosure: Nothing to disclose.

Coauthor(s)

Raj D Sheth, MD Chief, Division of Pediatric Neurology, Nemours Children's Clinic; Professor of Neurology, Mayo College of Medicine; Professor of Pediatrics, University of Florida College of Medicine

Raj D Sheth, MD is a member of the following medical societies: American Academy of Neurology, American Academy of Pediatrics, American Epilepsy Society, American Neurological Association, Child Neurology Society

Disclosure: Nothing to disclose.

Chief Editor

Amy Kao, MD Attending Neurologist, Children's National Medical Center

Amy Kao, MD is a member of the following medical societies: American Academy of Neurology, American Epilepsy Society, Child Neurology Society

Disclosure: Have stock from Cellectar Biosciences; have stock from Varian medical systems; have stock from Express Scripts.

Acknowledgements

James J Riviello Jr, MD George Peterkin Endowed Chair in Pediatrics, Professor of Pediatrics, Section of Neurology and Developmental Neuroscience, Professor of Neurology, Peter Kellaway Section of Neurophysiology, Baylor College of Medicine; Chief of Neurophysiology, Director of the Epilepsy and Neurophysiology Program, Texas Children's Hospital

James J Riviello Jr, MD is a member of the following medical societies: American Academy of Pediatrics

Disclosure: Up To Date Royalty Section Editor

Francisco Talavera, PharmD, PhD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Reference Salary Employment

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