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Asymmetric hypsarrhythmia: clinical electroencephalographic and radiological findings
I Drury1, A Beydoun, E A Garofalo
1EEG Laboratory, University of Michigan Medical School, Ann Arbor.
Insights
Asymmetric hypsarrhythmia in infantile spasms (IS) affects 23% of cases. Identifying focal hemispheric abnormalities, even subtle ones, is crucial for successful surgical treatment in children with IS.
Area of Science:
- Pediatric Neurology
- Clinical Neurophysiology
- Epileptology
Background:
- Infantile spasms (IS) with hypsarrhythmia can present with focal neurological findings.
- Asymmetric hypsarrhythmia, a specific EEG pattern, is observed in a subset of these children.
- Identifying the underlying cause and localization of epileptogenic activity is critical for treatment.
Purpose of the Study:
- To investigate the prevalence and characteristics of asymmetric hypsarrhythmia in children with infantile spasms.
- To correlate EEG findings with clinical and imaging data in symptomatic IS.
- To assess the significance of focal hemispheric abnormalities in the context of IS management.
Main Methods:
- Retrospective analysis of EEG data from 26 children diagnosed with hypsarrhythmia and IS.
- Review of clinical examinations, neuroimaging studies, and patient outcomes.
- Classification of hypsarrhythmia as symmetric or asymmetric based on EEG findings.
Main Results:
- Asymmetric hypsarrhythmia was identified in 23% (6 out of 26) of the studied children.
- All 6 children with asymmetric hypsarrhythmia had symptomatic IS, often associated with structural brain abnormalities.
- Focal EEG abnormalities correlated with lesion location in most cases, though contralateral findings were also noted.
Conclusions:
- Asymmetric hypsarrhythmia is a significant finding in a notable proportion of infantile spasms cases.
- EEG is valuable in detecting focal hemispheric abnormalities that may not be clinically or radiologically apparent.
- Early identification of focal abnormalities through EEG is essential for guiding potential surgical interventions in IS.
Abstract:
Twenty-six children (16 boys and 10 girls) with hypsarrhythmia and infantile spasms (IS) were studied at the University of Michigan EEG Laboratory in a 4-year period. Six (2 boys, 4 girls), had asymmetric hypsarrhythmia with a preponderance of both slowing and epileptiform activity over one hemisphere. All 6 had the symptomatic form of IS, 4 with dysplastic conditions, 1 with porencephaly from a cerebral infarct, and 1 with hypoxicischemic encephalopathy. Five children had focal abnormalities on either physical examination or imaging studies. Four had the highest amplitude slowing and most epileptiform activity ipsilateral to the lesion, in 1, it was contralateral. Asymmetric hypsarrhythmia constituted 23% of cases with hypsarrhythmia examined at our EEG laboratory. The significant success in surgical therapy for some children with IS indicates the importance of identifying focal hemispheric abnormalities even if they are not apparent clinically. EEG may suggest focal changes not detected clinically or radiologically.