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Midline foci of epileptiform activity in children and neonates
Insights
Focal epileptogenic discharges from midline sagittal vertices (Fz, Cz, Pz) in children are often missed by standard EEG montages. These midline foci require specific electrode placement for accurate diagnosis, especially in cases with neuropathology.
Area of Science:
- Pediatric Neurology
- Clinical Neurophysiology
- Epileptology
Background:
- Focal epileptogenic discharges can arise from various brain regions, including midline sagittal vertices.
- Standard electroencephalography (EEG) montages may not always capture discharges from these specific midline locations.
- Accurate identification of epileptogenic foci is crucial for diagnosis and management of pediatric epilepsy.
Purpose of the Study:
- To investigate the clinical and electroencephalographic (EEG) characteristics of focal potentially epileptogenic discharges originating from midline sagittal vertices (Fz, Cz, Pz) in children.
- To determine the diagnostic yield of specific electrode placements for midline epileptogenic foci.
- To highlight the potential for misinterpretation of these discharges in standard EEG montages.
Main Methods:
- Prospective identification of 21 children with focal potentially epileptogenic discharge from midline sagittal vertices (Fz, Cz, Pz) out of 7,051 consecutive EEGs.
- Analysis of clinical data, including seizure types and patient age range (neonates to 13 years).
- Evaluation of EEG findings during wakefulness and sleep, noting the distribution of epileptogenic foci.
Main Results:
- Midline epileptogenic foci were identified in 21 children, with presentations including seizures, attention deficit disorder, psychomotor retardation, and headache.
- The majority of patients (13/21) had an identifiable etiology, with two cases showing mass lesions on CT scans.
- Midline foci were confined to Fz, Cz, and/or Pz in 6 of 17 older children, potentially missed by montages lacking vertex electrodes.
- In five children, midline foci spread to central-parietal regions, mimicking benign rolandic discharges and risking misinterpretation.
Conclusions:
- Focal discharges from midline sagittal vertices (Fz, Cz, Pz) are a distinct finding in pediatric EEG.
- Specific electrode placement including vertex electrodes is essential for detecting these midline epileptogenic foci.
- Misinterpretation of midline foci, particularly when they spread to adjacent regions, can occur and has significant implications given the high incidence of neuropathology in affected children.
Abstract:
We report the clinical and electroencephalographic (EEG) correlates of focal potentially epileptogenic discharge arising from midline sagittal vertices (Fz, Cz, Pz) in 21 children prospectively identified from among 7,051 consecutive EEGs recorded during a 27-month period. The patients range in age from neonates to 13 years. EEGs were obtained during evaluations for solitary or recurrent seizures (17/21), attention deficit disorder (2/21), psychomotor retardation (1/21), and headache (1/21). Clinical seizure types were diverse and included simple partial (5/17), complex partial (2/17), generalized tonic-clonic (4/17), mixed (2/17), and neonatal (4/17). The majority (13/21) of patients had an identifiable etiology for their disorder; CT scans verified mass lesions in two patients. Midline epileptogenic foci were present during wakefulness in 14 of 17 older children and restricted to sleep in the others. Sleep states were indeterminate in the four neonates. Midline foci were exquisitely confined to Fz, Cz, and/or Pz in 6 of 17 older children and would have been entirely missed by a recording montage that did not include vertex electrodes. In five other children, midline foci spread preferentially to the adjacent central-parietal regions and closely resembled the appearance of benign rolandic foci in the longitudinal EEG montages, a potentially serious cause of EEG misinterpretation in view of the high incidence of neuropathology in this patient group.