Differentiating ictal/subclinical spikes and waves in childhood absence epilepsy by spectral and network analyses: A pilot study

OBJECTIVE

Childhood absence epilepsy (CAE) is a disease with distinct seizure semiology and electroencephalographic (EEG) features. Differentiating ictal and subclinical generalized spikes and waves discharges (GSWDs) in the EEG is challenging, since they appear to be identical upon visual inspection. Here, spectral and functional connectivity (FC) analyses were applied to routine EEG data of CAE patients, to differentiate ictal and subclinical GSWDs.

METHODS

Twelve CAE patients with both ictal and subclinical GSWDs were retrospectively selected for this study. The selected EEG epochs were subjected to frequency analysis in the range of 1-30 Hz. Further, FC analysis based on the imaginary part of coherency was used to determine sensor level networks.

RESULTS

Delta, alpha and beta band frequencies during ictal GSWDs showed significantly higher power compared to subclinical GSWDs. FC showed significant network differences for all frequency bands, demonstrating weaker connectivity between channels during ictal GSWDs.

CONCLUSION

Using spectral and FC analyses significant differences between ictal and subclinical GSWDs in CAE patients were detected, suggesting that these features could be used for machine learning classification purposes to improve EEG monitoring.

SIGNIFICANCE

Identifying differences between ictal and subclinical GSWDs using routine EEG, may improve understanding of this syndrome and the management of patients with CAE.

Absence seizure provocation during routine EEG: Does position of the child during hyperventilation affect the diagnostic yield?

PURPOSE

When performed correctly, hyperventilation (HV) for three minutes provokes absence seizures in virtually all children, a finding suggestive of a diagnosis of childhood absence epilepsy (CAE). Interestingly, some children experience absence seizures while performing HV in the office yet do not experience absences during HV on subsequent routine EEG. In most instances, HV during routine EEG is performed in the supine position, while in the office HV is done with the child sitting-up. Therefore, we hypothesized that the position in which HV is performed may influence its yield in provoking absence seizures.

METHODS

We conducted a randomized multi-center controlled trial among children (4-10 years old) with suspected CAE. During a routine EEG, children were asked to perform HV twice, in the supine and sitting positions.

RESULTS

Twenty children (four males) diagnosed with CAE were included in the analysis. Seventeen of the 20 patients experienced absence seizures while sitting and 13 experienced seizures during supine HV (p = 0.031). All patients that had absence seizures during supine HV also had seizures during sitting HV. Among patients with absences in both positions, seizure duration was significantly shorter during sitting HV (mean 8.69 seconds) than during supine HV (mean 12 seconds) (p = 0.042). An opposite tendency was seen in the younger age group (4-7 years), with shorter seizures in the supine HV group (5.6 seconds supine, 7.57 seconds sitting, p = 0.019).

CONCLUSIONS

HV in the sitting position may increase the yield of provoking absence seizures during routine EEGs, thereby improving its sensitivity in the diagnosis of CAE.