Improving the identification of High Frequency Oscillations
Rina Zelmann1, Maeike Zijlmans, Julia Jacobs
1Montreal Neurological Institute and Hospital, EEG Department, McGill University, Que., Canada. rina.zelmann@mail.mcgill.ca
Summary
Five minutes of recording provides stable measurements of High Frequency Oscillations (HFOs) and spikes in most epilepsy patients. This duration offers comparable information to longer intervals for identifying these events during sleep.
Area of Science:
- Neuroscience
- Epileptology
- Signal Processing
Background:
- High Frequency Oscillations (HFOs), encompassing Ripples (80-250Hz) and Fast Ripples (250-500Hz), are crucial biomarkers in epilepsy.
- Intracranial macroelectrodes are used to record HFOs in patients with intractable epilepsy.
- Determining the optimal recording duration for stable HFO measurement is essential for reliable analysis.
Purpose of the Study:
- To implement and validate a procedure for establishing the minimum recording duration required for stable High Frequency Oscillation (HFO) rate measurements.
- To assess the information content and channel ranking concordance using different recording durations.
- To provide methods for identifying when a stable measurement is not achieved.
Main Methods:
- Analysis of HFO and spike rates from intracranial macroelectrodes in 30 epilepsy patients.
- Computation of Kappa coefficient to determine concordance between different recording durations.
- Evaluation of information gained by increasing recording duration, focusing on HFO/spike rates and channel rankings.
Main Results:
- Kappa coefficients indicated good concordance for ripples (0.7), fast ripples (0.7), and spikes (0.67).
- Five minutes of recording yielded comparable rate information to 10 minutes in 90% of patients and similar channel rankings in 80%.
- A subset of patients (5/30) required 10-minute recordings for stable HFO or spike measurements.
Conclusions:
- A 5-minute recording interval is generally sufficient for obtaining stable and informative measurements of HFOs and spikes during slow-wave sleep.
- The study presents a validated procedure to assess the stability of HFO and spike measurements.
- This method aids in ensuring consistency between readers and evaluating the adequacy of selected recording intervals for both automatic and visual event identification.
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