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Prevalence and etiology of false normal aEEG recordings in neonatal hypoxic-ischaemic encephalopathy.

Marics G, Csekő A, Vásárhelyi B, Zakariás D, Schuster G, Szabó M - BMC Pediatr (2013)

Bottom Line: High frequency component (HFC) was found as a cause of normal appearing aEEG in 10 neonates.HFC disappeared while P and MF decreased significantly upon NDMR administration in each observed case.High frequency EEG artifacts suggestive of shivering were found to be the most common cause of false normal aEEG in hypothermic neonates while high voltage ECG artifacts are less common.

View Article: PubMed Central - HTML - PubMed

Affiliation: First Department of Pediatrics, Semmelweis University, Budapest, Bókay u, 53-54, H-1083, Hungary. marics.gabor@gmail.com.

ABSTRACT

Background: Amplitude-integrated electroencephalography (aEEG) is a useful tool to determine the severity of neonatal hypoxic-ischemic encephalopathy (HIE). Our aim was to assess the prevalence and study the origin of false normal aEEG recordings based on 85 aEEG recordings registered before six hours of age.

Methods: Raw EEG recordings were reevaluated retrospectively with Fourier analysis to identify and describe the frequency patterns of the raw EEG signal, in cases with inconsistent aEEG recordings and clinical symptoms. Power spectral density curves, power (P) and median frequency (MF) were determined using the raw EEG. In 7 patients non-depolarizing muscle relaxant (NDMR) exposure was found. The EEG sections were analyzed and compared before and after NDMR administration.

Results: The reevaluation found that the aEEG was truly normal in 4 neonates. In 3 neonates, high voltage electrocardiographic (ECG) artifacts were found with flat trace on raw EEG. High frequency component (HFC) was found as a cause of normal appearing aEEG in 10 neonates. HFC disappeared while P and MF decreased significantly upon NDMR administration in each observed case.

Conclusion: Occurrence of false normal aEEG background pattern is relatively high in neonates with HIE and hypothermia. High frequency EEG artifacts suggestive of shivering were found to be the most common cause of false normal aEEG in hypothermic neonates while high voltage ECG artifacts are less common.

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Related in: MedlinePlus

High frequency component (HFC) on EEGs. A and D shows normal like background pattern before NDMR administration. Pre-NDMR raw EEG shows HFC (B,E), with delta, theta activity (B) and with a burst (E). Post-NDMR EEG turned to abnormal, HFC disappeared (C,F).
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Figure 3: High frequency component (HFC) on EEGs. A and D shows normal like background pattern before NDMR administration. Pre-NDMR raw EEG shows HFC (B,E), with delta, theta activity (B) and with a burst (E). Post-NDMR EEG turned to abnormal, HFC disappeared (C,F).

Mentions: The second part of the study focused on a subpopulation of neonates with normal appearing aEEG background activity, which was inconsistent with the clinical signs and symptoms of encephalopathy. Detailed retrospective reevaluation of the raw EEG recordings with Fourier analysis was performed to identify and describe the frequency patterns of the raw EEG signal. Presence of dominant delta and theta waves was considered as normal, while presence of high frequency components (HFC) with or without delta and theta waves was suspected as false normal (Figures 2, 3). HFC was defined as at least 20 peaks per seconds with amplitudes above 5 μV on raw EEG, which refers to an activity above 10 Hz. In each case, a 10 minutes long digital raw EEG sample was exported and power spectral density (PSD) was computed by Fast Fourier Transformation [12,13] based on twenty randomly selected 6 seconds long periods. The EEG activity was filtered below 0.5 Hz. The power spectrum was limited to 0–50 Hz. In each case we determined the power (P) and the median frequency (MF) in the following frequency ranges: 0–50 Hz, 10–50 Hz. P is the area under PSD curves and MF is the frequency where the power is equal to 50 percent of P 0–50. For a more accurate interpretation see Figure 4. Data regarding NDMR administration, ordered by the attending clinician, were retrieved from the medical records. Samples of EEG recordings were exported exactly 5 minutes before and 5 minutes after the drug exposure and we compared pre- and post-NDMR data.


Prevalence and etiology of false normal aEEG recordings in neonatal hypoxic-ischaemic encephalopathy.

Marics G, Csekő A, Vásárhelyi B, Zakariás D, Schuster G, Szabó M - BMC Pediatr (2013)

High frequency component (HFC) on EEGs. A and D shows normal like background pattern before NDMR administration. Pre-NDMR raw EEG shows HFC (B,E), with delta, theta activity (B) and with a burst (E). Post-NDMR EEG turned to abnormal, HFC disappeared (C,F).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4222766&req=5

Figure 3: High frequency component (HFC) on EEGs. A and D shows normal like background pattern before NDMR administration. Pre-NDMR raw EEG shows HFC (B,E), with delta, theta activity (B) and with a burst (E). Post-NDMR EEG turned to abnormal, HFC disappeared (C,F).
Mentions: The second part of the study focused on a subpopulation of neonates with normal appearing aEEG background activity, which was inconsistent with the clinical signs and symptoms of encephalopathy. Detailed retrospective reevaluation of the raw EEG recordings with Fourier analysis was performed to identify and describe the frequency patterns of the raw EEG signal. Presence of dominant delta and theta waves was considered as normal, while presence of high frequency components (HFC) with or without delta and theta waves was suspected as false normal (Figures 2, 3). HFC was defined as at least 20 peaks per seconds with amplitudes above 5 μV on raw EEG, which refers to an activity above 10 Hz. In each case, a 10 minutes long digital raw EEG sample was exported and power spectral density (PSD) was computed by Fast Fourier Transformation [12,13] based on twenty randomly selected 6 seconds long periods. The EEG activity was filtered below 0.5 Hz. The power spectrum was limited to 0–50 Hz. In each case we determined the power (P) and the median frequency (MF) in the following frequency ranges: 0–50 Hz, 10–50 Hz. P is the area under PSD curves and MF is the frequency where the power is equal to 50 percent of P 0–50. For a more accurate interpretation see Figure 4. Data regarding NDMR administration, ordered by the attending clinician, were retrieved from the medical records. Samples of EEG recordings were exported exactly 5 minutes before and 5 minutes after the drug exposure and we compared pre- and post-NDMR data.

Bottom Line: High frequency component (HFC) was found as a cause of normal appearing aEEG in 10 neonates.HFC disappeared while P and MF decreased significantly upon NDMR administration in each observed case.High frequency EEG artifacts suggestive of shivering were found to be the most common cause of false normal aEEG in hypothermic neonates while high voltage ECG artifacts are less common.

View Article: PubMed Central - HTML - PubMed

Affiliation: First Department of Pediatrics, Semmelweis University, Budapest, Bókay u, 53-54, H-1083, Hungary. marics.gabor@gmail.com.

ABSTRACT

Background: Amplitude-integrated electroencephalography (aEEG) is a useful tool to determine the severity of neonatal hypoxic-ischemic encephalopathy (HIE). Our aim was to assess the prevalence and study the origin of false normal aEEG recordings based on 85 aEEG recordings registered before six hours of age.

Methods: Raw EEG recordings were reevaluated retrospectively with Fourier analysis to identify and describe the frequency patterns of the raw EEG signal, in cases with inconsistent aEEG recordings and clinical symptoms. Power spectral density curves, power (P) and median frequency (MF) were determined using the raw EEG. In 7 patients non-depolarizing muscle relaxant (NDMR) exposure was found. The EEG sections were analyzed and compared before and after NDMR administration.

Results: The reevaluation found that the aEEG was truly normal in 4 neonates. In 3 neonates, high voltage electrocardiographic (ECG) artifacts were found with flat trace on raw EEG. High frequency component (HFC) was found as a cause of normal appearing aEEG in 10 neonates. HFC disappeared while P and MF decreased significantly upon NDMR administration in each observed case.

Conclusion: Occurrence of false normal aEEG background pattern is relatively high in neonates with HIE and hypothermia. High frequency EEG artifacts suggestive of shivering were found to be the most common cause of false normal aEEG in hypothermic neonates while high voltage ECG artifacts are less common.

Show MeSH
Related in: MedlinePlus