How is maturation identified in the visual analysis of neonatal electroencephalogram (EEG)?

Updated: Aug 20, 2019
  • Author: Samuel Koszer, MD; Chief Editor: Selim R Benbadis, MD  more...
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Answer

Answer

Maturation: EEG maturation from PT to FT and beyond occurs in a predictable time-linked fashion. The observation that the maturation of the EEG is primarily dependent on the postconceptional age renders the EEG a valuable tool in assessing central nervous system physiological maturation.

  • A number of indices are used in determining whether the EEG is appropriate for the infant's postconceptional age. These indices include the percentages of interhemispheric synchrony during TA, amount of delta brushes in both REM and NREM states, and sleep-state transitions including concordance between EEG and other bioelectric and behavioral parameters.

  • The neonatal record is considered to have a pattern of dysmaturity when the background patterns lag behind postconceptional age by at least 2 weeks. Dysmaturity may be either transient or persistent.

  • A constellation of electroencephalographic and physiological information goes into determining whether a record is mature or not. The following criteria may be helpful in determining when an EEG is maturationally delayed:

    • By 32-34 weeks' postconceptional age, the background activity should have some periods of continuous activity as periods of better-organized REM and NREM states begin to emerge. The average interburst interval should be less than 20 seconds. The range of interhemispheric synchrony between bursts of the emerging TD varies between 50% and 70%. Delta brushes still abound, tending to localize more over rolandic and occipital areas. The high-voltage temporal theta of younger PT infants is less frequent, while lower voltage, multifocal, sharp transients occur between bursts. In the absence of an isoelectric reading, distinguishing immature records in this age group from those with more severe disturbances of background activity may be difficult.

    • By 34-36 weeks' postconceptional age, clear EEG distinction between REM and NREM states should be observed. REM should consist of a continuous pattern with mixed delta and theta waves of variable voltage (usually 30-100 µV). Delta brushes are present more frequently in NREM than in REM sleep. Interhemispheric synchrony of bursts of NREM TD ranges from 70-85%.

    • By 36-38 weeks, TD prevails in NREM sleep, and activity >20 µV is present during most of the interburst interval. Brief periods (< 3 s) of lower voltage activity still can be seen during the interburst interval. During REM sleep, abundant clusters of rapid eye movements, frequent body movements, decreased muscle tone, and irregular respiration are present. In NREM sleep, only rare eye movement, general body quiescence, increased muscle tone, and regular respirations (in the absence of pulmonary disease) are present. Interhemispheric synchrony of bursts in TD ranges from 85-95%. Delta brushes still occur but are diminished during NREM sleep, with an average of approximately 20 during every 5 minutes of REM sleep.

    • By 38-40 weeks' postconceptional age, the infant should cycle through clear sleep states. TA occurs during NREM sleep. Bursts are 90-100% synchronous (< 2 s difference in time of onset). Bursts and interburst intervals are of similar duration. Occurrence of delta brushes decreases, with only 1 or 2 during every 5 minutes of REM sleep.

    • By 40-42 weeks, no delta brushes are present. If present, delta brushes occur only during NREM sleep, at most 4 per 5-minute epoch. Complete interhemispheric synchrony between bursts of TA is observed. The infant should cycle through clear sleep states.

    • By 44 weeks, continuous slow-wave pattern should be predominant during NREM sleep.

    • By 48 weeks, TA should be minimal with NREM sleep dominated by high-voltage, slow-wave activity. Some sleep spindles also should emerge.


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