Median Power Frequency of Electroencephalogram (EEG)

What This Measurement Represents

The EEG records electrical activity from the brain. When that activity is analyzed mathematically, power can be distributed across a range of frequencies. The median power frequency is the frequency that splits this power distribution into two equal halves—half of the power falls at lower frequencies and half at higher frequencies. It gives a single number that reflects how "fast" or "slow" the dominant brain activity is.

Why Frequency Analysis Is Used

Visual review of an EEG tracing is the standard approach, but computer-based frequency analysis can provide objective, quantitative summaries of brain activity. Measures like the median power frequency may be used in clinical research and specialized settings to characterize background rhythms, monitor changes over time, or support interpretation of the EEG in context.

How the Test Is Performed

The recording is obtained through standard EEG electrode placement on the scalp. After the raw EEG is recorded, a computer analysis calculates the power spectrum and identifies the median power frequency. No additional electrodes or procedures are needed beyond the routine EEG setup; the value is derived from the recorded signal.

Interpreting the Result

Interpretation depends on the patient's age, state (awake, drowsy, or asleep), and the recording conditions, as normal frequency characteristics differ across these situations. The median power frequency is not a stand-alone diagnostic result—it should be reviewed together with the full EEG, the patient's history, and any other testing. Your care team can explain what the value means in the context of your specific recording.