background slowing
Abnormal reduction in the frequency of normal background EEG rhythms, indicating diffuse cerebral dysfunction.
Full Definition
Background slowing refers to a pathological decrease in the frequency of the dominant posterior rhythm and other background EEG activity. Normal adult alpha rhythm frequencies range from 8-13 Hz, and slowing occurs when these frequencies drop into the theta (4-8 Hz) or delta (1-4 Hz) ranges. Background slowing can be generalized, affecting the entire brain, or focal, affecting specific regions. This finding suggests metabolic dysfunction, medication effects, degenerative processes, or structural brain abnormalities. The degree and distribution of slowing correlate with the severity and location of underlying pathology.
Usage
Usage note: Specify whether slowing is generalized, focal, or multifocal, and indicate the frequency range.
In Context
- "Generalized background slowing in the theta range was observed throughout the recording." — EEG report
- "The patient's background slowing improved following correction of the metabolic abnormality." — Follow-up documentation