Waveform morphology in EEG (electroencephalography) refers to the shape, structure, and characteristics of the electrical waves recorded from the brain. EEG waveforms are composed of various types of waves, each with specific characteristics that help in diagnosing and understanding brain activity. The key components of EEG waveform morphology include:

1. Phases of a Wave

  • Monophasic: A waveform that crosses the baseline once, typically characterized by a single up-and-down slope (e.g., a simple spike).
  • Biphasic: A waveform that crosses the baseline twice, often consisting of an initial up-slope followed by a down-slope, and then an opposite phase (e.g., epileptiform spike and wave discharges).
  • Polyphasic: A waveform with multiple phases, where the signal crosses the baseline several times, indicating more complex or prolonged electrical activity.

2. Monomorphic vs. Polymorphic Waves

  • Monomorphic Waves: These waves have consistent frequency and amplitude, often appearing in rhythmic patterns. For instance, rhythmic spike and wave activity seen in seizures is typically monomorphic.
  • Polymorphic Waves: These waves show variation in frequency and amplitude, and may be associated with conditions like slow-wave sleep or brain abnormalities, such as tumors or brain injuries.

3. Wave Types Based on Frequency

EEG waves can be classified into different types based on their frequency:

  • Delta Waves: Low-frequency waves (0.5–4 Hz), typically associated with deep sleep.
  • Theta Waves: Moderate-frequency waves (4–8 Hz), often seen in drowsiness or light sleep.
  • Alpha Waves: Higher-frequency waves (8–13 Hz), seen during relaxed wakefulness with closed eyes.
  • Beta Waves: Even higher-frequency waves (13–30 Hz), associated with active thinking or concentration.
  • Gamma Waves: Very high-frequency waves (>30 Hz), related to intense mental activity and processing.

4. Clinical Significance

  • Epileptiform Activity: Specific waveforms like spikes, sharp waves, and spike-and-wave complexes are often indicative of epilepsy and can help identify seizure activity.
  • Sleep and Resting States: Delta and theta waves are common during sleep, with specific patterns associated with different sleep stages.
  • Pathological Patterns: Abnormal waveforms, such as focal slowing (polymorphic) or generalized rhythmic activity, can suggest conditions like tumors, strokes, or other neurological disorders.

Understanding the morphology of EEG waveforms is essential for clinicians to diagnose various neurological conditions, monitor brain activity during surgeries, and assess overall brain function.