From the Guidelines
In the context of Electroencephalography (EEG), Postictal (post-seizure) and Positivity (positive spike) are distinct concepts, with Postictal referring to the period after a seizure and Positivity relating to specific electrographic patterns, such as spike/sharp-wave patterns, which are crucial for diagnosing electrographic seizures and status epilepticus 1.
Key Differences
- Postictal states are characterized by slowing of background rhythms, decreased amplitude, and sometimes focal abnormalities that gradually normalize after a seizure.
- Positivity, in the context of EEG, refers to specific patterns like spike/sharp-wave discharges, which are part of the diagnostic criteria for electrographic seizures and status epilepticus, as outlined by the American Clinical Neurophysiology Society Criteria 1.
Clinical Significance
- Distinguishing between post-seizure states and positivity in EEG interpretations is crucial for understanding the underlying pathophysiology and for guiding appropriate treatment strategies.
- The presence of specific electrographic patterns, such as those described in the criteria for electrographic seizures, can indicate the occurrence of a seizure or status epilepticus, necessitating specific interventions 1.
Diagnostic Criteria
- The American Clinical Neurophysiology Society provides specific criteria for diagnosing electrographic seizures, status epilepticus, and the ictal-interictal continuum, which include patterns such as epileptiform discharges averaging >2.5 Hz for ≥10 s or any pattern with definite evolution lasting ≥10 s 1.
- These criteria help in differentiating between various hyperexcitable phenomena in EEG readings, ensuring accurate diagnosis and management of seizure disorders.
From the Research
Difference between Postictal and Positivity in EEG
- Postictal refers to the period following a seizure, during which the brain may exhibit abnormal electrical activity 2.
- Positivity, on the other hand, refers to a specific type of EEG waveform, such as positive spikes, which can be seen in certain normal variants or patterns 2.
Characteristics of Postictal and Positivity
- Postictal patterns may include slow waves, spikes, or other abnormal discharges that can be focal or generalized 3.
- Positive spikes, such as 14 and 6 Hz positive spikes, are considered normal variants and may be seen in healthy individuals 2.
Clinical Significance
- Postictal patterns can be indicative of seizure activity and may be used to diagnose and monitor epilepsy 4.
- Positive spikes, while generally considered normal, can be misinterpreted as abnormal and may lead to overdiagnosis or misdiagnosis of epilepsy 2.
EEG Interpretation
- Correct identification of postictal patterns and positive spikes requires careful analysis of the EEG waveform and consideration of the clinical context [(2,4)].
- Artifacts, normal rhythms, and normal patterns must be recognized and distinguished from abnormal patterns to avoid misinterpretation 2.