How should I interpret abnormal EEG findings in a patient with suspected epilepsy?

When interpreting abnormal electroencephalogram (EEG) findings in a patient with suspected epilepsy, it is essential to contextualize the EEG abnormalities within the clinical presentation and seizure history, as EEG alone cannot definitively diagnose epilepsy NICE NG217.

Key considerations include:

• Recognizing that certain EEG patterns, such as sharp waves, spikes, or spike-and-wave discharges, are suggestive but not pathognomonic of epilepsy; these findings must be correlated with clinical seizure semiology and history NICE NG217.
• Being aware that normal variants and physiological patterns during awake, drowsy, and sleep states can mimic epileptiform abnormalities, leading to potential overinterpretation; thus, expertise in distinguishing these is critical to avoid misdiagnosis Asadi-Pooya 2019 NICE NG217.
• Considering that EEG sensitivity is limited; a normal EEG does not exclude epilepsy, and repeated or prolonged EEG monitoring, including sleep EEG, may increase diagnostic yield NICE NG217.
• Interpreting EEG abnormalities in the context of the patient’s age, epilepsy syndrome, and comorbidities, as some epilepsies have characteristic EEG signatures that aid diagnosis and classification NICE NG217.
• Understanding that in complex clinical settings, such as ICU patients or those with systemic illness, EEG abnormalities may reflect encephalopathy or other non-epileptic processes, requiring careful clinical correlation Gélisse et al. 2020 NICE NG217.

In summary, abnormal EEG findings should be interpreted as part of a comprehensive clinical assessment, with caution to avoid overinterpretation of normal variants, and recognition that EEG is a supportive rather than definitive diagnostic tool in epilepsy NICE NG217.