Clinical EEG Interpretation
Recognizing epileptiform discharges, normal variants, and encephalopathy.
Normal Background Rhythms
- Alpha (8-13 Hz): Posterior dominant rhythm in awake, relaxed adults with eyes closed. Attenuates with eye opening.
- Beta (>13 Hz): Anterior prominent, often enhanced by sedating medications (e.g., benzodiazepines).
- Theta (4-7 Hz) & Delta (<4 Hz): Normal during sleep, but abnormal if prominent in awake adults (diffuse slowing suggests encephalopathy).
Epileptiform Discharges
Spikes (<70 ms) and sharp waves (70-200 ms) are the hallmarks of interictal epileptiform activity, highly correlated with seizure risk.
Common Clinical Mistakes
- Premature anchoring on common diagnoses without evaluating red flags.
- Over-reliance on neuroimaging while neglecting detailed physical exams.
- Suboptimal dosing of first-line agents before declaring treatment failure.
Frequently Asked Questions
- When is immediate specialist referral required?
- Urgent referral is indicated for sudden onset of severe symptoms, rapidly progressive deficits, or when standard therapies fail.
- What are the primary outcome measures in recent clinical trials?
- Most contemporary trials focus on slowing disease progression (e.g., EDSS in MS, UPDRS in Parkinson's) and reducing relapse/event rates.
- How does this condition impact patient life expectancy?
- While highly variable, modern disease-modifying therapies have significantly improved long-term survival rates across neurodegenerative and neuroimmunological disorders.