A 58-year-old man undergoes routine EEG for evaluation of "spells." During the recording, the technician notes an abrupt-onset rhythmic discharge at 5–7 Hz over bilateral temporo-parietal regions (marked **A** in the diagram). The patient remains fully alert, responsive, and denies any symptoms during the discharge. The discharge lasts approximately 90 seconds and returns to baseline without post-ictal slowing. Which of the following is the most appropriate clinical interpretation and management?

Explanation

## Why Option 1 is correct The discharge marked **A** exhibits the pathognomonic features of SREDA (Subclinical Rhythmic Electrographic Discharges of Adults): abrupt-onset, monomorphic 5–7 Hz theta activity over bilateral temporo-parietal regions, lasting 40 seconds to several minutes, with **complete absence of clinical accompaniment** and **no post-ictal slowing**. First formally described by Westmoreland and Klass (1981), SREDA is a rare benign normal EEG variant occurring predominantly in adults over 50 years of age (prevalence 0.04–0.07% of routine EEGs) and is the most commonly misinterpreted normal variant as a seizure. The key diagnostic criterion is that the patient remains fully alert and asymptomatic during the discharge—confirmed here by the clinical observation. SREDA has no association with epilepsy, stroke risk, or cognitive decline and requires no antiepileptic therapy. The appropriate management is reassurance and investigation of alternative causes for the patient's presenting symptoms. ## Why each distractor is wrong - **Option 2 (focal seizure with secondary generalization)**: Focal seizures characteristically **evolve** in frequency, amplitude, and morphology during the discharge and are followed by **post-ictal slowing**. The discharge in **A** is monomorphic (unchanging) and returns immediately to baseline without post-ictal changes. Additionally, seizures cause clinical symptoms or impaired awareness; this patient is asymptomatic and fully responsive. - **Option 3 (nonconvulsive status epilepticus)**: Nonconvulsive status epilepticus presents with altered mental status, confusion, or behavioral changes during the EEG discharge. The patient in this case is alert and asymptomatic, explicitly ruling out status epilepticus. Inappropriate labeling of SREDA as nonconvulsive status has historically led to harmful antiepileptic loading in benign cases. - **Option 4 (metabolic encephalopathy)**: Metabolic encephalopathy (e.g., hepatic encephalopathy) produces generalized periodic discharges (GPDs) or triphasic waves (marked **C** and **D** in the diagram), not the bilateral symmetric theta activity seen in **A**. Additionally, metabolic encephalopathy is accompanied by altered mental status, whereas this patient is fully alert. **High-Yield:** SREDA = benign normal variant in older adults; monomorphic, no post-ictal slowing, asymptomatic = do NOT treat with antiepileptics. [cite: Westmoreland BF, Klass DW. Mayo Clin Proc 1981; Niedermeyer's Electroencephalography, 7th ed., Ch. 12 (Normal Variants); ACNS guidelines on EEG terminology]