A 9-year-old boy presents with recurrent episodes of multicolored circular visual patterns appearing in the peripheral visual field, followed by forced rightward eye deviation and postictal headache with nausea. EEG shows the pattern marked **B** in the diagram. Which of the following best characterizes this EEG finding?
A. High-amplitude occipital discharges that persist regardless of fixation status and indicate a structural brain lesion
B. Occipital spike-wave discharges that appear or increase with eyes closed and diminish with visual fixation
C. Centrotemporal spike-wave complexes that are activated by sleep and hyperventilation
D. Generalized 3 Hz spike-and-wave discharges that are unaffected by eye opening or closure
Explanation
Why option 1 is correct
The structure marked B represents occipital spike-wave discharges with fixation-off sensitivity, which is the diagnostic hallmark of Childhood Occipital Epilepsy of Gastaut (COE-G). The key distinguishing feature is that these paroxysmal discharges APPEAR or INCREASE when visual fixation is removed (eyes closed in darkness) and DISAPPEAR or ATTENUATE when the eyes are open with active visual fixation. This fixation-off sensitivity is pathognomonic for COE-G and is best demonstrated by EEG recording with alternating periods of eyes open and eyes closed. The clinical presentation—elementary visual hallucinations (multicolored circular patterns in peripheral field), forced eye deviation, and postictal migraine-like headache—combined with this specific EEG pattern confirms the diagnosis (ILAE Classification 2017, Childhood Occipital Epilepsies).
Why each distractor is wrong
Option 2 (Centrotemporal spike-wave): This describes the EEG pattern of Benign Epilepsy with Centrotemporal Spikes (BECTS), which is marked as A in the diagram. BECTS occurs during sleep, has a different seizure semiology (orofacial symptoms, speech arrest), and lacks fixation-off sensitivity. The clinical presentation in this case is clearly occipital, not centrotemporal.
Option 3 (Generalized 3 Hz spike-and-wave): This pattern (marked C in the diagram) is characteristic of Childhood Absence Epilepsy, which presents with brief staring spells without visual symptoms, lacks fixation-off sensitivity, and is unaffected by eye opening/closing. The patient's visual hallucinations and postictal headache are incompatible with absence seizures.
Option 4 (Persistent discharges with structural lesion): While occipital discharges can occur in symptomatic occipital lobe epilepsy due to structural lesions, COE-G is defined as an idiopathic focal epilepsy with NORMAL MRI. Moreover, symptomatic occipital epilepsy does not exhibit fixation-off sensitivity; the discharges persist regardless of fixation status. The normal neuroimaging in this case rules out symptomatic epilepsy.
High-YieldNEET PG
Fixation-off sensitivity (paroxysms appear with eyes closed, disappear with eyes open) is the diagnostic hallmark of Gastaut-type occipital epilepsy and distinguishes it from symptomatic occipital lobe epilepsy and other generalized epilepsies.
