Presentation, Etiology, Outcome, and Differentiation of Visual Semiology of Adult Occipital Epilepsy From Visual Aura of Migraine Headache: A Prospective Study in a Tertiary Care Center in Bangladesh

Background: Occipital epilepsy is an uncommon and likely underdiagnosed type of epilepsy that is often misdiagnosed as a migraine with aura. High clinical suspicion and subsequent electroencephalogram (EEG) and brain imaging lead to early diagnosis. Methods: We recruited patients with occipital epilepsy based on visual semiology, structural abnormalities in the occipital region, or EEG changes who visited the Department of Neurology of Dhaka Medical College from June 2019 to January 2020. We documented the presentations, etiology, and outcomes at the 12-month follow-up. Additionally, we compared the clinical features of patients with occipital epilepsy (n = 10) and those with migraine with aura (n = 18). Results: We identified three and seven cases of idiopathic and symptomatic occipital epilepsy, respectively, all presenting with visual semiology. Symptomatic occipital epilepsy occurred due to space-occupying lesions, post-hypoxic damage, post-stroke encephalomalacia, gyral calcification from Sturge-Weber syndrome, and Wilson’s disease. Age, sex, illness duration, headache severity, and associated features were similar between the migraine with aura and epilepsy groups. In occipital epilepsy, the median (IQR) age was 22 (15-47) years, and the patients were predominantly female (8, 80%). The visual auras lasted 35 (3-375) seconds and included colored dots or light flashes that persisted for seconds (50%) before (60%), during (30%), and after (10%) the headache. Compared to migraines, the headaches were global (90%), compressive (90%), and of shorter duration (210 minutes, IQR: 150-630). Except for nausea or osmophobia, vomiting (80%), photophobia (80%), and phonophobia (70%) occurred. Most cases had associated focal or bilateral tonic-clonic seizures (60%; p-value < 0.001). In contrast, the visual auras in migraine were scotomas, white or golden dots, or light flashes lasting for minutes (83.3%; p-value = 0.02) before the headache. The headaches lasted longer (720 minutes, IQR: 345-1,440, p-value < 0.03), were unilateral (44%) or bilateral (50%), and throbbing (72%; p-value = 0.003). Headache was associated with photophobia (94.4%; p-value = 0.28), phonophobia (88.9%; p-value 0.31), and osmophobia (38.9%; p-value 0.03); no associated convulsions occurred. At the 12-month follow-up, most occipital epilepsy patients (9, 90%) responded well to carbamazepine. Conclusions: Patients with transient and distinct elementary visual hallucinations headache characteristics different from migraines with associated convulsions warrant evaluation for occipital epilepsy.