Prognostic Value of Elementary Visual Hallucinations in Patients with Occipital Lobe Epilepsy

Abstract

Purpose: Although an elementary visual hallucination (EVH) is one of the most important symptoms in patients with occipital lobe epilepsy (OLE), a detailed analysis of its clinical significance has not been performed. To clarify the prognostic value of different characteristics of the EVHs, we analysed the illustrations by the patients with OLE and their clinical course. Methods; We selected 22 (12 male and 10 female) patients aged 8–22 years with OLE and excluded the patients without interictal paroxysmal discharges in the occipital regions. We followed up their clinical course for ∼3 years during treatment with various anti‐epileptic drugs (AEDs). All patients could illustrate each EVH with respect to the binocular visual field on a sheet with I2 kinds of color markers with regard to its localization, size, number, and color. The sheet was similar to the one used in the Goldmann perimeter. Patients were divided into two groups according to the existence of complex partial seizures (CPSs) after the EVHs. Group A consisted of patients whose EVHs were not followed by CPSs, whereas the patients in group B had EVHs followed by CPSs. We compared the prognosis between groups A and B with regard to (a) seizure control, (b) tapering dosage of AEDs, and (c) discontinuations of AEDs. We also analyzed the characteristics of the EVHs with regard to (a) the localization in the binocular visual field, (b) the number of EVHs, (c) the color, and (d) the duration. The localizations of the EVHs illustrated by the patients were divided into four patterns; peripheral, intermediate, central, and diffuse. The intermediate pattern indicated a position between the peripheral and the central area. Statistical analysis was performed with Fisher's Exact probability test. Results: The epileptic seizures disappeared soon after the administrations of AEDs in 19 (86%) of the 22 patients. All patients in group A were treated with monotherapy, whereas only half of the patients in B were treated with monotherapy. In group A, all patients stayed seizure free with treatment, and three patients had a good outcome even after the discontinuation of AEDs. In B, nine of the 12 patients stayed seizure free with treatment. The tapering or discontinuation of AEDs in the patients of group A could be made in six (60%) of 10 compared with one (8%) of 12 in B (p < 0.05). All patients in group A showed the central (n = 8) or diffuse (n = 2) patterns of EVHs, whereas of the 12 patients in B, five showed central (n = 4) or diffuse (n = 1), and the remaining seven patients showed peripheral (n = 3) or intermediate (n = 4, p < 0.01) localizations. No correlation could be found between the two groups for the other characteristics of the EVHs, including the number, color, and duration. Conclusions: The clinical prognosis of patients with OLE showing EVHs was generally good. Group A showed a better prognosis than group B, and the localization patterns of the EVHs were different between groups A and B. This difference suggested that the localization of the EVHs has a significant prognostic value. Accordingly, patients who have the EVHs located laterally in their binocular field of vision may show an intractable clinical course.