Visual Hallucinations: More Diagnoses

To the Editor.—  While Dr Newmark's answer¹ offered a good discussion, I would like to add some comments. Peduncular hallucinations are not synonymous with "release" phenomena. The latter occur with any focal lesion along the visual pathways, and as such have little localizing value, although they are most often placed in the temporal, parietal, and occipital lobes; the release hallucinations are formed, variable in content, and modified by opening or closing the eyes and are seen within the visual field defect.^2-4 Peduncular hallucinations are vivid, animated, short-lived, and often recognized as unreal; most of the patients reported have had signs of brain-stem dysfunction pointing to lesions in this region. As noted, a sleep abnormality is prominent and the hallucinations often occur at a specific time, usually in late daytime or evening. One patient was treated successfully when 5-hydroxytryptophan restored normal sleep.^4,5Ictal visual hallucinations are brief, stereotyped,