Major reviewPalinopsia revamped: A systematic review of the literature
Introduction
Palinopsia [Greek: palin for “again” and opsia for “seeing”], defined by Bender et al as “the persistence or recurrence of visual images after the stimulus has been removed”,17 encompasses many different visual symptoms. The heterogeneous group of symptoms cannot be accurately classified as either visual illusions or visual hallucinations, leading to ambiguity in the nosology of palinopsia and of related terms such as akinetopsia, illusory visual spread, and cerebral polyopia. Palinopsia is synonymous with visual perseveration.137
Kolmel first subdivided palinopsia in 1982 based on the latency between the observation of the true image and the appearance of the palinoptic image.81 Palinopsia may be described as “immediate” for a latency up to a few seconds or “delayed” for a latency greater than a few seconds. Although this temporal relationship is important, there is now ample evidence to show that it should not be the primary factor for categorization.
After thoroughly reviewing the 127 cases of palinopsia in the literature (Appendix), we discuss its symptomology, etiology, pathophysiology, diagnostic evaluation, prognosis, and treatment. We split palinopic symptoms into two clinically relevant categories. Hallucinatory palinopsia describes afterimages that are not usually affected by environmental conditions of light or motion and are long-lasting, isochromatic, and of high resolution. This category of palinopsia represents a dysfunction in visual memory and is caused by posterior cortical lesions or seizures. Illusory palinopsia describes afterimages that are unformed, indistinct, or of low resolution and are affected by ambient light and motion. This category of palinopsia represents a dysfunction in visual perception and is a result of migraines, prescription drugs, illicit drugs, or head trauma.
Section snippets
Physiological afterimages
Palinopsia should be distinguished from physiological afterimages, a common and benign phenomenon. Physiological afterimages regularly appear after viewing a bright stimulus and shifting visual focus. These afterimages occur in the same location in the visual field as the original stimulus and lack clarity. The generation of physiological afterimages relies on the intensity and contrast of the original stimulus, the time of fixation, and the retinal adaptation state.11, 17, 137 Physiological
Etiology and pathophysiology
Palinopsia has a wide variety of etiologies and mechanisms that relate to the previously defined symptomatic groups.
Correlation between pathophysiology, etiology, and symptomology
Reflecting the etiology and symptomology, we now split the pathophysiology of palinopsia into two categories: dysfunction of visual memory and dysfunction of visual perception (Fig. 2).
Clinical encounter
It is important to recognize that palinopsia is a collection of symptoms, not a diagnosis. The diversity in the etiologies of palinopsia necessitates a thorough history, physical exam, and work-up.
Conclusion
Palinopsia is not a diagnosis, but a broad term that describes a heterogeneous group of symptoms. We divided the symptoms into two clinically relevant categories. Hallucinatory palinopsia consists of formed image perseveration, scene perseveration, categorical incorporation, and patterned visual spread. These symptoms typically arise from post-geniculate cortical lesions and various seizure etiologies and resolve after treating the underlying pathology. The perseverated images are long-lasting,
Method of literature search
We conducted a PubMed and Web of Science search of the English language literature using the search terms palinopsia, paliopsia, visual perseveration, cerebral polyopia, illusory visual spread, visual trails, visual snow, visual trailing, hallucinogen persisting perception disorder, positive spontaneous visual phenomena, akinetopsia, and dyskinetopsia from 1968 through 2013. Reference lists from retrieved articles were examined for additional citations. The accepted definition of palinopsia was
Disclosures
The authors report no proprietary or commercial interests in any product or concept discussed in this article.
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