James Dolbow, DO PGY-3 Neurology Resident Case Western Reserve University University Hospitals Cleveland Medical Center Cleveland, Ohio
Sean Duke, MD PGY-4 Neurology Resident Case Western Reserve University University Hospitals Cleveland Medical Center Cleveland, Ohio
Neel Fotedar, MD Staff Epileptologist Epilepsy Center, Neurological Institute University Hospitals Cleveland Medical Center Cleveland, Ohio Assistant Professor Department of Neurology Case Western Reserve University School of Medicine Cleveland, Ohio ORCID ID 0000-0003-0424-7767
Disclosures The authors report no financial relationships with any companies whose products are mentioned in this article, or with manufacturers of competing products.
The visual field(s) in which the hallucination occurs can help differentiate possible causes in patients with seizure, brain tumor, migraine, or visual impairment. In patients with psychosis, delirium, peduncular hallucinosis, or hypnagogia/hypnopompia, hallucinations can occur in any visual field. Those with neurodegenerative disease, particularly PD, commonly describe seeing so-called passage hallucinations and presence hallucinations, which occur outside of the patient’s direct vision. Visual hallucinations associated with seizure are often unilateral (homonymous left or right hemifield), and contralateral to the affected neurologic structures in the visual neural pathway; they start in the left or right peripheral vision and gradually move to the central visual field. In hallucinations experienced by patients with brain tumors, the hallucinated entities typically appear on the visual field contralateral to the underlying tumor. Visual hallucinations seen in migraine often include a figure that moves from central vision to more lateral in the visual field. The visual hallucinations seen in eye disease (namely Charles Bonnet syndrome) are almost exclusively perceived in the visual fields affected by decreased visual acuity, though non-side-locked visual hallucinations are common in patients with age-related macular degeneration.
Content and complexity. The visual hallucinations perceived in those with psychosis, delirium, neurodegenerative disease, and sleep disorders are generally complex. These hallucinations tend to be of people, animals, scenes, or faces and include color and associated sound, with moving parts and interactivity with either the patient or the environment. These are in contrast to the simple visual hallucinations of visual cortex seizures, brain tumors, and migraine aura, which are often reported as brightly colored or black/white lights, flashes, and shapes, with or without associated auditory, olfactory, or somatic sensation. Furthermore, hallucinations due to seizure and brain tumor (also likely due to seizure) are often of brightly colored shapes and lights with curved edges, while patients with migraine more commonly report singular sparkling black/white objects with straight lines.
Bottom Line
Though there are no features known to be specific to only 1 cause of visual hallucinations, some characteristics of both the patient and the hallucinations can help direct the diagnostic differential. The most useful characteristics are the patient’s age, the visual field in which the hallucination occurs, and the complexity/ simplicity of the hallucination.
O’Brien J, Taylor JP, Ballard C, et al. Visual hallucinations in neurological and ophthalmological disease: pathophysiology and management. J Neurol Neurosurg Psychiatry. 2020; 91(5):512-519. doi:10.1136/jnnp-2019-322702
