Strokes can and do cause hallucinations, and they are more common than most people realize. In one prospective study of acute stroke patients, roughly one in six experienced visual hallucinations during their hospital stay. The type of hallucination, whether a person sees vivid figures, hears music, or perceives phantom limbs, depends heavily on which part of the brain the stroke damages, but emerging research suggests these varied experiences share a surprisingly unified underlying network.
How Common Are Post-Stroke Hallucinations
The best available estimate of visual hallucinations in acute stroke comes from a prospective study that followed patients closely during hospitalization and found an incidence of 16.7%. The hallucinations were mostly complex, meaning patients saw formed images like people, animals, or scenes rather than just flashes of light or shapeless colors. They were often in black and white and tended to resolve on their own over time.1PubMed. Visual hallucinations in patients with acute stroke: a prospective exploratory study That number is almost certainly an undercount. Many stroke patients never mention their hallucinations to clinicians, partly because they fear being diagnosed with a psychiatric illness.2European Neurological Review. Charles Bonnet Syndrome as a Rare Complication in an Ischaemic Stroke
Visual hallucinations get the most research attention, but strokes also produce auditory hallucinations, musical hallucinations, phantom body perceptions, and in rare cases even distorted smell. The variety is wide enough that clinicians and researchers have had to draw careful boundaries around what counts as a post-stroke hallucination versus something else, like delirium or a seizure-related phenomenon. The standard approach in research requires that hallucinations occur in full consciousness, be complex in nature, and not be explainable by another condition such as delirium.3PubMed Central. Poststroke psychosis: a systematic review
Where the Stroke Hits Determines What You Perceive
The single biggest factor shaping the kind of hallucination a stroke produces is which brain region loses its blood supply. Different areas handle different sensory functions, and when those areas are damaged, the hallucinations tend to match the specialty of the affected tissue.
Occipital Strokes and Visual Hallucinations
The occipital lobe, at the back of the brain, is the primary processing center for vision. When a stroke damages this area, patients can develop a condition known as Charles Bonnet syndrome, where the brain generates vivid visual experiences in the absence of real visual input. Patients with occipital infarctions who develop these hallucinations typically have no prior history of psychiatric or neurological problems, and the hallucinations appear suddenly alongside the vision loss the stroke causes.4Journal of Neurosonology and Neuroimaging. Charles Bonnet Syndrome after Occipital Infarction Imaging studies of such patients have revealed changes in the white matter tracts connecting the visual cortex to frontal and temporal regions, as well as disrupted connections between the two halves of the visual cortex.5PubMed Central. Altered white matter connectivity associated with visual hallucinations following occipital stroke
Thalamic and Brainstem Strokes
When a stroke hits the thalamus or the upper brainstem (the midbrain), it can produce a phenomenon called peduncular hallucinosis. First described in 1922 by the French neurologist Jean Lhermitte, this involves vivid, dream-like visual hallucinations that often appear in the evening or at night.6PubMed. From Dreams to Hallucinations: Jean Lhermitte’s Contribution to the Study of Peduncular Hallucinosis and the Dissociation of States While classically linked to midbrain lesions, case reports have documented peduncular hallucinosis after strokes confined entirely to the thalamus, with no visible midbrain damage at all.7PubMed. Peduncular hallucinosis associated with posterior thalamic infarction8PubMed Central. Peduncular hallucinosis after a thalamic stroke
Thalamic strokes are particularly interesting because the thalamus is a relay hub that sits between almost every sensory input and the cortex. A small infarction in the right mediodorsal nucleus of the thalamus can produce not just hallucinations but a full psychiatric syndrome, with confusion, amnesia, emotional instability, and both visual and auditory hallucinations appearing suddenly.9PubMed. Connectional diaschisis associated with acute psychosis after right thalamic stroke: A case report That case also demonstrated that the thalamic damage caused the prefrontal cortex to become structurally and functionally disconnected, even though the prefrontal cortex itself was not directly harmed by the stroke.
Temporal Lobe Strokes and Auditory Hallucinations
The temporal lobes process sound, and when they are damaged, the hallucinations tend to be auditory rather than visual. In a series of patients with post-stroke auditory hallucinations, all four cases involved strokes in the right temporal lobe.10PubMed Central. Auditory hallucinations in acute stroke A subset of auditory hallucinations involves music. Patients have reported hearing songs, instrumental melodies, or orchestral pieces playing continuously. Case reports have documented musical hallucinations arising from strokes involving the right frontal and anterior temporal lobes, and from right temporal ischemic strokes alone.11PubMed. Musical hallucinations with a right frontotemporal stroke12PubMed. Neurofunctional assessment in a stroke patient with musical hallucinations In one of those musical hallucination cases, brain imaging showed increased activity in the right temporal cortex, specifically in the area damaged by the stroke, suggesting the injured tissue was producing abnormal signals that the brain interpreted as music.
Why Damaged Brain Tissue Produces False Perceptions
Understanding why a stroke causes hallucinations, rather than simply silence in the affected sense, requires grappling with a counterintuitive idea: the brain does not go quiet when it loses input. Instead, it often becomes more active in specific ways that generate experiences from nothing.
The leading explanation is the release phenomenon, sometimes called deafferentation. When a stroke destroys part of the visual pathway, the brain regions downstream of the damage stop receiving their normal input. Rather than staying dormant, those deprived neurons become spontaneously active, firing without being triggered by any real signal from the eyes. The brain then interprets this spontaneous activity the same way it would interpret genuine visual information, and the result is a hallucination.13Austin Journal of Cerebrovascular Disease & Stroke. Complex Visual Hallucinations Following Stroke: Epileptic origin or a Deafferentation Phenomenon? This same logic applies across sensory modalities: deprived auditory cortex can generate phantom sounds, just as deprived visual cortex generates phantom images.
The analogy often used is phantom limb pain, where an amputee feels sensations in a limb that no longer exists. The cortical territory that used to process input from that limb does not simply shut down. It starts firing on its own, and the person feels something that is not there. Post-stroke hallucinations work on a similar principle, except the “amputation” is of sensory input to the brain rather than a physical body part.
For thalamic and brainstem strokes, an additional mechanism comes into play. When cortical areas lose their normal thalamic relay signals, the thalamic neurons themselves shift into an abnormal firing pattern. Instead of their normal steady signaling, they start producing slow, rhythmic bursts. Computational modeling of this process has shown that a cortical lesion causes the thalamic relay neurons to become hyperpolarized, which flips them from their normal firing mode into a pathological bursting regime. This bursting then spreads through thalamic circuits and propagates low-frequency oscillations into cortical areas well beyond the original stroke damage.14PubMed Central. The Impact of Cortical Lesions on Thalamo-Cortical Network Dynamics after Acute Ischaemic Stroke: A Combined Experimental and Theoretical Study The disrupted rhythm between the thalamus and cortex, a framework researchers call thalamocortical dysrhythmia, creates conditions in which neighboring cortex responds with heightened high-frequency activity. That mismatch between slow deep-brain rhythms and fast cortical activity is thought to underlie not just hallucinations but a range of positive neuropsychiatric symptoms after thalamic stroke.15International J of Psychiatric Trainees. Late-onset acute psychosis due to right thalamic infarct
A third possibility, which is not mutually exclusive with the first two, is that the lesion triggers seizure-like activity in damaged cortex. Some researchers have proposed that abnormal electrical discharges from the stroke-damaged tissue activate neural networks that produce hallucinations, essentially a focal epileptic event masquerading as a purely perceptual phenomenon. The distinction matters for treatment, because seizure-driven hallucinations might respond to anti-seizure medications rather than antipsychotics.16PubMed Central. Yellow-Coloured Left Homonymous Visual Hemi-Field after Ischaemic Stroke
A Shared Brain Network Behind Different Types of Hallucinations
For decades, the field treated post-stroke hallucinations as location-specific events: damage the occipital lobe, get visual hallucinations; damage the temporal lobe, get auditory ones. That picture is accurate as far as it goes, but a large lesion-mapping study brought something more surprising to light. Researchers examined 89 brain lesions that caused hallucinations across a range of locations and found that, despite appearing in many different brain regions, these lesion sites all fell within a single functionally connected network.17Molecular Psychiatry. Lesions causing hallucinations localize to one common brain network
The network was defined by its connectivity to the cerebellar vermis, the inferior cerebellum on both sides, and the right superior temporal sulcus. Within that shared network, additional connections determined the sensory type of hallucination. Lesions causing visual hallucinations were connected to the lateral geniculate nucleus in the thalamus, the main visual relay station. Lesions causing auditory hallucinations were instead connected to the dentate nucleus in the cerebellum. So even though the individual stroke locations were scattered across the brain, the downstream circuitry that each one disrupted converged on common territory.
This finding also helps explain why small strokes in seemingly unrelated locations can all produce hallucinations. A lesion does not need to directly destroy the visual or auditory cortex. It only needs to disrupt a node in this broader network. Lesion network mapping has shown that both positive connections (where the damaged area normally excites another region) and negative connections (where it normally inhibits another region) matter, and that hallucinations, delusions, and other post-stroke behavioral changes can be better localized by mapping these networks than by looking at the stroke location alone.18Brain. Lesion network mapping predicts post-stroke behavioural deficits and improves localization
Risk Factors That Raise the Odds
Not every stroke patient develops hallucinations, even when the stroke hits a “high-risk” location. The same prospective study that found the 16.7% visual hallucination rate also identified what did and did not predict their appearance. Age, sex, cognitive performance during admission, and disability level at discharge made no difference. What did matter were two things: the stroke involving the occipital cortex, and the presence of sleep disturbances, both during the hospital stay and in the period before the stroke.1PubMed. Visual hallucinations in patients with acute stroke: a prospective exploratory study
The sleep connection is worth pausing on. Brainstem and thalamic regions that regulate the transition between waking, dreaming, and deep sleep overlap with the areas implicated in peduncular hallucinosis. When those areas are damaged by a stroke, the boundary between dreaming and waking may blur, allowing dream-like imagery to intrude on waking consciousness. Researchers have long noted that peduncular hallucinations are often most intense during drowsy states or in the evening, and that lesions outside the primary visual system can cause hallucinations by disrupting the modulation of connections between the thalamus and cortex, a process closely tied to sleep-wake regulation.
Why Many Patients Never Report Their Hallucinations
One of the most practical issues with post-stroke hallucinations is how often they go undiagnosed. Patients who start seeing people who are not there or hearing music with no source frequently assume they are losing their minds. The prospect of being labeled with a psychiatric disorder discourages many from mentioning hallucinations as a symptom at all, which prevents clinicians from identifying the cause and offering reassurance.2European Neurological Review. Charles Bonnet Syndrome as a Rare Complication in an Ischaemic Stroke
This silence has real consequences. If a patient’s hallucinations are driven by seizure activity, missing the diagnosis means missing a treatable cause. If the hallucinations are a release phenomenon from visual loss, simply telling the patient what is happening and why can dramatically reduce their anxiety. Many Charles Bonnet syndrome patients report that the hallucinations become far less distressing once they understand that their brain is compensating for lost input and that they are not developing dementia or psychosis. The reassurance itself is therapeutic, but it can only happen if the patient speaks up and the clinician knows what to ask.
The Treatment Gap
Here is where the clinical picture gets frustrating. Despite post-stroke hallucinations being well-documented in the literature, no clinical trials have been conducted to test whether antipsychotic medications are safe and effective for this specific population.19PubMed Central. Dilemma of Treating Psychosis Secondary to Stroke That leaves clinicians in a bind. Antipsychotic drugs are the standard treatment for hallucinations in psychiatric conditions, but stroke patients are not psychiatric patients. Their brains are structurally damaged, their medication sensitivities may differ, and some antipsychotics carry cardiovascular risks that are particularly concerning in someone who just had a stroke.
In practice, clinicians tend to take a tiered approach. For hallucinations that are mild, non-distressing, and self-limited, reassurance and monitoring are often sufficient. This is especially true for Charles Bonnet syndrome, where the hallucinations frequently diminish as the brain adapts to its new sensory landscape over weeks to months. For hallucinations that are distressing, persistent, or accompanied by delusions and behavioral disturbance, low-dose antipsychotics are sometimes tried on a case-by-case basis, with careful attention to side effects. If seizure activity is suspected, anti-epileptic drugs become the first-line consideration instead. The lack of formal evidence means that every treatment decision is essentially a clinical judgment call rather than a guideline-driven protocol.
Hallucinations Beyond Sight and Sound
Most research and clinical attention focuses on visual and auditory hallucinations after stroke, but the phenomenon extends to other senses too. Olfactory disturbances have been documented after insular strokes, where smells that were once pleasant become unpleasant or indistinguishable from one another. The evidence, still limited, suggests that left-sided insular lesions may more frequently cause this kind of olfactory change.20PubMed Central. Insula and Olfaction: A Literature Review and Case Report
Perhaps the most unusual post-stroke perceptual disturbance is the supernumerary phantom limb, in which a patient perceives an extra limb that does not exist. In one documented case, a patient with a left hemisphere stroke developed right-sided paralysis, sensory loss, and spatial neglect, and then began perceiving an additional right arm. Brain imaging revealed an infarction in the left corona radiata. The phantom limb persisted for months, though it gradually improved as the patient’s spatial awareness recovered.21Cureus. Supernumerary Phantom Limb After Stroke in the Left Hemisphere: A Case Report Experiences like this underscore that post-stroke hallucinations are not limited to seeing or hearing things. Any sensory or body-mapping function the brain performs can generate false perceptions when the underlying circuitry is disrupted.
The range of these experiences, from black-and-white visions to phantom musical concerts to extra limbs, all stemming from the same basic mechanism of brain tissue losing its expected input and responding with spontaneous activity, is a reminder that hallucinations are not inherently a sign of psychiatric illness. In the stroke context, they are a neurological symptom with an identifiable structural cause. Clinicians who ask about them directly, and patients who feel safe enough to describe them, are far more likely to land on the right explanation and the right response.