Chart Summary Exploring the "Illusion of Vision"

Hallucination is an illusory perceptual experience produced internally by the brain itself without objective stimuli acting on the corresponding perceptual ^{organs [1].}

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classify

➤ Classified according to the content, it is divided into simple visual illusion (or "non-formed") and complex visual illusion (or "formed"

➤ According to the patient's self-awareness of the existence or non-existence of classification, that is, whether the hallucination is recognized as a non-real experience, it is divided into visual hallucinations with self-knowledge and visual hallucinations

Pathophysiology^[2].

1.

2.

3.

differential diagnosis

1.

Hallucinations are common in migraines, and about 30 percent of migraine patients have visual aura ^[3].

2.
Epilepsy

Focal seizures involving the visual cortex present visual hallucinations and are a major feature of late-onset occipital lobe epilepsy, but are uncommon in early-onset benign childhood occipital lobe seizures
.

Its characteristics depend on the location of the epileptic lesion and the nature of the
epilepsy syndrome.

Different locations can produce different types of visual illusions
.

The visual hallucinations produced by occipital lobe seizures are usually short-lived, lasting seconds to minutes, rarely longer, and are stereotypically simple, such as geometric shapes
.

Patients usually complain of small, colorful circular patterns in the surrounding visual field that become larger, more numerous, and often move
horizontally during the attack.

Seizures that begin in the occipital or anterior medial area of the temporal lobe are usually brief and stereotyped, as are occipital seizures, and seizures in the posterior right temporal region have been reported to be "cinematic seizures," in which a series of flickering stills ^{appear [5,6].}

Epilepsy can also produce other non-visual seizure symptoms, such as brief blindness at the time of seizures and headache after seizures, which may need to be differentiated from migraines
.

Epilepsy auras differ from migraine auras in several ways: 1) epilepsy auras last shorter than migraines, usually for a few minutes or less, while most migraine auras last more than 5 minutes, usually 20-30 minutes; 2) The content of hallucinations is usually different: the hallucinations produced by epilepsy aura are usually rounded rather than jagged lines, and color is more common in epilepsy than in migraines; 3) The typical centrifugal or centripetal spread of migraine aura does not occur in epileptic hallucinations ^[7].

Fig.
1 ^[7]: A.
Occipital lobe epileptic hallucinations; B.
Migraine optic hallucinations

3.
Parkinson's disease (PD) and related diseases

Hallucinations occur in 20 to 60% of PD, mainly visual hallucinations
^[8].

Seizures are intermittent, without trigger points or aura, last from seconds to minutes, and occur in dim environments or in the evening, at night, and when the patient is
resting or alone.

There are several types: 1) Typical visual hallucinations, i.
e.
complex visual hallucinations, in which the patient sees a fully formed person, a furry animal, or an inanimate object, usually occurring when the environment is under-illuminated (such as at night), the image may be normal size or miniaturized, black and white, or colored, and may be incomplete
.

Usually not "interactive" and disappearing as they approach or gaze, patients sometimes describe them as threatening, with early patients becoming more self-aware and progressively losing self-awareness as the disease progresses ^[9
].

2) Another major category is small hallucinations, which last very short, and the patient's self-awareness is retained, including through sexual hallucinations, existential hallucinations, utopian visual hallucinations, etc
.

Sexual hallucinations refer to the flashing of a person, animal, or object around the patient's field of vision, some of which are described as recognized, such as people who
have just left the room.

Existential visual hallucinations are when the patient feels that someone is nearby and no one is actually there
.

Utopian visual hallucinations are the phenomenon of seeing objects in invisible visual stimuli (e.
g.
, seeing faces in clouds) ^[10].

Fluctuating visual hallucinations are the core criteria for diagnosing Dementia with Lewy bodies (DLB), and 50% to 80% of patients have visual hallucinations in the early stages of the disease, and the content is vivid, which can be painful and scary impressions or pleasant hallucinations
.

4.
Other syndromes

4.
1 Charles Bonnet Syndrome (CBS)

Charles Bonner first described in 1769 that his cognitively functioning 87-year-old grandfather was nearly completely blind due to cataracts, but could see men, women, birds, cars, and buildings of different shapes and sizes
.

CBS refers to a distinct and complex visual hallucination produced in mentally healthy people, mostly secondary to visual impairment (eg, severe macular degeneration, glaucoma, cataracts
).

In patients with visual impairment, simple visual hallucinations caused by CBS are about 40%-60%, and complex visual hallucinations are about 10%-15%.


Simple can take the form of a grid, shape or line, and can appear in vivid or vivid colors
.

Complex may involve people, places, animals and insects
.

Most people don't see people they know or events they've
experienced.

Hallucinations are usually not threatening, but may be slightly frightening the first time they appear, appear suddenly, and last for minutes or hours
.

They may be mobile or stationary
.

Symptoms usually vary with stress, fatigue, and environmental lighting, but there is usually no clear trigger
.

Most patients are self-aware, and some are able to control hallucinations to some extent ^[7,11].

4.
2 Visual snow syndrome (VSS)

VSS is a syndrome with a persistent visual sensation of snowflakes on television sets as the main clinical manifestation, and the 2018 International Classification of Headache Disorders has determined its diagnostic criteria, but the current understanding of the disease is still insufficient
.

Clinical manifestations are visual and non-visual ^[12
].

Visual symptoms include: 1) snow paralysis: dynamic, continuous dots with a full visual field that lasts more than 3 months; 2) Persistent posterior image: remove the phenomenon that visual symptoms persist after stimulation, that is, the posterior image of the graphic, moving object or the trajectory of the movement; 3) Enhanced internal vision phenomenon: For a visual perception phenomenon caused by the structure of the visual system itself under a specific stimulus, VSS patients do not need specific stimulation to occur that is, enhanced internal vision phenomenon
.

Phenomena of internal vision include extreme binocular floaters; Excessive blue background internal vision, i.
e.
when the eyes gaze at a homogeneous bright surface such as a blue sky, countless small gray, white, black dots or ring-like apertures can be seen; 4) Photophobia; 5) Impaired
night vision.

Non-visual symptoms include migraine, tinnitus, tremor, anxiety, or depression
.

There is no consensus on treatment, color filter lenses can be used to improve patient visual symptoms, and drug treatment is mainly based on migraine drug treatment, of which lamotrigine is effective
for most patients.

Fig.
2^[13]:(A) Snow vision in the dark; (B) Bright sight snow disease; (C) phenomenon of internal vision (floaters); (D) Continuous post-image; (E) The phenomenon of internal vision on a blue background; (F) Sustained post-image

4.
3 Alice in Wonderland Syndrome (AIWS)

AIWS, also known as "microvision", patients observe a thing for a long time, and suddenly like Alice roaming wonderland, things around them suddenly become larger, or suddenly become smaller
.

Patients sometimes have a mosaic visual effect in front of their eyes, and some patients will have a sense of distortion of
time and space.

These include somatic symptoms (primarily disturbances of perception of body size), optical illusions (primarily deformities related to size or distance), and disorders of consciousness (including de-conscious, depersonalized, and somatic duality).


Common in children and adolescents, the cause is unknown, but it is associated with many conditions, including infections, brain lesions, eye and ear disorders, psychiatric disorders, drugs, substance abuse, and paroxysmal neurological disorders such as epilepsy and migraines, where EPV infection is the most common cause of AIWS in children and migraines are the most common cause in adults ^[14,15].

Attached: Differential diagnosis of visual hallucinations ^[16] (click to view larger)

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