Visual Hallucinations Review
Published and edited by Terrence Li M.D.
2010

Types of hallucinations –

Visual Hallucinations

First, differentiate between simple or complex hallucinations:
1)    Simple – “elemental or non formed”
a.    Lights, colors, lines, shapes or geometric shapes
b.    Light simple hallucinations can be delinated further into lights without structure (phosphenes) OR lights with structure (photopsias)
2)    Complex – “formed”
a.    Images of people, animals, objects or lifelike scene

Auditory Hallucinations  - one or more talking voices
Usually associated with psychotic disorders such as schizophrenia or mania, but can be caused by lesions in the brainstem, tumors, encephalitis or abscesses

Tactile hallucinations – sensation of tactile sensory input simulating various sensations of pressure to the skin or other organs “feels bugs crawling on them”
Usually always associated with exogenous substance abuse.

History

Description
Monocular vs binocular
Involved area of visual field
Motion – motion within the hallucination or movement of hallucination across field of vision
Triggers (dark room, anxiety, bright light)
Duration
Frequency
Insight?

Differential Diagnosis

Retinal pathology
Charles Bonnet hallucinations
Migraine with aura
Seizures – occipital, occipitotemporal, posterior temporal
Dementia with Lewy bodies, Parkinson disease
EtOH withdrawal
Peduncular hallucinosis
Narcolepsy
Psychiatric illness
Metabolic encephalopathy
Stroke
Others

Retinal Pathology

Etiologies include traction, irritation, injury or disease of retina, posterior vitreous detachment. Hallucinations are SIMPLE (streaks of light, sparks, flashes), lasting seconds, variable frequency, insight retained., invariably monocular except in cancer associated retinopathy which it may be binocular.

Migraine with aura – 90% auras in migraine are visual. Hallucinations are SIMPLE, typically linear and geometric (zig zag lines, scintillating scotoma, spots, shooting stars, fortification spectra), lasting 4-60 minutes, variable frequency, insight retained, binocular and usually start in the central of the visual field with growth and spread of the aura.
Always have associated symptoms such as nausea, vomiting, photophobia, phonophobia, and they always follow the aura.
There is a special entity called acephalgic migraine in which there is a visual area as described above and there is no associated headache.

Seizures

Depending on the focus of the seizure, the hallucinations can be SIMPLE or COMPLEX:
1)    Occipital, occipitotemporal, occipitoparietal regions of cortex – SIMPLE hallucinations
a.    Brightly colored circles or spherical patterns
b.    Intrinsic motion of hallucination or move across the visual field is a hallmark!
2)    Occipitotemporal or posterior temporal regions of cortex – COMPLEX hallucinations

Epileptic visual phenomenon last for seconds, variable frequency, insight is usually retained, binocular usually occurring in one hemifield.

There are associated symptoms including déjà vu, jamais vu (temporal), somatosensory (parietal), forced head and eye deviation (frontal), motor activity (frontal and/or secondary generalization). There can be a posticital headache afterwards, making the distinction between migraine with aura and seizures difficult at times.

Dementia with Lewy bodies, Parkinson’s disease

Hallucinations are complex, binocular, occur throughout the visual field. Some examples are people, animals to abstract such as shapes and colors. These episodes last seconds to minutes, frequency usually is at least weekly. Insight may or may not be retained depending on the level of dementia/cognitive impairment. These images may spark feelings from indifference to fear (as in Phillip’s patient).
The difference is visual hallucinations are an early hallmark for DLB occurring in 2/3 of patients in the disease course. Parkinson’s disease hallucinations develop later in the disease course and can be exacerbated by dopamine agonists or carbidopa/levodopa.

Alcohol and drug use –
Alcohol and BDZ withdrawal – complex hallucinations without insight with VIVID imagery causing agitation, tremulousness and autonomic hyperactivity.
Medication induced or recreational drug use – complex, bilateral and full field with associated confusion and/or delirium. + tactile and auditory hallucinations.
Digoxin and sidenafil – there is RETINAL toxicity, simple hallucinations are produced such as “TV static”, tint of yellow or green in the visual field, dots of light, black spots. Long term supratherapeutic digoxin levels known to cause permanent retinal injury. ?? long term effect with sidenafil.

Non-psychotropic – digoxin, glucocorticoids, amantadine, H2 blockers, BB, sildenafil
Psychotropic – L-dopa, dopamine agonists, TCA, benztropine, BDZ, narcotics
Drugs of abuse – EtOH, LSD, PCP, cocaine, narcotics, ecstasy, amphetamine

Peduncular hallucinosis

Rare manifestation of stroke/neoplasm affecting the midbrain in particular the medial midbrain region affecting the reticular formation, red nucleus, raphe nucleus and oculomotor nucleus.  Pontine and thalamic lesions have been described with this phenomenon.
Hallucinations are complex, binocular, vivid and colorful imagery, +/- auditory and tactile content, and insight is variably retained. Duration variable from a few minutes to a few hours, frequency varies from 1-15 times a day. Predilection to occur in the evening. Usually self limited, resolving within a few weeks to months.
Invariably associated with other cranial nerve and consciousness symptoms: sleep wake cycle disturbances (daytime somnolence + night time insomnia), vertical gaze palsies, hemiparesis, ataxia, poor papillary light reaction, confusion.
Etiology has been postulated that the reticular activating system may be involved.

Narcolepsy

Hallucinations are complex, vivid, colored images, occurring immediately BEFORE falling asleep (hypnagogic) or just AFTER waking (hypnopompic). +/- auditory or tactile sensations, duration and frequency are variable. Insight is variably retained.
Associated symptoms include excessive daytime sleepiness, sleep paralysis and cataplexy.
Etiology is REM sleep into wakefulness, however, medications that disrupt sleep architecture (SSRI, anticholinergics) can do this as well.

Psychiatric illness

Hallucinations are visual, complex, associated with auditory hallucinations and usually occur in concert. Content is disturbing and antagonistic and patients lack insight. Duration and frequency is highly variable.
Associated symptoms include mania, anxiety, disordered thoughts, and delusions.

Metabolic Encephalopathy

Visual hallucinations occur in the context of waxing and waning confusion and agitation. Tactile and auditory hallucinations and delusions may occur too. The differential diagnosis of delirium is numerous: CNS infection,  systemic infection, hypoxia, medications, hepatic, renal encephalopathy, hypothyroidism, electrolyte abnormality.

Stroke

Beware of medial occipital + parahippocampal gyrus + hippocampus stroke, which causes delirium with visual hallucinations AND hemianopsia.

Others

Papilledema can cause photopsias or brief visual obscurations, lasting seconds, monocular, secondary to the elevated ICP induced edema of retinal ganglion cell axons, causing irritation of the retinal photoreceptor.

Optic neuritis can have visual hallucinations with eye movement in 30%.

Posterior reversible leukoencephalopathy syndrome can produce visual hallucinations with associated symptoms of visual field deficits, visual distortions, headache, altered mental status, seizures.

Diagnostic Approach

Complete physical and neurological examination,
Ophthalmological examination (esp if monocular and acute)
Review of medication list
Urine toxicology screen
CBC, BMP, LFT, TSH
ABG
MRI brain without contrast
EEG
Psychiatric consultation (if psych associated symptoms are appreciated)