Hallucinations and related conditions

from S Tekin and JL Cummings, Clinical Neuropsychology, fourth edition, ed by Heilman KM and Valenstein E, chapter 17. An overview of semiology and terminology:

Unusual syndromes

Hallucinations with eye disorders: trauma, cataracts, macular degeneration, choroidal revascularization, retinal detachment, retinal traction, central retinal vein occlusion, and serous retinopathy. Moore's lighting streaks are vertical bands of light in temporal fields during eye movements. Saccades may cause flick phosphenes which are streaks of light in the central visual field. Photopsias are light with geometric structure. Phantom vision may occur after visual loss or enucleation. Hallucinations are rare after visual loss in the young.

The Charles Bonnet syndrome are visual hallucinations in normal elderly usually due to deprivation often with insight, usually pleasant formed images lasting for a few seconds to all day and disappearing with eye closure. Age, poor vision and binocular vision loss are risk factors. They are worse in demented patients and can be precipitated by beta blockers.

Entopic phenomena are actual visual phenomena, not hallucinations, occurring due to particles in the vitreous, macular edema or elements of one's own retinal circulation (Scheere's phenomena). Vitreous deposits (floaters) occur as amoeba shaped or shadow like forms.

Optic neuritis or compressive ischemic optic neuropathy may cause unformed visual hallucinations, including phosphenes, which occur in dim lighting often with horizontal saccades. Sudden sounds can cause auditory visual synesthesia.

Peduncular hallucinosis as part of the top of the basilar syndrome are vivid and full of motion including small (Lilliputian) people, animals, or kaleidoscopic views of landscapes. They occur in the evening or night and last a few seconds or minutes over days to weeks. Visual acuity and fields are normal. They are pleasant. Associations are abnormal SWS, impaired EOM's, and abnormal balance between serotonin and dopaminergic stimulation.

Release hallucinations occur with homonymous hemianopsia in 13 % of such patients, and consist of complex visual patterns, colored patterns or formed images in the area of the defect, and last minutes to hours. The "picture within a picture " sign was described in someone with a right parietal lesion, who saw people "milling around" only in the lower left quadrantanopic field.

Epileptic hallucinations are brief and stereotyped and in the occipital cortex are usually unformed, consisting of colored lights, weaving patterns, zig-zag lights, spots or amaurosis. Complex or formed visual hallucinations usually originate in the parietal or temporal association cortex. Epileptic hallucinations usually occur in one quadrant or hemifield and may be associated with motion, often rapid motion contralateral to the seizure focus. Headache may follow a seizure.

Migraines cause unformed flashes of light, or color, scintillating scotomas and zig zag lines called "fortification spectra." Reproductions of self or body parts in external space are called autoscopic phenomena. Migraine fortification spectra tend to be linear and black and white and last longer than epileptic phenomena, which tend to be multicolored circular or spheroid patterns.
Migraine visual phenomena tend to move across one fourth or one half the visual field and to grow in size as they do. Blurring of part or all of the field with scintillating lights around a scotoma is more common than fortification spectra.

Narcoleptics have hypnagogic and hypnopompic hallucinations which may be formed or unformed and associated with sleep paralysis.

In Parkinson's disease, hallucination are realistic nonthreatening images of people or animals and may be treatment associated. In Lewy body dementia hallucinations (by definition) occur in the first year.

Hallucinations in AD are as high as 67 % in facilities (much lower at home) and are associated with aggressive behavior. Such patients may also have visual processing deficits.

In DT's, patients usually see animals but may see Lilliputian hallucinations.

LSD usually causes visual hallucinations exacerbated by eye closure, geometric colors or audiovisual synesthesia. In general hallucinosis correlates with serotoninergicity. Other drugs include PCP, mescaline, cocaine, and meth (ecstasy) cause hallucinations.

Eidetic imagery is vivid internal imagery expressed onto the outside.

In depression, hallucinations are mood congruent, whereas in schizophrenia they are not.

Musical hallucinations occur in deafness, encephalitis, epilepsy, , and temporal lobe lesions.

Tactile hallucinations occur after amputations including children born without limbs. If they have the feeling of amputated limbs moving they are called kinesthetic hallucinations.Formication hallucinations (of bugs crawling) occur in DT's, schizophrenia, complex partial seizures, the use of hallucinogens, or if unilateral,with thalamic or parietal lesions.They also can be paraneoplastic in origin.

Narcoleptics may experience auditory hallucinations such as collections of sounds or melodies or tactile ones such as pinching, rubbing, light touching, or feeling above the bed and seeing one's own body below. They are complex and realistic.

Olfactory hallucinations may be part of an aura or complex partial seizure, and emanate from the olfactory bulb, posterior medial frontal cortex, olfactory cortex, uncus or anterior temporal lobe.

Gustatory hallucinations are especially common with uncinate gyrus seizures with a bitter, sweet, salty or tobacco like metallic or indescribable strange taste. They occur in 4 % of TLE, and parietal opercula seizures. Visceral hallucinations are common in TLE.

Drugs can cause hallucinations. Notably, digoxin can cause a yellow green tinge and sildafenil a blue tinged hallucination.