Hallucination

Dr. Debjani Datta, Principal

Edited by: Anis Ahmed

The word "hallucination" was introduced into the English language by the 17th-century physician Sir Thomas Browne in 1646 from the derivation of the Latin word alucinari meaning to wander in the mind. For Browne, hallucination means a sort of vision that is "depraved and receive[s] its objects erroneously".

A hallucination is a perception in the absence of external stimulus that has qualities of real perception. Hallucinations are vivid, substantial, and are perceived to be located in external objective space. They are distinguishable from several related phenomena, such as dreaming, which does not involve wakefulness; pseudohallucination, which does not mimic real perception, and is accurately perceived as unreal; illusion, which involves distorted or misinterpreted real perception; and imagery (imagination), which does not mimic real perception and is under voluntary control.Hallucinations also differ from "delusional perceptions", in which a correctly sensed and interpreted stimulus (i.e., a real perception) is given some additional (and typically absurd) significance.

Hallucinations can occur in any sensory modality—visual, auditory, olfactory, gustatory, tactile, proprioceptive, equilibrioceptive, nociceptive, thermoceptive and chronoceptive.

Types of hallucination

There are many different types of hallucinations, including:

Visual

Visual hallucinations involve seeing things that aren’t there. The hallucination may be of objects, visual patterns, people, or lights. It is "the perception of an external visual stimulus where none exists".

Visual hallucinations are classified as simple or complex:

• Simple visual hallucinations (SVH) are also referred to as non-formed visual hallucinations and elementary visual hallucinations. These terms refer to lights, colors, geometric shapes, and indiscrete objects. These can be further subdivided into phosphenes which are SVH without structure, and photopsias which are SVH with geometric structures.
• Complex visual hallucinations (CVH) are also referred to as formed visual hallucinations. CVHs are clear, lifelike images or scenes such as people, animals, objects, places, etc.

Numerous hypotheses have been suggested to explain the genesis of visual hallucinations. These have been summarized and categorized by Asaad and Shapiro: psychophysiologic (i.e., as a disturbance of brain structure), psychobiochemical (as a disturbance of neurotransmitters), and psychodynamic (as an emergence of the unconscious into consciousness). Visual hallucinations can be the result of all 3 processes, given the interplay among disturbances of brain anatomy, brain chemistry, prior experiences, and psychodynamic meaning.

Olfactory

Olfactory hallucinations involve sense of smell. Phantosmia (olfactory hallucinations), smelling an odor that is not actually there,and parosmia (olfactory illusions), inhaling a real odor but perceiving it as different scent than remembered,are distortions to the sense of smell (olfactory system) that, in most cases, are not caused by anything serious and usually go away on their own in time.

 

Auditory

Auditory hallucinations are among the most common type of hallucination. Auditory hallucinations or paracusia are the perception of sound without outside stimulus.

Other examples of this type of hallucination include hearing sounds, like someone walking in the attic or repeated clicking or tapping noises.

Auditory hallucinations can be divided into two categories: elementary and complex.

Elementary hallucinations are the perception of sounds such as hissing, whistling, an extended tone, and more. In many cases, tinnitus is an elementary auditory hallucination. However, some people who experience certain types of tinnitus, especially pulsatile tinnitus, are actually hearing the blood rushing through vessels near the ear. Because the auditory stimulus is present in this situation, it does not qualify it as a hallucination.

Complex hallucinations are those of voices, music, or other sounds that may or may not be clear, may be familiar or completely unfamiliar, and friendly or aggressive, among other possibilities. A hallucination of a single individual person of one or more talking voices is particularly associated with psychotic disorders such as schizophrenia, and hold special significance in diagnosing these conditions.

Musical hallucinations are also relatively common in terms of complex auditory hallucinations and may be the result of a wide range of causes ranging from hearing-loss (such as in musical ear syndrome, the auditory version of Charles Bonnet syndrome), lateral temporal lobe epilepsy, arteriovenous malformation, stroke, lesion, abscess, or tumor.

Auditory hallucinations are one of the most important symptoms for the diagnosis of psychosis, especially schizophrenia. Auditory hallucinations are commonly associated with psychiatric disorders such as schizophrenia, psychotic depression, mania, and posttraumatic stress disorder.

High caffeine consumption has been linked to an increase in likelihood of one experiencing auditory hallucinations.

Command

Command hallucinations are hallucinations in the form of commands; they can be auditory or inside of the person's mind or consciousness. The contents of the hallucinations can range from the innocuous to life threatening. People experiencing command hallucinations may or may not comply with the hallucinated commands, depending on the circumstances. Patients with command hallucinations (voices ordering particular acts, often violent or destructive ones) are commonly assumed to be at high risk for dangerous behavior. Command hallucinations are often associated with schizophrenia.

Tactile

Tactile hallucinations involve an abnormal or false sensation of touch or perception of movement on the skin or inside the body. Usually, the condition causes unpleasant, uncomfortable, disturbing sensations. Some people may feel that bugs are crawling over their body or something is inside them trying to get out. One subtype of tactile hallucination, formication, is the sensation of insects crawling underneath the skin and is frequently associated with prolonged cocaine use.However, formication may also be the result of normal hormonal changes such as menopause, or disorders such as peripheral neuropathy, high fevers, Lyme disease, skin cancer etc.

Gustatory

A gustatory hallucination is a sensation of taste without having tasted or eaten something.It is the perception of taste without a stimulus. These hallucinations, which are typically strange or unpleasant, are relatively common among individuals who have certain types of focal epilepsy, Gustatory hallucinations can also be a symptom of schizophrenia. Typically the tastes experienced are unusual and not pleasant.

For example, a person experiencing a gustatory hallucination may perceive they are eating spoiled food even when they are not.

General somatic sensations

General somatic sensations of a hallucinatory nature are experienced when an individual feels that their body is being mutilated, i.e. twisted, torn, or disemboweled. Other reported cases are invasion by animals in the person's internal organs.

Reason of Hallucinations

There are different reasons or causes for Hallucinations. Some of the reasons are discussed below:-

Delirium tremens

One of the more enigmatic forms of visual hallucination is the highly variable, possibly polymodal delirium tremens. Individuals suffering from delirium tremens may be agitated and confused, especially in the later stages of this disease. Insight is gradually reduced with the progression of this disorder. Sleep is disturbed and occurs for a shorter period of time, with rapid eye movement sleep.

Hypnagogic hallucination

These hallucinations occur just before falling asleep, and affect a high proportion of the population The hallucinations can last from seconds to minutes; all the while, the subject usually remains aware of the true nature of the images. These may be associated with narcolepsy. Hypnagogic hallucinations are sometimes associated with brainstem abnormalities.

Peduncular hallucinosis

Peduncular means pertaining to the peduncle, which is a neural tract running to and from the pons on the brain stem. These hallucinations usually occur in the evenings, but not during drowsiness, as in the case of hypnagogic hallucination. The subject is usually fully conscious and then can interact with the hallucinatory characters for extended periods of time.

Parkinson's disease and Lewy body dementia

Parkinson's disease is linked with Lewy body dementia for their similar hallucinatory symptoms. The symptoms strike during the evening in any part of the visual field, and are rarely polymodal. Hallucination may begin with illusions. where sensory perception is greatly distorted, but no novel sensory information is present. These typically last for several minutes, during which time the subject may be either conscious and normal or drowsy/inaccessible.

Charles Bonnet syndrome

Charles Bonnet syndrome causes a person whose vision has started to deteriorate to see things that aren't real. It is visual hallucinations experienced by a partially or severely sight impaired person. The hallucinations can occur at any time and can distress people of any age. The hallucinations may be simple patterns, or detailed images of events, people or places. They're only visual and don't involve hearing things or any other sensations. There are 2 main types of hallucination that people with Charles Bonnet syndrome tend to experience.

They are :

·         simple repeated patterns

·         complex images of people, objects or landscapes.

Migraine coma

This type of hallucination is usually experienced during the recovery from a comatose state. The migraine coma can last for up to two days, and a state of depression is sometimes comorbid.

Focal epilepsy

Visual hallucinations due to focal seizures differ depending on the region of the brain where the seizure occurs. For example, visual hallucinations during occipital lobe seizures are typically visions of brightly colored, geometric shapes that may move across the visual field, multiply, or form concentric rings and generally persist from a few seconds to a few minutes.

Temporal lobe seizures, can produce complex visual hallucinations of people, scenes, animals, and more as well as distortions of visual perception. Complex hallucinations may appear to be real or unreal, may or may not be distorted with respect to size, and may seem disturbing or affable, among other variables.

Schizophrenia

Psychiatric illnesses, in particular schizophrenia, are probably one of the conditions most commonly associated with hallucinations in general. The hallucinations of schizophrenia tend to be of the auditory type, although visual hallucinations can certainly occur.

Drug-induced hallucination

Drug-induced hallucinations are caused by hallucinogens, dissociatives, and deliriants, including many drugs with anticholinergic actions and certain stimulants, which are known to cause visual and auditory hallucinations. Some psychedelics such as lysergic acid diethylamide (LSD) and psilocybin can cause hallucinations that range in the spectrum of mild to intense. In addition, many drugs that are available in the market have side effects that include hallucinations. 

Sensory deprivation hallucination

Hallucinations can be caused by sensory deprivation when it occurs for prolonged periods of time, and almost always occur in the modality being deprived (visual for blindfolded/darkness, auditory for muffled conditions, etc.). Sensory deprivation or perceptual isolation is the deliberate reduction or removal of stimuli from one or more of the senses.

Experimentally-induced hallucinations

Anomalous experiences, such as so-called benign hallucinations, may occur in a person in a state of good mental and physical health, even in the apparent absence of a transient trigger factor such as fatigue, intoxication or sensory deprivation.

Treatments

There are few treatments for many types of hallucinations. However, for those hallucinations caused by mental disease, a psychologist or psychiatrist should be consulted, and treatment will be based on the observations of those doctors. Antipsychotic and atypical antipsychotic medication may also be utilized to treat the illness if the symptoms are severe and cause significant distress.

Some of the approaches used to treat hallucination are described below:

• General measures that can be taken to reduce the frequency or severity of hallucinations include stress management, healthy living, regular exercise and sleeping well.
• The use of illicit drugs such as cocaine, LSD, amphetamines or ecstasy can cause hallucinations. Excessive alcohol consumption is another cause. These hallucinations can occur during periods of withdrawal from drugs or alcohol if the substances are stopped too suddenly. People experiencing hallucinations due to drugs or alcohol withdrawal can be given medication to help prevent the hallucinations occurring. Rehabilitation programs are also available to help the patient recover from their addiction.
• Psychosocial strategies used to help manage hallucination include education and counselling to help the patient and their family cope with the hallucinations and understand the importance of medication compliance.
• Examples of antipsychotic medications used to treat hallucinations include haloperidol, olanzapine and risperidone.
• Hallucinations can occur as a side effect of the treatment for Parkinson’s disease. If this occurs, the patient’s medication may require adjustment. Usually, amantadine and anticholinergics are stopped first. Thereafter, dopamine agonists may be withdrawn. Clozapine and quetiapine are examples of neuroleptic drugs that may help treat hallucinations in Parkinson’s disease.
• Other problems that occur as a result of hallucination such as memory disturbance, sleep disorder, depression, anxiety and associated panic attacks may also need to be managed with treatment.

 

 

References

1) Chen E, Berrios GE (1996). "Recognition of hallucinations: a multidimensional model and methodology".

2) Johnson FH (1978). The Anatomy of Hallucinations.

3) www.nhs.uk