Olfactory hallucinations are delusions of smell, characterized by the perception of a smell that is not present in reality. Patients may experience neutral, repulsive, and pleasant odors. Smells can be perceived as arising from somewhere outside, coming from within the body, localized in the intrapsychic space and captured by the “inner sense of smell”. Common options are the smell of burning, rotting meat, smoldering, poison. Diagnosis is carried out during the conversation, observation, tests for the identification of odors. Symptomatic therapy is based on the use of neuroleptics.
general characteristics
Olfactory hallucinations are diverse in content. Unpleasant imaginary odors are associated mainly with depressive mood, including anxiety, fear, suspicion. Patients smell rotting, decomposition, toxic substances, sewage. To ease the sensations, they cover their nose with their hands, insert cotton swabs into the nasal passages, ventilate the room for no objective reason, use air fresheners. Such hallucinations often form the basis for the formation of delusional ideas, for example, about the use of poisons by malefactors or the storage of corpses.
Olfactory hallucinations of pleasant content are represented by the aromas of flowers, delicious food, and favorite perfumes. Often, patients cannot guess what is the source of the smell, they describe it as unearthly, giving joy, inspiring. Hallucinatory experiences accompany ecstatic, manic states. Imaginary perceptions of smells of a neutral nature are usually not noticed by people, they do not act as grounds for complaints.
Olfactory hallucinations differ in where patients identify their source. It can be localized in the environment (on the street, in the next room), in the patient's body or in an imaginary space (in the air, "in the soul" - in the mental space). As a rule, the unpleasant smell of poison, putrefaction, sewage is defined as coming from external objects; the smell of sweat, urine, decomposition of organs - from one's own body. The imaginary causes of pleasant smells are magical, mystical sources that are not present in the physical world.
Causes of olfactory hallucinations
Olfactory hallucinations are found in people with mental disorders, neurological diseases, alcoholism or drug addiction. The underlying causes are acute psychotic states and organic brain damage. In both cases, pathological activation of the brain structures responsible for the processing of olfactory stimuli and the formation of an appropriate image of perception occurs. Therefore, people who feel imaginary aromas can describe them in detail, react with a loss of appetite, a feeling of nausea, or an increase in salivation.
Neurological diseases
Organic damage to the brain structures responsible for olfactory perception is the most common cause of hallucinations. Observed in local traumatic and tumor processes, neurodegenerative pathologies, epileptic foci. The possibility of forming a critical attitude of patients to imaginary odors depends on the severity and nature of the course of the disease, hallucinatory origin is recognized by patients with reversible forms of pathologies (injuries, regressing tumors). As possible causes of olfactory hallucinations are considered:
- Epilepsy. Olfactory hallucinations are often diagnosed in people with epilepsy. The causes of this symptom continue to be studied. According to one of the confirmed theories, the basis is the increased ictal activity of the anterior piriform cortex (section of the olfactory system). Its forced stimulation leads to the development of convulsive seizures. Approximately 1% of patients experience olfactory auras, which are characterized by the smell of sulfur, burnt rubber, feces.
- Traumatic brain injury. Olfactory hallucinations and impaired recognition of odors are observed when the cortical olfactory cortex is damaged in the temporal and frontal mediobasal regions. With severe injuries, these disorders occur during the recovery period in 48% of patients, with moderate injuries - in 15%. Typically, the perception of smoke, hydrogen sulfide, burning - neutral or unpleasant imaginary stimuli.
- Alzheimer's disease. Patients are diagnosed with olfactory disorders, the most common of which are violations of identification and discrimination of smells. Olfactory hallucinations are determined in 1.2% of patients. Often they become the basis for delusions of persecution, such as the idea of a spilled poison or poison gas released by neighbors. The reason is atrophic changes in the cerebral cortex, in which the primary olfactory cortex, areas of the hippocampus, thalamus and hypothalamus are affected. The degree of olfactory disturbances directly correlates with the severity of the decrease in speech and intelligence.
- Tumors of the brain. Hallucinations of various types develop with neoplasms in the area of the temporal lobes of the cortex or the bottom of the third ventricle. Olfactory phenomena are represented by smells of burning, rotten eggs, smoke. Their localization is determined near the nose, from the mouth, from the body. With tumors of the left hemisphere, a prolonged anxious depression increases, which is replaced by euphoria when the tumor spreads to the frontal region of the right hemisphere.
- Parkinson's disease. The causes of olfactory disturbances in Parkinson's disease continue to be studied. According to recent studies, disorders are associated with atrophic processes in the structures of the limbic system - in the piriform cortex, amygdala. Many patients have reduced ability to recognize odors. Olfactory hallucinations are much less common.
Mental disorders
Olfactory hallucinations are characteristic of the acute phase of mental illness. For some pathologies, for example, for bipolar affective disorder, they are specific markers of an approaching exacerbation. With a sluggish process, changes in the olfactory function are hardly noticeable. In the prodromal period, they serve as harbingers of severe psychotic states, behavioral disorders. The following mental illnesses are the causes of olfactory hallucinatory symptoms:
- Schizophrenia. In schizophrenia, the disruption of the olfactory system is associated with pathological changes in the cortical and peripheral zones of the analyzer. There is a decrease in innervation, distortion of the regulation of intracellular transmission of the nerve signal. Most patients have odor recognition disorders, and approximately 35% have olfactory hallucinations. Patients feel smells of a different nature, the origin of which is often interpreted as delusional ideas.
- Bipolar disorder . The brain cortical areas responsible for emotions and for the perception of smells overlap each other. Studies of olfactory functions in depressed patients have shown a decrease in response to odors that provoke an emotional response. Many patients found it difficult to determine the localization of the source, felt unpleasant odors more strongly, almost did not feel pleasant ones. Severe depressive episodes with psychotic symptoms are often accompanied by delusions, olfactory hallucinations, and depressive stupor. Typical smells of rotting flesh, dirt.
- Stimulant psychosis . Psychotic disorders caused by the use of psychostimulants are acute, with paranoid ideas, hallucinations, and disorganization of behavior. The causes of hallucinations of the olfactory type are the use of large doses of the drug, chronic drug addiction. For example, olfactory perceptual delusions with relational delusions often occur in the development of methamphetamine psychosis. In rare cases, hallucinatory symptoms unfold when taking therapeutic doses of psychostimulants under medical supervision.
- Alcoholic psychoses . Olfactory hallucinations can occur as part of alcoholic delirium - a state of clouded consciousness during the period of alcohol withdrawal after prolonged continuous use. Most often they are accompanied by delusions of poisoning: a person smells poisonous gas or poison, is alarmed, hides at home or seeks protection from others. The causes of hallucinosis are acute alcoholic psychosis, which develops at the height of intoxication or a hangover, as well as subacute meta-alcoholic psychosis, which lasts several months.
Diagnostics
Olfactory hallucinations are a frequent symptom of mental disorders and organic lesions of the central nervous system. Patients are examined by a psychiatrist and a neurologist, and an otolaryngologist is appointed to exclude diseases of the nasal cavity. If a neurological disease is suspected, instrumental brain studies are performed - EEG, CT, MRI. Mental illnesses are diagnosed by the method of clinical conversation, pathopsychological testing. The following procedures are used to detect olfactory disorders:
- Clinical survey. While maintaining a critical perception of the symptoms of the disease, patients report sudden influxes of strong odors without an external cause. Often such conditions are accompanied by fear, anxiety, emotional stress. In acute psychotic disorders, patients more often perceive hallucinations as a reality, report them when describing a crazy idea (poisoning, intoxication, witchcraft effects). The doctor receives objective clinical information from the patient's family members.
- observation. Patients with hallucinations are characterized by inadequate behavior, focused on hallucinatory images as real-life stimuli. They can sniff, wrinkle their nose, cover it with their hand or handkerchief. Sometimes patients begin to breathe frequently, complain of a lack of fresh air, nausea. They ask to open a window for ventilation, they tend to leave the room as soon as possible if they think that the source of the smell is somewhere nearby.
- Olfactometric tests. Smell disorders are diagnosed using sets of odorous substances. In clinical practice, the use of the Bernstein kit and adapted versions of the Sniffin Sticks test are common. The results allow to determine the threshold of smell, the function of distinguishing and identifying odors, the risk of developing olfactory hallucinations. Tests act as provoking factors in identifying a hallucinatory-delusional syndrome (patients tend to interpret the origin and effect of each smell in a peculiar way).
Treatment
The main therapy is aimed at eliminating the cause of hallucinations - a mental disorder, a neurological disease, a state of drug or alcohol intoxication. With severe olfactory hallucinations that change the patient's behavior and pose a threat to himself or others, antipsychotic drugs are selected. If the patient is available for contact, responds correctly to the words of other people, sessions of cognitive psychotherapy are held, focused on the formation of a critical assessment of the symptoms of the disease, the ability to distinguish reality from hallucinatory phenomena.