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Delirium - Diagnosis
Last reviewed: 03.07.2025

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The diagnosis of delirium is based on the data of the examination of the patient for a certain period of time, sufficient to detect changes in the level of consciousness and cognitive impairment. For a rapid assessment of cognitive functions directly at the patient's bedside, the Short Orientation-Memory-Concentration Test of Cognitive Impairment is used. To assess orientation, the patient is asked to state his name, location, date, time of day. To assess short-term memory, the patient is asked to remember a name and address, which are repeated until the patient can name them. Concentration is checked by checking the countdown from 20 to 1, and then listing the months of the year in reverse order. Finally, the patient is asked to repeat the name and address he remembered. The assessment is based on the number of errors. The test can be repeated in whole or in part several times a day or over several days to detect fluctuations in its performance. The Mini-Mental State Examination (MMSE) can also be used to assess orientation, concentration, memory and recall, praxis, naming, repetition, and command execution. Various screening tests for delirium have been proposed, but they lack reliability, validity, and ease of use. Many focus on cognitive function, ignoring the non-cognitive manifestations of delirium.
Because patients with delirium cannot provide reliable information to the physician, the physician should attempt to obtain information about the premorbid state and previous symptoms from relatives and friends of the patient, as well as from medical personnel. Medical personnel records may contain useful information about the duration and quality of sleep, the presence of confusion, and disturbances in perception.
Sleep disorders, especially sleep-wake cycle disturbances, are common in patients with delirium. Patients are often frightened upon awakening and often report vivid dreams and nightmares. Sundowing, an increase in behavioral disturbances at night, is another common manifestation of delirium. Although the prevalence of sundowing in hospitalized patients has not been studied, it has been reported to occur in one in eight patients admitted to care facilities.
Perceptual disturbances can be assessed by asking open-ended questions, such as how the patient has been treated in the past and whether any unusual events have occurred. This can be followed by more targeted questions about the presence of hallucinations, such as: “Sometimes with this disorder a special state of consciousness occurs in which a person hears voices (or sees objects) that he or she does not normally hear (or see). Has this ever happened to you?” Patients with hallucinations or delusions may hide under the covers or pull the sheets over themselves. Sometimes they talk to themselves or turn their head or eyes to the side under the influence of some internal stimuli.
Affective disorders, particularly depression, can be assessed using the Hamilton Depression Rating Scale or the Geriatric Depression Rating Scale. The Hamilton Depression Rating Scale is based on a physician's scoring of depressive symptoms. The Geriatric Depression Rating Scale requires the patient to assess symptoms themselves. However, it does not assess symptoms that may be associated not only with depression but also with a somatic or neurological disorder, such as sleep or appetite disorders. The Jung Mania Rating Scale can be used to assess manic symptoms. The use of standardized scales during a patient examination provides more reliable and valid data than a routine clinical examination. In addition, these scales provide a more objective quantitative assessment of existing disorders. As an addition to a clinical examination, the scales can be used dynamically to assess the effectiveness of treatment.
Diagnostic criteria for delirium
- A. Disturbance of consciousness (eg, incomplete awareness of surroundings) with limited ability to focus, sustain, and shift attention
- B. Impaired cognitive function (memory loss, disorientation, speech disorder) or impaired perception that is not better explained by the presence of a previous, established, or developing dementia
- B. The disturbances develop over a short period of time (usually hours or days) and tend to fluctuate throughout the day.
- G. Data from the anamnesis, fiscal examination or additional research methods confirm that the disorders are a direct physiological consequence of a general disease
[ 5 ], [ 6 ], [ 7 ], [ 8 ], [ 9 ]
Diagnostic criteria for intoxication delirium
- A. Disturbances of consciousness (eg, incomplete awareness of surroundings) with limitations in the ability to focus, maintain, and shift attention
- B. Impaired cognitive function (memory loss, disorientation, speech disorder) or impaired perception that is not better explained by the presence of a previous, established, or developing dementia
- B. The disturbances develop over a short period of time (usually hours or days) and tend to fluctuate throughout the day.
- D. History, physical examination, or additional testing confirms (1) or (2):
- the symptoms indicated in criteria A and B develop during the period of intoxication
- disorders are etiologically associated with the use of drugs
[ 10 ], [ 11 ], [ 12 ], [ 13 ], [ 14 ]
Diagnostic criteria for withdrawal delirium
- A. Disturbances of consciousness (eg, incomplete awareness of surroundings) with limitations in the ability to focus, maintain, and shift attention
- B. Impaired cognitive function (memory loss, disorientation, speech disorder) or impaired perception that is not better explained by the presence of a previous, established, or developing dementia
- B. The disturbances develop over a short period of time (usually hours or days) and tend to fluctuate throughout the day.
- D. History, physical examination, or additional testing confirm that symptoms identified in criteria A and B developed during or shortly after withdrawal.
Diagnostic criteria for delirium of multiple etiology
- A. Disturbances of consciousness (eg, incomplete awareness of surroundings) with limitations in the ability to focus, maintain, and shift attention
- B. Impaired cognitive function (memory loss, disorientation, speech disorder) or impaired perception that is not better explained by the presence of previous, established, or developing dementia
- B. The disturbances develop over a short period of time (usually hours or days) and tend to fluctuate throughout the day.
- D. The history, physical examination, or additional investigations confirm that delirium is caused by more than one cause (for example, a combination of several common diseases or a combination of one of the diseases with the action of a toxic substance or a side effect of a drug)
Additional research methods
Laboratory data are helpful in determining the etiology of delirium. After a thorough history and physical examination, a serum test is performed, including a complete blood count, electrolytes (including calcium and magnesium), glucose, folate, vitamin B12, renal function tests, liver function tests, thyroid function tests, serologic tests for syphilis and HIV infection, and ESR. It is advisable to include a complete urinalysis, urine toxicity tests, blood gas tests, as well as a chest X-ray and ECG. In addition, an EEG, lumbar puncture, body fluid cultures, and neuroimaging may be necessary in some cases. There is no standard set of tests that are routinely used to establish the etiology of delirium. The more extensive the test, the more information it provides, but the more expensive it is. The general practitioner may involve a consultant to help determine the necessary scope of the test and the optimal treatment.
- Clinical blood test with determination of formula and ESR
- Electrolytes
- Kidney function
- Liver function
- Glucose
- Thyroid function
- Serological tests for syphilis
- HIV test
- Calcium
- Magnesium
- Folic acid
- General urine analysis
- Urine toxicology test
- Arterial blood gases
- Chest X-ray
- ECG
- EEG
- Lumbar puncture
- Neurovisualization
[ 20 ], [ 21 ], [ 22 ], [ 23 ]
Instrumental methods for diagnosing delirium
Electroencephalography. EEG may be useful in the diagnosis of delirium. About 50 years ago, Romano found a correlation between decreased alertness, background frequency, and disorganization of the EEG. They later coined the term “acute cerebral insufficiency” to describe the condition we now call delirium. Quantitative EEG may be useful in the differential diagnosis of delirium and dementia in elderly patients with unclear diagnoses. Increased theta activity is associated with a correct diagnosis of delirium in 89% of cases and a false negative diagnosis of dementia in only 6%.
Neuroimaging
In patients taking antidepressants, who have a higher risk of developing delirium, MRI reveals structural changes in the basal ganglia. Moderate or severe damage to the white matter increases the likelihood of developing delirium during electroconvulsive therapy. In patients with delirium, CT more often revealed focal changes in the association areas of the right hemisphere, cortical atrophy, and ventricular enlargement than in the control group.
Differential diagnosis of delirium
DSM-IV identifies variants of delirium depending on its etiology. The differential diagnosis of delirium coincides with the differential diagnosis of psychotic disorders. Delirium can be caused by dementia, schizophrenia, affective disorders with psychotic manifestations, general diseases, intoxications and withdrawal syndromes. Often, the development of delirium is caused by several reasons.
Memory impairment is common in both dementia and delirium. However, a patient with early dementia usually retains clear consciousness without fluctuations in the level of alertness. Since patients with dementia are predisposed to developing delirium, it should be taken into account that worsening attention deficit and other cognitive impairments may be associated not only with the disease itself that causes dementia. In this case, the condition of a patient with dementia should be analyzed for the possible development of delirium. Often, these patients are unable to report acute discomfort that may arise due to an exacerbation of a chronic somatic disease or the addition of an infection. In a patient with dementia, the cause of behavioral disorders may be delirium. If delirium develops, the patient should undergo a physical examination, it is necessary to conduct a blood serum and urine test, chest X-ray, ECG, since its cause may be a severe intercurrent disease. In addition, a careful drug history should be taken, as medications that the patient is taking to treat comorbidities or behavioral disorders associated with dementia may be a cause of delirium.
In some cases, delirium acts as a kind of precursor to dementia or draws attention to developing cognitive impairments that previously went unnoticed. The short period during which delirium develops distinguishes it from dementia.
[ 24 ], [ 25 ], [ 26 ], [ 27 ], [ 28 ]
Schizophrenia
A well-collected anamnesis often helps in the differential diagnosis of delirium with schizophrenia or schizophreniform psychoses. For example, the impairment of the ability to concentrate and switch attention distinguishes delirium from schizophrenia. In addition, schizophrenia is not characterized by memory and orientation disorders. Sometimes dementia develops in a patient with schizophrenia. In the diagnosis of such situations, the points mentioned earlier are taken into account. In the differential diagnosis between delirium and schizophrenia, it is important to consider the relationship of delirium with the use of certain medications, concomitant diseases, intoxications, or withdrawal syndrome. Delirium in delirium usually does not have such a bizarre and systematic nature as in schizophrenia. In addition, schizophrenia and delirium are not mutually exclusive, since a patient with schizophrenia can develop delirium.
Neuroleptics used to treat schizophrenia may cause delirium. Side effects of neuroleptics associated with delirium include neuroleptic malignant syndrome, a medical emergency, and akathisia, a subjective feeling of restlessness usually accompanied by psychomotor agitation. Signs of neuroleptic malignant syndrome include fever, rigidity, autonomic hyperactivity, elevated CPK, and leukocytosis. In addition, many neuroleptics have anticholinergic activity, which may contribute to the development of delirium.
Affective disorders with psychotic manifestations
Affective disorders such as depression or mania accompanied by psychotic manifestations (affective psychoses) may be mistaken for delirium, and vice versa. It is important to differentiate these conditions correctly, since their prognosis and treatment are quite different. Unrecognized and untreated depression is associated with increased morbidity, disability, increased health care costs, and increased mortality. Mania is also associated with disability and increased morbidity. The mood changes in delirium are not as pronounced as in affective disorders, although patients with delirium may have dysphoria, expansive mood, or affective lability. Patients with a history of affective disorders are more likely to have mood changes. The content of psychotic disturbances in patients with affective disorders is often of a depressive or manic nature, including delusions of self-blame, suicidal and pejorative ideas in depression, or delusions of grandeur in mania. At the same time, delirium in delirium has a more fragmented nature. Persistent mood changes are more typical of affective disorders than of delirium. The detection of attention deficit and other cognitive functions during neuropsychological examination also helps in the differential diagnosis of delirium and affective disorder with psychotic manifestations. Depression with psychotic disorders is usually well treated with antidepressants and neuroleptics or electroconvulsive therapy. In patients with bipolar disorder, the manic phase with psychotic manifestations is amenable to treatment with normothymic drugs, neuroleptics or electroconvulsive therapy. At the same time, delirium, erroneously diagnosed as affective psychosis, will worsen with the use of these drugs - due to the fact that they can increase confusion, and the cause of delirium, which remains unrecognized, is not corrected accordingly.