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Emergency And Acute Medicine – Hallucinations
Overview And Definitions
Hallucinations represent a clinical symptom rather than a definitive diagnosis. They may be auditory, visual, tactile, gustatory, or olfactory in nature. A hallucination is defined as a sensory perception experienced as real in the absence of external stimulation of the relevant sensory organ and is perceived as originating from that organ. Insight into the unreality of the experience may or may not be present. An illusion refers to a misinterpretation of an actual external stimulus. A flashback is the re-experiencing of a prior memory, sensation, or perceptual event with a compelling sense of reality. A pseudohallucination describes a hallucination-like experience that is not perceived through a sensory organ, such as voices perceived internally rather than externally.
Epidemiology And Frequency
The lifetime prevalence of auditory hallucinations in the general population is estimated at 4–8%, although rates vary depending on definitions and inclusion of pseudohallucinations. More than half of elderly patients with dementia experience hallucinations or paranoid symptoms.
Causes And Contributing Factors
Hallucinations arise from a wide range of psychiatric, medical, neurologic, metabolic, infectious, and substance-related causes. Psychiatric causes include schizophrenia, bipolar disorder with mania, and major depressive disorder. Acute intoxications associated with hallucinations include ethanol, cannabis, and synthetic cannabinoids such as K2 and Spice. Sympathomimetic agents include amphetamine, methamphetamine, cocaine, and synthetic cathinones. NMDA antagonists such as ketamine, PCP, and dextromethorphan are well-known precipitants. Serotonergic substances include MDMA, LSD, mescaline, psilocybin, 2C compounds, and 5-MeO derivatives. Salvia divinorum acts as a kappa opioid receptor agonist and may cause synesthesia. Opiates and inhalants such as toluene and nitrous oxide are additional contributors. Medications associated with hallucinations include anticholinergic agents, corticosteroids, and methylphenidate. Withdrawal states from ethanol, benzodiazepines, barbiturates, and GHB commonly produce hallucinations. Substance-induced psychotic disorders include methamphetamine-associated psychosis, which may persist or recur even without ongoing use, and cannabis-induced psychosis. Infectious causes include meningitis and encephalitis, and in patients with dementia, common infections such as urinary tract infection or pneumonia may trigger hallucinations. Metabolic causes include hypoglycemia, electrolyte disturbances, thyroid or adrenal disease, Wilson disease, and thiamine deficiency. Neurologic etiologies include seizures, migraines, intracranial hemorrhage, brain tumors, stroke, and Tourette syndrome. Neurodegenerative disorders such as Parkinson disease, Lewy body dementia, Alzheimer disease, and HIV are also associated. Ocular conditions include glaucoma, macular degeneration, and Charles Bonnet syndrome. Other causes include sensory or sleep deprivation, extreme fatigue or stress, heat illness, religious or ritual practices, and transitions between sleep and wakefulness.
Special Population Considerations
In pediatric patients, hallucinations are relatively common and often developmentally normal. Most children with hallucinations do not have psychosis. Hallucinations may occur during delirium associated with fever, and a medical or neurologic cause should always be considered. In geriatric patients, hallucinations are most often due to organic causes and commonly accompany dementia, depression, medication reactions, or substance use. They are frequently associated with agitation, and atypical antipsychotics may be effective but must be used cautiously due to adverse effects.
Clinical Evaluation And Presentation
Obtaining an accurate history is often challenging, and collateral information from family, EMS, police, or caregivers is critical. Clinicians should assess for behavioral changes from baseline, delusions, persecutory beliefs, prior hallucinations, medication changes, and substance use. Rapidly fluctuating cognition suggests delirium. Headache may indicate migraine or intracranial pathology. Physical examination findings vary by etiology. Acute psychosis may present with disorganized thought and response to internal stimuli. Mania is characterized by pressured speech and excessive talking. Delirium presents with altered consciousness, disorientation, and abnormal vital signs. CNS lesions may cause cranial nerve deficits, aphasia, focal neurologic findings, or gait abnormalities. Systemic or infectious illness may present with fever, nuchal rigidity, asterixis, myoclonus, jaundice, or ascites. Intoxication or withdrawal syndromes may show mydriasis, tachycardia, hypertension, hyperthermia, diaphoresis, agitation, miosis, bradypnea, hyperreflexia, clonus, tremor, or nystagmus depending on the agent involved.
Diagnostic Testing And Interpretation
Initial evaluation commonly includes a complete blood count, serum chemistries, ethanol, acetaminophen, and salicylate levels, and urinalysis. Additional testing is guided by clinical suspicion and may include urine drug screening, ECG, thyroid studies, liver function tests, RPR, folate, vitamin B12, thiamine levels, and specific drug concentrations. Brain imaging with CT or MRI and chest radiography may be indicated. Lumbar puncture should be considered if infection is suspected, and EEG may be useful when seizures are a concern. Emergent psychiatric consultation is indicated for acute psychiatric illness or decompensation of chronic psychiatric disease.
Core Emergency Department Workup
Patients with a known psychiatric disorder and characteristic symptoms typically require limited testing. Patients with undifferentiated hallucinations, especially those in high-risk populations, require comprehensive medical evaluation to exclude organic causes.
Differential Diagnosis Considerations
The primary goal of emergency evaluation is to distinguish psychiatric from nonpsychiatric causes. Psychiatric etiologies are more likely when hallucinations are auditory or command in nature, incorporated into a delusional system, occur between ages 13 and 40, and are associated with flat affect, normal orientation, and disorganized attention. Nonpsychiatric causes are more likely in elderly patients, individuals with substance use history, those without prior psychiatric illness, patients with underlying medical conditions, and those of lower socioeconomic status. Visual hallucinations are more common in delirium, dementia, migraines, dopamine agonist therapy, posterior cerebral infarcts, and narcolepsy.
Management Principles
Prehospital providers should note environmental clues such as unsafe living conditions or drug paraphernalia. Initial management focuses on airway, breathing, and circulation, correction of abnormal vital signs, finger-stick glucose testing, and consideration of thiamine administration. Agitation should be managed with de-escalation techniques, physical restraints when necessary, and chemical sedation. Identified medical causes should be treated directly, and antipsychotics are often unnecessary in these cases. Acute psychosis or psychiatric decompensation is treated with antipsychotics and benzodiazepines. Hallucinations associated with intoxication and excited delirium require supportive care and benzodiazepines. In dementia-related hallucinations, reversible causes should be treated first, and antipsychotics used cautiously due to risks.
Safety Alert
In patients with hallucinations and excited delirium due to acute intoxication, except ethanol-related cases, benzodiazepines are preferred and antipsychotics should be avoided.
Disposition And Follow-Up
Hospital admission is required for patients with medical conditions necessitating inpatient care or acute psychiatric illness requiring hospitalization. Discharge may be considered when symptoms resolve after treatment of a reversible cause or when psychiatric decompensation is stabilized with a safe home environment and reliable follow-up. Referral for substance use treatment should be arranged when appropriate. Follow-up should be tailored to the underlying medical or psychiatric condition.
Clinical Pearls And Common Errors
Do not assume auditory hallucinations are psychiatric or that visual or tactile hallucinations are medical without a full evaluation. In older adults, hallucinations should never be attributed to psychiatric disease without extensive medical workup. Antipsychotics should not be used for excited delirium due to acute intoxication except in ethanol withdrawal; benzodiazepines are the treatment of choice.
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