Hallucinations

Basics

Description

  • Hallucination: Wakeful perceptions of any of the five senses that occur in the absence of external stimuli:
    • Patients may or may not have insight that they are having a hallucination
  • Auditory hallucinations:
    • Most reported type of hallucination with an estimated lifetime incidence of 4–8% in the general population
    • Associated with primary psychiatric disorders (schizophrenia spectrum disorders) and temporal lobe seizures
    • 60–80% of individuals diagnosed with schizophrenia experience auditory hallucinations
  • Visual hallucinations:
    • Occur with occipital lobe dysfunction, delirium, Lewy body dementia, and occipital seizures
    • Simple visual hallucinations: Lines, geometric designs, colors, lights, but no complex or formed images
  • Olfactory hallucinations:
    • Arise from temporal lobe pathology, particularly mesial temporal sclerosis and tumors
  • Gustatory hallucinations:
    • Linked to temporal lobe epilepsy and rare brainstem lesions
  • Tactile hallucinations:
    • Seen in substance withdrawal (alcohol, cocaine), neuropathy, and delirium tremens
  • Illusion: Misperception or misinterpretation of a real external stimulus
  • Flashback: Recurrence of a memory, feeling, or perceptual experience from the past that may have the compelling sense of reality
  • Synesthesia: Stimulation of one sensory or cognitive modality results in an automatic experience in another modality (ie, hearing colors or smelling sounds)
  • More than 50% of older adults with dementia have paranoia or hallucinations

Etiology

  • Psychiatric:
    • Primary psychotic disorder (eg, schizophrenia)
    • Bipolar disorder, mania
    • Major depression
    • Personality disorders (eg, borderline)
    • PTSD
  • Acute intoxications:
    • Ethanol
    • Cannabis
    • Synthetic cannabinoids (eg, K2, Spice)
    • Sympathomimetics:
      • Amphetamines
      • Cocaine (also causes parasitosis)
      • Synthetic cathinones (“bath salts”)
    • NMDA antagonists:
      • Ketamine
      • PCP
      • Dextromethorphan
    • Serotonergic:
      • MDMA (Ecstasy)
      • LSD
      • Peyote cactus (mescaline)
      • Mushrooms (psilocybin)
      • Designer phenethylamines and tryptamines (eg, 2CB, 5-MeO-DMT)
    • Kappa opioid receptor agonist:
      • Salvia divinorum (causes synesthesias)
    • Inhalants (eg, toluene)
  • Medications:
    • Anticholinergic agents
    • Glucocorticoids
    • Opioids
    • ADHD agents (eg, methylphenidate)
    • Acyclovir
    • Antiparkinsonian agents
  • Withdrawal:
    • Ethanol
    • Benzodiazepines
    • Barbiturates, GHB
    • Baclofen, phenibut
  • Substance use disorders:
    • Methamphetamine-associated psychosis:
      • Prolonged duration of psychosis, auditory hallucinations, and recurrence without relapse of using drug
    • Cannabis-induced psychosis
    • Kratom misuse
    • Nitrous oxide misuse
    • Infectious/autoimmune:
    • Meningitis
    • Encephalitis (eg, herpes simplex)
    • COVID-19
    • Neurosyphilis
    • Systemic lupus erythematosus
    • Multiple sclerosis
    • Anti-NMDA receptor encephalitis
    • Any infection (eg, UTI, pneumonia) in patients with dementia
  • Metabolic:
    • Hypoglycemia
    • Electrolyte imbalances
    • Thyroid disease
    • Adrenal disease
    • Wilson disease
    • Thiamine deficiency (Wernicke)
    • Hepatic or uremic encephalopathy
    • Porphyria
  • Neurologic:
    • Seizures:
      • Partial simple or complex seizures can result in visual, auditory, olfactory, and gustatory hallucinations
    • Migraine aura (usually binocular, simple)
    • CNS hemorrhage, tumor, vascular malformation
    • CVA
    • Tourette syndrome
    • Peduncular hallucinosis (midbrain, pontine, or thalamic lesion)
    • Neurodegenerative disorders:
      • Parkinson
      • Dementia with Lewy bodies
      • HIV/AIDS
      • Huntington disease
  • Ocular:
    • Glaucoma
    • Macular degeneration
    • Charles Bonnet syndrome (release hallucinations from visual acuity loss)
  • Others:
    • Food, sensory, sleep deprivation
    • Fatigue, extreme stress/grief
    • Heat-related illness
    • Religious and ritual activities
    • Falling asleep (hypnagogic) and awakening from sleep (hypnopompic)

Pediatric Considerations

  • Hallucinations are relatively common in children and adolescents and are often developmentally normal
  • Most children with hallucinations do not have psychosis
  • Hallucinations can occur as part of a delirium, such as from fever
  • As with the adult patient, carefully conduct a search for a medical or neurologic etiology

Geriatric Considerations

  • In the older adult patient, hallucinations are most often from a nonpsychiatric cause
  • They can commonly accompany delirium, dementia, depression, medication reactions, and substance use, and are often associated with agitation
  • Atypical antipsychotic agents are effective treatment for hallucinations with agitation in a patient with dementia, but should be used cautiously since associated with increased risk of CVA, MI, and death

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