Hallucinations: Common features and causes Awareness of manifestations, nonpsychiatric etiologies can help pinpoint a diagnosis ot all patients who experience hallucinations have a psychotic disorder. Many physical and Npsychiatric disorders can manifest with hal- lucinations, and some patients have >1 disorder that could cause different types of hallucinations. To avoid providing unnecessary or ineffective treatments—and to ensure that patients receive proper care for nonpsy- chiatric conditions—it is important to accurately diag- nose the disorder causing a patient’s hallucinations. In this article we describe common features and psy- chiatric and nonpsychiatric causes of auditory, visual, olfactory, gustatory, tactile, and somatic hallucinations. Awareness of typical presentations of hallucinations associated with specific disorders can help narrow the © IMAGEZOO/CORBIS diagnosis and provide appropriate treatment. Shahid Ali, MD Assistant Professor, Clinical Psychiatry Milapkumar Patel, MD Auditory hallucinations Research Associate Also known as paracusia, auditory hallucinations are Jaymie Avenido, MD perceptions of sounds without identifiable external Research/Forensic Psychiatry Associate stimuli. This type of hallucination has various causes Rahn K. Bailey, MD, FAPA 1 Associate Professor (Table 1). A frequent symptom of schizophrenia, audi- Shagufta Jabeen, MD tory hallucinations can cause substantial distress and Assistant Professor, Clinical Psychiatry functional disability.2 Approximately 60% to 90% of pa- Wayne J. Riley, MD, MPH, MBA, MACP tients with schizophrenia and up to 80% of those with Professor of Family Medicine affective psychoses experience auditory hallucinations.1 • • • • Auditory hallucinations in psychosis usually are Department of Psychiatry and Behavioral Sciences formed and complex.3 A common manifestation is Meharry Medical College Nashville, TN hearing ≥1 voices. A patient might experience 2 voic- es talking about him in the third person. The voices Current Psychiatry 22 November 2011 may be perceived as coming from inside or outside the patient’s head. Some might hear their Table 1 own thoughts spoken aloud. According to DSM-IV-TR, “hearing voices” is sufficient Common causes of auditory to diagnose schizophrenia if the hallucina- hallucinations tions consist of a voice keeping up a run- Peripheral lesions ning commentary on the person’s behavior Middle ear disease or ≥2 voices conversing with each other.4 Inner ear disease Auditory hallucinations also are seen in Auditory nerve disease mood disorders but tend to be milder than CNS disorders their psychosis-induced counterparts. Temporal lobe epilepsy Simple (unformed) auditory halluci- nations—referred to as tinnitus—can be Pontine lesions caused by disease of the middle ear (oto- Stroke sclerosis) or inner ear. These unformed hal- Arteriovenous malformations lucinations consist of buzzing or tones of Syncope varying pitch and timbre.1 Toxic metabolic disturbances Partial seizures may cause auditory Alcoholic hallucinosis Clinical Point hallucinations. Perceptions of music have Delirium Auditory perceptions 5 been associated with partial seizures. Hallucinogens of music have been Curie and colleagues found that 17% of 514 Schizophrenia associated with patients with temporal lobe epilepsy had Mania auditory hallucinations as a component Psychotic depression partial seizures of their seizures.6 These hallucinations Dissociative identity disorder typically are brief, stereotyped sensory Posttraumatic stress disorder impressions and, if formed, may be trivial Source: Reference 1 sentences, previously heard phrases, or commands. Alcoholic hallucinosis is a hallucinatory syndrome caused by alcohol withdrawal. may consist of formed images (eg, people) These hallucinations usually are vocal and or unformed images (eg, flashes of light).12 typically consist of accusatory, threaten- Visual hallucinations occur in numerous ing, and/or critical voices directed at the ophthalmologic, neurologic, medical, and patient.1 Patients with alcohol hallucino- psychiatric disorders (Table 2, page 24).13 sis also may experience musical auditory DSM-IV-TR lists visual hallucinations hallucinations.7,8 as a primary diagnostic criterion for sev- CNS neoplasms can produce auditory eral psychotic disorders, including schizo- hallucinations in 3% to 10% of patients.9 phrenia and schizoaffective disorder,4 and Hemorrhages and arteriovenous malfor- they occur in 16% to 72% of patients with mations in the pontine tegmentum and these conditions.14,15 Patients with major lower midbrain have been associated with depressive disorder or bipolar disorder acute onset of auditory hallucinations. The also may experience visual hallucinations. sounds typically are unformed mechanical Visual hallucinations in those with schizo- or seashell-like noises or music.10 phrenia tend to involve vivid scenes with Patients with migraines rarely report family members, religious figures, and/or auditory hallucinations. When they occur, animals.16 they typically consist of perceived unilat- Delirium is a transient, reversible cause eral tinnitus, phonophobia, or hearing loss. of cerebral dysfunction that often presents with hallucinations. Several studies have shown that visual hallucinations are the Visual hallucinations most common type among patients with Visual hallucinations manifest as visual delirium. Webster and Holroyd found vi- sensory perceptions in the absence of ex- sual hallucinations in 27% of 227 delirium Current Psychiatry ternal stimuli.11 These false perceptions patients.17 Vol. 10, No. 11 23 continued Table 2 These simple visual hallucinations are most common; more complex hallucina- Common causes of visual tions are seen more frequently in migraine hallucinations coma and familial hemiplegic migraine. Neurologic disorders Approximately 5% of patients with epilepsy have occipital seizures, which al- Migraine most always have visual manifestations. Epilepsy Hallucinations Epileptic visual hallucinations often are Hemispheric lesions simple, brief, stereotyped, and fragmen- Optic nerve disorders tary. They usually consist of small, bright- Brain stem lesions (peduncular hallucinosis) ly colored spots or shapes that flash.22 Narcolepsy Complex visual hallucinations in epilepsy are similar to hypnagogic hallucinations Ophthalmologic diseases but are rare. Intracranial electroencepha- Glaucoma lography recordings have shown that Retinal disease pathological excitation of visual cortical Clinical Point Enucleation areas may be responsible for complex vi- Up to one-half Cataract formation sual hallucinations in epilepsy.19 Choroidal disorder Dementia with Lewy bodies (DLB) is of patients with 23 Macular abnormalities associated with visual hallucinations. Parkinson’s disease Visual hallucinations occur in >20% of pa- Toxic and metabolic conditions may experience tients with DLB.24 Patients with DLB may Toxic-metabolic encephalopathy visual hallucinations see complex scenarios of people and items Drug and alcohol withdrawal syndromes that are not present. Visual hallucinations Hallucinogens have an 83% positive predictive value for Schizophrenia distinguishing DLB from dementia of the 25 Affective disorders Alzheimer’s type. There is a strong cor- Conversion disorders relation between Lewy bodies located in the amygdala and parahippocampus and Sensory deprivation well-formed visual hallucinations.26 Sleep deprivation Visual hallucinations are common in Hypnosis Parkinson’s disease and may occur in Intense emotional experiences up to one-half of patients.27 Patients with Source: Reference 13 Parkinson’s disease may experience hallu- cinations similar to those observed in DLB, which can range from seeing a person or animal to more complex, formed, and mo- Delirium tremens typically is accom- bile people, animals, or objects. panied by visual hallucinations. Visions of small animals and crawling insects are common.18 Hallucinations due to drug in- Olfactory hallucinations toxication or withdrawal generally vary Also known as phantosmia, olfactory hal- in duration from brief to continuous; such lucinations involve smelling odors that ONLINE 19 ONLY experiences often contribute to agitation. are not derived from any physical stimu- Migraines are a well-recognized cause lus. They can occur with several psychi- Discuss this article at of visual hallucinations. Up to 31% of those atric conditions, including schizophrenia, www.facebook.com/ with migraines experience an aura, and depression, bipolar disorder, eating dis- CurrentPsychiatry nearly 99% of those with aura have visual orders, and substance abuse.28 Olfactory symptoms.20,21 The classic visual aura starts hallucinations caused by epileptic activity as an irregular colored crescent of light are rare. They constitute approximately with multi-colored edges in the center of 0.9% of all auras and typically are described the visual field that gradually progresses as unpleasant. Tumors that affect the me- Current Psychiatry 24 November 2011 toward the periphery, lasting <60 minutes. dial temporal lobe and mesial temporal sclerosis are associated with olfactory hal- lucinations.29 Olfactory hallucinations also Related Resource have been reported in patients with multi- • Teeple RC, Caplan JP, Stern TA. Visual hallucinations: differ- ential diagnosis and treatment. Prim Care Companion J Clin infarct dementia, Alzheimer’s disease, and Psychiatry. 2009;11(1):26-32. alcoholic psychosyndromes. In patients Disclosures with schizophrenia, the smell