The most common causes of new-onset psychosis in later life are:
- dementia-related syndromes with psychosis, delirium, or drug-induced psychosis
- primary psychiatric disorders, most commonly depression.1
Alzheimer’s disease has been associated with up to a 60% incidence of psychotic symptoms at some point in the disease course.2 Although Mrs. L’s short-term memory had declined in recent years, she does not have aphasia, apraxia, agnosia, or decrease in mental executive functioning to meet Alzheimer’s dementia criteria.
Perceptual disturbance is a feature of delirium that can cause agitation and hallucinations in elderly patients. However, Mrs. L did not have a decreased level of consciousness or an acute medical illness that would explain delirium.
Despite Mrs. L’s symptoms and progressive hearing and vision loss with resultant disability, she generally was organized in terms of basic self-care, hygiene, and activities of daily living. She was able to have a conversation when she could hear the physician. Surprisingly, her Mini-Mental State Examination (MMSE) score was within normal limits or only mildly impaired at office visits. This was not compatible with the initial diagnosis of dementia, although it may suggest mild cognitive impairment.
Mrs. L took donepezil as prescribed by her primary care physician for only a few weeks before we stopped it. We attributed Mrs. L’s slightly impaired concentration and short-term memory in the ER to the anxiety and stress of oscillating visual hallucinations.
Schizophrenia is another cause of psychosis, but Mrs. L had no history of negative symptoms, delusions, disorganized speech/behavior, or family history of psychotic disorders. In addition, schizophrenia is most likely to appear in a patient’s third decade. Although more common in women than men, late-onset schizophrenia—defined as onset after age 40—has a 1-year prevalence rate of 0.6%3 and therefore is an unlikely cause of Mrs. L’s symptoms.
Mrs. L had no history of neurologic deficit to suggest cerebrovascular disease or space-occupying brain lesion. Her TSH, which was slightly increased when she presented in the ER, was normal on subsequent testing. Folic acid and vitamin B12 were normal. We ordered brain MRI to rule out organic causes not seen with CT, but Mrs. L felt claustrophobic in the machine and could not finish the test.
EEG was ordered to rule out epilepsy. Hallucinations can be a prominent component of seizures and are more common when the seizure focus is in the left temporal lobe.4 However, the development of psychotic symptoms often follows the onset of seizures by approximately 14 to 17 years.5 Although Mrs. L never obtained the ordered EEG, the absence of a history of clinical seizures or focal neurologic signs makes it unlikely that epilepsy accounted for her hallucinations. The normal workup ruled out most possible medical/organic causes of Mrs. L’s visual hallucinations.
We considered depression with psychotic features because Mrs. L had occasional depressed mood, feelings of worthlessness, and low self-esteem. These symptoms started only after she began losing her vision and hearing and she did not experience them most of the time. Furthermore, her predominant negative feeling was anxiety related to the hallucinations. Mrs. L had no other depressive symptoms such as guilt or loss of appetite.
Table 2
Differential diagnosis of hallucinations in elderly patients
| Diagnosis | Comments |
|---|---|
| Delirium | Secondary to a generalized medical condition, substance-induced, or substance withdrawal |
| Dementia | Alzheimer’s, vascular, Lewy body, or less common types |
| Parkinson’s disease | Medications can induce visual hallucinations |
| Brain tumor/mass/CVA | Usually accompanied by other neurologic symptoms and signs |
| Schizophrenia | Usually starts in early adulthood |
| Mood disorder with psychotic features | Depression can present as pseudodementia in elderly patients |
| Drug abuse/withdrawal or side effect | Numerous medications are known to worsen delirium in elderly patients |
| Other causes | HIV, tertiary syphilis, Charles Bonnet syndrome |
| CVA: cerebrovascular accident; HIV: human immunodeficiency virus | |
A diagnosis of exclusion
We began to suspect that Mrs. L had Charles Bonnet syndrome (CBS), a condition in which visually impaired persons experience visual hallucinations without other known mental illnesses. These hallucinations tend to be complex, vivid, and elaborate, lasting from a few seconds to most of the day.6,7 CBS occurs in 10% to 15% of patients with visual impairment, including up to 3.5% of elderly patients referred to psychiatrists for visual hallucinations.7,8 CBS is most common among the elderly because of the high prevalence of visual impairment in this population.
Many patients with CBS are aware that their hallucinations are not real.7 Mrs. L’s presentation was atypical because she believed what she was seeing was real and because most images were terrifying, which also is not usually the case in CBS.