Introduction
Hallucinations, defined as the perception of an object or event in the absence of an external stimulus are experienced by patients with conditions that span several medical fields including psychiatry, neurology, general medicine and ophthalmology. They are underreported because of poor insight into their unreal nature and often because of the perceived psychiatric implication. When noted by non-psychiatrists visual hallucinations often trigger referrals for psychiatric consultation, although they are not pathognomonic of a primary psychiatric illness, but rather reflect underlying organic brain disease or dysfunction.
Visual hallucinations can be simple (elementary or non-formed) or complex. Simple hallucinations are characterised by the absence of form, for example photopsias, or geometric patterns or shapes. Complex hallucinations are characterised by visions, which are clearly defined with a specific form such as animals or objects. The differentiation is important because of their localisation value. Simple hallucinations point towards occipital lobe pathology and complex hallucinations are more suggestive of a lesion in the temporal lobe. The elderly can of course hallucinate as part of a severe depressive disorder or an enduring psychiatric illness such as paranoid schizophrenia, however, the clinician should assume that there is an organic basis when an elderly individual begins to develop visual hallucinations for the first time. The following representative cases illustrate visual hallucinations due to ophthalmological, vascular and degenerative processes.
Objectives
The aim of this paper is to present three cases of elderly patients presenting with visual hallucinations due to different pathologies and to discuss their respective aetiologies and management.
Case one: Charles Bonnet syndrome
JT was a 78-year-old male referred for admission to our acute psychiatric unit because of a of 6 months history of distressing visual hallucinations occurring on a background of macular degeneration. These hallucinations began during a previous medical admission, for stabilisation of his angina. At that time on a couple of occasions he had hallucinated two children standing at the end of his bed who subsequently ‘vanished’. These experiences were not distressing. He had no further hallucinations for some months. Prior to admission, he reported to see people with him constantly in the house, watching television with him and sitting on his chairs. He was distressed by the hallucinations, especially when he asked them to leave and they did not. He had been treated unsuccessfully with two antipsychotics: low dose quetiapine (50 mg BD) and a therapeutic dose of Aripiprazole (20 mg daily).
His past medical history included ischaemic heart disease and macular degeneration. His medications on admission included: Quetiapine 50 mg BD, a β blocker, a diuretic, Aspirin, an ACE inhibitor, a statin, a proton pump inhibitor, a type II α 2 reductase inhibitor and Ranolazine (an antianginal medication). He had no personal or family history of psychiatric illness. His mother had suffered from a dementia.
On Mental State Examination, he presented as an elderly, frail well-groomed gentleman. His vision was very poor such that he could not see a pen held up directly in front of him. His hearing was also poor. He was pleasant and cooperative during interview. His gait was slow. He was not depressed or anxious. He did not appear to respond to external stimuli. His thought form and content were normal. He scored 22/24 on MMSE, six items were omitted due to poor hearing and vision. He was able to recall 2/3 items on short-term recall and his concentration was normal. During interview, he had only partial insight into the unreal nature of his hallucinations. He acknowledged that they could be due to an illness affecting his brain, however, at the same time asked why the people would not leave.
A diagnosis of CBS was made. The differential included visual hallucinations due to other organic causes including cerebrovascular disease or possibly Lewy body dementia.
On admission, physical examination and an organic workup (which included a dementia screen) was normal. A computed tomography (CT) brain scan showed periventricular deep white matter changes with appearances suggestive of chronic small vessel microvascular ischaemic change. A DAT indicated that a diagnosis of Parkinson’s disease or Lewy body dementia was unlikely. He was commenced on Amisulpiride at a dose of 25 mg twice a day to good effect. The hallucinations resolved within 1 week and he remained hallucination free for 1 year. He is now blind and despite his antipsychotic treatment being withdrawn over the last 3 months, he remains free of hallucinations.
Case two: vascular dementia
M.W. was an 83-year-old female, nursing home resident, referred for psychiatric assessment because of visual and auditory hallucinations over the previous year. She described a history of experiencing vivid visual hallucinations of people she did not recognise. On assessment, she stated she frequently saw women walking behind her, past her and then through the wall of her house. She said they mostly occurred at nighttime but could happen at any time of day. She found these experiences distressing. She also described auditory hallucinations. She frequently heard voices she did not recognise saying things such as ‘won’t you say hello to your mother’. These hallucinations were usually second party and could be command in nature. She did not find these as upsetting as the visual experiences. She had been prescribed Aripiprazole 10 mg daily with little or no response and subsequently Quetiapine 50 mg daily for 3 months.
Her past medical history included a right-sided cerebrovascular accident 1 year previously. She also had a previous history of thyrotoxicosis requiring treatment with radioactive iodine but was euthyroid on assessment. She had history of polymyalgia rheumatica, which was treated with long-term steroids. She also had a history of hypertension, hypercholesterolaemia, type II diabetes mellitus, an essential tremor, diverticular disease, osteoporosis, spasmodic dysphonia, cataracts and a previous leg ulcer. She had no past psychiatric history. Her medications on assessment included Eltroxin, Frusemide, Prednisolone, Levitaracetam, Amitryptyline, Quetiapine, Atorvastatin and Zopiclone. She had no history of alcohol abuse and she was a non-smoker.
With regard to her family history, her father had suffered from hypertension and her mother died at the age of 63 years from stroke disease. There was no family history of psychiatric illness.
Her daughter reported that since her mother’s stroke she had been experiencing visual hallucinations. Initially these were intermittent and not distressing and tended to be exacerbated during periods of delirium caused by urinary tract infections. Her daughter described how at times she believed that the hallucinated people were trying to steal her clothes. Mostly, her daughter told us, she completely lacked insight into their unreal nature. The most disturbing recurrent hallucination she experienced had been a complex hallucination of her house being on fire. While experiencing this she reported to see smoke and ashes and was understandably terrified. She also told us M.W. hallucinated animals including cats and mice, both during the day and at nighttime and she often attempted to push them away. She reported that her short-term memory had been reasonable but there had been a progressive cognitive deterioration.
On Mental State Examination, she presented as an elderly frail lady. She was well groomed. She was pleasant and amenable. Her mood was euthymic. She did not describe any delusional beliefs. Her vision was impaired and therefore she could not read. Her hearing was intact. Her eye contact was normal. Her speech was forthcoming and coherent and relevant in content. Her Mini Mental State Examination score was 24/28. She scored 2/3 on short-term recall. She had partial insight into her symptoms.
On physical examination she had an essential tremor. She also had bilateral cataracts. She had unilateral weakness of both right upper and lower limbs.
A previous CT brain showed extensive periventricular ischaemic changes with an established right occipital lobe infarct. There was no new focal infarct identified. There was marked vascular calcification. Routine blood investigations including: full blood count, urea and electrolytes, liver function tests, thyroid function tests, haematinics and fasting lipids and glucose were all normal.
Her hallucinations responded quickly to Amisulpiride 25 mg BD; however, she died 18 months later consequent to pneumonia.
Case three: Parkinson’s disease
T.H. was a 76-year-old married man who was referred for psychiatric assessment because of increased disorientation, paranoia and visual hallucinations. He had a background history of Parkinson’s disease. He had previously attended our service in 2006 and had been diagnosed with a moderate depressive disorder and pathological jealousy, which had been treated successfully with Venlafaxine.
On interview he described frequent distressing visual hallucinations of several people in his bedroom. He did not recognise these people and he found them threatening. He did not experience auditory hallucinations. He was insightful into a decline in his short-term memory and intermittent episodes of worsened confusion but not the hallucinations when they occurred. He had a past medical history of Parkinson’s disease, hyperlipidemia, trigeminal neuralgia, spinal stenosis and a spinal laminectomy and a trans urethral resection of the prostate.
On Mental State Examination, he presented as a frail elderly gentleman who established good eye contact. He had mask-like facies. He presented as listless and apathetic rather than objectively depressed. He denied a death wish, suicidal or homicidal ideation. He did not experience any perceptual abnormalities during assessment. He admitted to overvalued ideas regarding his wife’s fidelity. He scored 28/30 on MMSE losing two points on short-term recall.
Collateral revealed that his mobility and his short-term memory had deteriorated gradually over the previous 12 months. The visual hallucinations had been ongoing for 6 months.
His medications included Clonazepam, Nuseals Aspirin, Pravastatin, Xatral, Stalevo, Mirapexin, Zolpidem, Venlafaxine, a proton pump inhibitor and laxatives.
Given his history of Parkinson’s disease, the provisional diagnosis of Parkinson’s disease dementia with visual hallucinations was made. The differential included anti-Parkinsonian drug-induced visual hallucinations.
His physical examination and organic workup were unremarkable. He was assessed by a neurologist and his anti-Parkinsonian medication was reviewed. He poorly tolerated the addition of Aripiprazole as it worsened his Parkinsonian symptoms, specifically his mobility. Amisulpride was also ineffective. He was commenced on a trial of a cholinesterase inhibitor: a Rivastigmine patch at a dose of 4.5 mg/24 hour. This was subsequently increased to 9.5 mg/24 hour after 6 weeks. His hallucinations resolved within weeks. However, months later they recurred and responded to low-dose Risperidone (0.25 mg), which he tolerated well.
Discussion
Visual hallucinations were first recognised as differing from other types of hallucinations in the 1930s. They are found in sight loss related to eye disease, in diseases affecting the brain including the dementias, stroke and Parkinson’s disease in psychiatric illnesses such as schizophrenia, in hospice settings at the end of life and as a side effect of medication. When all causes are added together, it is estimated that 2 million people in the United Kingdom have experienced visual hallucinations, over the previous 6 months (Collerton et al. Reference Collerton, Perry and Mc Keith2005) The aetiology of visual hallucinations is complex as is their treatment. In order to look at the proposed aetiologies, we need to first review the anatomy of the visual pathway. In normal vision information about an image is transmitted to the brain along the optic nerve. A total of 90% of the axons in the optic nerve go to the lateral geniculate nucleus (LGN) in the thalamus. Other axons go to the superior colliculus in the midbrain, which assists in eye movements and motor responses. A final group of neurones send information to several structures that control circadian rhythms such as the ventrolateral preoptic nucleus. The optic nerves from both eyes meet and cross at the optic chiasm at the base of the hypothalamus. Information from both eyes is then combined and splits according to the visual field into a right and left optic tract. Each optic tract terminates in the LGN in the thalamus. Neurons of the LGN then relay the visual image to the primary visual cortex located in the occipital lobe (also called V1 and the striate cortex). The visual information then flows through a cortical hierarchy (the extrastriate visual cortex/visual association cortex). Basic information about colour and motion is processed in the extrastriate visual cortex.
Three different aetiologies of visual hallucinations have been proposed. The first is that of an irritative process acting on the higher visual centres or pathways, for example discharges in the association cortex due to epilepsy can be falsely interpreted as sensory inputs. The association cortex refers to any of the expanses of the cerebral cortex that are not sensory or motor, but instead are associated with advanced stages of sensory information processing and multisensory integration. The second is that of defective visual processing, which occurs where inputs are normal but lesions somewhere along the cerebral visual pathway result in an inappropriate pattern of cortical excitation (peripheral and central), for example brainstem modulation of thalamo-cortical connections (e.g. lesions/infarctions in the brainstem). The third is that of release phenomena, which occur where there is defective visual input causing faulty cortical stimulation as would happen in reduced visual acuity (West, Reference West1962). We will look at this last postulated aetiology first as this is most pertinent to our first case.
Visual hallucinations may arise from a pure peripheral pathology caused by lesions of the optic nerves or an ocular pathology as in macular degeneration, retinopathy or cataracts (Burke, Reference Burke2002). This association of impairment of peripheral vision and complex visual hallucinations in aged psychologically normal people is called Charles Bonnet syndrome (CBS). The disorder was described by de Morsier in 1967. It was named after Charles Bonnet who first described the phenomenon in his blind and cognitively intact grandfather. The prevalence of CBS was found to be 27.5%, in a UK population with age-related macular degeneration (Khan et al. Reference Khan, Shahid, Thurlby, Yates and Moore2008). It is prevalence is probably underestimated. This may be due to reluctance to disclose visual hallucinations or because they are misattributed to various medical conditions associated with the syndrome, or indeed due to lack of knowledge about the condition among physicians.
Despite widespread recognition and acceptance of the hallmarks of the condition, a universally accepted definition has not been agreed upon. The usual hallucinations are typically stereotyped and can last for hours. Typically, there are no concomitant psychotic symptoms and the patient is usually conscious of their fictitious nature. The hallucinations are usually not distressing. They occur when the eyes are open especially every night. Patients may be able to stop the hallucinations by manoeuvres such as closing and opening the eyes and fixing vision far away from the hallucinations. Risk factors for developing the syndrome have been described by many authors including visual impairment, cerebral damage, cognitive deficits, social isolation, sensory deprivation and aging (Menon et al. Reference Menon, Rahman, Menon and Dutton2003).
Little is known about the underlying pathophysiology of hallucinations in CBS. A widely accepted hypothesis postulates a reduced afferent input to the visual association cortex (the area surrounding the primary visual cortex) or the extrastriate cortex, which causes the release of stored visual memories. A functional MRI study has shown an increased activation of the ventral extrastriate cortex (Ffytche et al. Reference Ffytche, Howard, Brammer, David, Woodruff and Williams1998). Some authors suggest that the hallucinations in CBS may be due to a common mechanism that also causes hallucinations in central disorders in general (e.g. after infarction of the visual cortex). These authors postulate changes in central neurotransmitters specifically, cholinergic and serotonergic systems. Alteration in serotonergic activity is probably linked to the genesis of visual hallucinations; visual information converging in the LGN is modulated by serotonergic projections from the brainstem (Seeburg et al. Reference Seeburg, Liu and Chen2004) and serotonin levels have been found to be lower in the visual deprived cortex (Qu et al. Reference Qu, Eysel, Vandesande and Arckens2000). Acetylcholine is also likely to play a role as it is concentrated in the visual thalamic nuclei and visual cortex (Manford & Andermann, Reference Manford and Andermann1998).
On review of the literature therapeutic options for CBS remain poor and of uncertain benefit for patients. Improvement in vision or even deterioration to total blindness can eliminate the hallucinations and non-pharmacological interventions such as altering the lighting level and reducing social isolation can be helpful. Even without any intervention in some patients the hallucinations can fade in a few weeks or month. However, for those patients who are significantly distressed by their symptoms a trial of pharmacotherapy is indicated.
Therapeutic options may be influenced by the way in which the syndrome is conceptualised. If the syndrome is conceived as an organic hallucinosis-causing disturbance to neurotransmitter systems then this would be a rationale for treatment with antipsychotics/serotonin-enhancing agents/cholinesterase inhibitors. If the causal hypothesis for CBS is the ‘visual release’ phenomenon described earlier it may be construed as an visual equivalent to the phantom limb phenomenon and consequently it would be expected that drugs used to treat this such as Gabapentin may be useful in treatment of CBS (Paulig & Mentrup, 2001).
Pharmacological interventions in CBS have been reported in single cases and case series. There have been no controlled trials published to date. Reports refer to spontaneous recovery, and positive outcomes in some cases but outcomes are variable probably due to patient heterogeneity. The majority of studies involve the use of anticonvulsants or antipsychotics. Anticonvulsants including Carbamazepine (Gorgens & Liedtke, Reference Gorgens and Liedtke1998). Valproate (Hori et al. 2000) have also been used successfully to treat the syndrome. Antipsychotics that have reported successful outcomes include Haloperidol (Valencia & Franco, Reference Valencia and Franco2008) and the atypical antipsychotic Risperidone (Maeda et al. Reference Maeda, Shirayama, Nukina, Yoshioka and Karahara2003). In our case two different antipsychotics had failed, however, interestingly our patient eventually, and very quickly (within 2 days) responded to low dose Amisulpiride (Bhatia et al. Reference Bhatia, Srivastava and Jhanjee2012). Amisulpiride is a highly selective D3/D2 receptor antagonist. In keeping with brain abnormalities in serotonin levels in these patients there have also been reports of selective serotonin reuptake inhibitors including Citalopram (Lang et al. Reference Lang, Stogowski, Schulze, Domula, Schmidt, Gallinat, Tugtekin and Felber2007) being used successfully. There have also been some reports concerning the use of acetlycholinesterase inhibitor agents such as Donepezil (Ukai et al. 2007) and the 5HT3 antagonist Cisapride (Ranen et al. Reference Ranen, Pasternak and Rovner1999).
Our second case was that of a patient with vascular dementia. There are many different types of vascular dementia, distinguished by what has caused the damage in the brain such as stroke, small vessel disease or amyloid angiopathy and which part of the brain has been damaged. Since the symptoms that a person experiences depend on the particular areas of the brain that are damaged, it is difficult to draw generalities about the prevalence and characteristics of specific symptoms such as hallucinations. Vascular dementia conceptually can be defined as any dementia resulting from cerebrovascular disease; it is the end-point of a complex process, which results in a broad spectrum of cognitive and behavioural changes. Extracranial vascular disease involving thrombi, emboli or atherosclerosis block one or more of the three major cerebral arteries, which results in abrupt changes in cortical functions and a stepwise progression characteristic of post-stroke dementia and multiinfarct dementia. Changes associated with intracranial vascular disease progress in a more insidious manner and involve either the long-penetrating arteries from the surface of the brain, affecting the cortical white matter or the subcortical vessels that support the basal ganglia, thalamus and internal capsule characteristic of Binswanger’s disease.
The aetiology of hallucinations in cerebrovascular disease is likely to be due to the second proposed theory of defective visual processing. Typically, there is a delay of days to weeks between the ischaemic event and the development of the visual hallucinations and typically they are transient lasting days to weeks but as our case demonstrates they can be persistent (Manford & Andermann, Reference Manford and Andermann1998). Lesions of the posterior parietal, occipital lobe and thalamus have been observed in patients with complex visual hallucinations and linked to the disruption of cortico-thalamic projection and the generation of hallucinations in the adjacent intact visual cortex. Formed visual hallucinations may also be produced by vertebro-basilar ischaemia. These hallucinations, which may last 30 minutes or more, may be associated with decreased consciousness, but they usually occur in an otherwise alert patient who is aware that the visual hallucinations are not real. The hallucinations are often complex. Some of the visual hallucinations that occur in patients with posterior cerebral artery occlusion are palinoptic. Palinopsia refers to a number of conditions, affecting the brain. It is a visual disturbance that causes images to persist to some extent even after their corresponding stimulus has left (Rushmore et al. Reference Rushmore, Payne and Lombar2005; Moecellin et al. Reference Burn, Emre and McKeith2006).
Certain drugs have been reported to be useful in patients with visual hallucinations either in the context of vascular dementia or following an infarction. Antipsychotics have again been reported to be useful in many cases of visual hallucinations associated with vascular dementia and post stroke. Recently there has been one published report of the use of Amisulpiride in post-stroke psychosis with visual hallucinations (Chen & Tzeng, Reference Chen and Tzeng2010), which is in keeping with our success in treating our lady with vascular dementia and visual hallucinations.
Neurodegenerative disorders are a disparate group of illnesses that share a loss of central nervous system cells. The clinical presentations reflect the different patterns and disturbances of the pathologies involved; ranging from focused loss within specific cerebral nuclei to well-distributed dysfunction involving virtually the entire cerebral cortex (Skovronsky et al. Reference Skovronsky, Lee and Trojanowski2006).
Parkinson’s disease patients suffer from cognitive impairment and can present for psychiatric assessment with symptoms such as apathy, personality change, speech disturbances and visual hallucinations. Hallucinations, usually of a visual nature, as described in the final case presented above, are considered to effect about one quarter of patients with Parkinson’s disease in the community (Williams-Gray et al. Reference Williams-Gray, Foltynie, Lewis and Barker2006). These are symptoms that can be easily missed because patients with Parkinson’s disease do not often volunteer information about them. The hallucinations are typically of people or animals, which often disappear when attention is directly focused on the presumed image. Detailed, formed visual hallucinations are often preceded by visual illusions or vivid dreams. The illusions commonly take the form of seeing faces or animals in the detailed textures of patterns on furniture, or in trees. Some patients complain of seeing smoke or fire, or water on surfaces. Hallucinations are commonly viewed as a side effect of anti-Parkinsonian treatment, but can be due to the disease itself. In fact while they may be made worse by anti-Parkinsonian medication, careful enquiry will generally elicit the presence of hallucinations before starting such medication. The presence of hallucinations in this population group have been identified as a risk factor for permanent nursing home placement, with its associated increased mortality rate (Goetz & Stebbins, Reference Goetz and Stebbins1995). The risk factors for the development of hallucinations in Parkinson’s disease include age, duration and severity of disorder, depression, sleep disturbance and cognitive impairment (Wolters, Reference Wolters2006).
Visual hallucinations are known to be a marker of more severe cholinergic deficits in Parkinson’s dementia. There is a strong relationship between the induction of hallucinations and the start of anti-cholinergic agents. Also diseases with Lewy bodies are associated with decreased choline-acetyl-transferase activity (Perry et al. Reference Perry, Kilford, Lees, Burn and Perry2003). The cholinergic system plays an important role in conscious awareness. A decrease in the cortical acetylcholine levels impairs the selection of subcortical information streams, causing unselected and chaotic cortical activation, which may give rise to hallucinations.
Neuropathologically, visual hallucinations in Parkinson’s disease are associated with increased Lewy body deposition in the temporal lobe, suggesting that they are at least in part attributable to the disease process itself (Harding & Halliday, Reference Harding and Halliday2001). Some authors have suggested that Lewy body dementia and dementia associated with Parkinson’s disease are more similar than different and noted that a major difference is the timing of symptom onset (Lippa et al. Reference Lippa, Duda, Grossman, Hurtig, Aarsland, Boeve, Brooks, Dickson, Dubois, Emre, Fahn, Farmer, Galasko, Galvin, Goetz, Growdon, Gwinn-Hardy, Hardy, Heutink, Iwatsubo, Kosaka, Lee, Leverenz, Masliah, McKeith, Nussbaum, Olanow, Ravina, Singleton, Tanner, Trojanowski and Wszolek2007). Imaging studies on visual hallucinations using functional MRI have consistently shown increased activation of the caudate nucleus during visual input in patients with Parkinson’s disease with visual hallucinations (Stebbins et al. Reference Stebbins, Goetz and Carillo2004). These striatal activations may possibly reflect the switching from external stimuli to internally generated images in this group of patients with visual hallucinations. Other studies show that visual processing itself seems to be impaired, for example studies have demonstrated a reduction of either activation, perfusion or metabolism in the visual association cortices during rest or visual stimulation (Matsui et al. Reference Matsui, Nishinaka, Oda and Hara2006a , Reference Matsui, Nishinaka, Oda and Hara2006b ; Boecker et al. Reference Boecker, Ceballos-Baumann and Volk2007). Patients with Parkinson’s disease and visual hallucinations also showed, as compared with controls and non-hallucinating patients, grey matter volume reductions in the lingual gyrus and superior parietal lobe areas, which are both involved in higher visual processing (Ramirez-Ruiz et al. Reference Ramirez-Ruiz, Junque, Marti, Valldeoriola and Tolossa2007).
This observation that patients with Parkinson’s disease dementia have extensive cholinergic deficits led to the hypothesis that cholinesterase inhibitors may provide benefit for patients with this condition. Our patient responded well initially to the addition of a cholinesterase inhibitor. On literature review, acetylcholinesterase inhibitors, Donepezil and Rivastigmine improve visual hallucinations in addition to cognitive function in patients with Lewy body disease (Bergman and Lerner, Reference Bergman and Lerner2002; Bullock & Cameron, Reference Bullock and Cameron2002). Rivastigmine has been found beneficial for patients with Parkinson’s disease dementia regardless of the presence or absence of visual hallucinations, but the treatment effect was most marked in patients who had visual hallucinations (Burn et al. Reference Burn, Emre and McKeith2006). In addition, a randomised control trial demonstrated the efficacy of Rivastigmine in dementia with Lewy bodies (McKeith et al. Reference McKeith, Del Ser, Spano, Emre, Wesnes, Anand, Cicin-Salin, Ferrara and Spiegel2000).
Most antipsychotic agents worsen extrapyramidal symptoms making them unsuitable to treat hallucinations in this condition in general, however, the management of these hallucinations requiring such treatment has been improved by the development of atypical agents, such as Clozapine, which may be used in patients with Parkinson’s disease as they have a lower propensity to exacerbate motor symptoms. Of particular interest, our patient with Parkinson’s disease dementia tolerated and his hallucinations responded to low-dose Risperidone, though previously was unable to tolerate Aripiprazole.
Within similar patient populations, the most frequent other association with hallucinations is delirium, with this accounting for more cases of hallucinations than all other causes put together (Collerton et al. Reference Collerton, Perry and Mc Keith2005). Hence, if hallucinations develop over hours or days in a person with a degenerative disorder, particularly in the context of physical ill health, delirium should be the first possibility to consider with fluctuating alertness and behavioural disturbance [National Institute for Clinical Excellence (NICE), 2010].
Delirium is a transient, reversible cause of cerebral dysfunction that often presents with hallucinations. It also involves an acute disturbance of consciousness as well as a reduced ability to sustain attention. It is caused by a myriad of physical conditions: metabolic derangements, infections, drug effects and intracranial processes. An additional disturbance in cognition such as a memory deficit, disorientation or language is usually present. This is usually evident in the history. The presence of visual hallucinations, but not delusions or auditory hallucinations, is significantly associated with more active medical diagnosis and multiple aetiologies causing the delirium. Psychotic symptoms may have different factors contributing to their development. Visual hallucinations appear to be associated with a greater number of active medical disorders, but other factors associated with the development of psychotic symptoms in delirium have yet to be established. One study noted visual hallucinations in 27% of patients with delirium (Webster & Holroyd, Reference Webster and Holroyd2000). In one type of delirium: delirium tremens, the hallucinations are quite distinct and vivid. Acute alcohol withdrawal is a recognised cause of visual hallucinations, which are common in chronic alcoholics but may occur in occasional binge drinkers (Victor & Adams, Reference Victor and Adams1952). The first symptom is typically tremor, followed by intermittent, brief visual hallucinations initially without alteration of consciousness. These may lead to profuse, almost continuous hallucinations occasionally associated with hallucinations in other modalities. The hallucinations are typically of animals of normal size (celebrated ‘pink elephant’), although lilliputian hallucinations may occur. Visions of small animals and crawling insects are common. Hallucinations due to drug intoxication or withdrawal, generally vary in duration from brief to continuous. Such experiences may lead to agitation.
There is a lack of strong evidence on the effectiveness of interventions for visual hallucinations. Most reports are of single cases or small case series that do not specifically target visual hallucinations. Potential advantages might include reducing the hallucinatory experience itself, either in frequency or duration or reducing its impact on the patient and their carer. Owing to the limited effectiveness of treatment on the occurrence of hallucinations, and the potential costs of interventions, concentrating efforts on the half of patients who are distressed by their experiences might be the most effective strategy.
One set of strategies is based on reducing factors that are thought to increase the frequency of visual hallucinations. Thus, improving lighting, reducing visual triggers and improving visual function with spectacles or cataract surgeries are all worth trying. If hallucinations are associated with specific times of day, targeting social contact at that time may be effective in reducing frequency or duration (Aarsland et al. Reference Aarsland, Ballard, Rongve, Broadstock and Svenningsson2012).
In line with the risk-reducing strategy, reducing existing medication is a sensible first step. A very wide range of medications have anticholinergic effects and can induce or worsen hallucinations; particularly in cases of polypharmacy (Mosimann & Collerton, Reference Mosimann and Collerton2010). A careful consideration of the risks and benefits of each medication followed by systematic reduction or elimination of non-essential drugs and monitoring of the effects on hallucinations may be effective.
All patients and their carers can potentially benefit from information on hallucinations. Key messages to convey are that hallucinations are common to be expected in neurodegenerative diseases, usually spontaneously reduce or disappear over time, can be controlled and do not have to be distressing (Mosimann & Collerton, Reference Mosimann and Collerton2010; Collerton et al. Reference Collerton, Dudley and Mosimann2011).
Patients spontaneously use a wide range of coping strategies (Diederich et al. Reference Diederich, Pieri and Goetz2003). Increasing cognitive impairment reduces, but does not eliminate their use, suggesting that they may be effective in advanced disease. Cognitive behavioural treatments, adapted from those developed to treat auditory hallucinations in younger people with psychosis, are starting to be applied to manage distress in neurodegenerative disorders (Collerton & Dudley, Reference Collerton and Dudley2004). Distress is posited to be maintained by a combination of dysfunctional beliefs and behaviours, which keep the patient more distraught than is necessary. Treatment depends upon collaboratively developing more functional beliefs and behaviours (Mosimann & Collerton, Reference Mosimann and Collerton2010).
Conclusions
Visual hallucinations are a relatively common phenomenon among the elderly. They can be attributed to diverse aetiological mechanisms. They are usually associated with organic brain disease or ocular pathology. We have chosen the above three cases to illustrate some possible aetiologies and treatment for this clinically important symptom. Given the broad variety of potential aetiologies of visual hallucinations outlined previously, it is clear that an accurate diagnosis is necessary before effective treatment can be implemented. A thorough history and comprehensive physical examination are the most important elements of a work-up for visual hallucinations. Associated symptoms and features of the hallucinations themselves may help inform diagnosis. The elicitation of signs or symptoms of psychosis, inattention, Parkinsonism, impaired vision, headache or focal neurological signs will narrow the diagnosis and prompt further diagnostic investigations.
Effective treatment of visual hallucinations is entirely dependent on the underlying cause so timely recognition and an understanding of causative mechanisms are crucial. It is vital to ensure diagnostic accuracy, especially since treatments that may be beneficial for one cause of visual hallucinations may worsen another. Antipsychotic medications are the mainstay treatment for visual hallucinations due to primary functional psychotic illness. These medications are also useful in the management of visual hallucinations occurring in the context of some dementias and CBS. Unfortunately, due to their dopamine-blocking activity, most antipsychotics will significantly worsen Parkinsonian symptoms in patients with dementia with Lewy bodies or dementia associated with Parkinson’s disease. Cholinesterase inhibitors have a niche role in the treatment of such patients. One of the most interesting findings of this small case series was the efficacy of low dose Amisulpride in the treatment of visual hallucinations in CBS and those associated with vascular dementia. The difference in receptor profile may be responsible for the superior efficacy of Amisulpride in these cases (Leucht et al. Reference Leucht, Pitschel-Waltz, Engel and Kissling2002).
The paucity of research in the domain of the treatment of visual hallucinations limits our therapeutic options. Given the lack of randomised controlled trials in the pharmacological management of such conditions, and the fact that our decision making, as clinicians is largely informed by case reports and case series we deem that further research in the area is required.
Acknowledgements
The authors wish to thank the multidisciplinary team at Seanoira Day Hospital, St. Camillus‘s Hospital, Shelbourne Rd., Limerick. We would also like to thank Dr. Seamus Geraghty for his IT expertise and his assistance in preparing the paper for publication.
