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PubMed2004

[Hallucinations and dementia. Prevalence, clinical presentation and pathophysiology].

Hallucinations are a common feature of certain degenerative diseases with a risk of dementia such as Alzheimer's disease, Lewy body dementia, and Parkinson's disease. Obtaining valid epidemiological data is nevertheless quite difficult because of methodological problems. As a rule, hallucinations are more prevalent in Lewy body disease than Parkinson's disease or Alzheimer's disease. The prevalence in parkinsonian dementia is about the same as in Lewy body disease. Complex visual hallucinations predominate, auditory or tactile hallucinations are more exceptional. Minor forms (illusions, sensation of presence) are also observed. Recurrence is common, mainly in the evening or at night. Patients with advanced mental impairment generally take the hallucinations for reality. The hallucinations can be associated with psychological and behavioral disorders such as delusionnal idea or identification disorders. It is important to search for other causes of hallucinations such as drugs, ocular disorders, or depression, but many of these disorders are common comorbidities in elderly patients with degenerative disease. There is no unique model fitting all the hypothesized pathogenic mechanisms. Complex visual hallucinations most likely arise from abnormal activation of the extra-striat temporal associative regions, but only hypothetical mechanisms have been proposed. Genetic studies and functional imaging have not provided convincing evidence. Current focus is placed on an imbalance between deficient cholinergic transmission and preserved or augmented monoaminergic transmission at the cortical level, but other neurotransmission systems could be involved. The dream dysregulation mechanism proposed in Parkinson's disease cannot be generalized. The link between cognitive disorders and hallucination is also poorly understood: hallucinations are associated with more severe cognitive impairments or more rapid cognitive deline in Parkinson's disease and Alzheimer's disease, but the association with specific cognitive disorders remains to be fully explored.

Cognition Disorders↗

PubMed1996

Visual hallucinations in psychologically normal people: Charles Bonnet's syndrome.

BACKGROUND: Charles Bonnet's Syndrome (CBS), characterised by the presence of complex visual hallucinations in psychologically normal people, was considered for a long time to be rare. Systematic research on CBS has been limited. However, it has been realised that CBS occurs frequently in elderly, visually handicapped patients, and we have been able to study the syndrome in a large number of patients. METHODS: After screening 505 visually handicapped patients, 60 were found to meet proposed diagnostic criteria for CBS (generally, the existence of hallucinations without delusions or loss of insightful cognition.) Psychopathological characteristics, personal meaning, and the emotional impact of hallucinations, as well as factors influencing the hallucinations, were analysed. FINDINGS: Although diagnostic criteria demand merely "partial insight", all patients had full insight into the unreal nature of their hallucinations. Other characteristics varied. In 46 (77%) patients, hallucinations lacked a personal meaning. Sensory deprivation and a low level of arousal seemed to favour the occurrence of hallucinations. CBS caused considerable distress in only 17 (28%) patients. However, all patients were glad to be told that their hallucinations were not due to mental disease. The proper diagnosis had been made in only one of the 16 patients who had consulted a doctor. INTERPRETATION: Although largely unrecognised in clinical practice, CBS should be considered as a diagnosis in patients who complain of hallucinations and who meet defined diagnostic criteria. There is no proven treatment, but many patients will benefit from reassurance that their hallucinations do not imply mental illness.

Aged↗

PubMed2002

Increased susceptibility to auditory conditioning in hallucinating schizophrenic patients: a preliminary investigation.

Auditory hallucinations have been elicited in the laboratory after repeated pairings of a tone (unconditioned stimulus) with a light (conditioned stimulus), until the presentation of the light alone resulted in subjects hearing the tone. This auditory sensory-conditioning phenomenon was first reported in normal subjects over a half-century ago. But the model remains, to date, untested in actively hallucinating patients. If sensory-conditioning mechanisms actually mediate the occurrence of clinical hallucinations, one would expect that hallucinating patients would more readily acquire and be more resistant to extinguish a conditioned hallucination than nonhallucinating psychotic patients. The present study examined the susceptibility of 15 hallucinating and 15 nonhallucinating acute schizophrenic inpatients to acquire and maintain a sensory-conditioned hallucination response. Consistent with the auditory sensory-conditioning model, evidence suggests that hallucinating patients acquire and maintain sensory-conditioned hallucinations more quickly than their nonhallucinating counterparts. Results are discussed in terms of hallucinators' susceptibility to sensory conditioning and suggestibility as important factors underlying hallucinatory behavior. The findings are interpreted with respect to the behavioral mechanisms underlying psychotic symptom formation.

Acoustic Stimulation↗

PubMed2003

Musical hallucinations in patients with Lyme disease.

Musical hallucinations are poorly understood auditory hallucinations that occur in patients with otologic or neurologic diseases. We report the first cases of musical hallucinations in two patients with neurologic Lyme disease. Both subjects were women with clinical and laboratory evidence of chronic Lyme disease, progressive neurologic dysfunction, and abnormal magnetic resonance imaging of the brain. There was no evidence of hearing loss in either case. Musical hallucinations had a sudden onset and took the form of patriotic or operatic music. The auditory hallucinations disappeared with intravenous (i.v.) antibiotic therapy in both patients, but the hallucinations recurred when i.v. antibiotic therapy was discontinued in one case. Response to therapy was accompanied by an increase in the CD57 lymphocyte subset in one patient, whereas recurrent hallucinations were associated with persistently low CD57 levels in the other case. We conclude that musical hallucinations may be associated with neurologic Lyme disease. These auditory hallucinations appear to respond to i.v. antibiotic therapy. Patients with musical hallucinations of unknown cause should be tested for infection with the Lyme disease spirochete.

Aged↗

PubMed1990

Hallucinations in schizophrenia.

The prevalence of different types of hallucinations and their clinical correlates were examined in 117 DSM-III-R schizophrenic or schizoaffective disorder patients. Auditory hallucinations were by far the most common, followed by visual hallucinations, and then by tactile and olfactory or gustatory hallucinations. Auditory hallucinations were associated with an earlier age of first hospitalization among the schizophrenics. Global severity of the illness for schizophrenics was related to the presence of visual hallucinations, but not other types of hallucinations. Tactile and olfactory or gustatory hallucinations were strongly correlated with each other and with the severity of delusions for both schizophrenic and schizoaffective patients. The results suggest that important clinical differences exist between patients with different types of hallucinations, and that these clinical variables need to be controlled for in cross-cultural studies of hallucinations.

Adolescent↗

PubMed2003

Visual hallucinations and Charles Bonnet syndrome after photodynamic therapy for age related macular degeneration.

AIMS: To report on visual hallucinations and Charles Bonnet syndrome (CBS) that may occur in patients with age related macular degeneration (AMD) treated by photodynamic therapy (PDT) with verteporfin for choroidal neovascularisation (CNV). METHODS: 100 consecutive patients were asked to respond to an orally administered questionnaire on visual hallucinations following PDT. Three groups of patients, respectively without visual hallucinations, with unstructured visual hallucinations, and with structured hallucinations-that is, CBS, were compared by ANOVA, Scheffe's test, or the chi(2) test, to establish whether age, sex, or visual acuity, as scored on ETDRS charts, are risk factors for the occurrence of visual hallucinations. RESULTS: Five patients (5%) described transient structured visual hallucinations, including known or unknown faces and geometric patterns. Fifteen patients (15%) reported photopsias and flashing lights of various colours. These symptoms usually occurred a few days after PDT. There was no significant difference between the group of patients with structured visual hallucinations and the two other groups, with regard to age (p =0.435), sex (p =0.406), or visual acuity (p =0.835). CONCLUSIONS: Visual hallucinations and CBS appear to be a possible, although unrecognised, side effect of PDT for CNV, which occur just after treatment. These results suggest the need to include the possibility of visual hallucinations in the information given to patients before PDT.

Aged↗

PubMed1992

Visual hallucinations in patients with macular degeneration.

OBJECTIVE: This study was undertaken to determine the prevalence of visual hallucinations in patients with macular degeneration, describe such hallucinations phenomenologically, and possibly determine factors predisposing to their development. METHOD: Using a case-control design, the authors screened 100 consecutive patients with age-related macular degeneration for visual hallucinations. Each patient with visual hallucinations was matched to the next three patients without hallucinations. The patients and comparison subjects were compared in terms of scores on the Beck Depression Inventory, Eysenck Personality Questionnaire, Telephone Interview for Cognitive Status, and a structured questionnaire including demographic characteristics, family history, and medical and psychiatric history. Ophthalmologic data were obtained by chart review. RESULTS: Of the 100 patients, 13 experienced visual hallucinations. Four variables were significantly associated with having hallucinations: living alone, lower cognition score, history of stroke, and bilaterally worse visual acuity. Hallucinations were not associated with family or personal history of psychiatric disorder or with personality traits. In 11 (84.6%) of the 13 patients, the hallucinations had begun in association with an acute change in vision. CONCLUSION: These results indicate that visual hallucinations are prevalent among patients with macular degeneration. They appear unrelated to primary psychiatric disorder. The predisposing factors of bilaterally worse vision and living alone support an association with sensory deprivation, while history of stroke and worse cognition support a decreased cortical inhibition theory.

Aged↗

PubMed2000

Hallucinations, REM sleep, and Parkinson's disease: a medical hypothesis.

BACKGROUND: Patients with PD can have disabling visual hallucinations associated with dopaminergic therapy. Sleep disorders, including vivid dreams and REM sleep with motor behaviors (RBD), are frequent in these patients. METHODS: The association of hallucinations and REM sleep both at night and during the day was examined in 10 consecutive nondemented patients with long-standing levodopa-responsive PD and hallucinations. Seven patients presented with paranoia and paranoid delusions. Overnight sleep recordings and standard multiple daytime sleep latency test were performed. The results were compared to those of 10 similar patients with PD not experiencing hallucinations. RESULTS: RBD was detected in all 10 patients with hallucinations and in six without. Although nighttime sleep conditions were similar in both groups, hallucinators tended to be sleepier during the day. Delusions following nighttime REM period and daytime REM onsets were observed in three and eight of the hallucinators, and zero and two of the others. Daytime hallucinations, coincident with REM sleep intrusions during periods of wakefulness, were reported only by hallucinators. Postmortem examination of the brain of one patient showed numerous Lewy bodies in neurons of the subcoeruleus nucleus, a region that is involved in REM sleep control. CONCLUSION: The visual hallucinations that coincide with daytime episodes of REM sleep in patients who also experience post-REM delusions at night may be dream imagery. Psychosis in patients with PD may therefore reflect a narcolepsy-like REM sleep disorder.

Aged↗

PubMed2004

The effects of emotional salience, cognitive effort and meta-cognitive beliefs on a reality monitoring task in hallucination-prone subjects.

OBJECTIVES: A tendency to externalize internal information on reality monitoring tasks has been documented in psychiatric patients with hallucinations. Furthermore, previous studies suggest that factors such as the emotional salience of the material, cognitive effort and meta-cognitive beliefs are important contributory factors in this tendency to externalize internal information on reality monitoring tasks. However, few studies have investigated these aspects in hallucination-prone subjects. Also, these factors have never been examined simultaneously. In the following study we wished to examine the effects of emotional salience, cognitive effort and meta-cognitive beliefs on reality monitoring functioning in hallucination-prone subjects. DESIGN: Between-participants group design. METHOD: One hundred normal subjects were administered a reality monitoring task. Words were presented by the experimenter. After each word, subjects were asked to say the first word that came to their mind. Words varied in terms of emotional valence and cognitive effort (high cognitive effort for words requiring longer latency times to associate a word and vice versa). Following a delay, words were presented consisting of those already presented by the experimenter or the subject (old) and those never presented before (new). For each word, subjects were required to identify whether the word was old or new. If the word was identified as old, subjects were required to identify the source of the word (subject or experimenter). Subjects also completed a questionnaire assessing meta-cognitive beliefs. RESULTS: Subjects were grouped according to their scores on a revised and elaborated version of the Launay-Slade Hallucinations Scale (LSHS). Those with scores within the top 25% were included in the hallucination-prone group (HP) (N = 25), whereas scores within the lower 25% were included in the non-hallucination-prone group (NHP) (N = 25). Results showed that the HP subjects had significantly more source discrimination errors than NHP subjects for self-generated items. In other words, HP subjects tended to misattribute to the experimenter items that they had produced themselves. This pattern was especially marked with emotionally charged material and with words that required more cognitive effort. In addition, HP subjects scored significantly higher on a scale assessing meta-cognitive beliefs compared with NHP subjects. Finally, scores on a scale assessing meta-cognitive beliefs were positively associated with source discrimination errors. CONCLUSIONS: These results suggest that cognitive effort, emotional salience and meta-cognitive beliefs all play a prominent role in the externalizing bias in hallucination-prone subjects. The results also provide evidence for the validity of the idea of a continuity between hallucination-prone subjects and psychotic patients with hallucinations on reality monitoring tasks, including a number of contributing factors in the occurrence of hallucinations.

Adult↗

PubMed1996

[Simple partial seizure consisting of complex visual hallucinations due to left temporo-occipital lesion].

We report a case of simple partial seizure consisting of elementary visual hallucinations and complex visual hallucinations due to left temporo-occipital lesion. The patient was a 45-year-old right-handed female who has been suffering from paroxysmal visual hallucinations in her right visual field for 15 days before admission. The properties of the hallucinations included several round colorful figures, the upper torsos of people in red, and green trees. CT scan showed a small low density area which, limited to the basal part of the left temporal and occipital lobes, was complicated partially by a high density area that was thought to be calcified. On T2-weighted MRI images, the lesion was shown as a small oval-shaped high signal intensity area surrounded by a low signal intensity area, and from its characteristic findings, a cavernous angioma was suspected. On the EEG, epileptic discharge was observed in the area limited to the left occipital region when elementary visual hallucinations occurred, and high amplitude diffuse slow waves were revealed predominantly on the left when complex visual hallucinations developed. It was thought that elementary visual hallucinations occurred in this patient following epileptic discharge of the occipital lobe, and complex visual hallucinations developed secondarily to the discharge which expanded from the occipital lobe to the surrounding area. Considering the investigation of non-epileptic visual hallucinations that are observed in the hemianopic visual field, we believe that disturbances of function of the temporo-parietal lobes around the occipital visual cortex has an important role in causing the development of complex visual hallucinations.

Brain Neoplasms↗

PubMed2006

Visual hallucinations in posterior cortical atrophy.

BACKGROUND: Visual hallucinations have been reported to occur in up to 25% of patients who meet the criteria for posterior cortical atrophy (PCA). It is not known, however, whether patients who meet the criteria for PCA and have hallucinations are different from those who meet the criteria and do not have hallucinations. OBJECTIVE: To compare the clinical and imaging features of patients with PCA with and without well-formed visual hallucinations. DESIGN: Case-control study. SETTING: Tertiary care medical center. PATIENTS: Fifty-nine patients fulfilling the criteria for PCA were retrospectively identified and divided into 2 groups based on the presence (n = 13) or absence (n = 46) of visual hallucinations. MAIN OUTCOME MEASURES: Statistically significant clinical differences and imaging differences using voxel-based morphometry between the 2 groups. RESULTS: In patients with PCA and hallucinations, parkinsonism and rapid eye movement sleep behavior disorder occurred more frequently, as did myoclonic jerks (P<.001 for both). Voxel-based morphometry showed greater atrophy in a network of structures, including the primary visual cortex, lentiform nuclei, thalamus, basal forebrain, and midbrain, in patients with hallucinations. CONCLUSIONS: Hallucinations in patients with PCA are associated with parkinsonism, rapid eye movement sleep behavior disorder, and myoclonic jerks. The voxel-based morphometry results suggest that hallucinations in PCA cannot be exclusively attributed to atrophy of the posterior association cortices and may involve a circuit of thalamocortical connections.

Age of Onset↗

PubMed2005

Complex visual hallucinations in the visually impaired: a structured history-taking approach.

OBJECTIVE: To study complex visual hallucinations in visually impaired individuals. METHODS: A prospective comparative study involving structured history taking and cognitive assessment in 48 consecutive visually impaired individuals with best-corrected visual acuity of 20/200 or worse and an age-matched cohort of 48 consecutive patients with visual acuity of 20/40 or better in at least 1 eye. RESULTS: Thirty visually impaired subjects (63%) experienced hallucinations, unrelated to specific ocular pathology. None volunteered the symptom; 2 admitted hallucinations on nonleading questioning and 28 on direct questioning. All displayed insight into the unreality of their hallucinations, although 18 (60%) achieved this after initial deception. Seventeen (57%) expressed concern; 7 (23%) experienced disturbing images. Nineteen (63%) feared being labeled as insane were they to admit to hallucinations, while 10 (33%) were fearful of impending insanity. Sixteen (94%) of 17 concerned patients derived comfort from sympathetic reassurance that their hallucinations did not represent sinister pathology. In contrast, none of the individuals with normal vision experienced any hallucinations (P<.001). Cognition was intact in all groups. CONCLUSIONS: Complex visual hallucinations with insight commonly occur in visually impaired, cognitively intact individuals due to acquired visual impairment and are unrelated to chronological age. Hallucinatory experiences are almost invariably admitted to only on direct questioning, due to fears of being considered insane. Although generally pleasant, hallucinations may cause distress, because of content or implications of the hallucinatory activity. Sympathetic explanation affords significant emotional relief.

Adult↗

PubMed1986

[Correlations between characteristics of the hallucinations in delirium tremens and psychological variables].

In 83 alcoholics admitted to the University of Würzburg mental hospital with delirium tremens, the relationship was studied between hallucinations occurring in the delirium and psychological variables in the post-delirium state. Psychological tests were used and resulted in 13 variables of cognitive achievement and 12 variables of emotion and motivation. The alcoholics were tested on the 4th day and in the 4th week after completing therapy. Alcoholics suffering from hallucinations in the delirium differed from those not suffering from hallucinations, but the differences were not significant. However, there were only a few alcoholics who were not suffering from hallucinations. On the other hand, there were statistically significant correlations between the nature of the hallucinations and personality traits. Patients suffering from "polymorphic" hallucinations differed from those suffering from "monomorphic" hallucinations in having lower cognitive deficits but increased anxiety. The latter subjects suffered more from inhibition; the former regained more of their cognitive abilities during the recovery period. The few significant correlations between the variables of sense modality of the hallucinations and psychological characteristics were interpreted as resulting from the differences between "polymorphic" and "monomorphic" hallucinations.

Adult↗

PubMed1987

Vocal activity in verbal hallucinations.

Vocal and forearm EMGs were recorded from 19 hallucinating and 22 nonhallucinating psychiatric inpatients. A microphone placed close to the lips was used to detect subvocal speech. The subjects' EMG and subvocal responses to pre-recorded statements were also assessed. Subjects who experienced hallucinations during assessment were asked to estimate the frequency of their hallucinations and rate phenomenological of their most recent hallucination. Results essentially replicated studies that found increased vocal potentials in hallucinators, but also showed that these increased potentials were nonsignificant when nonvocal measures are included in the statistical analysis. Subvocal speech and coincident increases in vocal EMG with reports of hallucinations, and with reports of pre-recorded statements, were not found. A significant negative correlation was found between the mean vocal potential of hallucinators and the perceived location of their most recent hallucination. The pre-recorded statements were generally perceived to be louder, clearer and more outside the head than the most recent hallucination.

Adult↗

PubMed2001

Verbal self-monitoring and auditory verbal hallucinations in patients with schizophrenia.

BACKGROUND: Contemporary cognitive models of auditory verbal hallucinations propose that they arise through defective self-monitoring. We used a paradigm that engages verbal self-monitoring to investigate this theory in patients with schizophrenia. METHODS: Ten patients with auditory verbal hallucinations and delusions (hallucinators), eight patients with delusions but no hallucinations (non-hallucinators), and 20 non-psychiatric control subjects were tested. Participants read single adjectives aloud, under the following randomized conditions: reading aloud; reading aloud with acoustic distortion of their own voice; reading aloud with alien feedback (someone else's voice); and reading aloud with distorted alien feedback. Immediately after articulating each word, participants identified the source of the speech they heard ('self'/'other'/'unsure'), via a button press. Response choice and reaction time were recorded. RESULTS: When reading aloud with distorted feedback of their own voice, patients in both groups made more errors than controls; they either misidentified its source or were unsure. Hallucinators were particularly prone to misattributing their distorted voice to someone else, and were more likely to make errors when the words presented were derogatory. Both patient groups made faster decisions than controls about the source of distorted or alien speech, but faster responses were only associated with errors in the former condition. CONCLUSIONS: Impaired verbal self-monitoring was evident in both hallucinators and non-hallucinators. As both groups had delusions, the results suggest an association between delusions and impaired judgements about ambiguous sensory stimuli. The specific tendency of hallucinators to misattribute their distorted voice to someone else may reflect impaired awareness of internally generated verbal material.

Adult↗

PubMed1998

Where the imaginal appears real: a positron emission tomography study of auditory hallucinations.

An auditory hallucination shares with imaginal hearing the property of being self-generated and with real hearing the experience of the stimulus being an external one. To investigate where in the brain an auditory event is "tagged" as originating from the external world, we used positron emission tomography to identify neural sites activated by both real hearing and hallucinations but not by imaginal hearing. Regional cerebral blood flow was measured during hearing, imagining, and hallucinating in eight healthy, highly hypnotizable male subjects prescreened for their ability to hallucinate under hypnosis (hallucinators). Control subjects were six highly hypnotizable male volunteers who lacked the ability to hallucinate under hypnosis (nonhallucinators). A region in the right anterior cingulate (Brodmann area 32) was activated in the group of hallucinators when they heard an auditory stimulus and when they hallucinated hearing it but not when they merely imagined hearing it. The same experimental conditions did not yield this activation in the group of nonhallucinators. Inappropriate activation of the right anterior cingulate may lead self-generated thoughts to be experienced as external, producing spontaneous auditory hallucinations.

Adult↗

PubMed2002

Visual hallucinations in Lewy body disease relate to Lewy bodies in the temporal lobe.

Consensus opinion characterizes dementia with Lewy bodies (DLB) as a progressive dementing illness, with significant fluctuations in cognition, visual hallucinations and/or parkinsonism. When parkinsonism is an early dominant feature, consensus opinion recommends that dementia within the first year is necessary for a diagnosis of DLB. If dementia occurs later, a diagnosis of Parkinson's disease with dementia (PDD) is recommended. While many previous studies have correlated the neuropathology in DLB with dementia and parkinsonism, few have analysed the relationship between fluctuating cognition and/or well-formed visual hallucinations and the underlying neuropathology in DLB and PDD. The aim of the present study was to determine any relationship between these less-studied core clinical features of DLB, and the distribution and density of cortical Lewy bodies (LB). The brains of 63 cases with LB were obtained over 6 years following population-based studies of dementia and parkinsonian syndromes. Annual, internationally standardized, clinical assessment batteries were reviewed to determine the presence and onset of the core clinical features of DLB. The maximal density of LB, plaques and tangles in the amygdala, parahippocampal, anterior cingulate, superior frontal, inferior temporal, inferior parietal and visual cortices were determined. Current clinicopathological diagnostic criteria were used to classify cases into DLB (n = 29), PDD (n = 18) or parkinsonism without dementia (n = 16) groups. Predictive statistics were used to ascertain whether fluctuating cognition or visual hallucinations predicted the clinicopathological group. Analysis of variance and regressions were used to identify any significant relationship(s) between the presence and severity of neuropathological and clinical features. Cognitive fluctuations and/or visual hallucinations were not good predictors of DLB in pathologically proven patients, although the absence of these features early in the disease course was highly predictive of PDD. Cases with DLB had higher LB densities in the inferior temporal cortex than cases with PDD. There was no association across groups between any neuropathological variable and the presence or absence of fluctuating cognition. However, there was a striking association between the distribution of temporal lobe LB and well-formed visual hallucinations. Cases with well-formed visual hallucinations had high densities of LB in the amygdala and parahippocampus, with early hallucinations relating to higher densities in parahippocampal and inferior temporal cortices. These temporal regions have previously been associated with visual hallucinations in other disorders. Thus, our results suggest that the distribution of temporal lobe LB is more related to the presence and duration of visual hallucinations in cases with LB than to the presence, severity or duration of dementia.

Adult↗

PubMed2005

Vivid dreams, hallucinations, psychosis and REM sleep in Guillain-Barré syndrome.

We conducted a prospective controlled study of the clinical and biological determinants of the mental status abnormalities in 139 patients with Guillain-Barré syndrome (GBS) and 55 patients without GBS placed in the intensive care unit (ICU controls). There were mental status changes in 31% of GBS patients and in 16% of controls (odds ratio = 2.3; P = 0.04). In GBS patients, they included vivid dreams (19%), illusions (30%, including an illusory body tilt), hallucinations (60%, mainly visual) and delusions (70%, mostly paranoid). They appeared a median 9 days after disease onset (range 1-40 days, during the progression or the plateau of the disease), and lasted a median 8 days. Seven (16%) patients experienced the symptoms before their admission to the ICU. Hallucinations were frequently hypnagogic, occurring as soon as the patients closed their eyes. Autonomic dysfunction, assisted ventilation and high CSF protein levels were significant risk factors for abnormal mental status in GBS patients. CSF hypocretin-1 (a hypothalamic neuropeptide deficient in narcolepsy) levels, measured in 20 patients, were lower in GBS patients with hallucinations (555 +/- 132 pg/ml) than in those without (664 +/- 71 pg/ml, P = 0.03). Since the mental status abnormalities had dream-like aspects, we examined their association with rapid eye movement sleep (REM sleep) using continuous sleep monitoring in 13 GBS patients with (n = 7) and without (n = 6) hallucinations and 6 tetraplegic ICU controls without hallucinations. Although sleep was short and fragmented in all groups, REM sleep latency was shorter in GBS patients with hallucinations (56 +/- 115 min) than in GBS patients without hallucinations (153 +/- 130 min) and in controls (207 +/- 179 min, P < 0.05). In addition, sleep structure was highly abnormal in hallucinators, with sleep onset in REM sleep periods (83%), abnormal eye movements during non-REM sleep (57%), high percentages of REM sleep without atonia (92 +/- 22%), REM sleep behaviour disorders and autonomic dysfunction (100%), reminiscent of a status dissociatus. The sleep abnormalities, that were almost absent in non-hallucinated GBS patients, were not exclusively related to ICU conditions, since they also appeared out of ICU, and were reversible, disappearing when the mental status abnormalities vanished while the patients were still in ICU. In conclusion, the mental status abnormalities experienced by GBS patients are different from the ICU delirium, are strongly associated with autonomic dysfunction, severe forms of the disease and possibly with a transitory hypocretin-1 transmission decrease. Sleep studies suggest that mental status abnormalities are wakeful dreams caused by a sleep and dream-associated disorder (status dissociatus).

Adolescent↗