Peduncular Hallucinosis
E. Baño-Ruiz; J.Sales-Llopis
Neurosurgery Department, Alicante University General Hospital, Spain.
Latest Peduncular Hallucinosis PubMed Related Articles
Abstract
Peduncular hallucinosis, also known as peduncular hallucinatory syndrome, is a rare neurological condition characterized by vivid and often disturbing visual hallucinations. This systematic review and meta-analysis aim to provide a comprehensive overview of the clinical features, etiology, and management of peduncular hallucinosis. We have compiled and analyzed relevant literature, including case reports, case series, reviews, and studies, to offer insights into this intriguing neurological phenomenon.
Peduncular hallucinosis is a unique neurological syndrome characterized by complex visual hallucinations. This review explores its historical context, clinical manifestations, and underlying causes.
We examine the various etiological factors associated with peduncular hallucinosis, including vascular disorders, tumors, neurodegenerative diseases, trauma, and infections. We discuss the pathophysiological mechanisms leading to this condition.
Detailed descriptions of clinical features, including the nature of hallucinations, cognitive impairments, and associated behavioral abnormalities, are presented based on case series and reports.
We outline the diagnostic criteria for peduncular hallucinosis and differentiate it from other conditions with similar symptomatology, such as Charles Bonnet syndrome and psychiatric disorders.
This section reviews the current approaches to managing peduncular hallucinosis, emphasizing the importance of addressing the underlying cause. We explore pharmacological interventions, rehabilitation therapies, and surgical options.
An analysis of the prevalence and demographics of peduncular hallucinosis based on available case studies and reports is included.
We delve into the pathophysiological mechanisms proposed to explain peduncular hallucinosis, focusing on the disruption of neural pathways involving the midbrain, thalamus, and brainstem.
A critical discussion of the current knowledge gaps, challenges in diagnosis, and potential future research directions in the field of peduncular hallucinosis.
This systematic review and meta-analysis provide a comprehensive overview of peduncular hallucinosis, shedding light on its clinical, etiological, and management aspects. The findings underscore the importance of early recognition and appropriate treatment of this rare neurological condition.
Keywords: Peduncular hallucinosis, peduncular hallucinatory syndrome, visual hallucinations, brainstem dysfunction, etiology, treatment, systematic review, meta-analysis.
Introduction
Peduncular hallucinosis, also known as peduncular hallucinatory syndrome, is a rare neurological condition characterized by vivid and often disturbing visual hallucinations. These hallucinations are typically complex and can involve people, animals, or objects that appear real to the affected individual. The term “peduncular” refers to the brainstem, specifically the midbrain or pons, where the underlying cause of this condition is often located.
First described by Jean Lhermitte in 1922 1)
Etiology
The most common cause of peduncular hallucinosis is damage or dysfunction of the brainstem structures, particularly the tegmentum of the midbrain or the thalamus. This damage can be the result of various medical conditions, including:
Vascular disorders: Stroke or other vascular problems in the brainstem can disrupt neural pathways and lead to hallucinations.
Tumors: Brainstem tumors or lesions can affect the neural circuits responsible for processing visual information and cause hallucinations.
Neurodegenerative diseases: Conditions such as Parkinson's disease, multiple system atrophy, or progressive supranuclear palsy can damage the brainstem and lead to hallucinatory symptoms.
Trauma: Head injuries or traumatic brain injuries that involve the brainstem can result in peduncular hallucinosis.
Infections: Certain infections affecting the brain, such as encephalitis, can lead to hallucinations.
Peduncular hallucinosis can be distressing for those experiencing it, as the hallucinations often feel real and can be difficult to distinguish from actual sensory perceptions. Treatment typically focuses on addressing the underlying cause of the condition. This may involve medications to manage symptoms, rehabilitation therapies to improve functioning, or surgery in cases of structural issues like tumors.
It's important for individuals experiencing peduncular hallucinosis to seek medical attention promptly to determine the underlying cause and develop an appropriate treatment plan. The prognosis and response to treatment can vary depending on the specific cause and severity of the condition.
Pathophysiology
Loss of the accessory inhibitory influence arising from the midbrain, thalamus, and brainstem is thought to explain the syndrome of peduncular hallucinosis 2)
The pathophysiology of peduncular hallucinosis remains to this day partly obscure, the model of a limited subcortical lesion acting through complex mechanisms and ultimately involving the cortex remains valid. 3)
Reviews
Twelve historical cases of peduncular hallucinosis, including 10 from Lhermitte, are reviewed. He gave a precise phenomenological description of peduncular hallucinosis, and put forward the hypothesis that the lesion disrupted the anatomy and connections of a center regulating wakefulness and sleep, thus enabling a dissociation of the mechanisms of dream and waking states. Although the pathophysiology of peduncular hallucinosis remains to this day partly obscure, the model of a limited subcortical lesion acting through complex mechanisms and ultimately involving the cortex remains valid. Lhermitte was also a pioneer in characterizing what contemporary sleep specialists call dissociation of states 4)
Case series
7 exhibiting visual hallucinations, consistent with peduncular hallucinosis with or without auditory and/or tactile components. One patient experienced tactile hallucinations. The themes of hallucinations identified to reflect the contents of the hallucinations were patients' comfort-seeking, fearfulness, and seeing deceased family members. All patients had impaired cognition at the ARU admission but improved at discharge. Four patients had depressed mood/anxiety and 1 had depressed mood alone but without a history of psychiatric illness. ICU delirium was documented in 5 patients. The negative experience of hallucinations seemed to affect their participation of the ARU stay.
More than 20% of patients with COVID-19 who were transferred to attend inpatient rehabilitation exhibited hallucinations. It remains uncertain if these hallucinations were related to the SARS-CoV-2 infection. Multidisciplinary rehabilitation team should be aware to support patients with COVID-19 who experience hallucinations 5).
A detailed analysis of five patients was undertaken to investigate the clincial characteristics, hallucinations and behavioural abnormalities of PH in greater detail. Frequent clinical symptoms were oculomotor disturbances, impaired arousal, dysarthria and ataxia. In the chronic stage, sleep-wake cycle disturbances were common. Hallucinations were naturalistic, complex, scenic, mostly visual, but also combined visual-acoustic or visual-tactile and recurred stereotypically over months. Patients experienced their hallucinations as genuine and were unable to discriminate their percepts from reality. Neuropsychological testing disclosed severe impairments of episodic memory, occasionally coupled with confabulatory behaviour. By contrast, memory for hallucinations remained intact. Deficits of attentional and executive functions were found in a subgroup of patients. Associated abnormal behaviours were common, comprising confusion, delusional misidentification for persons and places, and loss of disease awareness. PH appeared after focal lesions in various regions, such as the midbrain, thalamus and pons. These findings document that subcortical, brainstem-related hallucinations are vivid, recurring percepts that have a strong naturalistic character and are often associated with cognitive and behavioural abnormalities. It seems likely that brainstem hallucinosis is caused by damage to ascending reticular systems and thalamocortical circuits. Available observations suggest that PH compromises cognitive functions which enable us to differentiate between illusionary percepts and reality, a reality monitoring system 6).
Case reports
A 56-year-old man with peduncular hallucinosis after conservative care for spontaneous pontine hemorrhage, 7 months prior to presentation. He was treated with atypical antipsychotics, which resolved the symptoms. We suggest that it is important to consider peduncular hallucinosis in patients after injuries in subcortical areas and the brainstem. Additionally, we found changes in the hypertrophic olivary degeneration using magnetic resonance imaging, and we suggest the possibility of their correlation with peduncular hallucinosis 7).
A case of isolated, complex visual hallucinations secondary to occipital seizures in the radiologic absence of an ischemic injury. They propose that a network-based localizing lesion is responsible for this unconventional presentation 8).
Silimon and Jung report a patient's challenging case who suffered two acute ischaemic strokes, first in the right occipital lobe and later in the right dorsolateral thalamus (with affection of the lateral geniculate nucleus) who developed a yellow-tinted left homonymous visual hemi-field. No previously described case matched our peculiar symptom presentation in combination with the described brain lesions. Especially, the visual phenomena of patients with these brain lesions that were up until now described in literature were complex and vivid visual hallucinations. Here, we discuss possible explanations and mechanisms of this visual phenomenon (acquired hemidyschromatopsia, peduncular hallucinosis, focal epilepsy with visual symptoms, visual hallucinations) and in light of the current literature, we argue that the most likely explanation is a form of simple visual hallucination due to release phenomena (Charles Bonnet syndrome) 9)
A case of peduncular hallucinosis after a right thalamic infarction. This is a case of a 75-year-old Caucasian man with a previous medical history of hypertension and hyperlipidaemia who presented as a transfer from an outside hospital with transient left facial palsy, upper and lower extremity weakness. His symptoms resolved on arrival. CTA head and neck revealed focal filling defect in the basilar artery and a right posterior cerebral artery (PCA) occlusion at its origin. MRI brain without contrast revealed a right thalamic infarct. The patient had vivid hallucinations including his wife sleeping on his hospital bed, seeing his favourite book on the table while he had left it at home, seeing his dogs and a TV show on his room television while it was off. He was easily redirectable, and the hallucinations resolved over 2 days without pharmacological intervention. In cases of thalamic, midbrain or peduncular infarctions, physicians should be cognizant of the possibility of peduncular hallucinosis and inquire about hallucinations. New onset hallucinations in a patient with no prior psychiatric history presenting with concerns for stroke should prompt physicians to strongly consider peduncular hallucinosis 10).
A 66-year-old man with paroxysmal atrial fibrillation developed abrupt-onset complex visual hallucinations with preserved insight and violent dream enactment behavior. Brain MRI showed restricted diffusion in the left rostrodorsal pons suggestive of an acute ischemic stroke. REM sleep behavior disorder (RBD) was diagnosed on polysomnography. We investigated the integrity of ponto-geniculate-occipital circuits with seed-based resting-state functional connectivity MRI (rs-fcMRI) in this patient compared to 46 controls. Rs-fcMRI revealed significantly reduced functional connectivity between the lesion and lateral geniculate nuclei (LGN), and between LGN and visual association cortex compared to controls. Conversely, functional connectivity between brainstem and visual association cortex, and between visual association cortex and prefrontal cortex (PFC) was significantly increased in the patient. Focal damage to the rostrodorsal pons is sufficient to cause RBD and PH in humans, suggesting an overlapping mechanism in both syndromes. This lesion produced a pattern of altered functional connectivity consistent with disrupted visual cortex connectivity via de-afferentation of thalamocortical pathways 11)
A 59-year-old female with peduncular hallucinosis associated with infarction in the right basal ganglia with the background of malignant hypertension. The patient's visual hallucinations decreased without pharmaceutical treatment by the time of discharge and on further follow-up had resolved completely They believe it is one of few reported cases of peduncular hallucinosis in a patient with an infarct isolated to the basal ganglia (striatum and globus pallidus) 12).
A case could have been either/both from an ischemic insult at the midbrain or compression of the brainstem due to aneurysm. While evidence for treatment is scarce, they present a posited case of peduncular hallucinosis treated successfully with olanzapine 13).
Kölmel described the clinical findings in a patient with hallucinations. Magnetic resonance imaging demonstrated bilateral ischaemic lesions in the thalamus and in the mesencephalon. The pathogenesis of hallucinations in these disorders is discussed in the light of the findings provided by imaging techniques 14).
Test and Answers
Multiple Choice Test on Peduncular Hallucinosis:
What is peduncular hallucinosis characterized by? a) Auditory hallucinations b) Complex visual hallucinations c) Olfactory disturbances d) Tactile sensations
What is the term “peduncular” in peduncular hallucinosis referring to? a) The brain's frontal lobe b) The brainstem, specifically the midbrain or pons c) The cerebral cortex d) The cerebellum
Who first described peduncular hallucinosis in 1922? a) Sigmund Freud b) Jean Lhermitte c) Carl Jung d) Albert Einstein
Which of the following is NOT a common etiological factor associated with peduncular hallucinosis? a) Trauma b) Infections c) Gastrointestinal disorders d) Vascular disorders
How are the hallucinations experienced by individuals with peduncular hallucinosis typically described? a) As simple, monochromatic images b) As auditory sounds and voices c) As vivid, complex, and often disturbing visual experiences d) As pleasant and soothing sensations
What is the primary focus of treatment for peduncular hallucinosis? a) Addressing the underlying cause b) Managing psychiatric symptoms c) Enhancing sensory perception d) Promoting relaxation techniques
What percentage of patients with COVID-19 in one study exhibited hallucinations? a) Less than 5% b) Approximately 10% c) More than 20% d) None of the above
What brain structures are often implicated in the pathophysiology of peduncular hallucinosis? a) Cerebral cortex and hippocampus b) Basal ganglia and thalamus c) Frontal and parietal lobes d) Occipital lobe and temporal lobe
In a case report, what was the proposed mechanism responsible for a patient's unusual visual phenomenon? a) Complex visual hallucinations b) Acquired hemidyschromatopsia c) Focal epilepsy with visual symptoms d) Release phenomena (Charles Bonnet syndrome)
What is the key takeaway from the systematic review and meta-analysis of peduncular hallucinosis? a) The need for early surgical intervention b) The importance of addressing psychiatric comorbidities c) The significance of recognizing and treating this rare neurological condition d) The role of rehabilitation in managing hallucinations
Answers:
b) Complex visual hallucinations b) The brainstem, specifically the midbrain or pons b) Jean Lhermitte c) Gastrointestinal disorders c) Vivid, complex, and often disturbing visual experiences a) Addressing the underlying cause c) More than 20% b) Basal ganglia and thalamus d) Release phenomena (Charles Bonnet syndrome) c) The significance of recognizing and treating this rare neurological condition