The Ochsner Journal 14:450–452, 2014 Ó Academic Division of Ochsner Clinic Foundation Peduncular Hallucinosis: A Case Report Lauren Penney, MBBS,1 David Galarneau, MD1,2 1The University of Queensland School of Medicine, Ochsner Clinical School, New Orleans, LA 2Department of Psychiatry, Ochsner Clinic Foundation, New Orleans, LA hallucinosis secondary to infarction in the basal ABSTRACT ganglia only. To the best of our knowledge, few Background: Peduncular hallucinosis is a rare form of visual cases involving only the basal ganglia have been hallucination often described as vivid, colorful visions of people reported. and animals. The exact pathophysiology is unknown; however, most cases have been described in relation to lesions in the CASE REPORT thalamus or midbrain. A 59-year-old female presented to the hospital Case Report: We present the case of a 59-year-old female with with a 3-week history of right-sided headache and a 1- peduncular hallucinosis associated with infarction in the right week history of irritability, confusion, and visual basal ganglia with the background of malignant hypertension. hallucinations with a background of malignant hyper- The patient’s visual hallucinations decreased without pharma- tension and hyperlipidemia. One week prior to ceutical treatment by the time of discharge and on further hospital admission, she had presented to an outpa- follow-up had resolved completely. tientclinicbecauseoftheheadachesandwas Conclusion: We believe ours is one of few reported cases of diagnosed with malignant hypertension and sinusitis. peduncular hallucinosis in a patient with an infarct isolated to Magnetic resonance imaging revealed an infarct in the basal ganglia (striatum and globus pallidus). the right globus pallidus, putamen, caudate, and anterior limb of the internal capsule. Magnetic resonance angiography showed multifocal areas of INTRODUCTION significant stenosis. The patient was transferred to our Peduncular hallucinosis is a rare form of visual institution for evaluation by vascular neurology. hallucination first described by Lhermitte in 1922. Psychiatry was consulted in regard to the visual The visions are usually reported to be vivid, colorful,1 hallucinations. and sometimes distorted images of animals and The patient described visions of animals and people. They are typically considered nonthreatening people that ranged from shadows to bright colors, by the patient. Peduncular hallucinosis has often as well as Lilliputian hallucinations (hallucinations of been described in relation to both vascular and people and objects of reduced size). She found these infective lesions of the mesencephalon and thalamus. hallucinations nonthreatening and was aware that Cases of peduncular hallucinosis have been they were not real. Visions occurred in daylight and at reported involving infarction of the basal ganglia as night and were not associated with sleep disturbance, 2 well as the thalamus. We report a case of peduncular agitation, or visual disorders. The patient had no past psychiatric history and denied auditory hallucinations and delusions. She was alert and orientated to person, place, and time. Cognition, attention, memo- Address correspondence to ry, and language were intact. David Galarneau, MD The patient’s medical history included malignant Department of Psychiatry hypertension with diastolic dysfunction and hyperlip- Ochsner Clinic Foundation idemia. She had been noncompliant with medication 1514 Jefferson Hwy. for the hypertension for about 3 years. Family history New Orleans, LA 70121 was significant for her father having heart disease and Tel: (504) 842-4025 transient ischemic attacks in his 60s. The patient did Email: [email protected] not smoke or drink alcohol and was not currently Keywords: Basal ganglia, hallucinations, infarction taking any medication except an antibiotic prescribed 1 week prior for sinusitis. During admission, the The authors have no financial or proprietary interest in the subject patient was newly diagnosed with type 2 diabetes matter of this article. mellitus, with a hemoglobin A1c of 6.7%. She was 450 The Ochsner Journal Penney, L also found to have chronic kidney disease stage 3 Determining how visual hallucinations can result with a baseline creatinine of 1.82 mg/dL. from lesions in areas of the brain that are not part of General physical examination was unremarkable. the visual pathway has been difficult. Two common On neurologic examination, cranial nerves II-XII were mechanisms have been suggested: imbalance be- intact and equal bilaterally. Upper and lower extrem- tween neurotransmitters in the reticular activating ity motor strength was 5/5, and sensation was system (RAS),2 and disruption of the basal ganglia normal. The patient was treated with clopidogrel (temporal lobe loop).5 bisulfate (Plavix) and aspirin for the infarct, metopro- TheRASmaybeinvolvedintheproductionof lol for hypertension, and atorvastatin calcium (Lip- peduncular hallucinosis because of the association itor) for hyperlipidemia. Her hypertension was with sleep-wake cycle disturbance. The RAS is treated with a combination of metoprolol, nifedipine, composed of neuronal circuits connecting the hydralazine, isosorbide mononitrate, and a clonidine brainstem to the cortex and is responsible for patch. Angiotensin-converting enzyme inhibitors regulating arousal and sleep-wake cycles. Lesions were avoided because of the patient’s decreased are thought to alter the ponto-geniculo-occipital renal function. (PGO) waves that are associated with rapid eye Treatment of the hallucinations with an antipsy- movement (REM) sleep. Interruption to serotonergic chotic was discussed with the patient, but because inhibitory afferents in the dorsal raphe nuclei are of the medication’s side effects and the fact that the suspended, resulting in an increase of PGO waves patient was not bothered by the visual hallucina- and thus an increase in REM sleep. Hallucinations may result from patients entering REM sleep quickly tions, pharmaceutical treatment was not recom- 2 mended. At the time of discharge, the visual from a higher level of arousal. hallucinations were still present but decreasing in Another possible mechanism for peduncular frequency. At further follow-up, they had completely hallucinosis involves a closed loop between the basal ganglia and the inferotemporal lobe.5 The resolved. basal ganglia are primarily known to control move- DISCUSSION ment and coordination, but Middleton and Strick Peduncular hallucinosis is characterized by visual suggested that the inferotemporal lobe, which is responsible for recognition and discrimination of hallucinations of concrete objects that are often vivid visual objects, may also be an output target for the and colorful. The patient does not mistake these basal ganglia.5 The basal ganglia loop involves a visions for reality, which is an important distinction direct pathway (through the substantia nigra pars between hallucinosis and psychiatric visual hallucina- reticulata and internal globus pallidus complex) and tion. This condition has primarily been reported in an indirect pathway (through the external globus single case reports, so information about associated pallidus and subthalamic nucleus) to the temporal symptoms is inconsistent.3 The exact lesion and lobe via the thalamus. Middleton and Strick hypoth- pathogenesis of peduncular hallucinosis are still esised that lesions of the substantia nigra and unknown, although many cases involve vascular brainstem compression may result in visual halluci- lesions in the midbrain or thalamus. nations by blocking the stimulatory signal from the Peduncular hallucinosis has commonly been subthalamic nucleus to the substantia nigra, in turn described in the setting of sleep-wake cycle distur- 1 decreasing the inhibitory signal to the thalamus and bance, with visions more pronounced nocturnally. resulting in overactivity of the thalamus and the This association led Lhermitte to propose that sleep 1 inferotemporal lobe. This mechanism may be re- disturbance was the decisive factor in the condition. sponsible for the peduncular hallucinosis experi- However, although sleep disturbance is common in enced by our patient after suffering an infarction in 2 peduncular hallucinosis, it is not essential. In our the striatum and globus pallidus. case, the patient experienced visual hallucinations In most situations, as in our case, peduncular day and night and did not exhibit any sleep cycle hallucinosis is self-limiting and does not require any dysfunction. treatment. One study suggested that the atypical Vascular lesions have been reported as the most antipsychotic olanzapine could be of potential bene- common cause of peduncular hallucinosis, with the fit.6 However, in the majority of cases reviewed, the thalamus, midbrain, and brainstem most commonly visual hallucinations experienced by the patient 4 affected. Similar to many reported cases, our patient resolved on their own. developed peduncular hallucinosis as a result of an infarction. However, our patient’s infarct was limited to CONCLUSION the right basal ganglia only with no direct involvement Peduncular hallucinosis is a rare form of visual of the thalamus or midbrain. hallucinations most commonly caused by lesions to Volume 14, Number 3, Fall 2014 451 Peduncular Hallucinosis the midbrain and thalamus, either alone or in REFERENCES combination with other areas of the brain. It may also 1. Lhermitte J. Syndrome de la calotte du pedoncule cerebral. les present