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Year : 2000  |  Volume : 48  |  Issue : 2  |  Page : 183-5

Peduncular hallucinosis : an unusual sequelae of medulloblastoma surgery.

Department of Neurosurgery, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, 226014, India.

Correspondence Address:
Department of Neurosurgery, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, 226014, India.

  »  Abstract

Peduncular hallucinations are formed visual images often associated with sleep disturbance and are caused by lesions in the midbrain, pons and diencephalon. In present case report, a four year child, who was operated for midline posterior fossa medulloblastoma developed peduncular hallucinations on 3rd post operative day. Traction trauma or the compression of mid brain was thought to be the most possible cause of hallucinations.

How to cite this article:
Kumar R, Kaur A. Peduncular hallucinosis : an unusual sequelae of medulloblastoma surgery. Neurol India 2000;48:183

How to cite this URL:
Kumar R, Kaur A. Peduncular hallucinosis : an unusual sequelae of medulloblastoma surgery. Neurol India [serial online] 2000 [cited 2022 Jan 23];48:183. Available from:

   »   Introduction Top

Peduncular hallucinations are formed, coloured, visual images of people, animals, plants, scenes or geometric patterns. They have been reported in vascular and infective lesions of the thalamus, the pars reticulata of substantia nigra, midbrain, pons and basal diencephalon as well as by compression of midbrain.[1] Transient peduncular hallucinations due to extrinsic compression of midbrain by cystic craniopharyngioma have also been reported. The case under discussion developed peduncular hallucinosis following the excision of posterior fossa medulloblastoma.

   »   Case report Top

A 4 year aged child was admitted with history of headache of two months and gait ataxia of 15 days duration. On examination he was conscious and cooperative. Vision was 6/18 bilaterally. He had bilateral papilloedema and bilateral gross cerebellar signs. CT scan head revealed a very large, hyperdense, irregularly enhancing midline posterior fossa mass, obliterating 4th ventricle and causing gross obstructive hydrocephalus. There was significant compression of the brain stem. Peritumoural oedema was evident on CT scan. The mass was extending upto the level of tentorium superiorly and foramen magnum inferiorly [Figure - 1]. Midline suboccipital craniectomy and near total, microsurgical excision of a highly vascular tumour was done. Tumour was soft to firm, partly suckable, infiltrating almost entire vermis. It was relatively firm superiorl compressing the aqueduct upward and anteriorly. Minimal traction was inevitable during the delivery of superior part of tumour, but near total excision of tumour could be achieved. Postoperatively the child was fully conscious and alert following recovery from anaesthesia. On 3rd post operative day he developed formed visual hallucinations, when he intermittently started seeing different objects i.e. started playing and talking with toys, dogs and birds etc. This child was examined and observed for about half an hour following which he became all right. To establish the cause of formed hallucinations, the MRI head was done to rule out the midbrain or brain stem infarct/insult. It, however, did not reveal any abnormality other than dilated CSF pathway dorsal to brain stem.
Tumour was reported as desmoplastic variant of medulloblastoma, substantiating the cause of its firmness.

   »   Discussion Top

In 1992, L'hermitte described the clinical syndrome of visual hallucinations in a 72 year old woman who developed headache, vomiting and vertigo, followed by left sided ptosis, opthalmoplegia and pyramidal and cerebellar signs, suggesting a lesion of the pons and midbrain.[2] Von Bogaert coined the term 'peduncular hallucinations' in the patients having visual hallucinations in whom the subsequent autopsy revealed infarction of the third nerve nucleus, red nucleus, superior colliculus, periaqueductal gray, substantia nigra and pulvinar.[3] Pigmentary degeneration of the periaqueductal gray and degeneration of occulomotor nucleus were found to be associated with peduncular hallucinations. Similar hallucinations were reported in the lesions of posterior thalamic lesions.[4]
MRI of patients manifesting visual hallucinations revealed vascular infarcts of paramedian thalamus and mesencephalon.[5] The case reports of similar hallucinations in lesions of the pons, ventromedial hypothalamus and pars reticulate of substantia nigra appeared in literature subsequently.[1] Kumar et al recently reported two cases developing peduncular hallucinosis following surgical intervention in suprasellar region. In one case it occurred as a sequel of endoscopic third ventriculostomy while in the other, it was due to diencephalon and mid brain
compression by a post operative clot, following surgical excision of hypothalamic astrocytoma.[1] The clinical syndrome of 'peduncular hallucinosis' consists of formed, vivid, visual hallucinations. These hallucinations may be highly coloured, mobile and are composed of concrete, often animate objects. These are not stereotyped and vary from one occasion to the next, are more pronounced nocturnally and are often associated with disordered sleep. These visual hallucinations may be of two types. In one type, the hallucinations are often detached from the patient's own thoughts and actions, thus are not mistaken for reality; in another the hallucinations are mistaken for reality and are associated with agitation and delusion.[1],[3] Peduncular hallucinations occur in the brainstem and diencephalon region in the setting of vascular stroke, encephalitis, intoxication, following vertebral angiography and by transient brain stem compression.[1],[4],[6],[7] The aetiology of the hallucinations in peduncular hallucinosis is unknown. Van Bogaert stated that peduncular hallucinations are a state of ego dissolutions with the loss of the ability to distinguish external reality from imaginations.[3] Damageto the ascending reticular activating system[2],[5] has also been proposed to result in these hallucination. Mackee has suggested that occlusion of the paramedian branches of the rostral basilar artery causes infarcts in the medial diencephalon, especially pars reticulata of the substantia nigra, and brain stem tegmentum.[8]
These regions are also connected to the pedunculopontine nuclei by efferent pathways.[9] Lesions in these areas produce disordered REM sleep, that is linked to dreams.[1],[8] Thus peduncular
hallucinations are due to release of dream activity that is normally suppressed during wakefulness. An evidence in favour of this hypothesis is the frequent occurrence of sleep disturbance with hallucinations.[5] Cogan divided visual hallucinations into release and irritative phenomena. Irritative phenomena are paroxysmal and stereotyped hallucinations that may assist in localization of lesion.[10] An occipital lobe focus produces light or colours, whereas a temporal lobe focus results in complex formed images.[7]
Though the peduncular hallucinations are described in association with intrinsic lesions of midbrain, the extrinsic compression of brain stem is also known to cause this phenomenon. Dunn et al reported the association of transient peduncular hallucinations due to compression of midbrain by cystic craniopharyngioma, which resolved following the drainage of cyst.[7]

In the present case, most probably, there had been minor traction trauma or vascular insult to either midbrain or pons during the delivery of firm part of tumour, which manifested on 3rd day for brief period in the form of peduncular hallucinosis, and improved spontaneusly. No lesion, however, though the insult could not be demonstrated on MRI.


  »   References Top

1.Kumar R, Behari S, Wahi J et al: Peduncular hallucinosis; an unusual sequel to surgical intervention in suprasellar region. Br J Neurosurgery 1999; 13: 500-503.   Back to cited text no. 1    
2.L'hermitte L: Syndrome de la calotte du pedoncule cerebral. Les troubles psycho - sensorials dans les lesions du mesocephale. Rev Neurol (Paris) 1922; 38: 1359-1365.   Back to cited text no. 2    
3.Van Bogaert L: L'hallucinose pedonculaire. Rev Neurol (Paris), 1927; 47: 608-617.   Back to cited text no. 3    
4.De Morsier G: Pathogenic de L'hallucinose pedonculaire: A propos d'un nouveaucas. Rev Neurol (Paris) 1935; 64: 606-608.   Back to cited text no. 4    
5.Feinberg WM, Rapcsak SZ: 'Peduncular hallucinosis' following paramedian thalamic infarction. Neurology 1989; 39: 1535-1536.   Back to cited text no. 5    
6.Rozanski J: Peduncular hallucinosis following vertebral angiography. Neurology 1952; 2: 341-349.   Back to cited text no. 6    
7.Dunn DW, Weisberg LA, Nadell J: Peduncular hallucinations caused by brain stem compression. Neurology (Cleveland) 1983; 33: 1360-1361.   Back to cited text no. 7    
8.Mackee AC, Levine DN, Richardson, Jr, EP: Peduncular hallucinosis associated with isolated infarction of the substantia nigra pars reticulata. Ann Neurol 1989; 27: 500504.   Back to cited text no. 8    
9.Beckstead RM, Domesick VB, Nauta WJH: Efferent connections of the substantia nigra and ventral tegmental area of the rat. Brain Res 1979; 175: 191-217.   Back to cited text no. 9    
10.Cogan DG: Visual hallucinations an release phenomena. Albrecht von Graefes Arch/Klin Exp Ophthalmol 1973; 188: 139-150.   Back to cited text no. 10    


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