Thalamic experiential hallucinosis.

Abstract

lucinations that consisted of vivid recollections of his old jobs. He described transient episodes in which he saw and dyed clothes, talked of town affairs with his friends, and obeyed his employer's instructions. He had experienced similar events about 50 years ago in his first job. Other scenes were related to his last job. He felt that each episode lasted about five minutes and was convinced the hallucinations were real while they were happening. The hallucinations arose involuntarily in objective space. They were normally coloured and encompassed the whole visual field. There were no diurnal fluctuations in the appearance of the hallucinations.The following laboratory investigations and analysis of CSF were normal: CBC, routine blood chemistry, antinuclear antibody, VDRL, triglycerides, cholesterol, vitamin B1,, T4 and T, resin uptake, thyroid-stimulating hormone (TSH), and arterial blood gases. An EEG when the patient was hallucinating demonstrated diffuse slow waves at 5 to 7 Hz with bifrontal intermittent delta waves. An EEG when the spells were not occurring showed similar findings.CT three days after onset showed a small, low density area in the central part of the right thalamus. CT 14 days after onset showed no lesion, but one month after onset the small, low density area reappeared in the same position, indicating a CT fogging effect.6The hallucinations slowly resolved over a two week period, although morphine sulphate (60 mg/day) was continued. At the end of this time, hallucinations were shorter and simpler. He frequently reported that he saw a dish of sweet potatoes on the table near his bedside or a cigarette between his fingers: they disappeared in a few seconds. He had often eaten sweet potatoes one month before the occurrence of hallucinosis and was a heavy smoker. These hallucinations developed when he was sitting on a chair or resting in bed without falling asleep. He was left without memory impairment or any other neurological deficits.Two months later, the patient died. Postmortem examination disclosed widespread carcinomatosis with involvement of both lungs, mediastinal nodes, liver, and left kidney. Small polypoidal growths were found on the mitral valve. The tumour histology revealed squamous carcinoma. The brain showed mild atherosclerosis. It was fixed in formalin and sliced serially.

Brain mechanisms associated with top-down processes in perception

“…Such hallucinations often cease when the patient is treated with antiepileptic drugs (Lance 1976). Other cases are associated with damage in the thalamus and the parietal cortex (Noda et al 1993;Critchley 1951). Both these areas are part of the circuit revealed by brain imaging to be involved in the modulation of sensory processes by attention.…”

‘Distorteidolias' - Fantastic Perceptive Distortion

“…Most isolated thalamic infarctions are due to small arterial vessel disease but involve the ventral posterolateral thalamic nucleus causing pure sensory stroke [6]. Visual hallucinations due to paramedial thalamic stroke may be accompanied by auditory [7] hallucinations. In most of the cases, the lesion involved the upper part of the midbrain along with the adjacent lower part of the paramedial thalamus.…”

Hallucinosis and Thalamic Infarcts

“…These so-called peduncular hallucinoses were first associated with mesencephalic infarcts [6] sometimes associated with thalamic lesions [3,7], but have since been reported in a few cases of thalamic infarcts without mesencephalon involvement [2,4,5] and striatocapsular infarction [8], However, these data arc rare or underestimated since they arc not mentioned in a large series of thalamic infarcts [1], Our data highlight that prominent hallucinations may be due to iso lated unilateral and essentially right-sided thalamic infarcts (case 2) [2,4,5]. Hallucinations due to left-sided [5] or bilateral infarcts (case 1) [3] seem less frequent.…”

“…These hallucinations had several characteris tics. They were usually visual, encompassed the whole visual field but may occur in a hemifield without visual field disturbances [4], They were vivid, colored, and full of motion, influenced by the cultural and personal background of each patient, and classically occur in the eve ning or in the dark over a period of days [2,3] to several weeks [5].…”

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Neuropsychological dysfunction, including dysphasia and hemincglcct with impaired visuospatial processing are usually encoun tered in thalamic lesions, especially in thalamic infarction [1], How ever, hallucinosis has been exceptionally reported in association with thalamic infarction [2][3][4][5], essentially in the territory of the posterior thalamosubthalamic paramedian artery. We report data on 2 pa tients who developed auditory' and visual hallucinations as the main clinical features in a unilateral tuberothalamic artery territory infarct and a bilateral paramedian artery territory infarct.

Case Reports Case 1.

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