Peduncular hallucinosis secondary to central pontine myelinolysis

Authors

  • Mark Walterfang MBBS, PhD, FRANZCP,

    Corresponding author
    1. Melbourne Neuropsychiatry Centre, University of Melbourne and North Western Mental Health, Melbourne, Australia
    • Neuropsychiatry Unit, Royal Melbourne Hospital, Melbourne, Australia
    Search for more papers by this author
  • Anita Goh BSc, DPsych,

    1. Neuropsychiatry Unit, Royal Melbourne Hospital, Melbourne, Australia
    2. Academic Unit for Psychiatry of Old Age, University of Melbourne, Melbourne, Australia
    Search for more papers by this author
  • Ramon Mocellin MBBS, MSc, MPM, FRANZCP,

    1. Neuropsychiatry Unit, Royal Melbourne Hospital, Melbourne, Australia
    2. Melbourne Neuropsychiatry Centre, University of Melbourne and North Western Mental Health, Melbourne, Australia
    Search for more papers by this author
  • Andrew Evans MBBS, MD, FRACP,

    1. Neuropsychiatry Unit, Royal Melbourne Hospital, Melbourne, Australia
    Search for more papers by this author
  • Dennis Velakoulis MBBS, MMed, DMedSci, FRANZCP

    1. Neuropsychiatry Unit, Royal Melbourne Hospital, Melbourne, Australia
    2. Melbourne Neuropsychiatry Centre, University of Melbourne and North Western Mental Health, Melbourne, Australia
    Search for more papers by this author

Correspondence: Mark Walterfang, MBBS, PhD, FRANZCP, Neuropsychiatry Unit, Level 2, John Cade Building, Royal Melbourne Hospital, Melbourne, Vic. 3050, Australia. Email: mark.walterfang@mh.org.au

Abstract

Peduncular hallucinations are generally associated with lesions in the midbrain. They have rarely been associated with central pontine myelinolysis, a condition associated with rapid alterations in serum sodium and chronic alcoholism. Described herein is the case of a 46-year-old man who developed typical peduncular hallucinations, whose imaging demonstrated central pontine myelinolysis. After alcohol cessation and neuroimaging resolution, the patient's hallucinatory phenomena abated.

COMPLEX VISUAL HALLUCINATIONS (CVH) can result from a variety of processes that disturb the transmission, processing and modulation of visual information.[1] We describe a case of CVH resulting from central pontine myelinolysis (CPM), in which both the hallucinosis and the pontine lesion resolved concomitantly.

Case report

A 46-year-old alcoholic man presented because of auditory and visual hallucinations. For some years, he heard multiple derogatory male voices saying he would be shot. He had been treated with 10 mg/day olanzapine for 3 years.

He also reported a 6-month history of complex visual hallucinations of Lilliputian figures, small malformed animals and faces, that moved in and out of walls, mostly during periods of low light. Figures would approach him and stare. These periods were not during periods of alcohol withdrawal, and did not occur on the periphery of sleep. He described some memory problems and reported drinking half to one bottle of spirits per day. He denied other substance use. He began to drink during a period of depression following divorce 10 years previously, but had not used alcohol for more than 1 week. His blood alcohol level at assessment was zero.

On mental state examination, he was cooperative and language was intact with no word-finding difficulty/thought disorder. He described complex visual hallucinations, in addition to simple auditory hallucinations of male voices. Insight was limited. Neurological examination indicated no focal signs other than reduced vibration sensation and proprioception peripherally, broad-based gait and positive pout/palmomental reflexes. He scored 57/100 on the Neuropsychiatry Unit COGnitive assessment tool (NUCOG),[2] with greatest deficits in memory, attention and executive functioning; a score on the NUCOG of <70 is consistent with moderate–severe cognitive impairment. Formal neuropsychological assessment indicated low average premorbid function, and difficulties with self-monitoring, abstraction and mental flexibility in addition to memory retrieval, attention, and psychomotor speed impairments. Visuospatial skills were intact.

He had elevated mean corpuscular volume and elevated γ-gluteryl transferase consistent with recent heavy alcohol intake. Serum sodium was normal. Magnetic resonance imaging (MRI) of the brain (Fig. 1) showed central cystic high signal within the pons, without extra-pontine change (Fig. 2). Computed tomography done 8 months earlier showed no pontine lesions. Overall, the imaging findings suggested recent CPM, superimposed on the likely central effects of chronic alcohol use. His hallucinosis responded to 10 mg per day of olanzapine, and alcohol abstinence.

Figure 1.

Magnetic resonance imaging at (top) first presentation and (bottom) follow up. (Left) Sagittal T1 shows hypointensity in the pons, while (middle) axial FLAIR and (right) T2 images show hyperintensity; note significant resolution at 30 months.

Figure 2.

Axial T2-weighted magnetic resonance imaging demonstrating a lack of basal ganglia hyperintensity at baseline.

The patient was reassessed 30 months later. At this time, he had not consumed alcohol for 12 months, and continued antipsychotic treatment. Auditory hallucinations continued intermittently. He had, however, not experienced visual hallucinations for 12 months. His NUCOG score had improved to 77/100, particularly in attention and executive function, and neurologically he demonstrated only mild antipsychotic-related parkinsonism. Neuropsychological assessment showed improvements in attention and working memory skills, executive function, and memory retention. On MRI, there was a significant resolution of his pontine lytic lesion with an area of increased signal, indicating residual gliosis. Informed consent to report his presentation was provided.

Discussion

Peduncular hallucinosis (PH) was first described in a mesencephalic lesion, with visual hallucinations of colorfully attired people and groups of children that occurred during low light.[3] It has since been associated with pathology in the pons, midbrain and thalamus.[1] Hallucinations in PH result from alterations to the ascending reticular activating system that intersects with the retinogeniculocalcarine pathways, particularly at the level of the thalamus.[1] Frequent hallucinatory content includes animals, (Lilliputian) people, deformed or frightening faces, or tessellated patterns and landscapes and commonly co-occur with significant impairments in memory, confabulation, impaired attention and executive dysfunction.[4]

Central pontine myelinolysis is a condition characterized by the destruction of myelin in the pons, but may be accompanied by extra-pontine (striatal, thalamic and cerebellar) demylination.[5] First described in patients with chronic alcohol abuse and malnourishment, it is also associated with rapidly corrected hyponatremia, and liver and renal transplantation. Approximately one-third of patients completely recover, one-third have minor deficits, and one-third are left with major motor or cognitive deficits.[6] Associated with rapid osmotic electrolyte shifts, it may be subsequent to oligodendrocyte sensitivity to osmotic stress, and local white matter anatomical features in the pons.[7] Motor features range from paraparesis, dystonia, dysphagia, and seizures or it may be asymptomatic. Neuropsychological findings include attentional, memory and executive disturbance.[8] Diagnosis is generally confirmed on MRI, with hypointense T1- and hyperintense T2-weighted lesions.[6] Preventing rapid correction of hyponatremia is paramount in management. It may improve significantly with supportive care, usually over a period of months,[9] with a resolution of imaging lesions.

Psychotic symptoms have rarely been described in association with CPM. One alcoholic patient developed symptoms during the timeframe of alcohol withdrawal,[10] and another with auditory hallucinations and delusions 3 months after initial presentation;[11] both also had extrapontine (basal ganglia) lesions. Catatonia without psychosis has been described,[12] but may be difficult to differentiate from profound dystonia. The present case differs from these reports, involving predominantly complex visual phenomena consistent with a peduncular hallucinatory syndrome. The disruption of myelinated tracts in the pons is likely to have resulted in impairments to ascending fibers from the reticular activating system to the thalamus, thus resulting in disturbed transmission through the retinogeniculocalcarine tract.[1] The co-resolution of both clinical and MRI features with sustained abstinence suggests their causal association.

This is the first presentation of typical PH associated with CPM. It illustrates the importance of thorough delineation of the psychopathology of psychotic symptoms, particularly when presentations are atypical, and also highlights the need for careful selection and interpretation of neuroimaging in psychotic presentations in which there are atypical features.

Acknowledgment

The authors declare no conflict(s) of interest.

Ancillary