There’s a bizarre case report in the latest edition of Psychological Medicine where some Australian psychiatrists who specialise in disorders of old age got called out to a zoo to assess an elderly gorilla who was behaving strangely.
Unfortunately, the case report is full of medical jargon although it becomes quite charming when you realise that the psychiatrists just went about assessing the gorilla, running their standard tests as best they could, as if it was just another patient.
The bit where the doctors test the gorilla’s eye-tracking by waving a date around in front of it is pure joy.
In July 2006, in response to a call from the Melbourne Zoo, a home visit was made to examine a 49-year-old female Western Lowland Gorilla (Gorilla gorilla gorilla), who had recently developed a confusional state with the following observed behaviors:
being apparently lost in her enclosure, which she had occupied for 15 years; unable to find her food; defecating in her nest; unable to locate the entry to her night den after being outside in the enclosure; loss of her dominant role as the senior matriarch and being bullied by younger females; apparently unable to see things in certain areas of her enclosure; being less responsive to her favorite keeper, who had cared for her since 1980.
The staff of the Zoo raised the question: is she developing a dementing illness? A domiciliary consultation by a psychogeriatrician from the University of Melbourne was therefore requested to assess this.
The female gorilla had a history of low-grade cardiac disease associated with hypertension, and a serious renal infection had resulted in surgical removal of one kidney in 2003.
She was enticed to the edge of her enclosure to accept her favorite snack of dates, walking with a slow but steady gait. Using offered dates as targets for an ocular [eye] movement examination, the presence of nystagmus was identified, together with bilateral upward gaze palsy. In a team discussion with her keepers and the veterinarian, an observation schedule was developed for use over the next three weeks to track her behavior. At follow-up review, one month later, the observation schedule revealed fluctuating but slow improvement in all domains. On further examination, her ocular signs had settled.
A diagnosis of post-TIA delirium was made. Her behavior and general function steadily improved over the next two months. Cerebral infarction [damage due to blood supply blockage] has previously been reported in a 29-year old chimpanzee, Pan troglodytes (Fish et al., 2004).
Her physical decline occurred during 2007, and she was euthanized in November 2007 at the age of 50 years.
There were multifocal to coalescing often aggregated, multiple small soft, white plaques within the meninges over the middle and posterior dorsal midline surface of the cerebrum (consistent with prominent arachnoid granulations).
Autopsy revealed cerebral hemorrhages at globus pallidus and internal capsule, thus confirming the clinical diagnosis. Examination of the heart confirmed chronic myocardial fibrosis, and a pancreatic islet cell carcinoma [cancer] had metastasized [spread] to lung and liver. We suggest that the observation schedule so developed may be of use in future to observe other primates in captivity which develop confusional states.
I was also delighted to read that the scientific name for a Western Lowland Gorilla is ‘gorilla gorilla gorilla’.
Link to PubMed entry for case report.