Cognitive disorders and late visual hallucinations in a 70-year-old man

M. C., a right-handed retired engineer, consulted his doctor for the first time about memory problems at the age of 65. The problems seemed to have developed gradually. A neurological examination did not reveal any abnormality at the time. Based on an assessment of cognitive function, an MRI brain scan and a Monophoton Emission Computed Tomography (MECT), a diagnosis of Alzheimer's disease (AD) with slight cerebro-vascular component was made. At the time, the Mini Mental State Examination (MMSE) score was 27/30. The illness seemed to be fairly stable from the MMSE score aspect, as four years later the latter was 26/30. At this point, however, "filament" or "spider's web" type visual hallucinations began to occur. Neurological examination results were unchanged and, as the patient did not appear distressed by these hallucinatory experiences, no treatment was prescribed. A year later, following rapid deterioration of the situation, involving "confusion", the patient required hospitalisation and the diagnosis was reconsidered. This decompensation was accompanied by more worrying visual hallucinations, including the onset of nyctohemeral rhythm inversion and significant fluctuation. The neurological examination was still unchanged and there were no focal signs or extrapyramidal symptoms. After improvement of sleep disturbance problems, there was still some cognitive fluctuation and variability of vigilance and attention, but these had reduced in intensity. The visual hallucinations described earlier were still present but once again did not trouble the patient. A neuropsychological assessment was then possible, revealing: significant dysexecutive syndrome, demonstrated by the BREF test (batterie rapide d'efficience frontale - Rapid screening battery to evaluate frontal dysfunction) pathological score of 8/18. The dysexecutive syndrome consisted mainly in difficulties with programming and activity organisation (failure with graphic and gestural series) and attention and control disorders (inhibition deficit). Moreover, there were numerous examples of perseveration throughout the examination - graphic, motor, verbal or task-based. There was also: 1) major disturbance of visuo-spatial organisation, involving difficulty in copying simple figures. The Clock Test could not be performed spontaneously and was no better when copied. The Trail Making Test (TMT) was also failed, owing to visuo-spatial and attention deficits; 2) qualitatively, there was fluctuation in test performance and blockages appeared; 3) with respect to memory, the profile established was of the information retrieval type, which corresponded with the observed dysexecutive syndrome. Thus, free recall was very poor (3 FR = 2,5; 2 out of 16 or 9/48, -2.9 standard deviations) but semantic indexing was very good, resulting in the normalisation of overall performance for total recall (TR) [3TR = 46/48]; 4) Gestural praxic ability (ideokinetic, ideatory) was unaffected as was confrontation naming. At the same time, another MRI scan of the brain had been carried out. The brain scintigraphy carried out six years previously was re-examined. A Datscan (R) brain scintigraphy was also carried out, in order to confirm the new diagnostic hypothesis.