Arsenic exposure, particularly the chronic type, can lead to poisoning with manifestations presenting in multiple organ systems. However, acute psychosis is not a commonly described manifestation of arsenic exposure. In this report, we present the case of a patient who developed acute psychosis with hallucinations, disorganized thinking, and obsessive-compulsive symptoms following chronic occupational arsenic exposure. The patient was treated with the combination of an antipsychotic and an antidepressant and he responded well with significant improvement in both the acute psychosis and obsessive-compulsive symptoms. The authors concluded that patients can develop atypical symptoms, including acute psychosis, following arsenic poisoning. In the case described in this report, the patient also presented with a new onset of obsessive-compulsive symptoms. Given this rare manifestation of arsenic poisoning for which there is no clearly defined treatment regimen, this case suggests that the use of a combination of an antipsychotic and an antidepressant may be considered in the rare event of psychosis with obsessive-compulsive features following arsenic poisoning.

“CADASIL” is a genetic microangiopathy with autosomal dominant inheritance. Its epidemiology and physiopathogenesis are poorly specified, but it is proven that this disease is due to a mutation of the NOTCH3 gene resulting in a loss of elasticity of the media of the affected vessels. The clinical expression is variable, dominated by migraine attacks with aura, ischemic vascular accidents and psychiatric disorders, in particular depression. MRI is essential for diagnosis even in the pre-symptomatic phase. It shows signal abnormalities in the basal ganglia and white matter, characteristic especially when located in the anterior part of the temporal lobes. The management of CADASIL is multidisciplinary, psychological for the most part without specificity of a particular treatment.

Dementia with Lewy bodies (DLB), the second most common cause of dementia, remains a difficult condition to accurately diagnose and manage. Variable involvement of motor and cognitive functions, plus psychiatric and behavioral symptoms, contributes to the difficulty in managing DLB. Additionally, DLB can cause severe sleep disruption through REM sleep behavior disorder, autonomic symptoms, disruptions of olfaction/taste and mood, hallucinations, and more. In this chapter, advances and remaining challenges in the diagnosis of DLB are discussed, including a review of the current consensus criteria for DLB. The spectrum of disorders with Lewy bodies (LBs) are described including their wide-range of clinical presentations and overlap with Alzheimer’s disease (AD) and Parkinson’s disease with and without dementia. Particular consideration is given to advancements in quantification of cognitive fluctuations through improved clinical instruments, EEG, and other advanced biomarkers. Detection of DLB has improved, but establishing the “primary” pathology in cases with concomitant LB andd AD remains difficult. Likelihood of a clinical DLB syndrome is thought to be a function of distribution of LBs and severity of AD-type pathology. Further work is needed to better understand LB disease subtypes and the underlying pathophysiological mechanisms to allow for more targeted and comprehensive therapies.