Psychosis secondary to infections

Introduction This section focuses on selected infectious diseases that have been directly associated with neuropsychiatric syndromes, specifically those resulting in secondary psychosis. Secondary psychosis is a severe abnormality of thought content or form due to an identifiable medical or neurological condition that can have many manifestations (Cummings, 1985; 1988). Although there is no single area where brain injury will reproducibly induce psychosis, temporo-parietal regions, caudate nuclei, and cholinergic and dopaminergic tracts appear to be important substrates in many cases of psychosis (Gaudreau & Gagnon, 2005; Iyo, Sekine, & Mori, 2004; Seeman et al., 2005; Shaw et al., 2004). Definition and diagnostic criteria Using the nomenclature of the Diagnostic and Statistical Manual of Mental Disorders (DSM IV; American Psychiatric Association, 1994), secondary psychosis may be classified as Delirium Due to a General Medical Condition, Psychotic Disorder Due to a General Medical Condition, or Mood Disorder Due to a General Medical Condition, with Psychotic Features. Psychosis in delirium occurs only during the episode of delirium. Delirium is an acute syndrome secondary to a medical condition with disturbance in consciousness, attention, and cognition, and which may fluctuate over hours (American Psychiatric Association, 1994). The latter two diagnoses refer to psychosis due to a general medical or neurological condition in which either the psychosis or the mood symptoms predominate. In this chapter we shall focus on psychosis secondary to infectious causes.