The Secondary Schizophrenias

Despite overwhelming evidence of its biological basis, primary schizophrenia remains a behavioral disorder that is a diagnosis of exclusion. Clinicians cannot rely upon routine laboratory tests, neuroimaging studies, electrophysiological paradigms or neuropsychological testing batteries to confirm the diagnosis of this disorder to the exclusion of phenocopies. Moreover, there are a number of disparate brain disorders that can, uncommonly, give rise to schizophrenia-like symptomatology. This chapter first outlines the nosological challenges and how recent classification systems have dealt with these, distinguishing secondary schizophrenia-like psychoses arising from defined neuropathological processes and those secondary to cerebral complications of systemic illness. Second, it attempts to estimate the prevalence of such secondary schizophrenias in relation to schizophrenia in general. Third, it examines the evidence for symptomatic differences between secondary and primary schizophrenia, and discusses their clinical diagnosis. Finally, the chapter reviews broadly which specific brain diseases seem to present a particularly increased risk of schizophrenic symptoms. In the past, mental disorders have been subdivided into "organic" and "functional" categories. These subdivisions are now less useful, as primary schizophrenia is as "organic" as any of the secondary schizophrenias. This chapter reviews the association of a variety of neurological and general medical conditions that are associated with schizophrenia-like signs and symptoms. These include epilepsy, cerebral trauma, space-occupying lesions of the central nervous system, cerebrovascular disease, movement disorders, demyelinating diseases, metabolic and autoimmune disorders, infections of the central nervous system, drug-related psychoses, and cytogenic/chromosomal disorders. Throughout, additional insights are offered relating the pathological bases of the secondary schizophrenias to primary schizophrenia.