Frontal Lobe Disorders

Many neurological and psychiatric disorders involve the frontal lobes either directly or through frontal-subcortical connections. In this chapter, we review the specific structural and functional frontal and/or frontal-subcortical abnormalities observed in these disorders and their associations to clinical and cognitive symptoms. First, we briefly describe the neuroanatomy of frontal lobes and frontal-subcortical circuits and the behavioral symptoms associated with focal lesions within these circuits. We then examine neurological disorders of the frontal lobe, including vascular disorders, traumatic brain injury and neurodegenerative disorders. Within this last category, we describe disorders in which the frontal lobe is either the primary site of the disease (e.g., frontotemporal dementia) or is impaired to a lesser extent than other brain regions (e.g., Alzheimer's disease). We also address motor disorders, which predominantly affect fronto-subcortical circuits (e.g., Parkinson's disease). Subsequently, we outline some representative psychiatric disorders consistently associated with frontal lobe abnormalities, such as schizophrenia, mood disorders and obsessive-compulsive disorder. Finally, we provide a number of conclusions regarding the involvement of frontal lobes across the reviewed disorders.