A previous review of the neuroimaging studies in obstructive sleep apnea (OSA) called for specific attention to longitudinal studies of the treatment effects of OSA on neuroimaging. This chapter focuses on those studies where treatment effects were considered. The structural studies suggest that there are some notable changes in the structure of the human brain when continuous positive airway pressure (CPAP) is used to correct OSA. Some of these changes are even associated with cognitive changes in the expected cognitive domains and are seen with as little as only three months of treatment. The functional imaging studies together suggest that changes in brain function associated with working memory are evident when comparing treatment with no-treatment conditions in patients with OSA. Specifically, treatment often results in the recruitment of fewer cognitive resources to perform at the same level or better.

This chapter discusses cortical dementias that include Alzheimer's disease, fronto-temporal dementia and dementia with Lewy bodies, subcortical dementias that include Parkinson's disease and Huntington's disease, and mixed dementias that include vascular dementia. Deficits characteristic of both cortical and subcortical dementias, depending on the location and extent of cerebrovascular lesions, may occur. Numerous neuropsychiatric sequelae are associated with traumatic brain injury (TBI), making it difficult to identify a well-defined syndrome. Thorough psychiatric and medical histories are critical in diagnosing patients who present with agitation and cognitive changes. Laboratory and neuroimaging studies are of variable utility in evaluating for reversible causes of altered mental status. A number of medications have been studied for their effects on dementia-related agitation. The most common categories include antipsychotics, antiepileptic medications, antidepressants, and cognitive enhancers. Controlled studies on pharmacologic treatment for agitation in Huntington's disease are rare.