Human immunodeficiency virus (HIV) infection has expanded to become a global pandemic which threatens health in most areas of the world, and is now the leading cause of death among some segments of the population. Infection with HIV-1, a member of the lentivirus subfamily of retroviruses, produces a wide spectrum of clinical manifestations, ranging from asymptomatic infection to severe, life-threatening opportunistic infections. The prevalence of HIV dementia is only 0.4% during the asymptomatic phase of infection. In patients with AIDS, dementia develops in 15-20%. The diagnosis of HIV dementia is established by a history of a progressive cognitive or behavioral decline with apathy, memory loss, or slowed mental processing and by appropriate ancillary studies. HIV-1 associated vacuolar myelopathy (HIV myelopathy) is characterized by a vacuolar degeneration affecting predominantly the thoracic spinal cord. Patients may have multiple concurrent opportunistic processes, or opportunistic processes may coexist with HIV-related neurological disorders.

This chapter provides an overview of survival analysis as it relates to the major disorders within neurology. Death is the predominant outcome measure in the discussion. Two commonly used methods are described in the chapter, to handle censoring and variable starting times include life table analysis and the Kaplan-Meier approach. There have been a number of studies to elucidate the survival characteristics of individuals with multiple sclerosis (MS). Other neurological diseases discussed in the chapter include stroke, HIV-related neurologic disease, dementia, primary CNS neoplasms, and status epilepticus. Cerebrovascular disease (CVD) or stroke is the third leading cause of death and a significant cause of long-term disability in most industrialized nations. Human immunodeficiency virus (HIV)-dementia is largely a subcortical disorder involving deficits in cognition, behavior, and the motor system. Within the past two decades, Alzheimer's disease (AD) has been confirmed to be responsible for the majority of primary degenerative dementias.