## INTRODUCTION

Neurologic illness accounts for significant, morbidity, mortality, and cost. This chapter provides an overview of three significant diseases commonly encountered by physiatrists: Alzheimer's disease, Parkinson's, and multiple sclerosis, with an emphasis on diagnosis, management, and rehabilitation.

## ALZHEIMER'S DISEASE

### Definition

Alzheimer's disease (AD) is a gradually progressive, neurodegenerative dementia affecting cognition, behavior, and functional status. It is the leading cause of dementia in late adult life and accounts for seventy five percent of the cases of dementia in the United States.

### Statistics and Costs

Alzheimer's disease is the sixth leading cause of death in the United States and the only cause of death in the top ten that cannot be prevented, cured, or slowed.

In 2015, Alzheimer's and other dementias cost the United States $225 billion in total medical costs; these costs are estimated to continue to increase each year. Today more than 5 million Americans are living with Alzheimer's disease and require more than 15 million caregivers.1 A report from the Alzheimer's Association, projects that Medicare spending on Alzheimer's disease will more than quadruple to$589 billion annually by 2050. This analysis showed that a treatment delaying the onset of Alzheimer's by just 5 years would save Medicare $345 billion in the first 10 years alone. A historic$350 million increase in research funding in the FY2016 budget was announced into law in December 2015.

### Epidemiology

An estimated 5.3 million Americans had Alzheimer's disease in 2015.1 Of these, two-thirds are women, and 5.1 million are above 65 years old. Additionally, the disease takes a devastating toll on its caregivers.

Approximately two-thirds of the caregivers are women and 34% are age 65 or older.

The incidence of Alzheimer's dementia dramatically increases after the age of 65 (53 new cases per 1,000 people aged 65 to 74; 170 per 1,000 people aged 75 to 84; and 231 per 1,000 people older than 85).2

### Pathology

Although the exact etiology of AD is unknown, several genetic and environmental factors have been explored as potential causes. The disorder is characterized by intracellular neurofibrillary tangles and extracellular amyloidal protein deposits contributing to plaque formation3 (Figs. 13–1 and 13–2).

###### Figure 13–1

Pathophysiology of Alzheimer's disease: Some processes involved in Alzheimer's disease. From the left: mitochondrial dysfunction, possibly involving glucose utilization; synthesis of protein tau and aggregation in filamentous tangles; synthesis of amyloid beta (Aβ) and secretion into the extracellular space, where it may interfere with synaptic signaling and accumulates in plaques. (From Roberson ED, Mucke L: 100 years and counting: prospects for defeating Alzheimer's disease. Science 2006;314:781. Reprinted with permission from AAAS.)

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