Which of the following is the most common cause of dementia among elderly persons?
A. Parkinson’s disease
B. Multiple sclerosis
C. Amyotrophic lateral sclerosis (Lou Gehrig’s disease)
D. Alzheimer’s disease
Correct Answer: D. Alzheimer’s disease
Alzheimer’s disease, sometimes known as senile dementia of the Alzheimer’s type or primary degenerative dementia, is an insidious; progressive, irreversible, and degenerative disease of the brain whose etiology is still unknown. Alzheimer’s is the most common cause of dementia among older adults. Dementia is the loss of cognitive functioning—thinking, remembering, and reasoning—and behavioral abilities to such an extent that it interferes with a person’s daily life and activities.
Option A: Parkinson’s disease is a neurologic disorder caused by lesions in the extrapyramidal system and manifested by tremors, muscle rigidity, hypokinesia, dysphagia, and dysphonia. Parkinson’s disease is a neurodegenerative disorder that mostly presents in later life with generalized slowing of movements (bradykinesia) and at least one other symptom of resting tremor or rigidity. Other associated features are a loss of smell, sleep dysfunction, mood disorders, excess salivation, constipation, and excessive periodic limb movements in sleep (REM behavior disorder).
Option B: Multiple sclerosis, a progressive, degenerative disease involving demyelination of the nerve fibers, usually begins in young adulthood and is marked by periods of remission and exacerbation. Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system (CNS) characterized by inflammation, demyelination, gliosis, and neuronal loss. Pathologically, perivascular lymphocytic infiltrates, and macrophages produce degradation of myelin sheaths that surround neurons.
Option C: Amyotrophic lateral sclerosis, a disease marked by progressive degeneration of the neurons, eventually results in atrophy of all the muscles; including those necessary for respiration. Amyotrophic lateral sclerosis (ALS), also known as “Lou Gehrig’s disease,” is a neurodegenerative disease of the motor neurons. No single etiology has been proven; rather, multiple pathways (both heritable and sporadic) have been shown to result in unmistakably similar disease entities. ALS necessarily affects both upper and lower motor neurons with variable patterns of onset, most commonly beginning with signs of lower motor neuron degeneration within proximal limbs.