The cause of Alzheimer’s disease is unknown. Nevertheless, several factors are thought to be closely connected to this disease. These include neurochemical factors, such as deficiencies of the neurotransmitters acetylcholine, somatostatin, substance P, and norepinephrine; environmental factors, such as intake of aluminum and manganese; and viral factors such as slow-growing central nervous system viruses.

Researchers believe that up to 70% of Alzheimer’s disease cases stem from a genetic abnormality. Recently, they located the abnormality on chromosome 21. They also isolated a genetic substance (amyloid) that causes brain damage typical of Alzheimer’s disease. The brain tissue of patients with this dementia has three distinguishing features: neurofibrillary tangles, neuritic plaques, and granulovacuolar degeneration.

Newer studies indicate a relationship between alleles of apolipoprotein E (apo E) gene on chromosome 19 and either a risk of the late development of Alzheimer’s disease (apo E₄) or a protection against the development of the disease (apo E₂ or apo E₃). Studies show a 30% to 40% occurrence of Alzheimer’s disease in those with homozygous apo E genotype and a 15% to 20% occurrence in older individuals with either the apo E₂or apo E₃ genotypes.

Complications of Alzheimer’s disease include injury from the patient’s own violent behavior or from wandering or unsupervised
activity; pneumonia and other infections, especially if the patient doesn’t receive enough exercise; malnutrition and dehydration, especially if the patient refuses or forgets to eat; and aspiration.

As you assess the patient, keep in mind that the onset of this disorder is insidious; initial changes are almost imperceptible but gradually progress to serious problems. The patient history is almost always obtained from a family member or caregiver.

Typically, the patient history shows initial onset of very small changes, such as forgetfulness and subtle memory loss without loss of social skills and behavior patterns. It also reveals that over time, the patient has begun to experience recent-memory loss and has had difficulty learning and remembering new information. The history also may reveal a general deterioration in personal hygiene and appearance and an inability to concentrate.

Depending on the severity of the disease, the patient history may reveal that the patient experiences several of the following problems: difficulty with abstract thinking and activities that require judgment; progressive difficulty in communicating; a severe deterioration of memory, language, and motor function that in the more severe cases finally results in coordination loss and an inability to speak or write; repetitive actions; restlessness; negative personality changes, such as irritability, depression, paranoia, hostility, and combativeness; nocturnal awakenings; and disorientation.

The person giving the history may explain that the patient is suspicious and fearful of imaginary people and situations, misperceives his environment, misidentifies objects and people, and complains of stolen or misplaced objects.

He also may report that the patient seems overdependent on caregivers and has difficulty using correct words and may often substitute meaningless words. He may report that conversations with the patient drift off into nonsensical phrases. The patient’s emotions may be described as labile. Also, the patient may laugh or cry inappropriately and have mood swings, sudden angry outbursts, and sleep disturbances.

Neurologic examination confirms many of the problems revealed during the history. In addition, it reveals an impaired sense of smell (usually an early symptom), impaired stereognosis (inability to recognize and understand the form and nature of objects by touching them), gait disorders, tremors, and loss of recent memory. The patient with Alzheimer’s disease also has a positive snout reflex. To check for this reflex, stroke or tap his lips or the area just under his nose. If he has a positive reflex, you’ll observe him grimacing or puckering his lips.

If the patient is in the final stages, he typically has urinary or fecal incontinence and may twitch and have seizures.

Alzheimer’s disease is diagnosed by exclusion. Various tests, such as those described below, are performed to rule out other disorders. However, the diagnosis can’t be confirmed until death, when pathologic findings are seen at autopsy.