Understanding Alzheimer’s pathology through diagnostic imaging
Dr. Wint begins his session with an overview of the pathology of AD, noting that the condition is typically marked by inflammation and cellular death. Specific markers include intercellular amyloid plaques and neurofibrillary tangles of hyperphosphorylated tau protein. Synaptic and neuronal dysfunction leads to mild and nonspecific symptoms of Alzheimer’s Disease; over time, patients progress to Alzheimer’s dementia.
Because this pathology can happen years before the effects are evident, diagnostic imaging can help detect changes in earlier stages. Such tools may include magnetic resonance imaging (MRI), which can show disproportionate atrophy in the mesial temporal and parietal lobes. Fluorodeoxyglucose-positron emission tomography (PET) can also show bilateral parietal hypometabolism, often extending into the temporal lobes.
Two other diagnostic measures can help detect pathologic changes of AD, but may not be covered by Medicare or other insurers, Dr. Wint says:
- Spinal fluid analysis can show decreased β-amyloid and increased phosphorylated tau protein with a high degree of sensitivity and specificity using amyloid-to-tau ratios.
- Amyloid-detecting PET can detect the type of amyloid present in AD.
Spotting Alzheimer’s symptoms
Signs of AD include cognitive, psychiatric and behavioral symptoms. While all three categories can affect a patient’s quality of life, Dr. Wint emphasizes that the latter two can disproportionally drive healthcare costs, institutionalization, and caregiver stress. Behavioral and psychiatric concerns may also present before cognitive problems.
“Although cognitive symptoms define the disease, behavioral symptoms really generate much of the misery of the condition,” Dr. Wint says.
- Behavioral symptoms include irritability, apathy, and depression. These symptoms may happen in conjunction or independently — such as when a patient experiences irritability, but not depression. Conversely, patients sometimes express elation, agitation, and anxiety.
- Psychiatric symptoms include delusions and hallucinations and may be associated with faster cognitive decline and impairment of activities of daily living (ADL).
- Cognitive symptoms include forgetfulness that happens quickly and completely, such as when patients say information was never given to them. AD patients may also have trouble tracking time, become lost in familiar places or misplace things.
Unfortunately, the pathologic changes of AD mean that providers can’t always trust patients to reliably self-report. Alternative assessments such as the SIGECAPS (sleep disorder, interest deficit, guilt, energy and concentration deficit, appetite disorder, psychomotor retardation or agitation, and suicidality) score can help.
Additionally, clinicians should be careful not to misdiagnose other problems as AD. For example, issues with gait, balance, or posture in someone with memory and cognitive issues may not be associated with AD.
Managing Alzheimer’s dementia
As Dr. Wint explains, treatments for AD can include both nonpharmacologic and pharmacologic options:
- Nonpharmacologic: Identifying and minimizing causal factors, such as medications, sleep deprivation, and environmental issues; increasing ambient lighting and inputs; and providing patients ongoing information about the people around them and other details to minimize ambiguities.
- Pharmacologic: Medications for dementia include olanzapine (5 mg) and risperidone (2 mg). Patients with certain behavioral symptoms may benefit from quetiapine (agitation) or aripiprazole (agitation and psychosis). However, given the risks of antipsychotic agents among older patients — including stroke or sudden death — durations of these medications should be minimized.
