Beyond Alzheimer's

For two years, they treated him for Alzheimer’s disease.

The diagnosis had seemed straightforward. He was seventy-one, retired, forgetting things. His doctor prescribed donepezil, the standard first-line medication. But something was wrong. He was not just forgetful; he was seeing people who were not there. His cognition fluctuated wildly, sharp one hour and unreachable the next. He began to shuffle when he walked. When they gave him a low-dose antipsychotic for the hallucinations, he became rigid, nearly catatonic.

A second opinion changed the diagnosis. Lewy body dementia, not Alzheimer’s. The antipsychotic that was supposed to help had triggered a severe reaction that occurs specifically in Lewy body patients. The two years of wrong treatment could not be undone, but the right diagnosis changed everything going forward: what medications to avoid, what symptoms to expect, how to plan.

This family’s story is not unusual. Alzheimer’s disease accounts for 60 to 80 percent of dementia cases, but the remaining conditions are not footnotes. They have distinct characters, distinct progressions, and distinct treatment considerations. Getting the diagnosis wrong has consequences. Sometimes severe ones.

Dementia Is Not a Single Disease

The word “dementia” describes a set of symptoms, not a specific condition. It means cognitive decline severe enough to interfere with daily life. The underlying cause can vary enormously.

This creates a diagnostic challenge. Symptoms overlap. Pathologies co-occur. Definitive diagnosis during life remains difficult for many conditions; some can only be confirmed through autopsy. Clinicians work with probability, pattern recognition, and educated judgment. They are not always right.

Why does accuracy matter? Because different dementias respond differently to medications. Some drugs that help one condition worsen another. Progression rates differ. Behavioral and safety concerns differ. Prognosis differs. The practical questions a family faces, from how much time they might have to what symptoms to prepare for, depend on which disease they are actually dealing with.

A diagnosis of “dementia” without specificity is not a complete answer. It is the beginning of a question.

Vascular Dementia

Vascular dementia is the second most common form, caused by impaired blood flow to the brain. Sometimes this happens through strokes, large or small. Sometimes it happens through chronic small vessel disease that quietly damages brain tissue over years.

The pattern often differs from Alzheimer’s. Where Alzheimer’s typically begins with memory problems and progresses gradually, vascular dementia frequently affects executive function early: planning, organizing, making decisions, shifting between tasks. The decline may be stepwise rather than smooth, with sudden drops following vascular events and plateaus in between.

The risk factors overlap substantially with cardiovascular disease: hypertension, diabetes, high cholesterol, smoking, obesity, physical inactivity. This overlap is the source of both the problem and the opportunity. Vascular dementia is among the most preventable forms of cognitive decline because the vascular risk factors that drive it are modifiable. What protects your heart often protects your brain.

The connection between diabetes and dementia runs through this territory. Chronic high blood sugar damages blood vessels throughout the body, including the small vessels that feed the brain. Managing diabetes is not just about blood sugar; it is about protecting cognitive function decades later. Series 3 of this publication will explore the body-brain connection in depth.

Lewy Body Dementia

Lewy body dementia is the third most common form and among the most misdiagnosed. It is caused by abnormal deposits of a protein called alpha-synuclein in brain cells. The same protein is involved in Parkinson’s disease, and the two conditions are closely related.

The hallmark features include visual hallucinations, often vivid and detailed; fluctuating cognition that can shift dramatically within hours or days; REM sleep behavior disorder, in which people physically act out their dreams; and motor symptoms resembling Parkinson’s, including rigidity, slow movement, and shuffling gait.

The diagnostic minefield is real. Early symptoms may look like Alzheimer’s, leading to that diagnosis. Motor symptoms may lead to a Parkinson’s diagnosis. The fluctuating cognition can be mistaken for delirium or psychiatric illness. Each misdiagnosis carries risk, but one carries particular danger: antipsychotic medications.

People with Lewy body dementia have a severe sensitivity to many antipsychotic drugs. Medications commonly prescribed to manage hallucinations or agitation in other conditions can cause profound worsening in Lewy body patients: extreme rigidity, sedation, and in some cases death. This is not a rare side effect. It is a known and significant risk. Yet antipsychotics are often prescribed before the correct diagnosis is made, because the hallucinations are alarming and the Lewy body diagnosis has not yet been considered.

The distinction between Parkinson’s disease dementia and dementia with Lewy bodies is somewhat technical. Both involve Lewy body pathology. The traditional dividing line is timing: if motor symptoms precede cognitive symptoms by more than a year, it is classified as Parkinson’s disease dementia; if cognitive symptoms come first or appear within a year of motor symptoms, it is dementia with Lewy bodies. The practical implications for care are similar, but the distinction affects research enrollment and sometimes treatment approaches.

Robin Williams, whose death in 2014 brought sudden visibility to Lewy body dementia, had been diagnosed with Parkinson’s disease. The Lewy body pathology was discovered only on autopsy. His widow later described the confusion, the misdiagnosis, and the lack of public awareness. His case changed visibility. It did not change clinical practice quickly enough for most families navigating the same uncertainty.

Frontotemporal Dementia

Frontotemporal dementia, or FTD, is different from the start. It is not primarily a memory disease, at least not initially. It attacks the frontal and temporal lobes of the brain, regions that govern personality, behavior, language, and emotional regulation.

The behavioral variant presents as personality change. A person may become disinhibited, saying inappropriate things, acting impulsively, losing social awareness. Or they may become apathetic, losing interest in activities and relationships that previously mattered. Families often describe the person as “not themselves” long before any cognitive testing shows abnormalities.

The language variants, collectively called primary progressive aphasia, involve progressive loss of speech and language abilities. A person may struggle to find words, to form sentences, to understand language. The decline is gradual and relentless.

FTD typically strikes younger than Alzheimer’s, often between ages forty-five and sixty-five. This means working-age adults, people with children still at home, people at the peak of careers and responsibilities. The disease is often unfamiliar to the families it strikes and to the primary care physicians who see it first. Misdiagnosis as a psychiatric condition is common, particularly in the behavioral variant.

The genetic component is stronger in FTD than in late-onset Alzheimer’s. Mutations in genes including C9orf72, MAPT, and GRN account for a significant minority of cases. Genetic testing and counseling are relevant for families with FTD history in ways that are less often the case for Alzheimer’s.

Bruce Willis’s diagnosis, announced in 2023, brought FTD into public awareness. But awareness has not translated into treatment. There are no approved disease-modifying therapies for frontotemporal dementia. Management focuses on symptoms, on safety, on supporting families through a disease that takes personality before it takes memory.

Mixed Dementia and the Complexity of Real Brains

The categories above are useful. They are also incomplete. Autopsy studies consistently show that in older adults, mixed pathologies are the norm rather than the exception.

A brain may contain amyloid plaques characteristic of Alzheimer’s alongside vascular damage from small strokes, Lewy bodies from alpha-synuclein deposits, and TDP-43 aggregations from a condition only recently recognized. The clinical presentation during life reflects the sum of these pathologies, not any single one.

LATE, or Limbic-predominant Age-related TDP-43 Encephalopathy, is one of the newer entries in this landscape. Identified as a distinct entity only in 2019, it mimics Alzheimer’s in its clinical presentation: memory loss, gradual decline, similar progression. But it involves different pathology, TDP-43 protein deposits rather than amyloid and tau. It appears most commonly in the oldest old, those over eighty. It may explain why some people with clinical Alzheimer’s show little amyloid on PET scans: they may have LATE instead, or LATE alongside Alzheimer’s pathology.

Mixed pathology complicates treatment. The new amyloid-targeting drugs work by clearing amyloid plaques. In a person whose cognitive decline is driven by vascular damage, or Lewy bodies, or TDP-43, clearing amyloid may help one component while leaving others untouched. This is not a reason to avoid treatment; it is a reason to have realistic expectations about what any single treatment can accomplish.

The honest complexity is this: the aging brain rarely fails in just one way. The neat categories that research requires and that diagnoses provide are simplifications of biological reality. They are useful simplifications, but they are simplifications nonetheless.

What This Means for Families

If you or someone you love has received a dementia diagnosis, the first question to ask is: what type?

A diagnosis of “dementia” without specificity is not enough. The type determines medication choices, including which medications to avoid. It shapes expectations about progression. It affects eligibility for clinical trials and for the new Alzheimer’s treatments. It guides care planning.

Ask what evidence supports the diagnosis. Was it based on clinical evaluation alone, or were biomarkers involved? For Alzheimer’s, amyloid PET scans or the newer blood biomarker tests can confirm the presence of Alzheimer’s pathology. For Lewy body dementia, a DaTscan can show dopamine transporter loss. For vascular dementia, MRI can reveal the signature of strokes or small vessel disease. Not every diagnosis requires every test, but understanding what the diagnosis rests on helps you know how certain it is.

Ask whether a second opinion would add value. In complex cases, in younger patients, in presentations that do not fit neatly into one category, a specialist at an academic medical center or a memory disorders clinic may see patterns that a general neurologist might miss.

Know the medication sensitivities. If the diagnosis is Lewy body dementia, make certain that every provider involved in care knows to avoid certain antipsychotics. Write it on the chart. Say it out loud. The risk is real.

The next installment in this series covers the new Alzheimer’s treatments in detail: what they do, who qualifies, and what they honestly offer. Those treatments are designed specifically for Alzheimer’s pathology. Understanding whether that pathology is present, and whether it is the primary driver of symptoms, matters for knowing whether those treatments make sense.

The landscape of dementia is more varied than the public conversation suggests. Alzheimer’s dominates the headlines, and for good reason: it is the most common cause and the focus of the most intensive research. But the other dementias are not rare. They are not footnotes. For the families navigating them, they are the whole story.

Getting the diagnosis right is the first step toward getting the care right. It is worth the effort to ask the questions.