No. Frontotemporal dementia and Lewy body dementia are two distinct brain diseases that happen to share some symptoms. After Alzheimer’s, they are two of the most common causes of dementia that comes from a brain disease that steadily worsens.1PubMed. Novel fluid biomarkers to differentiate frontotemporal dementia and dementia with Lewy bodies from Alzheimer’s disease: A systematic review Because they overlap with each other and with Alzheimer’s, people with either one often wait longer for a diagnosis and are often told the wrong one first.2PubMed. A Systematic Review on the Evidence of Misdiagnosis in Dementia and Its Impact on Accessing Dementia Care3PubMed. Novel fluid biomarkers to differentiate frontotemporal dementia and dementia with Lewy bodies from Alzheimer’s disease: A systematic review Getting it right matters, because the diagnosis shapes which medicines are safe.
What Goes Wrong in the Brain in Each Disease
In frontotemporal dementia (FTD), nerve cells die mainly in the frontal and temporal lobes, the areas behind the forehead and above the ears.4Medisearch. The Key Difference Between FTD and LBD The cause is that abnormal forms of proteins called tau, TDP-43 or, less often, FUS build up there.5American Brain Foundation. Understanding the Connections Between FTD, ALS, and Alzheimer’s Disease6Medisearch. The Key Difference Between FTD and LBD In Lewy body dementia (LBD), which includes dementia with Lewy bodies (DLB), the culprit is a different protein, alpha-synuclein, which forms clumps called Lewy bodies in many brain regions.7American Brain Foundation. Understanding the Connections Between FTD, ALS, and Alzheimer’s Disease8Medisearch. The Key Difference Between FTD and LBD
The frontal lobes handle judgment, self-control, planning and social behavior, and the temporal lobes handle language and the meaning of words. So when FTD damages them, the person’s character and speech change, often before memory is affected.
Brain scans in FTD typically show shrinkage and reduced activity concentrated in the frontal and temporal lobes.9PubMed. Diagnostic imaging of dementia with Lewy bodies, frontotemporal lobar degeneration, and normal pressure hydrocephalus10PubMed. Molecular and Anatomical Imaging of Dementia With Lewy Bodies and Frontotemporal Lobar Degeneration Lewy body dementia tends to reduce blood flow across much of the brain, with the temporal lobes often relatively spared.11PubMed. Distinct perfusion patterns in Alzheimer’s disease, frontotemporal dementia and dementia with Lewy bodies
“Lewy body dementia” is an umbrella term. It covers dementia with Lewy bodies, where thinking problems come first, and Parkinson’s disease dementia, where movement problems appear years before the thinking changes. The protein type can be confirmed for certain only after death, so in life doctors diagnose from symptoms and tests.
Symptoms That Set Them Apart
FTD typically begins with personality and behavior changes.12PubMed. Frontotemporal dementia mimicking dementia with Lewy bodies Loss of inhibition, inappropriate cheerfulness and changes in appetite and eating are more common in FTD than in other dementias.13PubMed. Neuropsychological correlates of behavioral symptoms in Alzheimer’s disease, frontal variant of frontotemporal, subcortical vascular, and lewy body dementias: a comparative study14PubMed Central. Behavioral and Psychological Symptoms of Dementia in Different Dementia Disorders: A Large-Scale Study of 10,000 Individuals Hallucinations, delusions and depression are less common than in other dementias.15PubMed Central. Behavioral and Psychological Symptoms of Dementia in Different Dementia Disorders: A Large-Scale Study of 10,000 Individuals Some forms of FTD mainly attack language, making it hard to find or understand words.16Discover Medicine. Dementia with lewy bodies featuring prominent nonfluent/agrammatic aphasia and response to cholinesterase inhibitor: a case report17PubMed Central. Study of visuospatial skill in patients with dementia
At home, this can look like a once-polite parent making rude remarks to strangers, spending sprees, binge eating of sweets or rigid routines. The person often doesn’t notice anything is wrong, and memory for recent events may stay fairly good early on.
Lewy body dementia’s hallmark signs are thinking and alertness that swing from hour to hour or day to day, detailed visual hallucinations, and Parkinson’s-like stiffness and slowness (the medical term is parkinsonism).18PubMed Central. REM Sleep Behavior Disorder (RBD) in Dementia with Lewy Bodies (DLB) Many people also act out their dreams, shouting or kicking in sleep.19PubMed Central. REM Sleep Behavior Disorder (RBD) in Dementia with Lewy Bodies (DLB) This sleep problem affects roughly 40% to 74% of people with dementia with Lewy bodies, compared with under 1% of the general population.20PubMed Central. REM Sleep Behavior Disorder (RBD) in Dementia with Lewy Bodies (DLB) These signs can appear before memory problems become obvious.21PubMed Central. REM Sleep Behavior Disorder (RBD) in Dementia with Lewy Bodies (DLB)
Problems judging shapes, distances and objects are common.22PubMed Central. Study of visuospatial skill in patients with dementia Falls and a shuffling walk can be early clues. The body’s automatic controls, such as those for heart rate, are often affected too, more than in Alzheimer’s.23PubMed. Heart rate variability in patients with dementia or neurocognitive disorders: A systematic review and meta-analysis
Some symptoms appear in both. Apathy, a loss of interest and drive, appears in all types of dementia.24PubMed. Neuropsychological correlates of behavioral symptoms in Alzheimer’s disease, frontal variant of frontotemporal, subcortical vascular, and lewy body dementias: a comparative study Some people with FTD develop Parkinson’s-like movement problems too.25PubMed. Frontotemporal dementia mimicking dementia with Lewy bodies26PubMed Central. Parkinsonism and motor neuron diseases: twenty-seven patients with diverse overlap syndromes
A symptom diary helps the doctor. Note when confusion comes and goes, record any sleep shouting or kicking a bed partner reports, and write down behavior changes with examples and dates.
Why the Two Get Mixed Up
In one reported group of six people with FTD, all met the official criteria for both FTD and Lewy body dementia.27PubMed. Frontotemporal dementia mimicking dementia with Lewy bodies They had FTD’s personality changes plus Parkinson’s-like movement problems, fluctuating thinking, sleep disturbances and hallucinations.28PubMed. Frontotemporal dementia mimicking dementia with Lewy bodies Both diseases also overlap with Alzheimer’s.29PubMed. Novel fluid biomarkers to differentiate frontotemporal dementia and dementia with Lewy bodies from Alzheimer’s disease: A systematic review30PubMed. A Systematic Review on the Evidence of Misdiagnosis in Dementia and Its Impact on Accessing Dementia Care
A wrong label can happen in several ways. Early FTD behavior is often mistaken for depression or a midlife crisis. Lewy body hallucinations can be mistaken for a psychiatric illness. Memory complaints get labeled Alzheimer’s by default. Either disease can begin with an unusual symptom, such as language trouble in FTD or fainting spells in Lewy body dementia, that doesn’t fit the textbook picture.
Consider a second opinion if the diagnosis doesn’t fit the symptoms you see, or if a new medicine sharply worsens behavior. Ask for a referral to a memory clinic or a behavioral neurologist.
How Doctors Tell Them Apart
A typical evaluation starts with a long interview with the patient and someone who knows them well. Then come memory and thinking tests, including drawing and word tasks, and a neurological exam for stiffness, tremor and balance. An MRI usually comes first, with special scans if needed.
An MRI or PET scan that shows frontal and temporal shrinkage points toward FTD.31PubMed. Diagnostic imaging of dementia with Lewy bodies, frontotemporal lobar degeneration, and normal pressure hydrocephalus32PubMed. Molecular and Anatomical Imaging of Dementia With Lewy Bodies and Frontotemporal Lobar Degeneration A DaTscan, a nuclear scan that checks dopamine nerve endings deep in the brain, is abnormal in most people with dementia with Lewy bodies, 9 of 10 in one study.33PubMed. Differentiation of frontotemporal dementia from dementia with Lewy bodies using FP-CIT SPECT But the DaTscan was also abnormal in about a third of people with FTD,34PubMed. Differentiation of frontotemporal dementia from dementia with Lewy bodies using FP-CIT SPECT so a positive result alone does not rule out FTD. Blood and spinal fluid tests to tell these dementias apart are still being researched.35PubMed. Novel fluid biomarkers to differentiate frontotemporal dementia and dementia with Lewy bodies from Alzheimer’s disease: A systematic review
The family’s history carries great weight. Fluctuating alertness, hallucinations and dream-acting often happen at home, not in the exam room. In FTD the person often does not notice changes in their own behavior, so a relative’s description may be the best evidence. Specific examples with rough dates, such as when the first fall or odd purchase happened, help the doctor judge what came first and how fast things are moving.
Useful questions for the appointment: Which diagnosis do you think fits, and how sure are you? Would a DaTscan or PET scan change the plan? What would make you revise the diagnosis?
Why the Difference Changes Treatment
Cholinesterase inhibitors such as donepezil and rivastigmine improve thinking and behavior symptoms in Lewy body dementia.36PubMed Central. Comprehensive treatment of dementia with Lewy bodies37PubMed. Systematic review of pharmacological interventions for people with Lewy body dementia Donepezil also reduces hallucinations in dementia with Lewy bodies.38PubMed. Systematic review of pharmacological interventions for people with Lewy body dementia Memantine has some supporting evidence too.39PubMed. Systematic review of pharmacological interventions for people with Lewy body dementia
These memory drugs can do harm in FTD. FTD does not involve the brain-chemical loss they target, so they usually don’t help and often worsen thinking and behavior.40PubMed. Use of Cholinesterase Inhibitors in Non-Alzheimer’s Dementias In one study, some people with FTD on donepezil became more disinhibited or compulsive, and this eased after stopping it.41PubMed. Preliminary findings: behavioral worsening on donepezil in patients with frontotemporal dementia Experts advise avoiding cholinesterase inhibitors and memantine in FTD.42PubMed. Advances in Treatment of Frontotemporal Dementia
FTD behavior is usually managed another way. Doctors often focus on structure, routine and changes to the environment. Some prescribe antidepressants for compulsive or disinhibited behavior, and speech therapy can help the language forms.
If behavior worsens on a new medicine, note the start date and what changed. Call the prescriber rather than stopping abruptly on your own, and ask whether the diagnosis should be rechecked.
People with Lewy body dementia can have severe, sometimes fatal reactions to antipsychotic drugs.43PubMed Central. Comprehensive treatment of dementia with Lewy bodies These should be used only briefly, when truly necessary, after other options fail.44PubMed Central. Comprehensive treatment of dementia with Lewy bodies Make sure every doctor, including hospital and emergency staff, knows the diagnosis. A wallet card listing the diagnosis and drugs to avoid is useful at hospital admissions, where agitation is often treated with antipsychotics.
How Each Disease Progresses
In people whose dementia began before old age, survival with FTD or Lewy body dementia averaged about 7 years, the shortest of the main types.45BMJ Group – Helping doctors make better decisions. Significant variations in survival times of early onset dementia by clinical subtype People with FTD plus motor neurone disease (ALS) lived about 2 years on average, reflecting the added effect of a disease that weakens the muscles used for breathing and swallowing.46BMJ Group – Helping doctors make better decisions. Significant variations in survival times of early onset dementia by clinical subtype Unlike most dementias, FTD and Lewy body dementia shorten life a lot even when diagnosed at older ages.47International Psychogeriatrics. Dementia time to death: a systematic literature review on survival time and years of life lost in people with dementia
These are averages and cannot say how long any one person will live. The doctor can say what signs to watch for.
The later stages differ. FTD gradually takes away speech, judgment and self-care. Lewy body dementia brings more falls, swallowing trouble and rigidity. Both eventually need full-time care.
That makes early planning worthwhile. Arrange power of attorney while the person can still take part, and discuss care wishes before speech or judgment declines.
Who Gets Them and Whether They Run in Families
FTD is most common between ages 60 and 69, and about 13% of cases begin before age 50.48PubMed Central. Considering sex and gender in Alzheimer disease and other dementias Up to half of FTD cases run in families.49PubMed Central. Considering sex and gender in Alzheimer disease and other dementias Changes in a gene called C9orf72 greatly raise the risk of FTD and ALS.50Alzheimer’s & Dementia. Structural variants in Lewy body dementia and frontotemporal dementia spectrum By contrast, genes known to cause other brain diseases are rare in dementia with Lewy bodies.51PubMed Central. Analysis of neurodegenerative disease-causing genes in dementia with Lewy bodies
“Runs in families” needs care. It means other relatives had dementia, ALS or psychiatric illness, not that each person with a family history will develop it. When a specific causal gene change has been identified in a family, each child has roughly even odds of inheriting it. Many people with FTD have no family history, and their disease is not thought to be inherited in a predictable way.
Genetic counseling makes sense if several relatives had FTD, ALS or early dementia. Counselors explain what a test result would mean for children and siblings. Testing is a personal choice with emotional and insurance implications.
Younger onset affects families in practical ways. FTD often hits during working years, job loss and money problems can come before diagnosis, and children at home may need support too.
What Caring for Each Looks Like
Caregivers of people with Lewy body dementia report a greater burden than Alzheimer’s caregivers.52PubMed Central. A Comparison of Caregiver Burden for Different Types of Dementia: An 18-Month Retrospective Cohort Study FTD caregivers’ burden also exceeds Alzheimer’s, and the gap grows over 18 months.53PubMed Central. A Comparison of Caregiver Burden for Different Types of Dementia: An 18-Month Retrospective Cohort Study Because the gap in FTD widens over time, it is wise to arrange help early rather than waiting for a crisis.
The strains differ. In FTD, personality loss can feel like grieving someone still alive, embarrassing public behavior can isolate families, and the person often lacks insight and resists help. In Lewy body dementia, unpredictable good and bad days make planning hard, night-time dream-acting and falls disrupt sleep and safety, and hallucinations can frighten both people.
Support exists. Disease-specific groups include the Association for Frontotemporal Degeneration and the Lewy Body Dementia Association. Respite care and day programs give caregivers a break, and caregiver support groups, including online ones, connect you with people in the same position.