Alzheimer's disease accounts for up to 80% of all dementia cases. Diagnosis may be complicated by other forms of dementia that have symptoms and pathologies similar to Alzheimer's disease. Knowing the key features and pathology of each type of dementia can help in the accurate diagnosis of patients, so they will receive the treatment and support services appropriate for their condition and maintain the highest possible quality of life.

The following table identifies some of the clinical differences between the major dementias.

Clinical Differentiation of the Major Dementias1

Disease First Symptom Mental Status Neuropsy-chiatry Neurology Imaging
AD Memory loss Episodic memory loss Initially normal Initially normal Entorhinal cortex and hippocampal atrophy
FTD Apathy; poor judgment/insight, speech/language; hyperorality Frontal/executive, language; spares drawing Apathy, disinhibition, hyperorality, euphoria, depression May have vertical gaze palsy, axial rigidity, dystonia, alien hand, or MND Frontal, insular, and/or temporal atrophy; spares posterior parietal lobe
LBD Visual hallucinations, REM sleep disorder, delirium, Capgras' syndrome, parkinsonism Drawing and frontal/executive; spares memory; delirium prone Visual hallucinations, depression, sleep disorder, delusions Parkinsonism Posterior parietal atrophy; hippocampi larger than in AD
CJD Dementia, mood, anxiety, movement disorders Variable, frontal/executive, focal cortical, memory Depression, anxiety Myoclonus, rigidity, parkinsonism Cortical ribboning and basal ganglia or thalamus hyperintensity on diffusion/FLAIR MRI
Vascular Often but not always sudden; variable; apathy, falls, focal weakness Frontal/executive, cognitive slowing; can spare memory Apathy, delusions, anxiety Usually motor slowing, spasticity; can be normal Cortical and/or subcortical infarctions, confluent white matter disease
Abbreviations: AD, Alzheimer's disease; CBD, cortical basal degeneration; CJD, Creutzfeldt-Jakob disease; DLB, Lewy body dementia; FTD, frontotemporal dementia; MND, motor neuron disease; PSP, progressive supranuclear palsy

Reproduced with permission. Seeley WW, Miller BL. Alzheimer's disease and other dementias. In: Harrison's Neurology in Clinical Medicine. 3rd edition. ©The McGraw-Hill Companies, Inc.

Click on links below for additional information about each condition's key features, treatment and pathology. 

For your patients and families, share this link about the different types of dementia.

Down syndrome and Alzheimer's disease

According to the National Down Syndrome Society, about 30 percent of people with Down syndrome who are in their 50s have Alzheimer’s dementia. Fifty percent or more of people with Down syndrome will develop Alzheimer’s dementia in their lifetimes. Recognition of adult cognitive change in this population is important to ensure appropriate services and support for individuals with Down syndrome and their caregivers. Diagnosing dementia in a person with Down syndrome can be difficult. The National Task Group on Intellectual Disabilities and Dementia Practices has developed the NTG-Early Detection Screen for Dementia to identify early signs and symptoms of dementia in adults with intellectual disabilities. They also issued a report, My Thinker’s Not Working, outlining 20 recommendations for the improvement of services for people living with Down syndrome and dementia.


1. Seeley WW, Miller BL. Alzheimer's disease and other dementias. In: Hauser SL, ed. Harrison's Neurology in Clinical Medicine. 3rd edition. New York: McGraw-Hill Medical; 2013.