What Are the Different Types of Dementia and How Do They Differ?

Dementia is not a single disease but an umbrella term for conditions causing progressive cognitive decline severe enough to interfere with daily life. Alzheimer’s accounts for 60 to 70% of all cases, but vascular dementia, Lewy body dementia, and frontotemporal dementia each follow different biological pathways and require different management. Misidentifying the type leads directly to incorrect treatment — in Lewy body dementia, certain medications can cause severe and potentially fatal reactions.

As Dr. Guruprasad Hosurkar, Neurologist in Bangalore, explains: “Getting the subtype right is not academic. A patient with Lewy body dementia given a standard antipsychotic for hallucinations can have a life-threatening reaction. A patient with frontotemporal dementia given a cholinesterase inhibitor gets no benefit and possible harm. The subtype determines what you prescribe and what you avoid.”

Each dementia subtype has a characteristic pattern of which symptoms appear first, how it progresses, and what the underlying pathology looks like and these differences are what specialists use to distinguish between them clinically.

• Alzheimer’s disease: Amyloid plaques and tau tangles disrupt hippocampal circuits first, producing short-term memory loss, repetitive questioning, and disorientation before language and executive function decline later.
• Vascular dementia: Caused by strokes or small vessel disease, it progresses in steps rather than gradually, with executive dysfunction, slowed processing, and gait problems often more prominent than memory loss early on.
• Lewy body dementia: Produces a characteristic triad of day-to-day cognitive fluctuation, detailed visual hallucinations, and spontaneous parkinsonism — with REM sleep behaviour disorder often predating all other symptoms by years.
• Frontotemporal dementia: Causes disinhibition, apathy, compulsive behaviours, and language difficulties in people typically aged 45 to 65, making it the most common cause of early-onset dementia and the one most often misdiagnosed as a psychiatric condition.

Identifying which type is present requires combining clinical history, neuropsychological testing, and MRI findings and in selected cases, biomarker testing. Symptom pattern alone is not sufficient. For a detailed overview of how each subtype is assessed and managed, see dementia treatment.

The same drugs that help in Alzheimer’s are ineffective or harmful in other subtypes which is why subtype diagnosis is a clinical necessity, not an academic exercise.

• Alzheimer’s dementia: Donepezil, rivastigmine, and galantamine slow symptom progression modestly, while lecanemab and donanemab entering practice in 2026 are the first therapies to address amyloid pathology directly in early-stage disease.
• Vascular dementia: Antiplatelet therapy, blood pressure optimisation, statins, and diabetes management slow further vascular injury and matter more than any cognitive medication in determining long-term trajectory.
• Lewy body dementia: Up to 50% of patients have severe neuroleptic sensitivity reactions to conventional antipsychotics including haloperidol and olanzapine — making accurate diagnosis life-saving. Rivastigmine has the strongest evidence base for this subtype.
• Frontotemporal dementia: Management focuses on SSRIs for disinhibition and compulsive behaviours, caregiver education, and speech therapy for language variants, with clinical trials targeting tau and TDP-43 pathology in early phases.

Correct subtype identification is the foundation on which every treatment decision rests, and it requires specialist neurological assessment rather than a general cognitive screen. For a broader understanding of how dementia risk can be modified before this stage is reached, see can dementia be prevented or slowed down.

Dr. Guruprasad Hosurkar practises at KIMS Hospital, Mahadevapura, with specialist expertise in differentiating Alzheimer’s disease from vascular, Lewy body, and frontotemporal dementia through detailed clinical assessment, neuropsychological testing, and neuroimaging. For patients who have received a general dementia diagnosis without subtype clarification, or whose treatment response has been unexpectedly poor, a specialist re-evaluation provides the diagnostic precision that guides safe and effective management.