- Last edited on April 30, 2020
Introduction to Dementia
Primer
Dementia is a progressive neurocognitive decline of sufficient magnitude to interfere with normal social or occupational functions, or with usual daily activities. It is a broad diagnostic category that includes Alzheimer's disease, Lewy Body dementia (15%), Frontotemporal dementia, Vascular dementia, Parkinson's disease, and Creutzfeldt–Jakob disease.
Differential Diagnosis
When being asked to see a patient with demenita, it is good to have a systematic approach. The following is one approach to diagnosing dementia.[1]
- Rule out delirium. Is there an acute onset and fluctuating course + inattention + disorganized thinking? Is there altered level of consciousness?
- Rule out depression (“pseudodementia”). Consider atypical presentations: anxiety, irritability, unexplained physical complaints, worsening cognition. Once the depression is treated, the dementia symptoms go away!
- Rule out any substance use disorders
- Rule out any reversible causes
- Order CBC (anemia), TSH (hypothyroidism), creatinine, electrolytes (hyponatremia), calcium (hypercalcemia), glucose (hyperglycemia), and vitamin B12 (vitamin B12 deficiency)
- Creatinine (to assess renal function and ability to clear medications)
- Consider rapid plasma reagin (RPR), LFTs
- Is it dementia, mild cognitive impairment (MCI), or normal aging?
- Dementia: objective findings of cognitive loss with impairment of ADLs
- MCI: objective findings of cognitive loss without impairment of ADLs Normal cognitive aging: no objective findings of cognitive loss
Dementia Subtypes
Common Dementia Subtypes and Presentation
Subtype | Percent of Dementia Cases | Typical presentation |
---|---|---|
Alzheimer's Disease (AD) | ~50% | Initial short-term memory loss |
Vascular Dementia* | ~25 % | Vascular risk factors; neuroimaging evidence of cerebrovascular involvement |
Dementia with Lewy Bodies (DLB) | 15% | Bradykinesia or features of parkinsonism, fluctuating cognition, visual hallucinations |
Frontotemporal Dementia (FTD) | 3% | Younger age, behavioural symptoms, or language impairment |
Parkinsons's Disease Dementia (PDD) | 0.5%[3] (most cases of Parkinson's will progress to dementia) | Dementia occurring > 1 year after onset of Parkinson disease motor symptoms |
Rare Dementia Subtypes and Presentation
Subtype | Prevalence | Typical presentation |
---|---|---|
Corticobasal Degeneration (CBD) | 5 per 100,000 [4] | Progressive asymmetric movement disorder with symptoms initially affecting one limb, plus cognitive or behavioural disturbances. |
Creutzfeldt-Jakob Disease (CJD) | 1 per 1 million | Rapid, progressive mental deterioration with myoclonus and abnormal movements. Survival rate is less than 1 year. |
Primary Progressive Aphasia (PPA) | 2.7 to 15 per 100,000[5] | Begins with gradual, subtle language deficits that progresses to a nearly complete inability to speak. |
Progressive Supranuclear Palsy (PSP) | 5.8 to 6.5 per 100,000[6] | Characterized by early postural instability, leading to falls, and a characteristic vertical supranuclear-gaze palsy on physical exam. |
Overlap
Dementia is often due to more than one pathology. Some studies have shown that in a general population, 40% of patients have a combination of Alzheimer's Disease (AD) and vascular dementia, while only 30% had pure Alzheimer's and 12% had pure vascular dementia (VaD). About 12% had Alzheimer's combined with Parkinsons's Disease Dementia (PDD) (PD) or Dementia with Lewy Bodies (DLB).[7]
Prevention
About 35% of dementia is attributable to nine modifiable factors across the lifespan.[8] These factors include: education, midlife hypertension, midlife obesity, hearing loss, late-life depression, diabetes, physical inactivity, smoking, and social isolation.[9]
The World Health Organization (WHO) Dementia Prevention Guidelines recommends the following to reduce the risk of dementia:[10]
- Physical exercise (there is some conflicting data[11])
- Tobacco cessation
- Reduce harmful drinking
- Lose excess weight in midlife
- Adhere to healthy diet (a Mediterranean-style diet may reduce dementia risk)
- Cognitive training can be tried for adults with normal cognition or mild impairment (but the quality of evidence to support this is low)
- Social participation and support are important throughout life (but limited evidence to support)
- Hypertension, diabetes, and depression should be managed according to existing guidelines (but it's not clear whether doing so will specifically lower dementia risk)
Vitamins B and E, polyunsaturated fatty acids, and multivitamins are not recommended for risk reduction of dementia.[12]
Behavioural and Psychological Symptoms of Dementia
Behavioural and Psychological Symptoms of Dementia (BPSD) will develop in more than 90% of individuals diagnosed with dementia. Symptoms include delusions, hallucinations, aggression, screaming, restlessness, wandering, depression, and anxiety.