May 2019 By PsychDB.com
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
Common Subtypes
Common Dementia Subtypes and Presentation
| Subtype | Prevalence | Typical presentation |
|---|---|---|
| Alzheimer's Disease (AD) | ~50% | Initial short-term memory loss |
| Vascular Dementia* | ~25 % | Vascular risk factors; neuroimaging evidence of cerebrovascular involvement |
| Lewy Body Dementia (LBD) | 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) | Most cases of PD will progress to dementia | Dementia occurring > 1 year after onset of Parkinson disease motor symptoms |
Overlap
Dementia is not often due to 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 Lewy Body Dementia (LBD).[3]