Dementia is an umbrella term, under which we can find numerous different types of syndromes and diseases. Alzheimer’s Disease (AD) is the most common type of dementia, estimated to account for up to 80% of total cases, and the terms are sometimes used interchangeably, but AD is by no means the only type of dementia.
Dementia with Lewy bodies (DLB) is the second most common type of dementia, and is estimated to account for 10% to 15% of all cases, and is closely related to Parkinson’s Disease (PD), so much so that they are considered by many professionals as occupying different parts of the same spectrum. While PD doesn’t always lead to dementia, it may do so in up to 78% of patients, leading to Parkinson’s disease dementia (PDD).
DLB was fully recognized only in the 90s, relatively recently. This means that to this day, many clinicians may not be able to accurately diagnose it early on, especially given its similarities to PDD. A general rule of thumb that is often used to differentiate between the two diseases, is to look at the onset of dementia in relation to the onset of parkinsonism (a term indicating the movement problems typical of PD, including tremors, slow movement and stiffness). If dementia appears within 12 months from the onset of parkinsonism, it often means that the patient is suffering from DLB, while if dementia appears after the 12 months mark, then PDD is more probable.
DLB is progressive, and generally cognitive test scores decline by about 10% each year, and survival time from onset is on average similar to AD.
While DLB is similar to PDD, it differs from AD and has specific symptoms. Specifically, in order for the clinician to be able to perform a DLB diagnosis, at least two of the following must be present:
- Fluctuating cognition with strong variations in attention and alertness.
- Recurrent visual hallucinations that are typically well formed and detailed.
- Spontaneous features of parkinsonism.
Since no specific tests exist to precisely diagnose DLB, the clinician must resort to obtaining a detailed medical history from the patient and an informant, and perform cognitive tests and neurological examinations.
Treatment of DLB is somewhat complicated, as many drugs tend to exacerbate symptoms if wrongly prescribed or taking at high dose. Levadopa, for example, a drug commonly used in PD, may be effective in treating motor symptoms associated with parkinsonism in DLB, but if doses are too high they are often associated with increased confusion and hallucinations.
Cholinesterase inhibitor drugs, which are often used to treat AD, are somewhat effective and relatively safe in treating neuropsychiatric and cognitive symptoms in both DLB and PDD, although they are not completely free from side effects, especially gastrointestinal.
One can easily notice how DLB is similar to other dementia syndromes, while still being its own specific type. Furthermore, as with most cases of dementia, it is often clinically difficult to identify typical cases of a specific dementia syndrome, with most patients presenting features of multiple syndromes. This is challenging with regards to both diagnosis and treatment. Hopefully, new treatments and more precise diagnostic procedures will be discovered in the near future.
source: McKeith, I. (2004), Dementia with Lewy bodies, Dialogues In Clinical Neuroscience, 6(3), pp. 333-341