Updated Key to the Diagnosis of Dementia

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RESEARCH UPDATE

Distinguishing dementia with Lewy bodies (DLB) from Alzheimer disease (AD) has been a challenge. DLB is often misdiagnosed as AD only to be correctly revealed at autopsy. Missed or misdiagnosed DLB has persisted despite consensus diagnostic criteria published at the end of 2005.¹ A recently updated consensus report of the DLB Consortium aims to bring greater clarity and diagnostic precision to the identification and management of DLB.²

Revised consensus criteria

The revised DLB consensus criteria provide clear guidance regarding the recognition and interpretation of clinical signs and symptoms and diagnostic biomarkers of DLB. Of note is that increased diagnostic weight is given to REM sleep behavior disorder (RBD) and ¹²³iodine-metaiodobenzylguanidine (MIBG) myocardial scintigraphy.

In defining the primary clinical criteria for DLB, the authors noted the importance of attention/executive function and visuospatial processing when assessing cognitive decline, as these measures can differentiate DLB from AD and normal aging. The panel noted that deficits in these areas are more pronounced in DLB than are memory deficits and may occur early in the disease process.

Core features

Core clinical features that can differentiate DLB from AD or other forms of dementia, as noted by the consensus panel, include fluctuations in cognition, attention, and arousal; hallucinations; parkinsonism; and RBD. The presence of 2 or more clinical features has been deemed grounds for a probable diagnosis of DLB. Fluctuations include episodes of erratic behavior, incoherent speech, or “zoning out.” Application of interview questions and rating scales regarding these symptoms can help distinguish DLB symptomatology from that of AD.

Hallucinations and parkinsonism are somewhat telltale symptoms: hallucinations occur in up to 80% of patients with DLB, and parkinsonism in up to 85%. RBD, a parasomnia characterized by the absence of REM sleep atonia, has been elevated to a core symptom in the updated consensus criteria; it is overwhelmingly prevalent in autopsy-confirmed DLB cases.³ Furthermore, it may act as a key sign of DLB risk, often emerging before signs and symptoms of DLB-associated cognitive decline occur.

Supportive features

Supportive clinical features-those that are common but lack diagnostic specificity-outlined by the panel include severe sensitivity to antipsychotic drugs, postural instability, fainting spells or related loss of consciousness, severe autonomic dysfunction, hypersomnia, loss of smell, hallucinations that differ from those common to DLB, delusions, apathy, anxiety, and depression. Hypersomnia and loss of smell (hyposmia) are the new additions to the updated criteria.

Biomarkers

Biomarkers that have shown high specificity and sensitivity in differentiating DLB from AD and are considered indicative biomarkers by the panel include reduced dopamine transporter uptake on single-photon emission computed tomography or positron emission tomography and reduced ¹²³iodine-MIBG uptake on myocardial scintigraphy. Polysomnographic confirmation of RBD (ie, REM sleep without atonia) is also among the indicative biomarkers of DLB. One or more of these found in association with one or more clinical features are cause for a diagnosis of probable DLB.

Management

In discussing management, the panel declared that cholinesterase inhibitors currently are the preferred pharmacotherapeutic option for management of cognitive and neuropsychiatric symptoms. Although some patients may benefit, the authors noted that dopaminergic therapies can worsen neuropsychiatric symptoms of DLB and that other strategies should be pursued to prevent fall injuries in patients with parkinsonism. Finally, the panelists stressed the urgent need for guidelines and outcome measures for clinical trials with the aim of developing disease-modifying drugs, effective pharmacologic and nonpharmacologic strategies, and support for patients with DLB and their caregivers.

References:

http://www.pediatricsconsultantlive.com/geriatric-psychiatry/updated-key-diagnosis-dementia1.http://www.pediatricsconsultantlive.com/geriatric-psychiatry/updated-key-diagnosis-dementia Vann Jones SA, O’Brien JT. The prevalence and incidence of dementia with Lewy bodies: a systematic review of population and clinical studies. Psychol Med. 2014;44:673-683.

2. McKeith IG, Boeve BF, Dickson DW, et al. Diagnosis and management of dementia with Lewy bodies: fourth consensus report of the DLB Consortium. Neurology. 2017 Jun 7. [Epub ahead of print]

3. Ferman TJ, Boeve BF, Smith GE, et al. Inclusion of RBD improves the diagnostic classification of dementia with Lewy bodies. Neurology. 2011;77:875-882.