neurologic disorders
Dementia with Lewy Bodies and Parkinson Disease Dementia
Diagnosis
Clinical criteria Neuroimaging to rule out other disorders Diagnosis is clinical, but sensitivity and specificity are poor. A general Clinical criteria requires all of the following: Cognitive or behavioral (neuropsychiatric) symptoms interfere with the ability to function at work or do usual daily activities. These symptoms represent a decline from previous levels of functioning. These symptoms are not explained by delirium or a major psychiatric disorder. Evaluation of cognitive function involves taking a history from the patient and from someone who knows the patient plus doing a bedside How to Assess Mental Status or, if bedside testing is inconclusive, Diagnosis of dementia with Lewy bodies is considered probable if 2 of the following 4 core features are present and is considered possible if only one is present: Fluctuations in cognition Visual hallucinations Rapid eye movement (REM) sleep behavior disorder Parkinsonism Supportive evidence includes repeated falls, syncope, autonomic dysfunction, excessive daytime sleepiness, and sensitivity to antipsychotics. Overlap of symptoms in dementia with Lewy bodies and Parkinson disease dementia may complicate diagnosis: When motor deficits (eg, tremor, bradykinesia, rigidity) precede and are more severe than cognitive impairment, Parkinson disease dementia is usually diagnosed. When early cognitive impairment (particularly executive dysfunction) and behavioral disturbances predominate, dementia with Lewy bodies is usually diagnosed. Patients with dementia with Lewy bodies often have impaired alertness, which is more characteristic of delirium than dementia; thus, Diagnosis should be done, particularly for common causes such as Drugs and medications, particularly anticholinergics, psychoactive drugs, and opioids Dehydration Infection Other causes of dementia should also be ruled out. The parkinsonian features in dementia with Lewy bodies (eg, axial rigidity, falls) may occur in early stages of other neurodegenerative disorders (eg, Progressive Supranuclear Palsy (PSP) [PSP]). People with PSP may also develop subcortical dementia. Identifying other characteristic features of PSP, such as impairment of vertical eye movements and CT and MRI show no characteristic changes in Lewy body dementia but can initially help rule out other causes of dementia. Single-photon emission CT (SPECT) of the brain with 123I-FP-CIT (N-3-fluoropropyl-2-beta-carbomethoxy-3beta-[4-iodophenyl]-tropane), a radioactive tracer ofdopaminetransporter, can help detect basal ganglia dopaminergic neuronal dysfunction and function as a biomarker for diagnosing dementia with Lewy bodies. Other imaging tests that may help identify dementia with Lewy bodies include Positron emission tomography (PET) of the brain with fluorine-18 (18F)–labeled deoxyglucose (fluorodeoxyglucose, or FDG) Myocardial scintigraphy with iodine 123-meta-iodobenzylguanidine (MIBG; in dementia with Lewy bodies, cardiac uptake of MIBG is reduced because the postganglionic cardiac sympathetic system is denervated) However, these tests are not routinely used in clinical practice. Confirmation of REM sleep behavior disorder using polysomnography may help establish the diagnosis of dementia with Lewy bodies. Definitive diagnosis requires autopsy samples of brain tissue. 