Because of the relative early age at onset of the disorder, the disorder oftens affects work- place and family life. Because of the involvement of language and / or behavior, function is often more severely impaired relatively early in the course. For individuals with the be- havioral variant, prior to diagnostic clarification there may be significant family disrup- tion, legal involvement, and problems in the workplace because of socially inappropriate behaviors. The functional impairment due to behavioral change and language dysfunc- tion, which can include hyperorality, impulsive wandering, and other dishinhibited be- haviors, may far exceed that due to the cognitive disturbance and may lead to nursing home placement or institutionalization. These behaviors can be severely disruptive, even in structured care settings, particularly when the individuals are otherwise healthy, non- frail, and free of other medical comorbidities.
Other neurocognitive disorders. Other neurodegenerative diseases may be distinguished from major or mild frontotemporal NCD by their characteristic features. In major or mild
NCD due to Alzheimer’s disease, decline in learning and memory is an early feature.
However, 10%—30% of patients presenting with a syndrome suggestive of major or mild frontotemporal NCD are found at autopsy to have Alzheimer’s disease pathology. This oc- curs more frequently in individuals who present with progressive dysexecutive syn- dromes in the absence of behavioral changes or movement disorder or in those with the logopenic variant.
In major or mild NCD with Lewy bodies, core and suggestive features of Lewy bodies must be present. In major or mild NCD due to Parkinson’s disease, spontaneous parkin- sonism emerges well before the cognitive decline. In major or mild vascular NCD, depend- ing on affected brain regions, there may also be loss of executive ability and behavioral changes such as apathy, and this disorder should be considered in the differential diagno- sis. However, history of a cerebrovascular event is temporally related to the onset of cog- nitive impairment in major or mild vascular NCD, and neuroimaging reveals infarctions or white matter lesions sufficient to account for the clinical picture.
Other neurological conditions. Major or mild frontotemporal NCD overlaps with pro- gressive supranuclear palsy, corticobasal degeneration, and motor neuron disease clinically as well as pathologically. Progressive supranuclear palsy is characterized by supranuclear gaze palsies and axial—predominant parkinsonism. Pseudobulbar signs may be present, and retropulsion is often prominent. Neurocognitive assessment shows psy- chomotor slowing, poor working memory, and executive dysfunction. Corticobasal degen- eration presents with asymmetric rigidity, limb apraxia, postural instability, myoclonus, alien limb phenomenon, and cortical sensory loss. Many individuals with behavioral-variant major or mild frontotemporal NCD show features of motor neuron disease, which tend to be mixed upper and predominantly lower motor neuron disease.
Other mental disorders and medical conditions. Behavioral—variant major or mild fron— totemporal NCD may be mistaken for a primary mental disorder, such as major depression, bipolar disorders, or schizophrenia, and individuals with this variant often present initially to psychiatry. Over time, the development of progressive neurocognitive difficulties will help to make the distinction. A careful medical evaluation will help to exclude treatable causes of NCDs, such as metabolic disturbances, nutritional deficiencies, and infections.
A. The criteria are met for major or mild neurocognitive disorder.
B. The disorder has an insidious onset and gradual progression.
C. The disorder meets a combination of core diagnostic features and suggestive diagnos- tic features for either probable or possible neurocognitive disorder with Lewy bodies.