Which conditions should be included in the differential diagnoses of frontotemporal dementia (FTD)?

Updated: Jun 14, 2018
  • Author: Howard S Kirshner, MD; Chief Editor: Jasvinder Chawla, MD, MBA  more...
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Answer

Answer

Frontotemporal lobe dementia (FTD) is somewhat intermediate between focal disorders of the brain and more generalized neurodegenerative diseases.

The most important differential diagnoses for FTD involve focal pathologies such as brain tumors, abscesses, and strokes, as well as Alzheimer disease, which is a more common dementing illness than FTD.

In distinguishing between FTD and other focal lesions, gradually progressive onset, usually over years, is the key feature.

Brain imaging studies are helpful in ruling out focal, destructive, or neoplastic lesions. Whitwell and colleagues used voxel-based morphometry on MRI to distinguish differing patterns of lobar atrophy in variants of FTD with and without motor neuron disease. [65] See below under imaging for the contributions of MRI and positron emission tomography (PET) imaging to the diagnosis of FTD.

Alzheimer disease can mimic almost any of the FTD variants when it presents with focal symptoms. Only a few cases of pathologically confirmed Alzheimer disease have been reported that presented with isolated nonfluent aphasia, but more have been described with the syndromes of semantic dementia (although most cases of semantic dementia have the pathology of frontotemporal lobar degeneration-ubiquitin [FTLD-U]) and with the logopenic variant of primary progressive aphasia (PPA), which is most commonly associated with Alzheimer disease. Other “focal” presentations of Alzheimer disease include the “frontal variant” referred to earlier and the “posterior cortical atrophy” variant, in which visual symptoms predominate.

Kertesz et al suggested the term Pick complex to include the various non-Alzheimer pathologies, with or without Pick inclusion bodies and with or without motor neuron disease. [66] This terminology has not become widely adopted, so we will continue to use the clinical term frontotemporal lobe dementia and the pathologic term frontotemporal lobar degeneration.


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