Kantarci, Kejal

ObjectiveThe new criteria for preclinical Alzheimer disease (AD) proposed 3 stages: abnormal levels of β‐amyloid (stage 1), stage 1 plus evidence of brain injury (stage 2), and stage 2 plus subtle cognitive changes (stage 3). However, a large group of subjects with normal β‐amyloid biomarkers have evidence of brain injury; we labeled them as the “suspected non‐Alzheimer pathophysiology” (sNAP) group. The characteristics of the sNAP group are poorly understood.MethodsUsing the preclinical AD classification, 430 cognitively normal subjects from the Mayo Clinic Study of Aging who underwent brain magnetic resonance (MR), 18fluorodeoxyglucose (FDG), and Pittsburgh compound B positron emission tomography (PET) were evaluated for FDG PET regional volumetrics, MR regional brain volumetrics, white matter hyperintensity volume, and number of infarcts. We examined cross‐sectional associations across AD preclinical stages, those with all biomarkers normal, and the sNAP group.ResultsThe sNAP group had a lower proportion (14%) with apolipoprotein E ε4 genotype than the preclinical AD stages 2 + 3. The sNAP group did not show any group differences compared to stages 2 + 3 of the preclinical AD group on measures of FDG PET regional hypometabolism, MR regional brain volume loss, cerebrovascular imaging lesions, vascular risk factors, imaging changes associated with α‐synucleinopathy, or physical findings of parkinsonism.InterpretationCognitively normal persons with brain injury biomarker abnormalities, with or without abnormal levels of β‐amyloid, were indistinguishable on a variety of imaging markers, clinical features, and risk factors. The initial appearance of brain injury biomarkers that occurs in cognitively normal persons with preclinical AD may not depend on β‐amyloidosis. ANN NEUROL 2013;73:472–480

Background and purposePrimary progressive apraxia of speech, a motor speech disorder of planning and programming, is a tauopathy that has overlapping histological features with progressive supranuclear palsy. We aimed to compare, for the first time, atrophy patterns, as well as white matter tract degeneration, between these two syndromes.MethodsSixteen primary progressive apraxia of speech subjects were age‐ and gender‐matched to 16 progressive supranuclear palsy subjects and 20 controls. All subjects were prospectively recruited, underwent neurological and speech evaluations and 3.0‐Tesla magnetic resonance imaging. Grey and white matter atrophy was assessed using voxel‐based morphometry and atlas‐based parcellation, and white matter tract degeneration was assessed using diffusion tensor imaging.ResultsAll progressive supranuclear palsy subjects had typical oculomotor/gait impairments, but none had speech apraxia. Both syndromes showed grey matter loss in supplementary motor area, white matter loss in posterior frontal lobes and degeneration of the body of the corpus callosum. Whilst lateral grey matter loss was focal, involving superior premotor cortex, in primary progressive apraxia of speech, loss was less focal extending into prefrontal cortex in progressive supranuclear palsy. Caudate volume loss and tract degeneration of superior cerebellar peduncles were also observed in progressive supranuclear palsy. Interestingly, area of the midbrain was reduced in both syndromes compared to controls, although this was greater in progressive supranuclear palsy.ConclusionsAlthough neuroanatomical differences were identified between these distinctive clinical syndromes, substantial overlap was also observed, including midbrain atrophy, suggesting these two syndromes may have common pathophysiological underpinnings.