FDG-PET patterns associated with ideomotor apraxia and imitation apraxia in patients with corticobasal syndrome

Pathomechanisms of neuropsychiatric disturbances in atypical parkinsonian disorders: a current view

Multiple system atrophy (MSA), corticobasal degeneration (CBD) and progressive supranuclear palsy (PSP) are the most common atypical parkinsonisms. These adult-onset and lethal neurodegenerative disorders of unknown etiology are clinically characterized by varying combinations of autonomic, levodopa-poorly responsive parkinsonsm, motor, non-motor, cerebellar syndromes, behavioral, cognitive and other neuropsychiatric disorders. Although their pathological hallmarks are different-MSA α-synucleinopathy, CBD and PSP 4-repeat (4R) tauopathies-their neuropsychiatric disturbances include anxiety, depression, agitations, attention-executive dysfunctions, less often compulsive and REM sleep behavior disorders (RBD), which may contribute to disease progression and reduced quality of life (QoL) of patients and caregivers. The present paper reviews the prevalence and type of neuropsychiatric profile in these atypical parkinsonian syndromes, their neuroimaging, and pathogenic backgrounds based on extensive literature research. MSA patients show anxiety, apathy (depression), initial RBD, attentional and executive dysfunction; PSP patients present with apathy, depression, disinhibition, and to a lesser extent, anxiety and agitation; CBD patients are featured by executive and visuospatial dysfunctions, irritability, alien limb phenomena, sleep and language disorders. Neuropsychiatric disorders in these syndromes are often similar, due to disruption of prefronto-subcortical (limbic) and striato-thalamo-cortical circuitries or default mode and attention network disorder. This supports the concept that they are brain network disorders due to complex pathogenic mechanisms related to the basic proteinopathies that are still poorly understood. Psychotic symptoms, hallucinations and delusions are rare. Neuropsychiatric changes in these disorders are often premature and anticipate motor dysfunctions; their assessment and further elucidation of their pathogenesis are warranted as a basis for early diagnosis and adequate treatment of these debilitating comorbidities.

Apraxia: From Neuroanatomical Pathways to Clinical Manifestations

PURPOSE OF REVIEW

Apraxia typically involves impairments in gesture production and tool use, affecting daily life activities. This article reviews current conceptualizations and developments in diagnostic and therapy.

RECENT FINDINGS

Apraxia has been studied in various neurological conditions, particularly stroke and dementia, but recent studies show gesturing deficits in psychiatric populations as well. Promising results have emerged from integrative treatment approaches involving intensive practice of gestures or daily activities. However, several reviews have noted the only marginal progress in apraxia therapy research despite new technologies, like virtual reality and brain stimulation, offering fresh opportunities for assessment and therapy. Advances in lesion-symptom mapping and connectivity analyses led to more detailed neuroanatomical models emphasizing parallel and gradual processing. These models facilitate the understanding of underlying mechanisms of motor cognitive performance and its decline. Finally, the digital era prompts the need to study digital tool use in apraxia, with initial efforts underway.

The enigma of depression in corticobasal degeneration, a frequent but poorly understood co-morbidity

Depression is one of the most frequent neuropsychiatric symptoms in corticobasal degeneration (CBD), a rare, sporadic, and late-onset progressive neurodegenerative disorder of unknown etiology. It is clinically characterized by a levodopa-poorly responsible akinetic-rigid syndrome, apraxia, limb dystonia, cognitive, mood, behavioral, and language disorders. This 4-repeat (4R) tauopathy is morphologically featured by asymmetric frontoparietal atrophy, neuronal loss, and gliosis in cortex and subcortex including substantia nigra, ballooned/achromatic neurons with filamentous 4R tau aggregates in cortex and striatum, widespread thread-like structures, pathognomonic "astroglial plaques", "tufted astrocytes", and numerous "coiled bodies" (in astrocytes and oligodendroglia) in cerebral white matter. CBD is non-specific, as pathologically proven cases include several clinical phenotypes. Pubmed and Google Scholar were systematically analyzed until October 2023, with focus on the prevalence, clinical manifestation, neuroimaging data, and treatment options of depression in CBD. Its prevalence is about 30-40% which is more frequent than in most other atypical parkinsonian syndromes. Depression usually does not correlate with motor and other clinical parameters, suggesting different pathophysiological mechanisms. Asymmetric atrophy and hypometabolism of frontoparietal cortical areas are associated with disruption of fronto-subcortical circuits, nigrostriatal dopaminergic, and cholinergic deficiency. Since no specific neuroimaging, neuropathological, or biomarker studies of depression in CBD are available, its pathobiological mechanisms and pathogenesis are poorly understood. Antidepressive therapy may be useful, but is often poorly tolerated. Depression in CBD, like in other parkinsonian syndromes, may be related to multi-regional patterns of cerebral disturbances and complex pathogenic mechanisms that deserve further elucidation as a basis for early diagnosis and adequate treatment to improve the quality of life in this fatal disease.

Pathomechanisms of cognitive and behavioral impairment in corticobasal degeneration

Corticobasal degeneration (CBD) is a rare, sporadic, late-onset progressive neurodegenerative disorder of unknown etiology, clinically characterized by an akinetic-rigid syndrome, behavior and personality disorders, language problems (aphasias), apraxia, executive and cognitive abnormalities and limb dystonia. The syndrome is not specific, as clinical features of pathologically proven CBD include several phenotypes. This 4-repeat (4R) tauopathy is morphologically featured by often asymmetric frontoparietal atrophy, ballooned/achromatic neurons containing filamentous 4R-tau aggregates in cortex and striatum, thread-like processes that are more widespread than in progressive supranuclear palsy (PSP), pathognomonic "astroglial plaques", and numerous inclusions in both astrocytes and oligodendroglia ("coiled bodies") in the white matter. Cognitive deficits in CBD are frequent initial presentations before onset of motor symptoms, depending on the phenotypic variant. They predominantly include executive and visuospatial dysfunction, sleep disorders and language deficits with usually preserved memory domains. Neuroimaging studies showed heterogenous locations of brain atrophy, particularly contralateral to the dominant symptoms, with disruption of striatal connections to prefrontal cortex and basal ganglia circuitry. Asymmetric hypometabolism, mainly involving frontal and parietal regions, is associated with brain cholinergic deficits, and dopaminergic nigrostriatal degeneration. Widespread alteration of cortical and subcortical structures causing heterogenous changes in various brain functional networks support the concept that CBD, similar to PSP, is a brain network disruption disorder. Putative pathogenic factors are hyperphosphorylated tau-pathology, neuroinflammation and oxidative injury, but the basic mechanisms of cognitive impairment in CBD, as in other degenerative movement disorders, are complex and deserve further elucidation as a basis for early diagnosis and adequate treatment of this fatal disorder.

Validity of cingulate–precuneus–temporo-parietal hypometabolism for single-subject diagnosis of biomarker-proven atypical variants of Alzheimer’s Disease

The aim of our study was to establish empirically to what extent reduced glucose uptake in the precuneus, posterior cingulate and/or temporo-parietal cortex (PCTP), which is thought to indicate brain amyloidosis in patients with dementia or MCI due to Alzheimer’s Disease (AD), permits to distinguish amyloid-positive from amyloid-negative patients with non-classical AD phenotypes at the single-case level. We enrolled 127 neurodegenerative patients with cognitive impairment and a positive (n. 63) or negative (n. 64) amyloid marker (cerebrospinal fluid or amy-PET). Three rating methods of FDG-PET scan were applied: purely qualitative visual interpretation of uptake images (VIUI), and visual reading assisted by a semi-automated and semi-quantitative tool: INLAB, provided by the Italian National Research Council, or Cortex ID Suite, marketed by GE Healthcare. Fourteen scans (11.0%) patients remained unclassified by VIUI or INLAB procedures, therefore, validity values were computed on the remaining 113 cases. The three rating approaches showed good total accuracy (77–78%), good to optimal sensitivity (81–93%), but poorer specificity (62–75%). VIUI showed the highest sensitivity and the lowest specificity, and also the highest proportion of unclassified cases. Cases with asymmetric temporo-parietal hypometabolism and a progressive aphasia or corticobasal clinical profile, in particular, tended to be rated as AD-like, even if biomarkers indicated non-amyloid pathology. Our findings provide formal support to the value of PCTP hypometabolism for single-level diagnosis of amyloid pathophysiology in atypical AD, but also highlight the risk of qualitative assessment to misclassify patients with non-AD PPA or CBS underpinned by asymmetric temporo-parietal hypometabolism.