Neuropsychiatry of corticobasal degeneration and progressive supranuclear palsy

Abstract

Corticobasal syndrome (CBS) and progressive supranuclear palsy syndrome (PSPS) are two of the atypical Parkinsonism syndromes, in that patients exhibit rigidity, occasional tremor and postural instability, but do not symptomatically respond to dopamine replacement. CBS and PSPS can often present with complex cognitive difficulties and neuropsychiatric disturbances. Symptoms of depression, apathy, or agitation can be subtle and are often overlooked as reactions to learning a new diagnosis of Parkinsonism. These symptoms may be the earliest presenting evidence of CBS or PSPS, and these syndromes can be misdiagnosed with a primary psychiatric disorder rather than a neurodegenerative condition. Patients may be inappropriately treated with antipsychotic medications that exacerbate the extra-pyramidal motor features of the syndromes. When symptoms are considered to comprise a neurodegenerative syndrome, it may be an inaccurate diagnosis as many features of CBS and PSPS not only overlap with each other, but also with other dementia syndromes. This review discusses similarities and differences between the syndromes of CBS and PSPS in terms of neuropsychiatric features. Improved characterization of the clinical syndromes is necessary to better predict underlying pathology. Improved education about these diseases would help patients, caregivers and clinicians to anticipate symptom progression and avoid premature nursing home placement.     

Pathological heterogeneity in progressive supranuclear palsy and corticobasal degeneration

Progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) are sporadic neurodegenerative disorders of late adult life. Focal asymmetric cortical atrophy with ballooned neurons, nigral degeneration, and tau‐positive neuronal and glial lesions in both the gray and white matter, especially astrocytic plaques in the affected cerebral cortex, are characteristic features of CBD. While cortical involvement may occur in PSP, ballooned neurons are sparse and limited to the limbic system, and tufted astrocytes are abundant in the precentral gyrus and striatum. The present findings suggest that PSP and CBD are distinct pathological entities. However, there exist ‘atypical’ cases of PSP and CBD. Severe cortical involvement or asymmetric cortical atrophy can be seen in PSP. Ballooned neurons are sparse or difficult to detect in some cases of CBD, in spite of typical cortical tau pathology. Cortical symptoms are absent or only mild in ‘minimal change’ CBD. Moreover, several neurodegenerative disorders can underlie CBD. This pathological heterogeneity leads to difficulty in the clinical and pathological diagnosis of both disorders.     

Astrocytic inclusions in progressive supranuclear palsy and corticobasal degeneration

Tufted astrocytes (TAs) in progressive supranuclear palsy (PSP) and astrocytic plaques (APs) in corticobasal degeneration (CBD) have been regarded as the pathological hallmarks of major sporadic 4‐repeat tauopathies. To better define the astrocytic inclusions in PSP and CBD and to outline the pathological features of each disease, we reviewed 95 PSP cases and 30 CBD cases that were confirmed at autopsy. TAs exhibit a radial arrangement of thin, long, branching accumulated tau protein from the cytoplasm to the proximal processes of astrocytes. APs show a corona‐like arrangement of tau aggregates in the distal portions of astrocytic processes and are composed of fuzzy, short processes. Immunoelectron microscopic examination using quantum dot nanocrystals revealed filamentous tau accumulation of APs located in the immediate vicinity of the synaptic structures, which suggested synaptic dysfunction by APs. The pathological subtypes of PSP and CBD have been proposed to ensure that the clinical phenotypes are in accordance with the pathological distribution and degenerative changes. The pathological features of PSP are divided into 3 representative subtypes: typical PSP type, pallido‐nigro‐luysian type (PNL type), and CBD‐like type. CBD is divided into three pathological subtypes: typical CBD type, basal ganglia‐ predominant type, and PSP‐like type. TAs are found exclusively in PSP, while APs are exclusive to CBD, regardless of the pathological subtypes, although some morphological variations exist, especially with regard to TAs. The overlap of the pathological distribution of PSP and CBD makes their clinical diagnosis complicated, although the presence of TAs and APs differentiate these two diseases. The characteristics of tau accumulation in both neurons and glia suggest a different underlying mechanism with regard to the sites of tau aggregation and fibril formation between PSP and CBD: proximal‐dominant aggregation of TAs and formation of filamentous NFTs in PSP in contrast to the distal‐dominant aggregation of APs and formation of less filamentous pretangles in CBD.     

Ballooned neurons in corticobasal degeneration and progressive supranuclear palsy

We examined the distribution and immunohistochemical characteristics of ballooned neurons (BN) in the cortex of patients with corticobasal degeneration (CBD) and progressive supranuclear palsy (PSP). In CBD, the BN were distributed mainly in the medial and superior areas of the frontal cortex, such as the cinglate cortex, superior frontal cortex, and precentral cortex. In six of the nine patients with PSP studied, BN were seen in the cerebral cortex. In two of these six patients, BN were abundant and cortical degeneration was present in the precentral cortex. On immunohistochemical examination, BN were positive for phosphorylated neurofilament protein (pNFP) and αB crystallin, and some BN were positive for ubiquitin and tau protein. On double immunohistochemical staining, all pNFP-positive neurons were stained with anti-αB crystallin antibody, whereas some αB crystallin-positive BN were not stained by anti-pNFP antibody. The presence of cortical BN does not differentiate PSP from CBD, although BN are sparse in patients with PSP when cortical degeneration is not present. The results of the double immunohistochemical staining suggested that αB crystallin might be expressed earlier than pNFP in the formation of BN.     

Comparison of apraxia in corticobasal degeneration and progressive supranuclear palsy

OBJECTIVE: To describe ideomotor apraxia in patients with corticobasal degeneration and those with progressive supranuclear palsy, two parkinsonian disorders that are often misdiagnosed due to the overlap in their clinical features, and to determine whether systematic apraxia testing is useful for differential diagnosis. METHODS: Fourteen patients fulfilling National Institute of Neurological Disorders and Stroke-Society for Progressive Supranuclear Palsy clinical criteria for progressive supranuclear palsy, 13 patients fulfilling modified Lang criteria for corticobasal degeneration, and 12 normal healthy control subjects were given the Test of Oral and Limb Apraxia, which was scored according to the Florida Apraxia Battery for occurrence of various types of apraxic errors. RESULTS: Both patients with progressive supranuclear palsy and corticobasal degeneration committed a greater number of apraxic errors than normal healthy control subjects on both transitive and intransitive tasks (p < 0.001 in both cases), but apraxia was much more severe in patients with corticobasal degeneration than progressive supranuclear palsy (p < 0.001). The index of apraxia severity, in combination with the assessment of the two key features of progressive supranuclear palsy (falls and vertical gaze palsy), correctly classified all patients. CONCLUSIONS: Patients with corticobasal degeneration show more severe ideomotor apraxia than patients with progressive supranuclear palsy, and systematic assessment of ideomotor apraxia facilitates the differential diagnosis between patients with progressive supranuclear palsy and those with corticobasal degeneration.     

Cerebral blood flow in corticobasal degeneration and progressive supranuclear palsy

To compare brain perfusion between corticobasal degeneration (CBD) and progressive supranuclear palsy (PSP), we investigated regional cerebral blood flow (rCBF) semiquantitatively with single-photon emission computed tomography and [123I]iodoamphetamine in six patients with CBD and five with PSP. Compared with 12 age-matched control subjects, the average of the left and right rCBF values for the CBD patients was significantly reduced in the inferior prefrontal, anterior cingulate, medial premotor, sensorimotor, posterior parietal, and superior temporal cortices as well as in the basal ganglia and thalamus, whereas only the medial premotor cortex was significantly hypoperfused in the PSP patients. Compared with the PSP patients, the CBD patients showed significantly decreased rCBF in the inferior prefrontal, sensorimotor, and posterior parietal cortices, but not in the subcortical regions. Compared with the controls, interhemispheric differences of rCBF were significant in the inferior prefrontal, sensorimotor, and posterior parietal cortices of the CBD patients but in only the medial prefrontal cortex of the PSP patients. These results indicate that rCBF reductions are more extensive and asymmetric in CBD than in PSP, although the two diseases share medial frontal involvement.     

Neuroimaging features in progressive supranuclear palsy and corticobasal degeneration]

Progressive supranuclear palsy (PSP) and cortocobasal degeneration (CBD) are often clinically confused with each other. In this paper, based our previous and on-going morphological and functional neuroimaging studies, the features characteristic of the two diseases are discussed. In PSP patients, the atrophic and metabolic changes are dominant in the frontal lobes, basal ganglia, and midbrain, while in CBD patients, the changes are dominant in the parietal lobe. There is little overlap of topographical distribution of atrophy and functional changes between PSP and CBD, despite the considerable similarity of symptoms of the two disorders. The clear distinction between the two diseases may be in part caused by the criteria-based subject selection process; based on stringent clinical diagnostic criteria for each disorder, which have a high specificity and a low sensitivity, only patients that are typical of each disease are compared. Nevertheless, these neuroimaging features appear to reflect different clinical and pathologic phenotypes between the two diseases. These findings suggest that neuroimagings facilitate the differential diagnosis between patients with PSP and those with CBD.     

Microglial activation parallels system degeneration in progressive supranuclear palsy and corticobasal degeneration

The role of microglia in progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) is unknown. To address this issue we examined 10 cases of PSP, 5 cases of CBD, and 4 normal controls. Microglial and tau burdens were determined with image analysis on brain sections that had been immunostained with monoclonal antibodies to HLA-DR and phospho-tau. We found that microglial activation was greater in PSP and CBD than normal controls, and that the microglial burden correlated with the tau burden in most areas. There were distinct patterns of microglial activation and tau pathology in PSP and CBD, with PSP showing more pathology in infratentorial structures and CBD showing more pathology in supratentorial structures. These results support the notion that PSP and CBD are distinct clinicopathologic entities. Microglial activation was not well correlated with tau pathology in the brainstem of PSP, which suggests that brainstem pathology in PSP is not exclusively due to tau pathology. While the results do not necessarily support a direct causal link between microglial activation and neurodegeneration in PSP or CBD, they nevertheless suggest that microglia play a role in disease pathogenesis.     

Co-occurrence of radiological features of progressive supranuclear palsy and corticobasal degeneration

We report an interesting case demonstrating co-occurrence of radiological features of progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD). The clinical features were typical of PSP but magnetic resonance imaging (MRI) showed both typical brainstem changes of PSP and an atypical pattern of cortical atrophy. While the MRI had markers of CBD, the clinical features were not classical of CBD.     

Longitudinal ocular motor study in corticobasal degeneration and progressive supranuclear palsy

OBJECTIVE: To evaluate the usefulness of ocular motor information in the early diagnosis of corticobasal degeneration (CBD) and progressive supranuclear palsy (PSP). METHODS: Seven PSP patients, six CBD patients, and three atypical CBD patients were followed longitudinally with repeated electrooculographic (EOG) recordings, at 6-month intervals, to search for features that could confirm or modify the diagnosis. Visually guided saccades and antisaccades were studied. Data from clinical evaluations were independently collected. RESULTS: PSP patients had decreased saccade velocity throughout the disease course. Patients with probable CBD showed preserved saccade velocity but important increased saccade latency ipsilateral to the apraxia side. Similar to patients with PSP, those with atypical CBD features exhibited clinically evident abnormalities of vertical saccades and early slowing of horizontal saccade velocity, but no increase in saccade latency or early square-wave jerks. When clinical "telltale signs" appeared and the clinical diagnosis was reviewed independent of EOG recording, the three patients with atypical CBD features were diagnosed as having PSP although new or overlapping syndromes cannot be excluded. CONCLUSIONS: Consecutive EOG recordings help diagnose atypical CBD and PSP disorders earlier.     

Cerebellar cortical tau pathology in progressive supranuclear palsy and corticobasal degeneration

Immunohistochemical localization of tau in the cerebellar cortex was carried out using a mouse monoclonal antibody against phosphorylation-dependent tau (AT8) in brain tissue (cerebellum) from 13 patients with progressive supranuclear palsy (PSP), 7 patients with corticobasal degeneration (CBD) and 5 age-matched control subjects. Purkinje cell somata that showed diffuse granular accumulation of cytoplasmic tau were found occasionally in 9 of the 13 patients with PSP (69%) and in 4 of the 7 patients with CBD (57%). Tau-positive doughnut-shaped structures were also found occasionally in the cerebellar molecular layer in 6 of the 13 patients with PSP (46%) and 2 of the 7 patients with CBD (29%). No tau immunoreactivity was detected in the cerebellar cortex in the control tissue. In the tissue from one patient with PSP, we also performed a double-labeling immunofluorescence study with anti-glial fibrillary acidic protein (GFAP) antibody and AT8, as well as an immuno-electron microscopic study with AT8. In tau-positive Purkinje cell somata and dendrites, the reaction product was localized mainly within the rough endoplasmic reticulum and free ribosomes. Tau-positive doughnut-shaped structures were located in the GFAP-positive radial processes of Bergmann's glia and were present in the outer areas of inclusions reminiscent of Lewy bodies, which consist of aggregated pathological tau filaments. In conclusion, we have demonstrated a novel tau pathology that affects Purkinje cells and Bergmann's glia in patients with PSP and CBD, indicating that the cerebellar cortex can be involved in the disease processes in PSP and CBD.     

Relationship between frontotemporal dementia and corticobasal degeneration/progressive supranuclear palsy

Progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) were described as separate entities, but prior to that an extrapyramidal variety of Pick's disease was recognized. Subsequently a pathological overlap between these conditions and clinical overlap between frontotemporal dementia, primary progressive aphasia, corticobasal degeneration syndrome and more recently PSP was recognized. Initially only the movement disorder had been emphasized, but now the behavioral and language symptoms are considered common. The syndromes of frontotemporal dementia/Pick's disease can be produced by underlying CBD, PSP or Pick pathology as well as with neural inclusions of the motor neuron disease type. The concept of this overlap has been confirmed genetically finding a similar spectrum of pathology with different tau mutations and even with tau negative pathology, which could be a deficiency of normal tau. The overlap of CBD with PSP and both with PPA and FTD allows to consider these relatively rare conditions as part of a more commonly occurring degenerative disease than previously recognized.     

MRI of progressive supranuclear palsy,corticobasal degeneration and multiple system atrophy

Journal of Neurology - The characteristics of progressive supranuclear palsy (PSP), corticobasal degeneration (CBD) and multiple system atrophy (MSA) on routine magnetic resonance imaging (MRI) are...