[1] 10w Pathology and Sensitivity of Current Clinical Criteria in Corticobasal Syndrome

[1] 256w The aim of this study was to investigate corticobasal syndrome with respect to underlying pathologies, the ability of current clinical criteria to detect early stages of disease, and symptoms and signs predicting background pathologies. We retrospectively analyzed the clinicopathological findings from patients with corticobasal syndrome. We also analyzed whether those findings fulfilled the diagnostic criteria for corticobasal degeneration (CBD). Finally, we investigated characteristic clinical features that are specific to each background pathology. Of 10 consecutive autopsied patients who had corticobasal syndrome (mean age 6 standard deviation, 67.9 6 9.3 years; male:female ratio, 6:4), three had corticobasal degeneration pathology, three had progressive supranuclear palsy, three had Alzheimer's disease, and one had atypical four-repeat tauopathy. Nine patients fulfilled Mayo criteria, and all 10 patients fulfilled modified Cambridge criteria at the later stage, but only two patients fulfilled either clinical criteria within 2 years of disease onset. Five patients fulfilled the clinical criteria for possible CBD (p-CBD), and one patient fulfilled the clinical research criteria for probable sporadic CBD (cr-CBD) at the later stage. Only two patients fulfilled the criteria for either p-CBD or cr-CBD within 2 years of disease onset. Although we could not find any predictive characteristic clinical features that were specific to CBD pathology, only patients with progressive supranuclear palsy developed apraxia of eyelid opening and cerebellar ataxia. Myoclonus and memory impairment, especially if they appear at an early stage of the disease, may predict Alzheimer's disease pathology. Sensitivity of the available clinical criteria for corticobasal syndrome was poor within 2 years of disease onset. V

[1] 112w We identified 11 patients (seven men and four women) who had a clinical diagnosis of CBS. We excluded one patient because he did not satisfy either the Mayo Clinic criteria or the modified Cambridge criteria. 10,11 None of the patients had a family history of similar symptoms. The male:female ratio was 6:4, the mean 6 standard deviation age at onset was 67.9 6 9.3 years (see Supporting Table 1), and the mean 6 standard deviation duration of illness was 6.9 6 3.3 years. Pathological analyses revealed that, of the 10 patients who had CBS, three had CBD pathology (CBS-CBD), three had PSP (CBS-PSP), and three had AD (CBS-AD) (see Supporting Table 1).

[2] 134w The pathological diagnosis of patient 10 (Supporting Table 1) was an atypical tauopathy that had been reported previously by our institute. 17,18 Her initial symptoms were asymmetrical parkinsonism, muscle weakness, and apraxia, which appeared 2 years after the initial symptoms. The patient exhibited neurodegeneration with widespread neuronal and glial fourrepeat tau lesions in the central nervous system, including the upper and lower motor neuron systems. Neuronal loss with gliosis was evident in the primary motor and premotor cortices, including the SMA (Fig. 1d,h), and was less severe in the basal ganglia (Fig. 1l) and substantia nigra (Fig. 1p). AT8-positive and Gallyas-Braak-negative neuronal cytoplasmic inclusions resembling NFTs and atypical astrocytic tau lesions, which were distinct from astrocytic plaques in CBD or tufted astrocytes in PSP, were observed. 17,18 Common Topographic Distribution of Patients With CBS

[3] 162w We examined the severity of neuronal loss with gliosis in all 10 patients and compared the patients according to pathology subgroup (Supporting Table 1). We found a specific pattern of neurodegeneration in which neuronal loss was evident with microvacuolation in layers II and III of the primary motor and SMA cortices with no reference to underlying pathology (Fig. 1a-h). Neuronal loss with gliosis in the globus pallidus was moderate in patients with CBS-CBD (Fig. 1i), mild to severe in patients with CBS-PSP (Fig. 1j) and CBSatypical tauopathy (Fig. 1l), but absent in patients with CBS-AD (Fig. 1k). Although free-melanin pigments with neuronal loss and gliosis in the substantia nigra were observed in patients with CBS-CBD (Fig. 1m), CBS-PSP (Fig. 1n), and CBS-atypical tauopathy (Fig. 1p), the overall pigmented neurons were well preserved in patients with CBS-AD (Fig. 1o). Moderate to severe neuronal loss with gliosis and tau pathology in the dentate nucleus were observed only in patients with CBS-PSP (Supporting Table 1).

[4] 109w We compared the clinical features among patients who had CBS with different pathologies (see Tables 2 and 3). Although we could not find any characteristic clinical features that were specific to CBD pathology, only patients who had PSP developed apraxia of eyelid opening, cerebellar ataxia, and dystonia. All three patients with AD pathology developed myoclonus of the extremities, whereas patients with CBD and PSP did not. Only one patient with AD pathology had a symmetric onset, and another patient with AD pathology developed memory impairment at an early stage of the disease. Only one patient classified with atypical four-repeat tauopathy had upper and lower motor neuron signs without dementia.

[1] 97w The demographic features of all patients during the entire disease course are summarized in Table 1. All patients had an insidious onset and gradual progression, and none had a significant response to L-dopa. The most common features were rigidity (100% of patients) followed by frontal signs and dementia (90%). Dystonia and aphasia were not common even late in the disease course (22% and 30%, respectively). Although asymmetric atrophy of the cerebral cortex on MRI was observed in only five of the 10 patients (50%), asymmetric cerebral hypoperfusion on SPECT was observed in five of seven patients (71%).

[2] 115w Next, we investigated whether the 10 patients with CBS had satisfied Mayo Clinic or modified Cambridge criteria 10,11 within 2 years of disease onset (Table 2). Rigidity (50%) and limb apraxia (44%) were frequently observed. One patient developed cortical symptoms or signs, two patients developed extrapyramidal signs, five patients developed both, and two patients developed other symptoms. Only two patients fulfilled either set of criteria within 2 years of disease onset. Early clinical diagnosis included four patients with CBS, two with parkinsonism, one with Parkinson's or diffuse Lewy body disease, one with spinocerebellar degeneration, and one with progressive nonfluent aphasia. The final diagnoses included eight patients with CBS and two patients with CBS or PSP.

[1] 470w The present study has demonstrated several novel findings with regard to CBS. First, this study has con-firmed, for the first time, a wide spectrum of pathological backgrounds in Japanese patients with CBS. We have demonstrated that the most frequent causes of CBS were CBD, PSP, and AD, consistent with previous reports from Western countries. Boeve et al. reported that the most common pathologies of CBS were CBD (18 of 34 patients; 52.9%), PSP (six of 34 patients; 17.6%), and AD (three of 34 patients; 8.8%) 10 ; whereas Ling et al. reported that the most common pathologies were PSP (six of 21 patients; 28.6%), CBD (five of 21 patients; 23.8%), AD (five of 21 patients; 23.8%), and FTLD-TDP (two of 21 patients; 9.5%). 19 Lee et al. reported that the most common pathologies were CBD (14 of 40 patients; 35.0%), AD (nine of 40 patients; 22.5%), PSP (five of 40 patients; 12.5%), and FTLD-TDP (five of 40 patients; 12.5%). 20 Because our cohort was small and did not include patients who had CBS with FTLD-TDP or Pick's disease, further analysis of more patients with CBS may be required to determine the pathological backgrounds of Japanese patients with CBS. In addition, our study confirms that all included patients with CBS shared a common topographic distribution of neurodegeneration, which was maximal in the frontal and parietal cortical regions, especially in the primary motor cortex and SMA, and our findings reveal that CBS occurred in the absence of basal ganglia and nigral degeneration, as previously reported in Western populations. 9 This raises the possibility that dysfunction of the primary motor cortex and SMA could cause extrapyramidal symptoms in CBS, because both have been shown to play roles in voluntary muscle relaxation as well as muscle contraction. [21][22][23] Second, we have also demonstrated that the sensitivity of the available clinical criteria for CBS is poor for classifying CBS within 2 years of disease onset. Although five patients developed symptoms or signs of both the cerebral cortex (cortical sensory motor symptoms/cognitive symptoms) and the extrapyramidal system (motor features) within 2 years, only two patients fulfilled the clinical criteria from the Mayo Clinic or Cambridge. 10,11 Mathew et al. also demonstrated that available criteria could be applied equally well in later disease stages, but not in the earlier stages. 11 Because available clinical criteria were established on the basis of clinical experience by experts in the field, future prospective studies need to be performed to determine natural history and clinicopathological correlations for the establishment of sensitive clinical criteria. With regard to the diagnostic criteria for CBD, we observed that their sensitivity within the first 2 years after disease onset may be low and that patients without CBD pathology can fulfill the cr-CBD criteria. Further studies are required to determine the sensitivity and specificity of these criteria.

[2] 362w Third, despite the small number of patients studied, our results suggest that several clinical features may be helpful in predicting the pathological backgrounds of patients with CBS. The present study has demonstrated that only patients with CBS-PSP developed apraxia of eyelid opening, cerebellar ataxia, and dystonia; that all patients with CBS-AD had myoclonus; and that only one patient with CBS-AD had a symmetric onset. It has been demonstrated that apraxia of eyelid opening is a frequently observed ophthalmologic feature in PSP but not in CBD or AD. 24 Cerebellar ataxia also may indicate CBS-PSP; recent studies have indicated that patients with PSP, but not patients with CBD or AD, may develop cerebellar ataxia as the initial and principal symptom. 25,26 In contrast, it is not believed that dystonia can predict CBS-PSP, because dystonia is also observed in CBS-CBD 27 and CBS-AD. 28 Myoclonus and memory impairment, especially when they appear at an early stage of the disease, may predict CBS-AD according to a previous report. 4,5 However, symmetric CBS might not predict CBS-AD, because symmetric CBS is also observed in CBS-CBD 29 and in CBS caused by progranulin mutation. 30 Early diagnosis of CBS-CBD is still difficult, because, to date, no characteristic features have been identified that can predict CBD pathology. However, our sample size was small, and we could not perform statistical analyses. In addition, studies with large sample sizes have proposed contrasting predictive clinical characteristics. 19,31,32 Future analyses of more patients may be required to draw more definitive conclusions. Finally, in our CBS cohort, there was a patient with atypical four-repeat tauopathy that did not satisfy the pathological diagnostic criteria for CBD or PSP despite the presence of neurodegeneration with tau-positive neuronal and glial cytoplasmic inclusions, as previously reported. 17,18 Clinical features in this patient were characterized by sporadic parkinsonism and motor neuron disease without dementia, and pathological features were four-repeat tauopathy with unique tau pathology: the astrocytic tau lesions were different in morphology from astrocytic plaques and tufted astrocytes, which are characteristic of CBD and PSP, respectively. Although the disease entity has not been established, this type of atypical four-repeat tauopathy may be considered a differential diagnosis for CBS.

[3] 44w In conclusion, we have established the wide spectrum of CBS clinicopathological manifestations in Japanese patients. We also have demonstrated that the sensitivity of the available clinical criteria for CBS and CBD was poor for detecting the disease within the first 2 years of onset.

[1] 97w We retrospectively reviewed our institutional database between October 1996 and February 2011 and identified the records of patients who satisfied the clinical criteria for CBS whose bodies were donated to our institute. The diagnosis of CBS was made when the patient met either set of clinical criteria proposed by Boeve et al. (Mayo Clinic criteria) 10 or Mathew et al. (modified Cambridge criteria). 11 We also analyzed whether these patients fulfilled the diagnostic criteria for CBD. 12 All procedures were carried out with the ethical approval of the Ethics Committee of the Niigata University School of Medicine.

[2] 225w Brains were fixed with formalin, and multiple tissue blocks were embedded in paraffin. Histological examinations were performed on 4-lm-thick sections with several stains, including hematoxylin and eosin (H&E), Kl€ uver-Barrera, and Gallyas-Braak. These sections also were immunostained with a mouse monoclonal antibody against hyperphosphorylated tau (AT8; Innogenetics, Ghent, Belgium; 1:200 dilution). We assessed neuronal loss with gliosis and the severity of tau pathology in several selected areas, including the cerebral cortices (prefrontal cortex, supplementary motor area [SMA], primary motor cortex, postcentral cortex, and insular cortex), the basal ganglia (globus pallidus, putamen, and caudate), the substantia nigra, and the cerebellum (Purkinje cells and the dentate nucleus). The selected cortical regions were determined by reference to previous studies of CBS. 13 Neuronal loss with gliosis was assessed semiquantitatively with H&E-stained sections and was recorded using a 4-point scale (0, absent; 1, mild; 2, moderate; 3, severe). The numbers of AT8positive neurofibrillary tangles (NFTs), which included pretangles/tangles, neuropil threads, and glial fibrillary tangles, were assessed using a 4-point rating scale (2, absent or nearly absent; 1, sparse; 11, moderate; and 111, numerous). The pathological diagnoses were based on the established consensus criteria for CBD, 14 PSP, 15 and AD. 16 A diagnosis of atypical tauopathy was made when pathological findings did not satisfy the above-mentioned criteria despite the presence of neurodegeneration with tau-positive neuronal and glial cytoplasmic inclusions.

[3] 188w We reviewed the patients' medical records and determined their clinical features. A feature was regarded as present if it appeared at any stage during the clinical course. We defined sign absent as cases in which the sign was described as absent in the medical record. We defined not examined as cases in which the sign was either not examined or was not described in the medical chart. The clinical features extracted were defined according to a previous report. 11 With respect to levodopa (L-dopa) resistance, the patient and clinician's interpretations of subjective improvement were assessed from the medical records. Patients were also examined for the presence of asymmetric atrophy of the cerebral cortex using magnetic resonance imaging (MRI) and for asymmetric cerebral blood flow using single-photon emission computed tomography (SPECT) in both the left and right hemispheres if they were examined with those neuroimaging tools. We also investigated the proportions of patients who satisfied the Mayo Clinic or modified Cambridge criteria 10,11 as well as the diagnostic criteria for CBD 12 at the early stage (within 2 years of onset) and at the later stage in their illness.

[1] 144w The terminology related to corticobasal degeneration (CBD) is confusing because a constellation of clinical features may be seen in patients with patholo-gies other than CBD. For example, the clinical features of CBD are observed in other neurodegenerative disorders, such as progressive supranuclear palsy (PSP), 1,2 Alzheimer's disease (AD), [3][4][5] Pick's disease, 6,7 and frontotemporal lobar degeneration with TAR DNA binding protein 43 (TDP-43)-immunoreactive inclusions (FTLD-TDP) 8 . Several proteinopathies, including tauopathy, amyloidopathy, and TDPopathy, can underlie the same clinical phenotype. Additionally, the topographic distribution of neurodegeneration may dictate the clinical phenotype. 9 Therefore, the term corticobasal syndrome (CBS) was proposed to characterize the constellation of clinical features that were initially considered the defining characteristics of CBD, and the use of the term CBD was reserved for the pathological disorder. 10 - -----------------------------------------------------------Additional Supporting Information may be found in the online version of this article.

[2] 70w This article was published online on 20 NOV 2013. An error in the title was subsequently identified. Corticobasal was misspelled. The article has since been corrected. *Correspondence to: Dr. Takayoshi Shimohata, Department of Neurology, Brain Research Institute, Niigata University, 1-757 Asahi-machi-dori Niigata, Niigata 951-8585, Japan; t-shimo@bri.niigata-u.ac.jp Relevant conflicts of interest/financial disclosures: Nothing to report. Full financial disclosures and author roles may be found in the online version of this article.

[3] 162w However, several issues need to be resolved. First, all of the aforementioned observations were based on reports from patients with CBS from Western populations, and the clinicopathological characteristics of other ethnicities remain to be elucidated. Second, although several clinical diagnostic criteria have been proposed, including those published by Boeve et al. (Mayo Clinic criteria) 10 and by Mathew et al. (modified Cambridge criteria), 11 as well as the diagnostic criteria for CBD, 12 the proportion of patients who satisfy early stage criteria remains unknown. Third, although accurate antemortem diagnoses will become increasingly important for designing future pharmacological trials, the characteristic symptoms or signs that could predict the pathological background of patients with CBS also remain unknown. Here, we analyzed Japanese patients with CBS who satisfied the current clinical criteria at their later disease stages to investigate the background of their pathologies, the sensitivity of these criteria for detection at early stages, and the symptoms and signs that were indicative of their pathologies.

[4] 85w We also investigated whether the 10 patients with CBS had satisfied the diagnostic criteria for CBD 12 within 2 years of disease onset and during the entire disease course (Table 3). No patients with CBS-CBD fulfilled either set of criteria within 2 years of disease onset, whereas all three patients fulfilled them during the entire disease course. In contrast, one patient with CBS-PSP fulfilled the clinical criteria for possible CBD (p-CBD) during the entire disease course, and two patients with CBS-AD fulfilled the clinical research